Get 20M+ Full-Text Papers For Less Than $1.50/day. Subscribe now for You or Your Team.

Learn More →

Constitutive basis of root system architecture: uncovering a promising trait for breeding nutrient- and drought-resilient crops

Constitutive basis of root system architecture: uncovering a promising trait for breeding... aBIOTECH https://doi.org/10.1007/s42994-023-00112-w aBIOTECH RESEARCH ARTICLE Constitutive basis of root system architecture: uncovering a promising trait for breeding nutrient- and drought-resilient crops 1 1 1 1 Zhigang Liu , Tongfei Qin , Michaella Atienza , Yang Zhao , 1 1 1 2 Hanh Nguyen , Huajin Sheng , Toluwase Olukayode , Hao Song , 1 3 1,4 1& Karim Panjvani , Jurandir Magalhaes , William J. Lucas , Leon V. Kochian Global Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4L8, Canada Department of Computer Science, University of Saskatchewan, Saskatoon, SK S7N 5C9, Canada Embrapa Maize and Sorghum, Brazilian Agricultural Research Corporation, Sete Lagoas, MG 35701-970, Brazil Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA Received: 1 May 2023 / Accepted: 20 July 2023 Abstract Root system architecture (RSA) plays a pivotal role in efficient uptake of essential nutrients, such as phosphorous (P), nitrogen (N), and water. In soils with heterogeneous nutrient distribution, root plasticity can optimize acquisition and plant growth. Here, we present evidence that a constitutive RSA can confer benefits for sorghum grown under both sufficient and limiting growth conditions. Our studies, using P efficient SC103 and inefficient BTx635 sorghum cultivars, identified significant dif- ferences in root traits, with SC103 developing a larger root system with more and longer lateral roots, and enhanced shoot biomass, under both nutrient sufficient and deficient conditions. In addition to this constitutive attribute, under P deficiency, both cultivars exhibited an initial increase in lateral root development; however, SC103 still maintained the larger root biomass. Although N deficiency and drought stress inhibited both root and shoot growth, for both sorghum cultivars, SC103 again main- tained the better performance. These findings reveal that SC103, a P efficient sorghum cultivar, also exhibited enhanced growth performance under N deficiency and drought. Our results provide evidence that this constitutive nature of RSA can provide an avenue for breeding nutrient- and drought-resilient crops. Keywords Constitutive root system architecture, Abiotic stress, Nutrient efficiency, Drought resilience, Plant breeding INTRODUCTION majority of global agricultural calories, indicates from current progress in yield enhancement that there is a It has been estimated that, by 2050, the global human significant need for novel crop improvement strategies population will reach 10 billion (Hickey et al. 2019), (Gao 2021; Ray et al. 2013). Due to abiotic stresses, hence, global agricultural production must increase to including drought, flooding, extreme temperatures, meet this demand. In this regard, evidence available salinity, and acid soil conditions, and limiting nutrient for maize, rice, wheat, and soybean, which produce the availability and cost, both crop growth and yield can be greatly impacted (Halford et al. 2015; Tyczewska et al. 2018). This issue is of great concern and requires immediate attention to ensure sustainable & Correspondence: leon.kochian@gifs.ca (L. V. Kochian) The Author(s) 2023 food production in the face of these environmental earlier identified in rice, as P efficiency genes (Gamuyao challenges. et al. 2012), in which breeding for this trait gave rise to Until recently, the underground component of crops, larger and deeper root systems. These RSAs clearly did namely their root systems, have received little attention not concentrate a significant fraction of their root within regarding crop improvement. Given the important the upper (topsoil) regions of the soil profile. functions of the root system, including water and To further explore the relationship between RSA and nutrient acquisition, and plant anchorage, recent studies yield performance, under field conditions with limiting have begun to explore the functional components of soil P availability, in the current study, we utilized two root system architecture (Gabay et al. 2023; Hodge et al. sorghum lines, SC103 and BTx635, having significant -1 2009;Ryan etal. 2016; Zheng et al. 2023). In monocots, differences in grain yield; BTx635 was 1.6 tons ha , -1 the root system contains seminal (primary), lateral and whereas SC103 was 2.8 tons ha —a yield increase of crown roots, whereas in dicots, a primary root (tap 75% (Hufnagel et al. 2014). Based on the SC103 yield root) system gives rise to multiple orders of lateral enhancement, we conducted an extensive study of their roots (Meister et al. 2014). Root system architecture RSAs to ascertain whether the distribution of their roots (RSA), the spatial configuration of the plant root system, conformed to either the topsoil pattern (Fig. 1A) or a plays a pivotal role in efficient uptake of essential broader and deeper distribution (Fig. 1B). Of special nutrients (e.g., nitrogen [N], phosphorous [P], and note, our findings failed to support the topsoil model, in potassium [K]) and water (Marschner 2011). that SC103 exhibited an ‘‘inverted triangle’’ RSA like that In agricultural soils, the spatial availability of these shown in Fig. 1B. Importantly, SC103 had enhanced essential components for growth are often heterogenous performance under both full nutrient and limiting P, N, in nature. Thus, soil characteristics must be integrated and drought conditions. Additionally, a similar RSA into breeding programs to achieve optimal nutrient pattern was identified for BTx635, but overall, this root acquisition for enhanced yield performance (Lynch 2022; system was significantly smaller, under these same Tracy et al. 2020). Numerous studies have focused on the growth conditions for N, P, and water. These studies role of RSA in efficient acquisition of the most diffusion- highlight the requirement for a coordination between limited mineral nutrient, phosphorous (as phosphate RSA studies and crop breeding programs. [Pi]) (Liu 2021; Mohammed et al. 2022). Here, in acid soils, Pi is tightly bound to clay minerals, within the top- soil, resulting in a marked vertical Pi gradient. These soil MATERIALS AND METHODS characteristics have driven researchers to focus on selection of P efficient lines, in which a majority of the RSA Plant materials is located within the topsoil (Liang et al. 2010; Rangarajan et al. 2018; Sun et al. 2018; Zhao et al. 2004) (Fig. 1A). Two sorghum (Sorghum bicolor) cultivars, SC103 and Under acid soil conditions, the mobile nutrients, BTx635, were used in this study. These cultivars rep- including N and K, are distributed throughout the soil resent widely employed sorghum breeding lines in the profile. Thus, in breeding P efficient lines, consideration is United States and Brazil (Casa et al. 2008). Further, needed in terms of acquisition of these mobile nutrients. Hufnagel et al. (2014) demonstrated that SC103 had In this regard, a topsoil RSA would likely require highly higher grain yields, compared to BTx635, when grown efficient N and K transport systems for capture during under on low P soil with high Pi soil fixation, reflecting fertilizer application. An alternative breeding approach limiting soil P availability. These studies established might utilize an RSA in which the roots are more uni- SC103 and BTx635 as relatively P efficient and ineffi- formly distributed throughout the soil profile (Fig. 1B). cient, respectively. Sorghum breeding programs have developed Pi effi- cient lines optimized for crop performance on acid soils. Plant growth for 2D root system architecture For example, Hufnagel et al. (2014) identified P efficient (RSA) assays and inefficient lines based on screening of a 243-line sorghum association panel for grain yield, when grown Seeds were surface-sterilized in 6% (v/v) sodium on a low P tropical soil. In this study, significant genetic hypochlorite for 20 min, rinsed with 18 Mega-ohm variation in P efficiency was identified. Also, by using water (MX), and germinated, in darkness, for 4 days at candidate gene genome-wide association study (GWAS), 27 C on moist germination paper (Anchor Paper, St. several PSTOL1 (Phosphorous Starvation Tolerance 1) Paul, MN, USA). Uniform seedlings were transferred, genes were discovered. Equivalent PSTOL1 genes were depending on the specific experiment, to hydroponic The Author(s) 2023 aBIOTECH solution [K] concentrations close to at 3.11 mM, with 0.2 mM being added as KH PO . To assess the effects of 2 4 N deficiency on plant RSA, seedlings of each cultivar were grown hydroponically for 10 days in a pouch system, with 4000 lM nitrogen as sufficient N (SN) and 400 lM as low N (LN) conditions. As N was added as 2? Ca(NO ) , to maintain the same Ca concentration in 3 2 the LN media, as used in the SN media, 900 lM CaCl was supplied in LN media. The nutrient solution was aerated continuously and renewed every 3 days. The solution pH value was maintained at 5.7. In longer term experiments where sorghum was grown in pots, seedlings of the sorghum cultivars SC103 and BTx635 were transferred to plastic pots (25 cm diameter, and 20 cm depth) containing silica sand and nutrient solutions of different [Pi] were added to the top of the pots. The plants were grown for 28 days, using the above-described nutrient solu- Fig. 1 Schematic representation of root system architectures tions, except that the Pi concentration used for control representing topsoil based and deep rooting systems. A Plants (CK) and low Pi (LP) conditions were adjusted to 500 that develop a shallow root system localized within the topsoil and 75 lM, respectively, and the N concentration used (broken rectangle). B Plants that develop an extended, deeper, for LN media was reduced to 600 lM. For experiments root system (broken inverted triangle). CR crown root, LR lateral root, PR primary root conducted with plants grown in silica sand, the appropriate concentrations of N and P for sufficiency solution, silica sand or Sunshine #1 potting mix (Sun and deficiency were determined empirically, by mea- Gro Horticulture, Inc.) as the appropriate growth system suring and comparing shoot biomass for plants grown for RSA studies. Plants were grown in a walk-in growth on LN and SN nutrient solution. For plants grown in chamber with controlled climate conditions of 16/8 h sand watered with LP and SP solutions, shoot growth (light/dark), 27/22 C (day/night) temperature, a light and root traits were evaluated as described for P -2 -1 intensity of approx. 350 lmol m s , at canopy deficiency in hydroponically grown plants in 2D pou- height, and 40–60% relative humidity. ches. Given that nutrient availability in silica sand is After germination, uniform sorghum seedlings were restricted to the pores within the sand, the nutrient transplanted to 100 L polypropylene containers and concentrations in the sand experiments were adjusted grown hydroponically in a specially designed pouch to ensure sufficient or deficient levels. For LP, a con- system, as described by (Gladman et al. 2022). Plants centration of 75 lM was determined to be moderately were supplied with a nutrient solution consisting of P deficient, whereas moderate P deficiency symptoms macronutrients (at mM levels): 3.5 Ca(NO ) , 1.3 NH developed in plants grown in hydroponic media with 3 2 4- NO , 0.58 K SO , 0.58 KCl, 0.56 KNO , 0.85 MgSO ; and 3 2 4 3 4 10 lM Pi. Regarding LN, 600 lM N generated moder- micronutrients (at lM levels): 2.5 H BO , 9.1 MnCl , 0.6 3 3 2 ately N deficient sand-grown plants, whereas 400 lM CuSO , 2.4 ZnSO , 0.8 Na MoO , 100 Fe-HEDTA. 4 4 2 4 N in hydroponic media resulted in moderate N defi- Nutrient solution phosphate (Pi) concentrations were 0, ciency symptoms. 2.5, 10 and 200 lM. Experiments were first conducted To evaluate drought performance of the sorghum to establish the appropriate Pi concentrations for severe cultivars, plants were grown in plastic pots, as above, plant P deficiency (0 and 2.5 lM), moderate Pi defi- containing 1.2 kg Sunshine #1 potting mix. Plants were ciency (10 lM) and sufficient plant Pi status (200 lM): fertilized biweekly using water-soluble fertilizer (Mas- the quantitative indicators of P deficiency are a strong ter Plant-Prod, Inc.), with a standard N–P–K (20–20–20) inhibition of shoot growth and a moderate stimulation treatment. Pot water content was measured using an of root growth, resulting in an increase in root:shoot HydroSense II Handheld Soil Moisture Sensor (Campbell ratio (Cakmak et al. 1994; Ericsson 1995; Chiera et al. Scientific, Inc.), based on the volumetric water content 2002). The Pi concentrations were obtained by adjust- (VWC) for porous media. Pots were initially filled with ing KH PO and KCl was added to maintain the nutrient 2 4 18 MX water and then allowed to drain to establish soil The Author(s) 2023 aBIOTECH ‘field capacity’. Seedlings were then transplanted, with Biomass, N and Pi measurements one seedling per pot, and 200 mL of 18 mX water (corresponding to near-full field capacity) was added, After root architecture determinations, plants were daily, for the first 14 days. dissected into shoots and roots, and both parts were heated at 105 C for 30 min and then oven-dried at After the initial two-week growth period, plants were divided into two treatment groups: well-watered (WW) 65 C for 72 h. The dry samples were then weighed to obtain shoot dry weight (SDW), root dry weight (RDW), and water stressed (WS). The WW plants continued to receive 200 mL of 18 MX water, daily, per pot, to and the root:shoot ratio (R/S). After weight measure- ments, the root and shoot samples were ground and maintain the water content near the full field capacity. For the WS plants water was withheld, and fourteen digested, using a solution of concentrated sulfuric acid days later leaf wilting was observed, coincident with a and selenium at 330 C. Total P and N concentrations measured potting mix water content of 7.5% VWC. were then determined, using a Skalar SAN-plus seg- Plants were subsequently removed from the pots and mented flow analyzer (Skalar Analytical BV, Breda, The their root systems were soaked in water to remove Netherlands), following the manufacturer’s protocols. potting mix, and then thoroughly cleaned by washing Root sectioning and imaging using low water pressure. Finally, RSA measurements were determined (Clark et al. 2013) and then roots and Sorghum seedlings were grown hydroponically for shoots were separated, following drying for biomass determination. 