Root Traits In Wheat Research Articles

Combined Genome-Wide Association Studies (GWAS) and Linkage Mapping Identifies Genomic Regions Associated with Seedling Root System Architecture (RSA) under Different Nitrogen Conditions in Wheat (Triticum aestivum L.)

The nitrogen (N) use efficiency (NUE) in the roots of seedlings is beneficial for increasing crop yield. Creating marker-assisted selection for wheat root traits can assist wheat breeders in choosing robust roots to maximize nutrient uptake. Exploring and identifying the effect of different N supply conditions on root system architecture (RSA) is of great significance for breeding N efficient wheat varieties. In this study, a total of 243 wheat varieties native to the Yellow and Huai Valley regions of China were utilized for genome-wide association studies (GWAS). Furthermore, a recombinant inbred line (RIL) population of 123 lines derived from the cross between Avocet and Chilero was utilized for linkage examination. A hydroponic seedling experiment using a 96-well tray was conducted in the lab with two treatments: normal N (NN) and low N (LN). Five RSA traits, including the relative number of root tips (RNRT), relative total root length (RTRL), relative total root surface area (RTRS), relative total root volume (RTRV), and relative average root diameter (RARD), were investigated. GWAS and linkage analysis were performed by integrating data from the wheat 660 k single nucleotide polymorphism (SNP) chip and diversity arrays technology (DArT) to identify genetic loci associated with RSA. The results showed that, based on the ratio of RSA-related traits under two N supply conditions, a total of 497 SNP markers, which are significantly associated with RSA-related traits, were detected at 148 genetic loci by GWAS. A total of 10 QTL loci related to RSA were discovered and identified by linkage mapping. Combining two gene localization methods, three colocalized intervals were found: AX-95160997/QRtrl.haust-3D, AX-109592379/QRnrt.haust-5A, and AX-110924288/QRtrl.haust-7D/QRtrs.haust-7D. According to the physical location of the colocalization of these two sites, between 39.61 and 43.74 Mb, 649.97 and 661.55 Mb, and 592.44 and 605.36 Mb are called qRtrl-3D, qRnrt-5A, and qRtrl-7D. This study has the potential to enhance the effectiveness of selecting root traits in wheat breeding programs, offering valuable insights into the genetic underpinnings of NUE in wheat. These results could help in breeding wheat varieties with higher NUE by implementing focused breeding strategies.

Regulation of root growth and elongation in wheat.

Currently, the control of rhizosphere selection on farms has been applied to achieve enhancements in phenotype, extending from improvements in single root characteristics to the dynamic nature of entire crop systems. Several specific signals, regulatory elements, and mechanisms that regulate the initiation, morphogenesis, and growth of new lateral or adventitious root species have been identified, but much more work remains. Today, phenotyping technology drives the development of root traits. Available models for simulation can support all phenotyping decisions (root trait improvement). The detection and use of markers for quantitative trait loci (QTLs) are effective for enhancing selection efficiency and increasing reproductive genetic gains. Furthermore, QTLs may help wheat breeders select the appropriate roots for efficient nutrient acquisition. Single-nucleotide polymorphisms (SNPs) or alignment of sequences can only be helpful when they are associated with phenotypic variation for root development and elongation. Here, we focus on major root development processes and detail important new insights recently generated regarding the wheat genome. The first part of this review paper discusses the root morphology, apical meristem, transcriptional control, auxin distribution, phenotyping of the root system, and simulation models. In the second part, the molecular genetics of the wheat root system, SNPs, TFs, and QTLs related to root development as well as genome editing (GE) techniques for the improvement of root traits in wheat are discussed. Finally, we address the effect of omics strategies on root biomass production and summarize existing knowledge of the main molecular mechanisms involved in wheat root development and elongation.

Comparative Transcriptome Analysis Reveals the Genes and Pathways Related to Wheat Root Hair Length.