10 days in 20 L polypropylene containers in the same nutrient solution, as described above, under sufficient Pi (SP; 200 lM) or low Pi (LP; 2.5 lM) conditions. Growth Root architecture measurements protocols were as described above. Primary and crown roots were excised at 5 cm from the root-stem junction Phenotyping experiments, using a hydroponic pouch and at 5 cm from the root tip, respectively. Lateral roots system, utilized a Nikon D7200 DSLR camera with a were excised at 5 cm from the primary-lateral root 50 mm lens and a 2D root imaging platform. Raw junction and 5 cm from the lateral root tip. All root images were collected and stored in a Plant Root samples collected were * 5 cm in length. Root samples Imaging and Data Acquisition (PRIDA) program, and were placed into 3D-printed polylactic acid molds for then extracted as TIFF files for further image pro- embedding (Atkinson and Wells 2017). Root tissues cessing and root trait computation (Gladman et al. were fixed in 5% (w/v) agarose, and after agarose 2022). For the phenotyping experiments performed in solidification, blocks were trimmed and sectioned, at silica sand and potting mix, root systems were cleaned 100 lm, using a Leica VT1000S (Vibrating blade after harvest, arranged to minimize any root overlap, microtome, Nussloch, Germany). Transverse sections and then a 2D root imaging platform was used to were examined using a Leica Thunder microscope sys- acquire and store data. Data from phenotyping exper- tem (Wetzlar, Germany). Images were collected using iments were then subjected to both commercial and 10 9 or 20 9 objectives, depending upon the tissue publicly available software packages for root trait size, and the background noise was removed from computation. WinRHIZO software (Regents Instru- images using Adobe Photoshop version 23.5 (Adobe ments, Inc.) was used to quantify root growth and Systems). Root cross-sectional area (SCA) and aerench- topology traits, and GiA Roots (Galkovskyi et al. 2012) yma area (AA) were measured, via pixel-counting, using was used to quantify 2D root architecture traits. Root ImageJ software (https://imagej.nih.gov/ij/). Propor- architecture traits, derived from the hydroponic pouch tion of root cross sections occupied by aerenchyma was system, included primary root length (cm), root system calculated using AA divided by SCA. Sample data were width (cm), and convex hull area (cm ), were assessed. normalized, based on a previously described method Root morphology traits, derived from the hydroponic (Burton et al. 2015). pouch system included average root diameter (cm), total root system surface area (cm ), total root system Statistical analysis length (cm), and total root system volume (cm ). Root morphology traits, derived from experiments in which All statistical analyses were performed using the R plants were grown in silica sand or potting mix, software package (Team 2013). Two-way analysis of included total root system length (cm), root system variance (ANOVA) was used to test for significant dif- surface area (cm ), and total root system volume ferences between treatments, cultivars, and treat- (cm ), were assessed. ment 9 cultivar interactions. Significant differences The Author(s) 2023 aBIOTECH Fig. 2 Response of sorghum root systems (lines SC103 and BTx635) grown under 200 lM Pi (sufficient P), and 10, 2.5 and 0 lM Pi (low P), for 7, 9 and 12 days after transplanting (Dat). A hydroponic pouch system was employed for these assays, and representative images are shown between means were analyzed by independent Stu- expected, a significant reduction in SDW was observed dent’s t test or Tukey’s honest significant difference in both SC103 and BTx635, in response to Pi stress. (HSD) tests, where appropriate. ANOVA was performed However, SDW in SC103 was significantly greater than using the ‘‘Anova’’ function, as implemented in the ‘‘car’’ in BTx635, under all levels of the imposed Pi stress package (Fox et al. 2012). Tukey’s HSD tests were per- (Fig. 3A). An increase in the root:shoot ratio (R/S) is formed using the ‘‘Tukey HSD’’ function in R. Additional commonly observed under Pi deficient conditions, visualization of the data was performed using the ‘‘gg- either by a reduction in shoot growth or an increase in plot2’’ package (Wickham 2016). root growth, or both (Cakmak et al. 1994; Ericsson 1995; Chiera et al. 2002). Under Pi stress, R/S ratio was increased by 27% (10 lM), 68% (2.5 lM) and 52% RESULTS (0 lM) in SC103, whereas an increase of 43% (10 lM), 75% (2.5 lM) and 60% (0 lM) was observed in Sorghum SC103 establishes a larger root system BTx635, compared with sufficient Pi conditions under both sufficient and deficient Pi conditions (Fig. 3B). The P deficiency severity was also increased by growth on 10, 2.5 and 0 lM Pi; here, a stronger Sorghum seedlings were grown in a hydroponic pouch inhibition of shoot growth and increased stimulation in system for 7, 9, and 12 days after transplanting (Dat). lateral root growth was observed as P deficiency This nutrient delivery system was used to provide Pi became more severe (Fig. 3A and Supplementary distribution to the root systems of these sorghum cul- Table 1). This resulted in increases in R/S ratios under tivars. Both cultivars exhibited significantly larger root increasing P deficiency, which, as noted above, has been systems in response to Pi deficiency (Fig. 2). However, well-established in previous studies (Cakmak et al. SC103 also exhibited a much larger root system than 1994; Ericsson 1995; Chiera et al. 2002). Collectively, BTx635 under Pi sufficient conditions. Furthermore, the these findings support the notion that SC103 has a P efficient SC103 exhibited 69 and 110% greater SDW genetic component that imparts a capacity for estab- and RDW, respectively, compared with the P inefficient lishing a larger root system under both sufficient and BTx635, under Pi sufficient conditions (200 lM). As deficient Pi conditions. The Author(s) 2023 aBIOTECH Fig. 3 Root system architecture of sorghum lines SC103 and BTx635, grown in a hydroponic pouch system, under the indicated phosphate (Pi) concentrations. Panels represent shoot dry weight (A), root:shoot ratio (B), total root system length (C), root system width (D), total root system surface area (E), and primary root length (F), analyzed at 7, 9 and 12 Dat. Data shown are means ± SE (n = 6). Asterisks indicate significant differences between the genotypes, under the same Pi concentrations, as determined by the Student’s t test. For these assays, significance differences are indicated as follows: *P \ 0.05; **P \ 0.01; ***P \ 0.001. Different lowercase letters indicate significant differences (P \ 0.05) among the four Pi concentrations, in the same genotype, as determined by Tukey’s HSD tests Sorghum SC103 developed a larger RSA As demonstrated by the data presented in Fig. 3 and compared with BTx635 evident from the images in Fig. 2 showcasing the root systems of the two cultivars, grown for 7, 9, and 12 Dat Traits associated with RSA, including primary root at varying growth solution Pi concentrations, it is length, total root system length, total root system sur- apparent that increasing P deficiency leads to greater face area, root system width (Fig. 3), and average root stimulation of lateral and tap root growth, compared to diameter, total root system volume, and convex hull area plants grown under sufficient P conditions (200 lM Pi). (total area occupied by the root system) (Supplemen- Furthermore, investigating the root system vertical tary Table 1), were assessed. Under sufficient Pi condi- distribution can be beneficial for an understanding of tions, total root system length (88%), root system the pattern of root Pi acquisition. For our study, the surface area (117%), total root system volume (157%), sorghum root system was divided into three equally- primary root length (21%), and convex hull area (60%) spaced regions, based on root system depth (Fig. 4A). In were greater in SC103, compared with BTx635, at 12 the top region (R1), we observed that SC103 had a Dat (Fig. 3C–F; Supplementary Table 1). Under Pi defi- significantly higher total root system length compared cient conditions, total root system length (55%), total with BTx635 at all time points, under sufficient and root system surface area (53%), and total root system deficient Pi conditions. Importantly, under Pi stress, volume (52%) were greater in SC103, compared with total root system length was increased significantly at BTx635, at 12 Dat (Fig. 3C–F; Supplementary Table 1). all time points in SC103 and BTx635 in region R1 The Author(s) 2023 aBIOTECH Fig. 4 Root system architecture profiles for SC103 and BTx635 grown in a hydroponic pouch system, under sufficient Pi (200 lM) and deficient Pi (0 lM) conditions, for 7, 10 and 14 Dat. A Root systems were divided into three equal regions, R1, R2 and R3, based on the root system depth. B Total root system length in each region. C Percentage of total root system length in each of the three regions. Asterisks indicate significant differences between the various Pi concentrations, in the same cultivar, in the same region, as determined by Student’s t test: for these assays, significance differences are indicated as follows: *P \ 0.05; **P \ 0.01; ***P \ 0.001. CR crown root, PR primary root, LR lateral root. Red dotted lines represent the locations where root sections were excised for cross-sectional analyses (see Figs. 5A, E, 6A, E, and Supplementary Fig. 2) Table 1 Shoot and root phosphorous (P) concentration and content in sorghum lines SC103 and BTx635 grown under increasing phosphate (Pi) treatments -1 Treatment Shoot P content (lg) Shoot P concentration (mg Root P content (lg) Root P concentration (mg g ) -1 g ) SC103 BTx635 SC103 BTx635 SC103 BTx635 SC103 BTx635 0 lM71 ± 3 c*** 50 ± 3 c 1.4 ± 0.1 b 1.4 ± 0.03 c 60 ± 2 c*** 32 ± 2 c 1.7 ± 0.1 c 1.4 ± 0.1 c 2.5 lM79 ± 5 bc** 48 ± 5 c 1.5 ± 0.1 b 1.3 ± 0.1 c 70 ± 4 c*** 34 ± 2 c 1.7 ± 0.04 c** 1.4 ± 0.1 c 10 lM 187 ± 20 b* 124 ± 17 b 2.6 ± 0.3 b 2.6 ± 0.3 b 142 ± 22 b* 78 ± 9 b 3.2 ± 0.3 b 3.0 ± 0.3 b 200 lM 599 ± 53 a** 349 ± 17 a 6.5 ± 0.5 a 6.3 ± 0.2 a 280 ± 28 a*** 121 ± 6 a 6.3 ± 0.3 a 5.7 ± 0.2 a Plants were grown in a hydroponic pouch system, with the indicated four different Pi conditions, and were harvested 12 days after transplanting. Data shown are means ± SE (n = 6). Different lowercase letters indicate significant differences (P \ 0.05) among the Pi conditions in the same genotype, as determined by Tukey’s HSD tests. Asterisks indicate significant differences between genotypes in the same condition, as determined by Student’s t test analysis: *P \ 0.05, **P \ 0.01, ***P \ 0.001. The Author(s) 2023 aBIOTECH (Fig. 4B). In Fig. 4C, we present the % changes for sections, excised from near the stem-root junction and at regions R1, 2 and 3, under P deficient conditions, least 5 cm back from the root tip, indicated the presence of showing that the % of roots distributed between these 3 extensive aerenchyma (Fig. 5A, E). However, under both regions were similar in nature between SC103 and sufficient Pi (200 lM; SP) and low Pi (2.5 lM; LP) condi- BTx635. tions, in SC103, the AA was significantly larger, as was the AA/CSA ratio, compared with BTx635 (Fig. 5B–D, F–H). P acquisition versus utilization A similar pattern was also observed for lateral root anatomy, near both the stem-root junction and at least Under sufficient Pi conditions (200 lM), SC103 exhibited a 5 cm back from the lateral root tip. Again, SC103 had the significant enhancement in P uptake (72% more shoot Pi larger AA and AA/CSA ratio, compared with BTx635, with content) than BTx635. As expected, Pi stress reduced these differences being enhanced under LP conditions uptake in both cultivars; however, P uptake was still sig- (Fig. 6A–H). Crown root anatomy was also investigated, nificantly higher in SC103. Here, SC103 accumulated 50%, from the same locations as described above, and again 64% and 43% more P in their shoots, compared with SC103 had the larger AA and AA/CSA ratio, compared BTx635, under the three imposed Pi stress conditions, with BTx635, with these differences also being enhanced respectively (Table 1). In both cultivars, the reduction in P under LP conditions (Supplementary Fig. 2). These shoot content displayed a similar pattern. Interestingly, findings indicate that both sorghum lines develop aer- although we observed significant differences in P acquisi- enchyma under SP and LP conditions. Furthermore, aer- tion, between these two cultivars, no physiologically sig- enchyma development in SC103 was significantly greater nificant differences were observed in shoot and root P compared with BTx635, under both SP and LP conditions. concentration under sufficient and deficient Pi conditions (Table 1). In addition, we observed higher P concentrations RSA response to N deficiency and drought stress (P\ 0.001) and P content (P\ 0.001) in SC103 seeds, compared with BTx635 (Supplementary Fig. 1). This Parameters associated with biomass and RSA were observed increase in plant P content, in SC103, is a assessed in response to an imposed N stress. Here, reflection of its larger root system. Based on these findings, SC103 exhibited a larger root system, compared with the lack of a difference in shoot and root P concentration BTx635, under both sufficient N (SN) and low N (LN) between both cultivars, and the much larger P content in conditions (Fig. 7A and Supplementary Table 2). As SC103, is consistent with P acquisition being a major shown in radar plots presented in Fig. 7B, under SN, all contributor to enhanced P efficiency in SC103. root and biomass traits, with the exception of average We have recently, from a genetic and physiological root diameter, were significantly larger in SC103 com- analysis of sorghum P efficiency, determined that when pared with BTx635. A similar pattern was observed dissecting sorghum P use efficiency into P utilization under LN, except that, again, average root diameter was efficiency (PUE) and P acquisition efficiency (PAE), PAE equivalent between the two cultivars, and BTx635 accounts for the majority of the genetic contribution to established a higher R/S ratio, compared to SC103 P efficiency. Specifically, we determined in our study (Fig. 7C and Supplementary Table 2), due largely to its that PAE contributes 82% to the overall PAE, whereas reduction in shoot biomass. These findings support the PUE accounts for 18% (Bernardino et al. 2019). A notion that the SC103 genetic composition can confer similar strong genetic influence of PAE on P efficiency superior performance, relative to BTx635, under both P was previously reported in maize by Parentoni et al. and N stress conditions. (2010), where PAE explained approximately 80% of To explore the effect of plant development, on shoot total P efficiency. and RSA traits, in these two sorghum cultivars, experi- ments were next conducted by growing plants in silica Pi stress impacts root anatomy in both SC103 sand, as substrate. Here, we tested the effects of LP and and BTx635 LN on RSA and growth. As anticipated, shoot biomass was reduced under both LP and LN conditions (Fig. 8A). Parameters associated with root anatomy, such as root Under control conditions, the relative changes in RSA cross-sectional area (CSA), total root cortical aerenchyma traits and growth characteristics, between SC103 and area (AA) and the proportion of root cross sectional area BTx635, are shown in Fig. 8B (see also Supplementary occupied byaerenchyma (AA/CSA), were evaluated (Figs. 5, Fig. 3 and Supplementary Table 3). The noteworthy 6, and Supplementary Fig. 2). Root segments were excised, differences were in total root system volume, length, from locationsasindicatedinFig. 4A, and cross sections and surface area, which were always higher in SC103. prepared for anatomical studies. Primary root cross Under LP growth conditions, significant differences The Author(s) 2023 aBIOTECH Fig. 5 Primary root anatomy of sorghum cultivars SC103 and BTx635 grown for 10 days in hydroponics under sufficient Pi (SP, 200 lM) and low Pi (LP, 2.5 lM) conditions. Representative transverse images of primary root cross sections, collected 5 cm below the stem-root junction (A), and * 5 cm from the primary root tip (E) (see Fig. 4A). Histograms represent root cross-sectional area, total root cortical aerenchyma area (AA), and proportion of root cross section occupied by aerenchyma, near the stem root junction (B–D) and * 5cm from the root tip (F–H) of the SC103 (green) and BTx635 (orange) primary root, respectively. Data shown are means ± SE (n = 6). Asterisks indicate significant differences between the cultivars, under the same condition, as determined by Student’s t test: for these assays, significance differences are indicated as follows: *P \ 0.05; **P \ 0.01; ***P \ 0.001. Different lowercase letters indicate significant differences (P \ 0.05) between the two Pi concentrations, in the same genotype, as determined by Tukey’s HSD tests. CSA 2 2 cross section area (mm ), AA total root cortical aerenchyma area, (mm ). Scale bar applies to all images The Author(s) 2023 aBIOTECH Fig. 6 Lateral root anatomyof sorghum cultivars SC103 and BTx635 grown for 10 days in hydroponics under sufficient Pi (SP, 200 lM) and low Pi (LP, 2.5 lM) conditions. Representative transverse images of lateral root cross sections, collected 5 cm below the primary-lateral root junction (A), and * 5 cmfromthe lateralroot tip(E)(seeFig. 4A). Histograms represent root cross-sectional area, total root cortical aerenchyma area (AA), and proportion of root cross section occupied by aerenchyma, near the primary-lateral root junction (B–D)and * 5 cm from the root tip (F–H)of the SC103 (green) and BTx635 (orange) lateral root, respectively. Data shown are means ± SE (n = 6). Asterisks indicate significant differences between the cultivars, under the same condition, as determined by Student’s t test: for these assays, significance differences are indicated as follows: *P\ 0.05; **P\ 0.01; ***P\ 0.001. Different lowercase letters indicate significant differences (P\ 0.05) between the two Pi concentrations, in the same genotype, as determined by Tukey’s HSD tests. CSA cross section area (mm ); AA total root cortical aerenchyma area (mm ). Scale bar applies to all images The Author(s) 2023 aBIOTECH Fig. 7 Root system architecture of sorghum cultivars, SC103 and BTx635, grown under sufficient N (SN, 4000 lM) and low N (LN, 400 lM) stress conditions. Plants were grown in a hydroponic pouch system and harvested at 10 Dat. A Representative root images of SC103 and BTx635, under SN and LN conditions. B Radar charts comparing the RSA traits of SC103 (green) and BTx635 (orange) under SN conditions. C Radar charts comparing the root system architecture traits of SC103 (green) and BTx635 (orange) under LN conditions. Asterisks indicate significant differences between the cultivars, under the same condition, as determined by Student’s t test: for these assays, significance differences are indicated as follows: *P \ 0.05; **P \ 0.01; ***P \ 0.001. SDW shoot dry weight, RDW root dry weight, R/S root:shoot ratio were observed for all characteristics examined, with Fig. 8 Phenotypic differences for sorghum cultivars SC103 and BTx635 grown under control (CK), low Pi (LP, 75 lM), and low N SC103 having the superior traits (Fig. 8C; see also (LN, 600 lM) stress conditions. A Representative images of SC103 Supplementary Fig. 3 and Supplementary Table 3). and BTx635, under CK, LP and LN stress conditions. Images were Under LN growth conditions, significant differences taken 28 Dat. B Radar plots quantifying the RSA traits of SC103 were also observed for all characteristics examined, and BTx635, under CK conditions. C Radar plots quantifying the RSA traits of SC103 and BTx635, under LP conditions. D Radar with SC103 having the superior traits, with the excep- plots quantifying the RSA traits of SC103 and BTx635, under LN tion that BTx635 had a higher root Pi content and R/S conditions. Asterisks indicate significant differences between the ratio (Fig. 8D; see also Supplementary Fig. 3 and Sup- cultivars under CK, LP and LN conditions, as determined by plementary Table 3). These findings are equivalent to Student’s t test: for these assays, significance differences are indicated as follows: *P \ 0.05; **P \ 0.01; ***P \ 0.001. SDW those observed for plants grown in the LP hydroponic shoot dry weight, RDW root dry weight, R/S root:shoot ratio pouch systems. The Author(s) 2023 aBIOTECH The Author(s) 2023 aBIOTECH Fig. 9 Phenotypic differences for sorghum cultivars SC103 and BTx635 in response to water stress. Plants were grown in potting mix for 28 Dat. At the 14-day timepoint, plants were separated into two groups; a control group was well-watered (WW), whereas water was withheld from the water stress (WS) group. A Representative images of SC103 and BTx635, grown under WW and WS conditions. B Radar plots quantifying the RSA traits of SC103 and BTx635, under WW treatment. C Radar plots quantifying the RSA traits of SC103 and BTx635, under WS treatment. D Radar plots quantifying the RSA traits of SC103 under WW and WS treatment. E Radar plots quantifying the RSA traits of BTx635 under WW and WS treatment. Asterisks indicate the significant differences between the cultivars and treatments, as determined by Student’s t test: for these assays, significance differences are indicated as follows: *P \ 0.05; **P \ 0.01; ***P \ 0.001. SDW shoot dry weight, RDW root dry weight, R/S root:shoot ratio The Author(s) 2023 aBIOTECH Drought conditions can impair crop performance and occupied a remarkably small volume; this pattern would yield. To explore whether SC103 and BTx635 are resi- be equivalent to root growth in the topsoil (see Fig. 1). lient to an imposed water stress condition, plants were If these two test cultivars were genetically adapted, via grown in potting mix for four weeks. At the two week breeding programs, to generate a shallow root system, timepoint, the plants were divided into two equal then we would anticipate that exposure to LP conditions groups; the control group continued to be well-watered would produce more and longer horizontally-oriented (WW), and the test group was subjected to water stress roots. As shown in Fig. 2, an entirely different response (WS), by withholding water (Fig. 9A). As might be was observed, in which the root systems expanded both anticipated, SC103 displayed superior growth and RSA laterally and vertically to occupy a greatly enlarged characteristics, compared with BTx635, under both WW volume (Figs. 3, 4). In this regard, both the primary and and WS treatments, except for R/S ratio (Fig. 9B, C; see lateral roots responded in a reactive manner to a also Supplementary Table 4). The impact of WS on reduction in available Pi. growth and RSA traits for each sorghum line is shown in The growth systems employed in our study did not Fig. 9D, E (see also Supplementary Table 4), and indi- mimic the soil conditions under which the differences in cates that, for both lines, all parameters were reduced yield performance, between SC103 and BTx635, were under WS conditions. recorded. It is noteworthy, that these plants were grown under field conditions, where available Pi, at limiting levels, was confined to the topsoil. However, this strat- DISCUSSION ification of soil P concentration to higher levels in the topsoil, in the field, does not apply to our studies on LN The root system is of fundamental importance for or water availability, as these resources are mobile and seedling establishment, to enable plant growth and are generally distributed deeper within the soil profile. survival through its pivotal role in uptake of essential Again, the root systems that developed under LN nutrients and water. During seedling establishment, the (Figs. 7, 8) and WS (Fig. 9), did not conform to the majority of plant development occurs within the root predicted topsoil model. Rather, under LN and WS, the system. The early establishment of roots has been clo- root patterns for both cultivars, were similar to those sely linked to grain yield, rather than to the subsequent observed under LP. One crucial objective in the future stages of root development (Cai et al. 2012). Further- will be to conduct field validation to ground truth the more, overexpression of OsMYB4P, an R2R3-type MYB differences in N efficiency and performance under transcriptional activator, in rice seedlings increased drought conditions for both sorghum cultivars. It should be noted, as mentioned in the ‘‘Materials and methods’’, seminal and lateral root length and density, which enhanced phosphate acquisition (Yang et al. 2014). With that the differences in P efficiency for SC103 and regards to breeding for crop improvement, attention to BTx635 were first determined and quantified in the identifying traits, associated with early establishment of field by measuring grain yield on a low P field site. an extensive root system, would likely provide pathways The findings from the current study provide insight for developing lines with efficient growth and subse- into an efficient pathway for developing crops with quent yield enhancement. enhanced soil performance characteristics. In general, as with SC103 and BTx635, many crop plants utilize an RSA RSAs for efficient performance under limiting Pi equivalent to an inverted triangular root system and/or N conditions (Fig. 1B). Hence, this RSA removes the need to engineer dramatic genetic reprogramming, in order to convert Our findings establish that, under phosphate stress from an inverted root system into one in which the conditions, neither SC103 nor BTx635 developed RSA majority of the roots are constrained to a more horizontal traits equivalent to those anticipated for plants that are plane. In this regard, SC103 may well provide a valuable optimized for yield performance on soils in which resource for such breeding activities. First, it has genetic available Pi is located primarily within the topsoil (Liang characteristics associated with enhanced resource allo- et al. 2010; Lynch 2011). Although our conditions used cation, resulting in more extensive aerenchyma devel- for plant growth and root trait analysis utilized hydro- opment (Figs. 5, 6, and Supplemental Fig. 2), which ponic pouches, sand culture, and potting soil, the RSAs optimizes the cost associated with the generation and obtained under SP and LP conditions provide insight maintenance of a large root system (Lynch 2018). The into the genetic program(s) underlying root develop- resultant enhanced root system surface area increased ment and growth. For example, in Fig. 2, under SP, the the capacity for resource acquisition, which in this study root systems developed by both SC103 and BTx635 resulted in enhanced P, N and water uptake. The Author(s) 2023 aBIOTECH Aerenchyma as a key growth and yield measured under laboratory and greenhouse conditions, determinant to be integrated into breeding programs for nutrient utilization efficiencies, including N, P, K, and also water. The amount of root cortical aerenchyma can vary, Presently, considerable sorghum genetic resources are depending on plant species, genotype, developmental available, including different mapping populations, and stage, root class, and position along the root axis, or multiple pangenomes. These provide an important within the transverse section (Armstrong 1972; Bour- platform for identifying genomic regions and/or genes anis et al. 2006; Evans 2004; Kawai et al. 1998). Addi- underlying these traits, which can be used for crop tionally, both nutrient limitation and WS can induce improvement by employing genome-design-based aerenchyma development (Chimungu et al. 2015; breeding, marker-assisted introgression, and gene- Postma and Lynch 2011; Saengwilai et al. 2014). The based editing. It is noteworthy that the constitutive basis for the observed difference in root system size, (hard-wired) versus induced genetic component of the between SC103 and BTx635, may reflect a significant SC103 RSA traits could facilitate trait engineering into difference in the degree to which aerenchyma devel- target crops due to a reduced impact by oped in these two lines. For both primary and lateral genome 9 environment interactions. In this manner, roots, in the recently developed zone of these root types, crop improvement be would available across a wider significant differences in aerenchyma existed between range of soil types and agroecologies. Lastly, as SC103 is SC103 and BTx635, under both SP and LP conditions; more efficient in terms of P and N acquisition and here, the extent of aerenchyma development was greatly drought resilience, this could allow for the efficient enhanced under SP and LP conditions in SC103 (Figs. 5, breeding for all three traits from one genetic source. 