Tube-like outgrowths from root epidermal cells, known as root hairs, enhance water and nutrient absorption, facilitate microbial interactions, and contribute to plant anchorage by expanding the root surface area. Genetically regulated and strongly influenced by environmental conditions, longer root hairs generally enhance water and nutrient absorption, correlating with increased stress resistance. Wheat, a globally predominant crop pivotal for human nutrition, necessitates the identification of long root hair genotypes and their regulatory genes to enhance nutrient capture and yield potential. This study focused on 261 wheat samples of diverse genotypes during germination, revealing noticeable disparities in the length of the root hair among the genotypes. Notably, two long root hair genotypes (W106 and W136) and two short root hair genotypes (W90 and W100) were identified. Transcriptome sequencing resulted in the development of 12 root cDNA libraries, unveiling 1180 shared differentially expressed genes (DEGs). Further analyses, including GO function annotation, KEGG enrichment, MapMan metabolic pathway analysis, and protein-protein interaction (PPI) network prediction, underscored the upregulation of root hair length regulatory genes in the long root hair genotypes. These included genes are associated with GA and BA hormone signaling pathways, FRS/FRF and bHLH transcription factors, phenylpropanoid, lignin, lignan secondary metabolic pathways, the peroxidase gene for maintaining ROS steady state, and the ankyrin gene with diverse biological functions. This study contributes valuable insights into modulating the length of wheat root hair and identifies candidate genes for the genetic improvement of wheat root traits.

Conservation tillage influences soil structure, earthworm communities and wheat root traits in a long-term organic cropping experiment

Conservation tillage influences soil structure, earthworm communities and wheat root traits in a long-term organic cropping experiment

QTL Mapping for Root Traits and Their Effects on Nutrient Uptake and Yield Performance in Common Wheat (Triticum aestivum L.)

Wheat is one of the most important crops in the world. Mapping QTLs for root traits is essential for the selection of wheat roots desirable for the efficient acquisition of nutrients. Here, a QTL analysis for wheat root traits was performed using 142 recombinant inbred lines derived from two wheat varieties Xiaoyan 54 and Jing 411 in a soil column culture trial. The genetic map used in this study contained 470 SSR markers and covered 3438.4 cM of wheat genome. A total of 25 QTLs for root and shoot traits were detected, located at 16 marker intervals of 13 chromosomes. The percentage of phenotypic variation explained by individual QTLs varied from 6.1% to 22.0%. The QTLs regulating RDW and root distribution on chromosomes 1A, 3A, 4A, and 5B are important for root growth in both the top- and subsoils. For qRDW-1A, qRDW-3A, and qRDW-5B, the nearest markers to the QTLs were much closer than that of qRDW-4A, with the genetic distances ranging from 0.01 to 1.18 cM. Combining these three QTLs not only increased RDW and nutrient uptake, but also increased GW, SDW, and BDW under low nitrogen conditions in the field trial. Therefore, these QTLs are valuable for marker-assisted selection of wheat root traits.

Fragmentation of soil-root complexes in sloping landscapes during tillage and soil translocation

It is well known that roots play a significant role in reducing water erosion in soil, yet few studies have reported the influence of crop roots on soil translocation induced by tillage in sloping fields. To examine the relationship between soil-root complexes (i.e., complexes of wheat roots and soil) and soil redistribution caused by tillage, a series of tillage experiments were carried out on bare soil and areas of wheat sown by drilling ( DS ) and nesting ( NS) using nine slopes with gradients varying from 0.19 to 0.32 m m −1 . The magnetic tracing technique was used to determine soil translocation rates under hoeing tillage in sloping landscapes in response to soil-root complexes and bare soil. The results indicated that mean displacement distance for DS and NS in the downslope direction was 0.15 m and 0.16 m, respectively. This was much shorter than that of bare soil which was 0.26 m. Mean tillage erosion rates ranged from 14.58 to 19.15 Mg ha −1 per tillage pass for DS and 13.90 –21.10 Mg ha −1 per tillage pass for NS , while reached 31.23–36.31 Mg ha −1 per tillage pass for bare soil. Tillage transport coefficients ( k 3 and k 4 ) were 6.31 and 106.46 kg m −1 per tillage pass for DS , 6.58 and 118.68 kg m −1 per tillage pass for NS , and 28.12 and 151.07 kg m −1 per tillage pass for bare soil, respectively. A significant difference in cohesive force ( C ) was found between DS ( NS ) and bare soil ( P < 0.05), thereby resulting in an increase in the soil shear strength of soil-root complexes. Compared with those of bare soil, the soil fractal dimension of soil-root complexes decreased significantly due to an increase in the percentage of coarse clods (>100 and 100–80 mm) and a decrease in the percentage of fine clods (50–20 and < 20 mm). Mean soil displacement distance caused by tillage displayed a negative relationship with C and wheat root traits (the root density, the root length density, and the root area ratio) within the hilly landscape of soil-root complexes ( P < 0.05), implying that wheat roots played a crucial part in soil translocation and soil fragmentation during hoeing tillage. Our study revealed that soil-root complexes markedly reduce the soil downslope transfer process during tillage and prevent the break-up of large clods by tillage implements on sloping farmland. • Wheat root attenuated the mechanical breakage of clods during tillage operation. • Root systems increase soil shear strength and reduce fragmentation of soil clods. • Displacement distance for soil-root complexes was smaller than that for bare soil. • Tillage erosion decreased with increasing structure stability and cohesive force.