6). Given that aerenchyma develops in these root sys- tems, under both SP and LP conditions, this may reflect the operation of a constitutive regulatory genetic CONCLUSIONS program. As SC103 establishes an enhanced level of aerench- The grain yield differential, between SC103 and BTx635, yma, relative to BTx635, this must reflect the presence established under low Pi field conditions, was clearly of different genetic elements in these two cultivars. This reflected in the measured RSA and growth characteris- difference likely indicates alterations in gene promoter tics, determined under LP, LN, and WS conditions properties in these two lines. For example, Schneider (Figs. 2, 3, 4, 7, 8, 9). Given that SC103 and BTx635 have et al. (2023) recently reported that ZmbHLH121 acts as equivalently structured root systems (Fig. 2), these a positive regulator of root cortical aerenchyma forma- performance differences likely reflect either changes in tion. Thus, differential expression of this gene homolog, the operational characteristics of a putative master in SC103 and BTx635, could contribute to their differ- controller, or higher expression levels of key genes ences in aerenchyma. Therefore, root cortical aerench- involved in resource allocation. These differences yma represents a promising target for the breeding of resulted in a larger and more dynamic root system in crop cultivars with improved stress tolerance, resilience, SC103, thereby supporting an enhanced shoot system, and carbon sequestration. Additionally, based on the resulting in the measured higher yield. Identifying the observed enhancement of aerenchyma, under LP con- genetic determinants responsible for the superior per- ditions, these lines appear to possess both constitutive formance of SC103 would provide a valuable resource and inductive genetic components. A similar conclusion for both further research into the establishment of can be drawn for the operation of regulatory compo- superior RSA traits and to facilitate breeding programs. nents controlling root growth traits under SP and LP conditions (Fig. 3). Supplementary Information The online version contains supplementary material available at https://doi.org/10.1007/ s42994-023-00112-w. Breeding for superior RSAs Acknowledgements This research was supported by funding Based on its performance in our studies, SC103 repre- from a Canada Excellence Research Chairs (CERC) Grant to LVK, funding from the Global institute for Food Security, and the sents an important genetic resource for identifying University of Saskatchewan, to LVK. Thanks are due to Brian Ham genes, or genomics regions, that can be employed for for assistance in figure development. breeding crops with an RSA for fitness under nutrient and/or water limitations. Furthermore, the high yielding Author contributions LVK and ZL conceived and designed the capacity of SC103, obtained on field soils with low project. ZL, TQ, MA, YZ and HN performed the experiments. HS, KP processed the root images. ZL, WJL, and LVK analyzed the data. ZL available Pi, also presents opportunities for RSA traits, The Author(s) 2023 aBIOTECH wrote the manuscript draft, and WJL, JM, and LVK revised it. All Chiera J, Thomas J, Rufty T (2002) Leaf initiation and development authors have reviewed the manuscript and have read and agreed in soybean under phosphorus stress. J Exp Bot 53:473–481 to the published version of the manuscript. Chimungu JG, Maliro MF, Nalivata PC, Kanyama-Phiri G, Brown KM, Lynch JP (2015) Utility of root cortical aerenchyma under water limited conditions in tropical maize (Zea mays L.). Field Data availability All data generated or analyzed during this Crops Res 171:86–98 study are available from the corresponding author upon request. Clark RT, Famoso AN, Zhao K, Shaff JE, Craft EJ, Bustamante CD, McCouch SR, Aneshansley DJ, Kochian LV (2013) High- Declarations throughput two-dimensional root system phenotyping plat- form facilitates genetic analysis of root growth and develop- Conflict of interest The authors claim no conflict of inter- ment. Plant Cell Environ 36:454–466 est. Authors William J. Lucas and Leon V. Kochian were not Ericsson T (1995) Growth and shoot: root ratio of seedlings in involved in the journal’s review of the manuscript. relation to nutrient availability. In: Paper presented at the nutrient uptake and cycling in forest ecosystems: proceedings Open Access This article is licensed under a Creative Commons of the CEC/IUFRO symposium nutrient uptake and cycling in Attribution 4.0 International License, which permits use, sharing, Forest Ecosystems Halmstad, Sweden, June, 7–10, 1993 adaptation, distribution and reproduction in any medium or for- Evans DE (2004) Aerenchyma formation. New Phytol 161:35–49 mat, as long as you give appropriate credit to the original Fox J, Weisberg S, Adler D, Bates D, Baud-Bovy G, Ellison S et al author(s) and the source, provide a link to the Creative Commons (2012) Package ‘car.’ R Foundation for Statistical Computing, licence, and indicate if changes were made. The images or other Vienna, p 16 third party material in this article are included in the article’s Gabay G, Wang H, Zhang J, Moriconi JI, Burguener GF, Gualano LD Creative Commons licence, unless indicated otherwise in a credit et al (2023) Dosage differences in 12-OXOPHYTODIENOATE line to the material. If material is not included in the article’s REDUCTASE genes modulate wheat root growth. Nat Com- Creative Commons licence and your intended use is not permitted mun 14:539. https://doi.org/10.1038/s41467-023-36248-y by statutory regulation or exceeds the permitted use, you will Galkovskyi T, Mileyko Y, Bucksch A, Moore B, Symonova O, Price need to obtain permission directly from the copyright holder. To CA et al (2012) GiA roots: software for the high throughput view a copy of this licence, visit http://creativecommons.org/ analysis of plant root system architecture. BMC Plant Biol licenses/by/4.0/. 12:1–12 Gamuyao R, Chin JH, Pariasca-Tanaka J, Pesaresi P, Catausan S, Dalid C et al (2012) The protein kinase Pstol1 from traditional rice confers tolerance of phosphorus deficiency. References Nature 488:535–539. https://doi.org/10.1038/nature11346 Gao C (2021) Genome engineering for crop improvement and Armstrong W (1972) A re-examination of the functional signifi- future agriculture. Cell 184:1621–1635 cance of aerenchyma. Physiol Plant 27:173–177 Gladman N, Hufnagel B, Regulski M, Liu Z, Wang X, Chougule K Atkinson JA, Wells DM (2017) An updated protocol for high et al (2022) Sorghum root epigenetic landscape during throughput plant tissue sectioning. Front Plant Sci 8:1721. limiting phosphorus conditions. Plant Direct. https://doi.org/ https://doi.org/10.3389/fpls.2017.01721 10.1002/pld3.393 Bernardino KC, Pastina MM, Menezes CB, de Sousa SM, Maciel LS, Halford NG, Curtis TY, Chen Z, Huang J (2015) Effects of abiotic Carvalho G Jr et al (2019) The genetic architecture of stress and crop management on cereal grain composition: phosphorus efficiency in sorghum involves pleiotropic QTL implications for food quality and safety. J Exp Bot for root morphology and grain yield under low phosphorus 66:1145–1156. https://doi.org/10.1093/jxb/eru473 availability in the soil. BMC Plant Biol 19:87. https://doi.org/ Hickey LT, Hafeez AN, Robinson H, Jackson SA, Leal-Bertioli SCM, 10.1186/s12870-019-1689-y Tester M et al (2019) Breeding crops to feed 10 billion. Nat Bouranis DL, Chorianopoulou SN, Kollias C, Maniou P, Protono- Biotechnol 37:744–754. https://doi.org/10.1038/s41587- tarios VE, Siyiannis VF et al (2006) Dynamics of Aerenchyma 019-0152-9 distribution in the cortex of sulfate-deprived adventitious Hodge A, Berta G, Doussan C, Merchan F, Crespi M (2009) Plant roots of maize. Ann Bot 97:695–704. https://doi.org/10. root growth, architecture and function. Plant Soil 1093/aob/mcl024 321:153–187. https://doi.org/10.1007/s11104-009-9929-9 Burton AL, Johnson J, Foerster J, Hanlon MT, Kaeppler SM, Lynch Hufnagel B, de Sousa SM, Assis L, Guimaraes CT, Leiser W, Azevedo JP et al (2015) QTL mapping and phenotypic variation of root GC et al (2014) Duplicate and conquer: multiple homologs of anatomical traits in maize (Zea mays L.). Theor Appl Genet PHOSPHORUS-STARVATION TOLERANCE1 enhance phospho- 128:93–106 rus acquisition and sorghum performance on low-phospho- Cai H, Chen F, Mi G, Zhang F, Maurer HP, Liu W et al (2012) rus soils. Plant Physiol 166:659–677. https://doi.org/10. Mapping QTLs for root system architecture of maize (Zea 1104/pp.114.243949 mays L.) in the field at different developmental stages. Theor Kawai M, Samarajeewa P, Barrero R, Nishiguchi M, Uchimiya H Appl Genet 125:1313–1324. https://doi.org/10.1007/ (1998) Cellular dissection of the degradation pattern of s00122-012-1915-6 cortical cell death during aerenchyma formation of rice roots. Cakmak I, Hengeler C, Marschner H (1994) Partitioning of shoot Planta 204:277–287 and root dry matter and carbohydrates in bean plants Liang Q, Cheng X, Mei M, Yan X, Liao H (2010) QTL analysis of root suffering from phosphorus, potassium and magnesium defi- traits as related to phosphorus efficiency in soybean. Ann Bot ciency. J Exp Bot 45:1245–1250 106:223–234. https://doi.org/10.1093/aob/mcq097 Casa AM, Pressoir G, Brown PJ, Mitchell SE, Rooney WL, Tuinstra Liu D (2021) Root developmental responses to phosphorus MR et al (2008) Community resources and strategies for nutrition. J Integr Plant Biol 63:1065–1090. https://doi.org/ association mapping in sorghum. Crop Sci 48:30–40 10.1111/jipb.13090 The Author(s) 2023 aBIOTECH Lynch JP (2011) Root phenes for enhanced soil exploration and Saengwilai P, Nord EA, Chimungu JG, Brown KM, Lynch JP (2014) phosphorus acquisition: tools for future crops. Plant Physiol Root cortical aerenchyma enhances nitrogen acquisition from 156:1041–1049 low-nitrogen soils in maize. Plant Physiol 166:726–735 Lynch JP (2018) Rightsizing root phenotypes for drought resis- Schneider HM, Lor VS, Zhang X, Saengwilai P, Hanlon MT, Klein SP tance. J Exp Bot 69:3279–3292. https://doi.org/10.1093/ et al (2023) Transcription factor bHLH121 regulates root jxb/ery048 cortical aerenchyma formation in maize. Proc Natl Acad Sci Lynch JP (2022) Harnessing root architecture to address global USA 120:e2219668120. https://doi.org/10.1073/pnas. challenges. Plant J 109:415–431. https://doi.org/10.1111/ 2219668120 tpj.15560 Sun B, Gao Y, Lynch JP (2018) Large crown root number improves Marschner H (2011) Function of macronutrients. In: Petra M (ed) topsoil foraging and phosphorus acquisition. Plant Physiol Marschner’s mineral nutrition of higher plants. Academic 177:90–104 Press, Elsevier, US, Waltham, pp 135–178 Team RC (2013) R: a language and environment for statistical Meister R, Rajani MS, Ruzicka D, Schachtman DP (2014) Challenges of computing modifying root traits in crops for agriculture. Trends Plant Sci Tracy SR, Nagel KA, Postma JA, Fassbender H, Wasson A, Watt M 19:779–788. https://doi.org/10.1016/j.tplants.2014.08.005 (2020) Crop improvement from phenotyping roots: high- Mohammed SB, Burridge JD, Ishiyaku MF, Boukar O, Lynch JP lights reveal expanding opportunities. Trends Plant Sci (2022) Phenotyping cowpea for seedling root architecture 25:105–118. https://doi.org/10.1016/j.tplants.2019.10.015 reveals root phenes important for breeding phosphorus Tyczewska A, Wozniak E, Gracz J, Kuczynski J, Twardowski T efficient varieties. Crop Sci 62:326–345 (2018) Towards food security: current state and future Parentoni SN, de Souza JC, de Carvalho AV, Gama E, Coelho A, De prospects of agrobiotechnology. Trends Biotechnol Oliveira A et al (2010) Inheritance and breeding strategies for 36:1219–1229. https://doi.org/10.1016/j.tibtech.2018.07. phosphorous efficiency in tropical maize (Zea mays L.). 008 Maydica 55:1 Wickham H (2016) Data analysis. ggplot2. Springer, Berlin, Postma JA, Lynch JP (2011) Root cortical aerenchyma enhances pp 189–201 the growth of maize on soils with suboptimal availability of Yang WT, Baek D, Yun D-J, Hwang WH, Park DS, Nam MH et al nitrogen, phosphorus, and potassium. Plant Physiol (2014) Overexpression of OsMYB4P, an R2R3-type MYB 156:1190–1201 transcriptional activator, increases phosphate acquisition in Rangarajan H, Postma JA, Lynch JP (2018) Co-optimization of axial rice. Plant Physiol Biochem 80:259–267. https://doi.org/10. root phenotypes for nitrogen and phosphorus acquisition in 1016/j.plaphy.2014.02.024 common bean. Ann Bot 122:485–499 Zhao J, Fu J, Liao H, He Y, Nian H, Hu Y et al (2004) Ray DK, Mueller ND, West PC, Foley JA (2013) Yield trends are Characterization of root architecture in an applied core insufficient to double global crop production by 2050. PLoS ONE collection for phosphorus efficiency of soybean germplasm. 8:e66428. https://doi.org/10.1371/journal.pone.0066428 Chin Sci Bull 49:1611–1620 Ryan PR, Delhaize E, Watt M, Richardson AE (2016) Plant roots: Zheng Z, Wang B, Zhuo C, Xie Y, Zhang X, Liu Y et al (2023) Local understanding structure and function in an ocean of com- auxin biosynthesis regulates brace root angle and lodging plexity. Ann Bot 118:555–559. https://doi.org/10.1093/aob/ resistance in maize. New Phytol. https://doi.org/10.1111/ mcw192 nph.18733 The Author(s) 2023 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png aBIOTECH Springer Journals

Constitutive basis of root system architecture: uncovering a promising trait for breeding nutrient- and drought-resilient crops

Loading next page...
 
/lp/springer-journals/constitutive-basis-of-root-system-architecture-uncovering-a-promising-zyipwUBcpL

References (46)

Publisher
Springer Journals
Copyright
Copyright © The Author(s) 2023
ISSN
2096-6326
eISSN
2662-1738
DOI
10.1007/s42994-023-00112-w
Publisher site
See Article on Publisher Site

Abstract

aBIOTECH https://doi.org/10.1007/s42994-023-00112-w aBIOTECH RESEARCH ARTICLE Constitutive basis of root system architecture: uncovering a promising trait for breeding nutrient- and drought-resilient crops 1 1 1 1 Zhigang Liu , Tongfei Qin , Michaella Atienza , Yang Zhao , 1 1 1 2 Hanh Nguyen , Huajin Sheng , Toluwase Olukayode , Hao Song , 1 3 1,4 1& Karim Panjvani , Jurandir Magalhaes , William J. Lucas , Leon V. Kochian Global Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4L8, Canada Department of Computer Science, University of Saskatchewan, Saskatoon, SK S7N 5C9, Canada Embrapa Maize and Sorghum, Brazilian Agricultural Research Corporation, Sete Lagoas, MG 35701-970, Brazil Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA Received: 1 May 2023 / Accepted: 20 July 2023 Abstract Root system architecture (RSA) plays a pivotal role in efficient uptake of essential nutrients, such as phosphorous (P), nitrogen (N), and water. In soils with heterogeneous nutrient distribution, root plasticity can optimize acquisition and plant growth. Here, we present evidence that a constitutive RSA can confer benefits for sorghum grown under both sufficient and limiting growth conditions. Our studies, using P efficient SC103 and inefficient BTx635 sorghum cultivars, identified significant dif- ferences in root traits, with SC103 developing a larger root system with more and longer lateral roots, and enhanced shoot biomass, under both nutrient sufficient and deficient conditions. In addition to this constitutive attribute, under P deficiency, both cultivars exhibited an initial increase in lateral root development; however, SC103 still maintained the larger root biomass. Although N deficiency and drought stress inhibited both root and shoot growth, for both sorghum cultivars, SC103 again main- tained the better performance. These findings reveal that SC103, a P efficient sorghum cultivar, also exhibited enhanced growth performance under N deficiency and drought. Our results provide evidence that this constitutive nature of RSA can provide an avenue for breeding nutrient- and drought-resilient crops. Keywords Constitutive root system architecture, Abiotic stress, Nutrient efficiency, Drought resilience, Plant breeding INTRODUCTION majority of global agricultural calories, indicates from current progress in yield enhancement that there is a It has been estimated that, by 2050, the global human significant need for novel crop improvement strategies population will reach 10 billion (Hickey et al. 2019), (Gao 2021; Ray et al. 2013). Due to abiotic stresses, hence, global agricultural production must increase to including drought, flooding, extreme temperatures, meet this demand. In this regard, evidence available salinity, and acid soil conditions, and limiting nutrient for maize, rice, wheat, and soybean, which produce the availability and cost, both crop growth and yield can be greatly impacted (Halford et al. 2015; Tyczewska et al. 2018). This issue is of great concern and requires immediate attention to ensure sustainable & Correspondence: leon.kochian@gifs.ca (L. V. Kochian) The Author(s) 2023 food production in the face of these environmental earlier identified in rice, as P efficiency genes (Gamuyao challenges. et al. 2012), in which breeding for this trait gave rise to Until recently, the underground component of crops, larger and deeper root systems. These RSAs clearly did namely their root systems, have received little attention not concentrate a significant fraction of their root within regarding crop improvement. Given the important the upper (topsoil) regions of the soil profile. functions of the root system, including water and To further explore the relationship between RSA and nutrient acquisition, and plant anchorage, recent studies yield performance, under field conditions with limiting have begun to explore the functional components of soil P availability, in the current study, we utilized two root system architecture (Gabay et al. 2023; Hodge et al. sorghum lines, SC103 and BTx635, having significant -1 2009;Ryan etal. 2016; Zheng et al. 2023). In monocots, differences in grain yield; BTx635 was 1.6 tons ha , -1 the root system contains seminal (primary), lateral and whereas SC103 was 2.8 tons ha —a yield increase of crown roots, whereas in dicots, a primary root (tap 75% (Hufnagel et al. 2014). Based on the SC103 yield root) system gives rise to multiple orders of lateral enhancement, we conducted an extensive study of their roots (Meister et al. 2014). Root system architecture RSAs to ascertain whether the distribution of their roots (RSA), the spatial configuration of the plant root system, conformed to either the topsoil pattern (Fig. 1A) or a plays a pivotal role in efficient uptake of essential broader and deeper distribution (Fig. 1B). Of special nutrients (e.g., nitrogen [N], phosphorous [P], and note, our findings failed to support the topsoil model, in potassium [K]) and water (Marschner 2011). that SC103 exhibited an ‘‘inverted triangle’’ RSA like that In agricultural soils, the spatial availability of these shown in Fig. 1B. Importantly, SC103 had enhanced essential components for growth are often heterogenous performance under both full nutrient and limiting P, N, in nature. Thus, soil characteristics must be integrated and drought conditions. Additionally, a similar RSA into breeding programs to achieve optimal nutrient pattern was identified for BTx635, but overall, this root acquisition for enhanced yield performance (Lynch 2022; system was significantly smaller, under these same Tracy et al. 2020). Numerous studies have focused on the growth conditions for N, P, and water. These studies role of RSA in efficient acquisition of the most diffusion- highlight the requirement for a coordination between limited mineral nutrient, phosphorous (as phosphate RSA studies and crop breeding programs. [Pi]) (Liu 2021; Mohammed et al. 2022). Here, in acid soils, Pi is tightly bound to clay minerals, within the top- soil, resulting in a marked vertical Pi gradient. These soil MATERIALS AND METHODS characteristics have driven researchers to focus on selection of P efficient lines, in which a majority of the RSA Plant materials is located within the topsoil (Liang et al. 2010; Rangarajan et al. 2018; Sun et al. 2018; Zhao et al. 2004) (Fig. 1A). Two sorghum (Sorghum bicolor) cultivars, SC103 and Under acid soil conditions, the mobile nutrients, BTx635, were used in this study. These cultivars rep- including N and K, are distributed throughout the soil resent widely employed sorghum breeding lines in the profile. Thus, in breeding P efficient lines, consideration is United States and Brazil (Casa et al. 2008). Further, needed in terms of acquisition of these mobile nutrients. Hufnagel et al. (2014) demonstrated that SC103 had In this regard, a topsoil RSA would likely require highly higher grain yields, compared to BTx635, when grown efficient N and K transport systems for capture during under on low P soil with high Pi soil fixation, reflecting fertilizer application. An alternative breeding approach limiting soil P availability. These studies established might utilize an RSA in which the roots are more uni- SC103 and BTx635 as relatively P efficient and ineffi- formly distributed throughout the soil profile (Fig. 1B). cient, respectively. Sorghum breeding programs have developed Pi effi- cient lines optimized for crop performance on acid soils. Plant growth for 2D root system architecture For example, Hufnagel et al. (2014) identified P efficient (RSA) assays and inefficient lines based on screening of a 243-line sorghum association panel for grain yield, when grown Seeds were surface-sterilized in 6% (v/v) sodium on a low P tropical soil. In this study, significant genetic hypochlorite for 20 min, rinsed with 18 Mega-ohm variation in P efficiency was identified. Also, by using water (MX), and germinated, in darkness, for 4 days at candidate gene genome-wide association study (GWAS), 27 C on moist germination paper (Anchor Paper, St. several PSTOL1 (Phosphorous Starvation Tolerance 1) Paul, MN, USA). Uniform seedlings were transferred, genes were discovered. Equivalent PSTOL1 genes were depending on the specific experiment, to hydroponic The Author(s) 2023 aBIOTECH solution [K] concentrations close to at 3.11 mM, with 0.2 mM being added as KH PO . To assess the effects of 2 4 N deficiency on plant RSA, seedlings of each cultivar were grown hydroponically for 10 days in a pouch system, with 4000 lM nitrogen as sufficient N (SN) and 400 lM as low N (LN) conditions. As N was added as 2? Ca(NO ) , to maintain the same Ca concentration in 3 2 the LN media, as used in the SN media, 900 lM CaCl was supplied in LN media. The nutrient solution was aerated continuously and renewed every 3 days. The solution pH value was maintained at 5.7. In longer term experiments where sorghum was grown in pots, seedlings of the sorghum cultivars SC103 and BTx635 were transferred to plastic pots (25 cm diameter, and 20 cm depth) containing silica sand and nutrient solutions of different [Pi] were added to the top of the pots. The plants were grown for 28 days, using the above-described nutrient solu- Fig. 1 Schematic representation of root system architectures tions, except that the Pi concentration used for control representing topsoil based and deep rooting systems. A Plants (CK) and low Pi (LP) conditions were adjusted to 500 that develop a shallow root system localized within the topsoil and 75 lM, respectively, and the N concentration used (broken rectangle). B Plants that develop an extended, deeper, for LN media was reduced to 600 lM. For experiments root system (broken inverted triangle). CR crown root, LR lateral root, PR primary root conducted with plants grown in silica sand, the appropriate concentrations of N and P for sufficiency solution, silica sand or Sunshine #1 potting mix (Sun and deficiency were determined empirically, by mea- Gro Horticulture, Inc.) as the appropriate growth system suring and comparing shoot biomass for plants grown for RSA studies. Plants were grown in a walk-in growth on LN and SN nutrient solution. For plants grown in chamber with controlled climate conditions of 16/8 h sand watered with LP and SP solutions, shoot growth (light/dark), 27/22 C (day/night) temperature, a light and root traits were evaluated as described for P -2 -1 intensity of approx. 350 lmol m s , at canopy deficiency in hydroponically grown plants in 2D pou- height, and 40–60% relative humidity. ches. Given that nutrient availability in silica sand is After germination, uniform sorghum seedlings were restricted to the pores within the sand, the nutrient transplanted to 100 L polypropylene containers and concentrations in the sand experiments were adjusted grown hydroponically in a specially designed pouch to ensure sufficient or deficient levels. For LP, a con- system, as described by (Gladman et al. 2022). Plants centration of 75 lM was determined to be moderately were supplied with a nutrient solution consisting of P deficient, whereas moderate P deficiency symptoms macronutrients (at mM levels): 3.5 Ca(NO ) , 1.3 NH developed in plants grown in hydroponic media with 3 2 4- NO , 0.58 K SO , 0.58 KCl, 0.56 KNO , 0.85 MgSO ; and 3 2 4 3 4 10 lM Pi. Regarding LN, 600 lM N generated moder- micronutrients (at lM levels): 2.5 H BO , 9.1 MnCl , 0.6 3 3 2 ately N deficient sand-grown plants, whereas 400 lM CuSO , 2.4 ZnSO , 0.8 Na MoO , 100 Fe-HEDTA. 4 4 2 4 N in hydroponic media resulted in moderate N defi- Nutrient solution phosphate (Pi) concentrations were 0, ciency symptoms. 2.5, 10 and 200 lM. Experiments were first conducted To evaluate drought performance of the sorghum to establish the appropriate Pi concentrations for severe cultivars, plants were grown in plastic pots, as above, plant P deficiency (0 and 2.5 lM), moderate Pi defi- containing 1.2 kg Sunshine #1 potting mix. Plants were ciency (10 lM) and sufficient plant Pi status (200 lM): fertilized biweekly using water-soluble fertilizer (Mas- the quantitative indicators of P deficiency are a strong ter Plant-Prod, Inc.), with a standard N–P–K (20–20–20) inhibition of shoot growth and a moderate stimulation treatment. Pot water content was measured using an of root growth, resulting in an increase in root:shoot HydroSense II Handheld Soil Moisture Sensor (Campbell ratio (Cakmak et al. 1994; Ericsson 1995; Chiera et al. Scientific, Inc.), based on the volumetric water content 2002). The Pi concentrations were obtained by adjust- (VWC) for porous media. Pots were initially filled with ing KH PO and KCl was added to maintain the nutrient 2 4 18 MX water and then allowed to drain to establish soil The Author(s) 2023 aBIOTECH ‘field capacity’. Seedlings were then transplanted, with Biomass, N and Pi measurements one seedling per pot, and 200 mL of 18 mX water (corresponding to near-full field capacity) was added, After root architecture determinations, plants were daily, for the first 14 days. dissected into shoots and roots, and both parts were heated at 105 C for 30 min and then oven-dried at After the initial two-week growth period, plants were divided into two treatment groups: well-watered (WW) 65 C for 72 h. The dry samples were then weighed to obtain shoot dry weight (SDW), root dry weight (RDW), and water stressed (WS). The WW plants continued to receive 200 mL of 18 MX water, daily, per pot, to and the root:shoot ratio (R/S). After weight measure- ments, the root and shoot samples were ground and maintain the water content near the full field capacity. For the WS plants water was withheld, and fourteen digested, using a solution of concentrated sulfuric acid days later leaf wilting was observed, coincident with a and selenium at 330 C. Total P and N concentrations measured potting mix water content of 7.5% VWC. were then determined, using a Skalar SAN-plus seg- Plants were subsequently removed from the pots and mented flow analyzer (Skalar Analytical BV, Breda, The their root systems were soaked in water to remove Netherlands), following the manufacturer’s protocols. potting mix, and then thoroughly cleaned by washing Root sectioning and imaging using low water pressure. Finally, RSA measurements were determined (Clark et al. 2013) and then roots and Sorghum seedlings were grown hydroponically for shoots were separated, following drying for biomass determination. 10 days in 20 L polypropylene containers in the same nutrient solution, as described above, under sufficient Pi (SP; 200 lM) or low Pi (LP; 2.5 lM) conditions. Growth Root architecture measurements protocols were as described above. Primary and crown roots were excised at 5 cm from the root-stem junction Phenotyping experiments, using a hydroponic pouch and at 5 cm from the root tip, respectively. Lateral roots system, utilized a Nikon D7200 DSLR camera with a were excised at 5 cm from the primary-lateral root 50 mm lens and a 2D root imaging platform. Raw junction and 5 cm from the lateral root tip. All root images were collected and stored in a Plant Root samples collected were * 5 cm in length. Root samples Imaging and Data Acquisition (PRIDA) program, and were placed into 3D-printed polylactic acid molds for then extracted as TIFF files for further image pro- embedding (Atkinson and Wells 2017). Root tissues cessing and root trait computation (Gladman et al. were fixed in 5% (w/v) agarose, and after agarose 2022). For the phenotyping experiments performed in solidification, blocks were trimmed and sectioned, at silica sand and potting mix, root systems were cleaned 100 lm, using a Leica VT1000S (Vibrating blade after harvest, arranged to minimize any root overlap, microtome, Nussloch, Germany). Transverse sections and then a 2D root imaging platform was used to were examined using a Leica Thunder microscope sys- acquire and store data. Data from phenotyping exper- tem (Wetzlar, Germany). Images were collected using iments were then subjected to both commercial and 10 9 or 20 9 objectives, depending upon the tissue publicly available software packages for root trait size, and the background noise was removed from computation. WinRHIZO software (Regents Instru- images using Adobe Photoshop version 23.5 (Adobe ments, Inc.) was used to quantify root growth and Systems). Root cross-sectional area (SCA) and aerench- topology traits, and GiA Roots (Galkovskyi et al. 2012) yma area (AA) were measured, via pixel-counting, using was used to quantify 2D root architecture traits. Root ImageJ software (https://imagej.nih.gov/ij/). Propor- architecture traits, derived from the hydroponic pouch tion of root cross sections occupied by aerenchyma was system, included primary root length (cm), root system calculated using AA divided by SCA. Sample data were width (cm), and convex hull area (cm ), were assessed. normalized, based on a previously described method Root morphology traits, derived from the hydroponic (Burton et al. 2015). pouch system included average root diameter (cm), total root system surface area (cm ), total root system Statistical analysis length (cm), and total root system volume (cm ). Root morphology traits, derived from experiments in which All statistical analyses were performed using the R plants were grown in silica sand or potting mix, software package (Team 2013). Two-way analysis of included total root system length (cm), root system variance (ANOVA) was used to test for significant dif- surface area (cm ), and total root system volume ferences between treatments, cultivars, and treat- (cm ), were assessed. ment 9 cultivar interactions. Significant differences The Author(s) 2023 aBIOTECH Fig. 2 Response of sorghum root systems (lines SC103 and BTx635) grown under 200 lM Pi (sufficient P), and 10, 2.5 and 0 lM Pi (low P), for 7, 9 and 12 days after transplanting (Dat). A hydroponic pouch system was employed for these assays, and representative images are shown between means were analyzed by independent Stu- expected, a significant reduction in SDW was observed dent’s t test or Tukey’s honest significant difference in both SC103 and BTx635, in response to Pi stress. (HSD) tests, where appropriate. ANOVA was performed However, SDW in SC103 was significantly greater than using the ‘‘Anova’’ function, as implemented in the ‘‘car’’ in BTx635, under all levels of the imposed Pi stress package (Fox et al. 2012). Tukey’s HSD tests were per- (Fig. 3A). An increase in the root:shoot ratio (R/S) is formed using the ‘‘Tukey HSD’’ function in R. Additional commonly observed under Pi deficient conditions, visualization of the data was performed using the ‘‘gg- either by a reduction in shoot growth or an increase in plot2’’ package (Wickham 2016). root growth, or both (Cakmak et al. 1994; Ericsson 1995; Chiera et al. 2002). Under Pi stress, R/S ratio was increased by 27% (10 lM), 68% (2.5 lM) and 52% RESULTS (0 lM) in SC103, whereas an increase of 43% (10 lM), 75% (2.5 lM) and 60% (0 lM) was observed in Sorghum SC103 establishes a larger root system BTx635, compared with sufficient Pi conditions under both sufficient and deficient Pi conditions (Fig. 3B). The P deficiency severity was also increased by growth on 10, 2.5 and 0 lM Pi; here, a stronger Sorghum seedlings were grown in a hydroponic pouch inhibition of shoot growth and increased stimulation in system for 7, 9, and 12 days after transplanting (Dat). lateral root growth was observed as P deficiency This nutrient delivery system was used to provide Pi became more severe (Fig. 3A and Supplementary distribution to the root systems of these sorghum cul- Table 1). This resulted in increases in R/S ratios under tivars. Both cultivars exhibited significantly larger root increasing P deficiency, which, as noted above, has been systems in response to Pi deficiency (Fig. 2). However, well-established in previous studies (Cakmak et al. SC103 also exhibited a much larger root system than 1994; Ericsson 1995; Chiera et al. 2002). Collectively, BTx635 under Pi sufficient conditions. Furthermore, the these findings support the notion that SC103 has a P efficient SC103 exhibited 69 and 110% greater SDW genetic component that imparts a capacity for estab- and RDW, respectively, compared with the P inefficient lishing a larger root system under both sufficient and BTx635, under Pi sufficient conditions (200 lM). As deficient Pi conditions. The Author(s) 2023 aBIOTECH Fig. 3 Root system architecture of sorghum lines SC103 and BTx635, grown in a hydroponic pouch system, under the indicated phosphate (Pi) concentrations. Panels represent shoot dry weight (A), root:shoot ratio (B), total root system length (C), root system width (D), total root system surface area (E), and primary root length (F), analyzed at 7, 9 and 12 Dat. Data shown are means ± SE (n = 6). Asterisks indicate significant differences between the genotypes, under the same Pi concentrations, as determined by the Student’s t test. For these assays, significance differences are indicated as follows: *P \ 0.05; **P \ 0.01; ***P \ 0.001. Different lowercase letters indicate significant differences (P \ 0.05) among the four Pi concentrations, in the same genotype, as determined by Tukey’s HSD tests Sorghum SC103 developed a larger RSA As demonstrated by the data presented in Fig. 3 and compared with BTx635 evident from the images in Fig. 2 showcasing the root systems of the two cultivars, grown for 7, 9, and 12 Dat Traits associated with RSA, including primary root at varying growth solution Pi concentrations, it is length, total root system length, total root system sur- apparent that increasing P deficiency leads to greater face area, root system width (Fig. 3), and average root stimulation of lateral and tap root growth, compared to diameter, total root system volume, and convex hull area plants grown under sufficient P conditions (200 lM Pi). (total area occupied by the root system) (Supplemen- Furthermore, investigating the root system vertical tary Table 1), were assessed. Under sufficient Pi condi- distribution can be beneficial for an understanding of tions, total root system length (88%), root system the pattern of root Pi acquisition. For our study, the surface area (117%), total root system volume (157%), sorghum root system was divided into three equally- primary root length (21%), and convex hull area (60%) spaced regions, based on root system depth (Fig. 4A). In were greater in SC103, compared with BTx635, at 12 the top region (R1), we observed that SC103 had a Dat (Fig. 3C–F; Supplementary Table 1). Under Pi defi- significantly higher total root system length compared cient conditions, total root system length (55%), total with BTx635 at all time points, under sufficient and root system surface area (53%), and total root system deficient Pi conditions. Importantly, under Pi stress, volume (52%) were greater in SC103, compared with total root system length was increased significantly at BTx635, at 12 Dat (Fig. 3C–F; Supplementary Table 1). all time points in SC103 and BTx635 in region R1 The Author(s) 2023 aBIOTECH Fig. 4 Root system architecture profiles for SC103 and BTx635 grown in a hydroponic pouch system, under sufficient Pi (200 lM) and deficient Pi (0 lM) conditions, for 7, 10 and 14 Dat. A Root systems were divided into three equal regions, R1, R2 and R3, based on the root system depth. B Total root system length in each region. C Percentage of total root system length in each of the three regions. Asterisks indicate significant differences between the various Pi concentrations, in the same cultivar, in the same region, as determined by Student’s t test: for these assays, significance differences are indicated as follows: *P \ 0.05; **P \ 0.01; ***P \ 0.001. CR crown root, PR primary root, LR lateral root. Red dotted lines represent the locations where root sections were excised for cross-sectional analyses (see Figs. 5A, E, 6A, E, and Supplementary Fig. 2) Table 1 Shoot and root phosphorous (P) concentration and content in sorghum lines SC103 and BTx635 grown under increasing phosphate (Pi) treatments -1 Treatment Shoot P content (lg) Shoot P concentration (mg Root P content (lg) Root P concentration (mg g ) -1 g ) SC103 BTx635 SC103 BTx635 SC103 BTx635 SC103 BTx635 0 lM71 ± 3 c*** 50 ± 3 c 1.4 ± 0.1 b 1.4 ± 0.03 c 60 ± 2 c*** 32 ± 2 c 1.7 ± 0.1 c 1.4 ± 0.1 c 2.5 lM79 ± 5 bc** 48 ± 5 c 1.5 ± 0.1 b 1.3 ± 0.1 c 70 ± 4 c*** 34 ± 2 c 1.7 ± 0.04 c** 1.4 ± 0.1 c 10 lM 187 ± 20 b* 124 ± 17 b 2.6 ± 0.3 b 2.6 ± 0.3 b 142 ± 22 b* 78 ± 9 b 3.2 ± 0.3 b 3.0 ± 0.3 b 200 lM 599 ± 53 a** 349 ± 17 a 6.5 ± 0.5 a 6.3 ± 0.2 a 280 ± 28 a*** 121 ± 6 a 6.3 ± 0.3 a 5.7 ± 0.2 a Plants were grown in a hydroponic pouch system, with the indicated four different Pi conditions, and were harvested 12 days after transplanting. Data shown are means ± SE (n = 6). Different lowercase letters indicate significant differences (P \ 0.05) among the Pi conditions in the same genotype, as determined by Tukey’s HSD tests. Asterisks indicate significant differences between genotypes in the same condition, as determined by Student’s t test analysis: *P \ 0.05, **P \ 0.01, ***P \ 0.001. The Author(s) 2023 aBIOTECH (Fig. 4B). In Fig. 4C, we present the % changes for sections, excised from near the stem-root junction and at regions R1, 2 and 3, under P deficient conditions, least 5 cm back from the root tip, indicated the presence of showing that the % of roots distributed between these 3 extensive aerenchyma (Fig. 5A, E). However, under both regions were similar in nature between SC103 and sufficient Pi (200 lM; SP) and low Pi (2.5 lM; LP) condi- BTx635. tions, in SC103, the AA was significantly larger, as was the AA/CSA ratio, compared with BTx635 (Fig. 5B–D, F–H). P acquisition versus utilization A similar pattern was also observed for lateral root anatomy, near both the stem-root junction and at least Under sufficient Pi conditions (200 lM), SC103 exhibited a 5 cm back from the lateral root tip. Again, SC103 had the significant enhancement in P uptake (72% more shoot Pi larger AA and AA/CSA ratio, compared with BTx635, with content) than BTx635. As expected, Pi stress reduced these differences being enhanced under LP conditions uptake in both cultivars; however, P uptake was still sig- (Fig. 6A–H). Crown root anatomy was also investigated, nificantly higher in SC103. Here, SC103 accumulated 50%, from the same locations as described above, and again 64% and 43% more P in their shoots, compared with SC103 had the larger AA and AA/CSA ratio, compared BTx635, under the three imposed Pi stress conditions, with BTx635, with these differences also being enhanced respectively (Table 1). In both cultivars, the reduction in P under LP conditions (Supplementary Fig. 2). These shoot content displayed a similar pattern. Interestingly, findings indicate that both sorghum lines develop aer- although we observed significant differences in P acquisi- enchyma under SP and LP conditions. Furthermore, aer- tion, between these two cultivars, no physiologically sig- enchyma development in SC103 was significantly greater nificant differences were observed in shoot and root P compared with BTx635, under both SP and LP conditions. concentration under sufficient and deficient Pi conditions (Table 1). In addition, we observed higher P concentrations RSA response to N deficiency and drought stress (P\ 0.001) and P content (P\ 0.001) in SC103 seeds, compared with BTx635 (Supplementary Fig. 1). This Parameters associated with biomass and RSA were observed increase in plant P content, in SC103, is a assessed in response to an imposed N stress. Here, reflection of its larger root system. Based on these findings, SC103 exhibited a larger root system, compared with the lack of a difference in shoot and root P concentration BTx635, under both sufficient N (SN) and low N (LN) between both cultivars, and the much larger P content in conditions (Fig. 7A and Supplementary Table 2). As SC103, is consistent with P acquisition being a major shown in radar plots presented in Fig. 7B, under SN, all contributor to enhanced P efficiency in SC103. root and biomass traits, with the exception of average We have recently, from a genetic and physiological root diameter, were significantly larger in SC103 com- analysis of sorghum P efficiency, determined that when pared with BTx635. A similar pattern was observed dissecting sorghum P use efficiency into P utilization under LN, except that, again, average root diameter was efficiency (PUE) and P acquisition efficiency (PAE), PAE equivalent between the two cultivars, and BTx635 accounts for the majority of the genetic contribution to established a higher R/S ratio, compared to SC103 P efficiency. Specifically, we determined in our study (Fig. 7C and Supplementary Table 2), due largely to its that PAE contributes 82% to the overall PAE, whereas reduction in shoot biomass. These findings support the PUE accounts for 18% (Bernardino et al. 2019). A notion that the SC103 genetic composition can confer similar strong genetic influence of PAE on P efficiency superior performance, relative to BTx635, under both P was previously reported in maize by Parentoni et al. and N stress conditions. (2010), where PAE explained approximately 80% of To explore the effect of plant development, on shoot total P efficiency. and RSA traits, in these two sorghum cultivars, experi- ments were next conducted by growing plants in silica Pi stress impacts root anatomy in both SC103 sand, as substrate. Here, we tested the effects of LP and and BTx635 LN on RSA and growth. As anticipated, shoot biomass was reduced under both LP and LN conditions (Fig. 8A). Parameters associated with root anatomy, such as root Under control conditions, the relative changes in RSA cross-sectional area (CSA), total root cortical aerenchyma traits and growth characteristics, between SC103 and area (AA) and the proportion of root cross sectional area BTx635, are shown in Fig. 8B (see also Supplementary occupied byaerenchyma (AA/CSA), were evaluated (Figs. 5, Fig. 3 and Supplementary Table 3). The noteworthy 6, and Supplementary Fig. 2). Root segments were excised, differences were in total root system volume, length, from locationsasindicatedinFig. 4A, and cross sections and surface area, which were always higher in SC103. prepared for anatomical studies. Primary root cross Under LP growth conditions, significant differences The Author(s) 2023 aBIOTECH Fig. 5 Primary root anatomy of sorghum cultivars SC103 and BTx635 grown for 10 days in hydroponics under sufficient Pi (SP, 200 lM) and low Pi (LP, 2.5 lM) conditions. Representative transverse images of primary root cross sections, collected 5 cm below the stem-root junction (A), and * 5 cm from the primary root tip (E) (see Fig. 4A). Histograms represent root cross-sectional area, total root cortical aerenchyma area (AA), and proportion of root cross section occupied by aerenchyma, near the stem root junction (B–D) and * 5cm from the root tip (F–H) of the SC103 (green) and BTx635 (orange) primary root, respectively. Data shown are means ± SE (n = 6). Asterisks indicate significant differences between the cultivars, under the same condition, as determined by Student’s t test: for these assays, significance differences are indicated as follows: *P \ 0.05; **P \ 0.01; ***P \ 0.001. Different lowercase letters indicate significant differences (P \ 0.05) between the two Pi concentrations, in the same genotype, as determined by Tukey’s HSD tests. CSA 2 2 cross section area (mm ), AA total root cortical aerenchyma area, (mm ). Scale bar applies to all images The Author(s) 2023 aBIOTECH Fig. 6 Lateral root anatomyof sorghum cultivars SC103 and BTx635 grown for 10 days in hydroponics under sufficient Pi (SP, 200 lM) and low Pi (LP, 2.5 lM) conditions. Representative transverse images of lateral root cross sections, collected 5 cm below the primary-lateral root junction (A), and * 5 cmfromthe lateralroot tip(E)(seeFig. 4A). Histograms represent root cross-sectional area, total root cortical aerenchyma area (AA), and proportion of root cross section occupied by aerenchyma, near the primary-lateral root junction (B–D)and * 5 cm from the root tip (F–H)of the SC103 (green) and BTx635 (orange) lateral root, respectively. Data shown are means ± SE (n = 6). Asterisks indicate significant differences between the cultivars, under the same condition, as determined by Student’s t test: for these assays, significance differences are indicated as follows: *P\ 0.05; **P\ 0.01; ***P\ 0.001. Different lowercase letters indicate significant differences (P\ 0.05) between the two Pi concentrations, in the same genotype, as determined by Tukey’s HSD tests. CSA cross section area (mm ); AA total root cortical aerenchyma area (mm ). Scale bar applies to all images The Author(s) 2023 aBIOTECH Fig. 7 Root system architecture of sorghum cultivars, SC103 and BTx635, grown under sufficient N (SN, 4000 lM) and low N (LN, 400 lM) stress conditions. Plants were grown in a hydroponic pouch system and harvested at 10 Dat. A Representative root images of SC103 and BTx635, under SN and LN conditions. B Radar charts comparing the RSA traits of SC103 (green) and BTx635 (orange) under SN conditions. C Radar charts comparing the root system architecture traits of SC103 (green) and BTx635 (orange) under LN conditions. Asterisks indicate significant differences between the cultivars, under the same condition, as determined by Student’s t test: for these assays, significance differences are indicated as follows: *P \ 0.05; **P \ 0.01; ***P \ 0.001. SDW shoot dry weight, RDW root dry weight, R/S root:shoot ratio were observed for all characteristics examined, with Fig. 8 Phenotypic differences for sorghum cultivars SC103 and BTx635 grown under control (CK), low Pi (LP, 75 lM), and low N SC103 having the superior traits (Fig. 8C; see also (LN, 600 lM) stress conditions. A Representative images of SC103 Supplementary Fig. 3 and Supplementary Table 3). and BTx635, under CK, LP and LN stress conditions. Images were Under LN growth conditions, significant differences taken 28 Dat. B Radar plots quantifying the RSA traits of SC103 were also observed for all characteristics examined, and BTx635, under CK conditions. C Radar plots quantifying the RSA traits of SC103 and BTx635, under LP conditions. D Radar with SC103 having the superior traits, with the excep- plots quantifying the RSA traits of SC103 and BTx635, under LN tion that BTx635 had a higher root Pi content and R/S conditions. Asterisks indicate significant differences between the ratio (Fig. 8D; see also Supplementary Fig. 3 and Sup- cultivars under CK, LP and LN conditions, as determined by plementary Table 3). These findings are equivalent to Student’s t test: for these assays, significance differences are indicated as follows: *P \ 0.05; **P \ 0.01; ***P \ 0.001. SDW those observed for plants grown in the LP hydroponic shoot dry weight, RDW root dry weight, R/S root:shoot ratio pouch systems. The Author(s) 2023 aBIOTECH The Author(s) 2023 aBIOTECH Fig. 9 Phenotypic differences for sorghum cultivars SC103 and BTx635 in response to water stress. Plants were grown in potting mix for 28 Dat. At the 14-day timepoint, plants were separated into two groups; a control group was well-watered (WW), whereas water was withheld from the water stress (WS) group. A Representative images of SC103 and BTx635, grown under WW and WS conditions. B Radar plots quantifying the RSA traits of SC103 and BTx635, under WW treatment. C Radar plots quantifying the RSA traits of SC103 and BTx635, under WS treatment. D Radar plots quantifying the RSA traits of SC103 under WW and WS treatment. E Radar plots quantifying the RSA traits of BTx635 under WW and WS treatment. Asterisks indicate the significant differences between the cultivars and treatments, as determined by Student’s t test: for these assays, significance differences are indicated as follows: *P \ 0.05; **P \ 0.01; ***P \ 0.001. SDW shoot dry weight, RDW root dry weight, R/S root:shoot ratio The Author(s) 2023 aBIOTECH Drought conditions can impair crop performance and occupied a remarkably small volume; this pattern would yield. To explore whether SC103 and BTx635 are resi- be equivalent to root growth in the topsoil (see Fig. 1). lient to an imposed water stress condition, plants were If these two test cultivars were genetically adapted, via grown in potting mix for four weeks. At the two week breeding programs, to generate a shallow root system, timepoint, the plants were divided into two equal then we would anticipate that exposure to LP conditions groups; the control group continued to be well-watered would produce more and longer horizontally-oriented (WW), and the test group was subjected to water stress roots. As shown in Fig. 2, an entirely different response (WS), by withholding water (Fig. 9A). As might be was observed, in which the root systems expanded both anticipated, SC103 displayed superior growth and RSA laterally and vertically to occupy a greatly enlarged characteristics, compared with BTx635, under both WW volume (Figs. 3, 4). In this regard, both the primary and and WS treatments, except for R/S ratio (Fig. 9B, C; see lateral roots responded in a reactive manner to a also Supplementary Table 4). The impact of WS on reduction in available Pi. growth and RSA traits for each sorghum line is shown in The growth systems employed in our study did not Fig. 9D, E (see also Supplementary Table 4), and indi- mimic the soil conditions under which the differences in cates that, for both lines, all parameters were reduced yield performance, between SC103 and BTx635, were under WS conditions. recorded. It is noteworthy, that these plants were grown under field conditions, where available Pi, at limiting levels, was confined to the topsoil. However, this strat- DISCUSSION ification of soil P concentration to higher levels in the topsoil, in the field, does not apply to our studies on LN The root system is of fundamental importance for or water availability, as these resources are mobile and seedling establishment, to enable plant growth and are generally distributed deeper within the soil profile. survival through its pivotal role in uptake of essential Again, the root systems that developed under LN nutrients and water. During seedling establishment, the (Figs. 7, 8) and WS (Fig. 9), did not conform to the majority of plant development occurs within the root predicted topsoil model. Rather, under LN and WS, the system. The early establishment of roots has been clo- root patterns for both cultivars, were similar to those sely linked to grain yield, rather than to the subsequent observed under LP. One crucial objective in the future stages of root development (Cai et al. 2012). Further- will be to conduct field validation to ground truth the more, overexpression of OsMYB4P, an R2R3-type MYB differences in N efficiency and performance under transcriptional activator, in rice seedlings increased drought conditions for both sorghum cultivars. It should be noted, as mentioned in the ‘‘Materials and methods’’, seminal and lateral root length and density, which enhanced phosphate acquisition (Yang et al. 2014). With that the differences in P efficiency for SC103 and regards to breeding for crop improvement, attention to BTx635 were first determined and quantified in the identifying traits, associated with early establishment of field by measuring grain yield on a low P field site. an extensive root system, would likely provide pathways The findings from the current study provide insight for developing lines with efficient growth and subse- into an efficient pathway for developing crops with quent yield enhancement. enhanced soil performance characteristics. In general, as with SC103 and BTx635, many crop plants utilize an RSA RSAs for efficient performance under limiting Pi equivalent to an inverted triangular root system and/or N conditions (Fig. 1B). Hence, this RSA removes the need to engineer dramatic genetic reprogramming, in order to convert Our findings establish that, under phosphate stress from an inverted root system into one in which the conditions, neither SC103 nor BTx635 developed RSA majority of the roots are constrained to a more horizontal traits equivalent to those anticipated for plants that are plane. In this regard, SC103 may well provide a valuable optimized for yield performance on soils in which resource for such breeding activities. First, it has genetic available Pi is located primarily within the topsoil (Liang characteristics associated with enhanced resource allo- et al. 2010; Lynch 2011). Although our conditions used cation, resulting in more extensive aerenchyma devel- for plant growth and root trait analysis utilized hydro- opment (Figs. 5, 6, and Supplemental Fig. 2), which ponic pouches, sand culture, and potting soil, the RSAs optimizes the cost associated with the generation and obtained under SP and LP conditions provide insight maintenance of a large root system (Lynch 2018). The into the genetic program(s) underlying root develop- resultant enhanced root system surface area increased ment and growth. For example, in Fig. 2, under SP, the the capacity for resource acquisition, which in this study root systems developed by both SC103 and BTx635 resulted in enhanced P, N and water uptake. The Author(s) 2023 aBIOTECH Aerenchyma as a key growth and yield measured under laboratory and greenhouse conditions, determinant to be integrated into breeding programs for nutrient utilization efficiencies, including N, P, K, and also water. The amount of root cortical aerenchyma can vary, Presently, considerable sorghum genetic resources are depending on plant species, genotype, developmental available, including different mapping populations, and stage, root class, and position along the root axis, or multiple pangenomes. These provide an important within the transverse section (Armstrong 1972; Bour- platform for identifying genomic regions and/or genes anis et al. 2006; Evans 2004; Kawai et al. 1998). Addi- underlying these traits, which can be used for crop tionally, both nutrient limitation and WS can induce improvement by employing genome-design-based aerenchyma development (Chimungu et al. 2015; breeding, marker-assisted introgression, and gene- Postma and Lynch 2011; Saengwilai et al. 2014). The based editing. It is noteworthy that the constitutive basis for the observed difference in root system size, (hard-wired) versus induced genetic component of the between SC103 and BTx635, may reflect a significant SC103 RSA traits could facilitate trait engineering into difference in the degree to which aerenchyma devel- target crops due to a reduced impact by oped in these two lines. For both primary and lateral genome 9 environment interactions. In this manner, roots, in the recently developed zone of these root types, crop improvement be would available across a wider significant differences in aerenchyma existed between range of soil types and agroecologies. Lastly, as SC103 is SC103 and BTx635, under both SP and LP conditions; more efficient in terms of P and N acquisition and here, the extent of aerenchyma development was greatly drought resilience, this could allow for the efficient enhanced under SP and LP conditions in SC103 (Figs. 5, breeding for all three traits from one genetic source. 6). Given that aerenchyma develops in these root sys- tems, under both SP and LP conditions, this may reflect the operation of a constitutive regulatory genetic CONCLUSIONS program. As SC103 establishes an enhanced level of aerench- The grain yield differential, between SC103 and BTx635, yma, relative to BTx635, this must reflect the presence established under low Pi field conditions, was clearly of different genetic elements in these two cultivars. This reflected in the measured RSA and growth characteris- difference likely indicates alterations in gene promoter tics, determined under LP, LN, and WS conditions properties in these two lines. For example, Schneider (Figs. 2, 3, 4, 7, 8, 9). Given that SC103 and BTx635 have et al. (2023) recently reported that ZmbHLH121 acts as equivalently structured root systems (Fig. 2), these a positive regulator of root cortical aerenchyma forma- performance differences likely reflect either changes in tion. Thus, differential expression of this gene homolog, the operational characteristics of a putative master in SC103 and BTx635, could contribute to their differ- controller, or higher expression levels of key genes ences in aerenchyma. Therefore, root cortical aerench- involved in resource allocation. These differences yma represents a promising target for the breeding of resulted in a larger and more dynamic root system in crop cultivars with improved stress tolerance, resilience, SC103, thereby supporting an enhanced shoot system, and carbon sequestration. Additionally, based on the resulting in the measured higher yield. Identifying the observed enhancement of aerenchyma, under LP con- genetic determinants responsible for the superior per- ditions, these lines appear to possess both constitutive formance of SC103 would provide a valuable resource and inductive genetic components. A similar conclusion for both further research into the establishment of can be drawn for the operation of regulatory compo- superior RSA traits and to facilitate breeding programs. nents controlling root growth traits under SP and LP conditions (Fig. 3). Supplementary Information The online version contains supplementary material available at https://doi.org/10.1007/ s42994-023-00112-w. Breeding for superior RSAs Acknowledgements This research was supported by funding Based on its performance in our studies, SC103 repre- from a Canada Excellence Research Chairs (CERC) Grant to LVK, funding from the Global institute for Food Security, and the sents an important genetic resource for identifying University of Saskatchewan, to LVK. Thanks are due to Brian Ham genes, or genomics regions, that can be employed for for assistance in figure development. breeding crops with an RSA for fitness under nutrient and/or water limitations. Furthermore, the high yielding Author contributions LVK and ZL conceived and designed the capacity of SC103, obtained on field soils with low project. ZL, TQ, MA, YZ and HN performed the experiments. HS, KP processed the root images. ZL, WJL, and LVK analyzed the data. ZL available Pi, also presents opportunities for RSA traits, The Author(s) 2023 aBIOTECH wrote the manuscript draft, and WJL, JM, and LVK revised it. All Chiera J, Thomas J, Rufty T (2002) Leaf initiation and development authors have reviewed the manuscript and have read and agreed in soybean under phosphorus stress. J Exp Bot 53:473–481 to the published version of the manuscript. Chimungu JG, Maliro MF, Nalivata PC, Kanyama-Phiri G, Brown KM, Lynch JP (2015) Utility of root cortical aerenchyma under water limited conditions in tropical maize (Zea mays L.). Field Data availability All data generated or analyzed during this Crops Res 171:86–98 study are available from the corresponding author upon request. Clark RT, Famoso AN, Zhao K, Shaff JE, Craft EJ, Bustamante CD, McCouch SR, Aneshansley DJ, Kochian LV (2013) High- Declarations throughput two-dimensional root system phenotyping plat- form facilitates genetic analysis of root growth and develop- Conflict of interest The authors claim no conflict of inter- ment. Plant Cell Environ 36:454–466 est. Authors William J. Lucas and Leon V. Kochian were not Ericsson T (1995) Growth and shoot: root ratio of seedlings in involved in the journal’s review of the manuscript. relation to nutrient availability. In: Paper presented at the nutrient uptake and cycling in forest ecosystems: proceedings Open Access This article is licensed under a Creative Commons of the CEC/IUFRO symposium nutrient uptake and cycling in Attribution 4.0 International License, which permits use, sharing, Forest Ecosystems Halmstad, Sweden, June, 7–10, 1993 adaptation, distribution and reproduction in any medium or for- Evans DE (2004) Aerenchyma formation. New Phytol 161:35–49 mat, as long as you give appropriate credit to the original Fox J, Weisberg S, Adler D, Bates D, Baud-Bovy G, Ellison S et al author(s) and the source, provide a link to the Creative Commons (2012) Package ‘car.’ R Foundation for Statistical Computing, licence, and indicate if changes were made. The images or other Vienna, p 16 third party material in this article are included in the article’s Gabay G, Wang H, Zhang J, Moriconi JI, Burguener GF, Gualano LD Creative Commons licence, unless indicated otherwise in a credit et al (2023) Dosage differences in 12-OXOPHYTODIENOATE line to the material. If material is not included in the article’s REDUCTASE genes modulate wheat root growth. Nat Com- Creative Commons licence and your intended use is not permitted mun 14:539. https://doi.org/10.1038/s41467-023-36248-y by statutory regulation or exceeds the permitted use, you will Galkovskyi T, Mileyko Y, Bucksch A, Moore B, Symonova O, Price need to obtain permission directly from the copyright holder. To CA et al (2012) GiA roots: software for the high throughput view a copy of this licence, visit http://creativecommons.org/ analysis of plant root system architecture. BMC Plant Biol licenses/by/4.0/. 12:1–12 Gamuyao R, Chin JH, Pariasca-Tanaka J, Pesaresi P, Catausan S, Dalid C et al (2012) The protein kinase Pstol1 from traditional rice confers tolerance of phosphorus deficiency. References Nature 488:535–539. https://doi.org/10.1038/nature11346 Gao C (2021) Genome engineering for crop improvement and Armstrong W (1972) A re-examination of the functional signifi- future agriculture. Cell 184:1621–1635 cance of aerenchyma. Physiol Plant 27:173–177 Gladman N, Hufnagel B, Regulski M, Liu Z, Wang X, Chougule K Atkinson JA, Wells DM (2017) An updated protocol for high et al (2022) Sorghum root epigenetic landscape during throughput plant tissue sectioning. Front Plant Sci 8:1721. limiting phosphorus conditions. Plant Direct. https://doi.org/ https://doi.org/10.3389/fpls.2017.01721 10.1002/pld3.393 Bernardino KC, Pastina MM, Menezes CB, de Sousa SM, Maciel LS, Halford NG, Curtis TY, Chen Z, Huang J (2015) Effects of abiotic Carvalho G Jr et al (2019) The genetic architecture of stress and crop management on cereal grain composition: phosphorus efficiency in sorghum involves pleiotropic QTL implications for food quality and safety. J Exp Bot for root morphology and grain yield under low phosphorus 66:1145–1156. https://doi.org/10.1093/jxb/eru473 availability in the soil. BMC Plant Biol 19:87. https://doi.org/ Hickey LT, Hafeez AN, Robinson H, Jackson SA, Leal-Bertioli SCM, 10.1186/s12870-019-1689-y Tester M et al (2019) Breeding crops to feed 10 billion. Nat Bouranis DL, Chorianopoulou SN, Kollias C, Maniou P, Protono- Biotechnol 37:744–754. https://doi.org/10.1038/s41587- tarios VE, Siyiannis VF et al (2006) Dynamics of Aerenchyma 019-0152-9 distribution in the cortex of sulfate-deprived adventitious Hodge A, Berta G, Doussan C, Merchan F, Crespi M (2009) Plant roots of maize. Ann Bot 97:695–704. https://doi.org/10. root growth, architecture and function. Plant Soil 1093/aob/mcl024 321:153–187. https://doi.org/10.1007/s11104-009-9929-9 Burton AL, Johnson J, Foerster J, Hanlon MT, Kaeppler SM, Lynch Hufnagel B, de Sousa SM, Assis L, Guimaraes CT, Leiser W, Azevedo JP et al (2015) QTL mapping and phenotypic variation of root GC et al (2014) Duplicate and conquer: multiple homologs of anatomical traits in maize (Zea mays L.). Theor Appl Genet PHOSPHORUS-STARVATION TOLERANCE1 enhance phospho- 128:93–106 rus acquisition and sorghum performance on low-phospho- Cai H, Chen F, Mi G, Zhang F, Maurer HP, Liu W et al (2012) rus soils. Plant Physiol 166:659–677. https://doi.org/10. Mapping QTLs for root system architecture of maize (Zea 1104/pp.114.243949 mays L.) in the field at different developmental stages. Theor Kawai M, Samarajeewa P, Barrero R, Nishiguchi M, Uchimiya H Appl Genet 125:1313–1324. https://doi.org/10.1007/ (1998) Cellular dissection of the degradation pattern of s00122-012-1915-6 cortical cell death during aerenchyma formation of rice roots. Cakmak I, Hengeler C, Marschner H (1994) Partitioning of shoot Planta 204:277–287 and root dry matter and carbohydrates in bean plants Liang Q, Cheng X, Mei M, Yan X, Liao H (2010) QTL analysis of root suffering from phosphorus, potassium and magnesium defi- traits as related to phosphorus efficiency in soybean. Ann Bot ciency. J Exp Bot 45:1245–1250 106:223–234. https://doi.org/10.1093/aob/mcq097 Casa AM, Pressoir G, Brown PJ, Mitchell SE, Rooney WL, Tuinstra Liu D (2021) Root developmental responses to phosphorus MR et al (2008) Community resources and strategies for nutrition. J Integr Plant Biol 63:1065–1090. https://doi.org/ association mapping in sorghum. Crop Sci 48:30–40 10.1111/jipb.13090 The Author(s) 2023 aBIOTECH Lynch JP (2011) Root phenes for enhanced soil exploration and Saengwilai P, Nord EA, Chimungu JG, Brown KM, Lynch JP (2014) phosphorus acquisition: tools for future crops. Plant Physiol Root cortical aerenchyma enhances nitrogen acquisition from 156:1041–1049 low-nitrogen soils in maize. Plant Physiol 166:726–735 Lynch JP (2018) Rightsizing root phenotypes for drought resis- Schneider HM, Lor VS, Zhang X, Saengwilai P, Hanlon MT, Klein SP tance. J Exp Bot 69:3279–3292. https://doi.org/10.1093/ et al (2023) Transcription factor bHLH121 regulates root jxb/ery048 cortical aerenchyma formation in maize. Proc Natl Acad Sci Lynch JP (2022) Harnessing root architecture to address global USA 120:e2219668120. https://doi.org/10.1073/pnas. challenges. Plant J 109:415–431. https://doi.org/10.1111/ 2219668120 tpj.15560 Sun B, Gao Y, Lynch JP (2018) Large crown root number improves Marschner H (2011) Function of macronutrients. In: Petra M (ed) topsoil foraging and phosphorus acquisition. Plant Physiol Marschner’s mineral nutrition of higher plants. Academic 177:90–104 Press, Elsevier, US, Waltham, pp 135–178 Team RC (2013) R: a language and environment for statistical Meister R, Rajani MS, Ruzicka D, Schachtman DP (2014) Challenges of computing modifying root traits in crops for agriculture. Trends Plant Sci Tracy SR, Nagel KA, Postma JA, Fassbender H, Wasson A, Watt M 19:779–788. https://doi.org/10.1016/j.tplants.2014.08.005 (2020) Crop improvement from phenotyping roots: high- Mohammed SB, Burridge JD, Ishiyaku MF, Boukar O, Lynch JP lights reveal expanding opportunities. Trends Plant Sci (2022) Phenotyping cowpea for seedling root architecture 25:105–118. https://doi.org/10.1016/j.tplants.2019.10.015 reveals root phenes important for breeding phosphorus Tyczewska A, Wozniak E, Gracz J, Kuczynski J, Twardowski T efficient varieties. Crop Sci 62:326–345 (2018) Towards food security: current state and future Parentoni SN, de Souza JC, de Carvalho AV, Gama E, Coelho A, De prospects of agrobiotechnology. Trends Biotechnol Oliveira A et al (2010) Inheritance and breeding strategies for 36:1219–1229. https://doi.org/10.1016/j.tibtech.2018.07. phosphorous efficiency in tropical maize (Zea mays L.). 008 Maydica 55:1 Wickham H (2016) Data analysis. ggplot2. Springer, Berlin, Postma JA, Lynch JP (2011) Root cortical aerenchyma enhances pp 189–201 the growth of maize on soils with suboptimal availability of Yang WT, Baek D, Yun D-J, Hwang WH, Park DS, Nam MH et al nitrogen, phosphorus, and potassium. Plant Physiol (2014) Overexpression of OsMYB4P, an R2R3-type MYB 156:1190–1201 transcriptional activator, increases phosphate acquisition in Rangarajan H, Postma JA, Lynch JP (2018) Co-optimization of axial rice. Plant Physiol Biochem 80:259–267. https://doi.org/10. root phenotypes for nitrogen and phosphorus acquisition in 1016/j.plaphy.2014.02.024 common bean. Ann Bot 122:485–499 Zhao J, Fu J, Liao H, He Y, Nian H, Hu Y et al (2004) Ray DK, Mueller ND, West PC, Foley JA (2013) Yield trends are Characterization of root architecture in an applied core insufficient to double global crop production by 2050. PLoS ONE collection for phosphorus efficiency of soybean germplasm. 8:e66428. https://doi.org/10.1371/journal.pone.0066428 Chin Sci Bull 49:1611–1620 Ryan PR, Delhaize E, Watt M, Richardson AE (2016) Plant roots: Zheng Z, Wang B, Zhuo C, Xie Y, Zhang X, Liu Y et al (2023) Local understanding structure and function in an ocean of com- auxin biosynthesis regulates brace root angle and lodging plexity. Ann Bot 118:555–559. https://doi.org/10.1093/aob/ resistance in maize. New Phytol. https://doi.org/10.1111/ mcw192 nph.18733 The Author(s) 2023

Journal

aBIOTECHSpringer Journals

Published: Dec 1, 2023

Keywords: Constitutive root system architecture; Abiotic stress; Nutrient efficiency; Drought resilience; Plant breeding

There are no references for this article.