Dynamics of root exuded carbon and its relationships with root traits of rapeseed and wheat

Quantifying carbon in root exudates and exploring their influencing factors are essential to understand soil organic carbon dynamics in cropland. A pot experiment was carried out to explore quantitative relations between root exuded carbon and root traits in wheat and rapeseed. The result showed that rapeseed had a similar pattern in root carbon exudation intensity (EI) as the wheat, but its EI per plant was obviously higher than that in wheat. Rapeseed plants had higher EI per root biomass than wheat plants in the early growth period but lower in the late growth period. EI per root biomass in both crops had significant exponential relationships with the specific root length (RL), surface area (RSA), volume (RV), root C/N ratio and root soluble sugar content. However, EI per plant of both crops had a markedly quadratic relationship with RL, RSA, RV and root biomass. During the whole growth period, the rapeseed had cumulative root carbon exudation of 14.09 g/plant, which was almost twice of that in the wheat plant. Root traits had close relations to root carbon exudation in both crops. Quantitative regression models between them could be referred to estimate root C exudation in rapeseed and wheat farmland.

Identification of Candidate Genes for Root Traits Using Genotype-Phenotype Association Analysis of Near-Isogenic Lines in Hexaploid Wheat (Triticum aestivum L.).

Global wheat (Triticum aestivum L.) production is constrained by different biotic and abiotic stresses, which are increasing with climate change. An improved root system is essential for adaptability and sustainable wheat production. In this study, 10 pairs of near-isogenic lines (NILs)—targeting four genomic regions (GRs) on chromosome arms 4BS, 4BL, 4AS, and 7AL of hexaploid wheat—were used to phenotype root traits in a semi-hydroponic system. Seven of the 10 NIL pairs significantly differed between their isolines for 11 root traits. The NIL pairs targeting qDSI.4B.1 GR varied the most, followed by the NIL pair targeting qDT.4A.1 and QHtscc.ksu-7A GRs. For pairs 5–7 targeting qDT.4A.1 GR, pair 6 significantly differed in the most root traits. Of the 4 NIL pairs targeting qDSI.4B.1 GR, pairs 2 and 4 significantly differed in 3 and 4 root traits, respectively. Pairs 9 and 10 targeting QHtscc.ksu-7A GR significantly differed in 1 and 4 root traits, respectively. Using the wheat 90K Illumina iSelect array, we identified 15 putative candidate genes associated with different root traits in the contrasting isolines, in which two UDP-glycosyltransferase (UGT)-encoding genes, TraesCS4A02G185300 and TraesCS4A02G442700, and a leucine-rich repeat receptor-like protein kinase (LRR-RLK)-encoding gene, TraesCS4A02G330900, also showed important functions for root trait control in other crops. This study characterized, for the first time, that these GRs control root traits in wheat, and identified candidate genes, although the candidate genes will need further confirmation and validation for marker-assisted wheat breeding.

QTL mapping of root traits in wheat under different phosphorus levels using hydroponic culture

BackgroundPhosphorus (P) is an important in ensuring plant morphogenesis and grain quality, therefore an efficient root system is crucial for P-uptake. Identification of useful loci for root morphological and P uptake related traits at seedling stage is important for wheat breeding. The aims of this study were to evaluate phenotypic diversity of Yangmai 16/Zhongmai 895 derived doubled haploid (DH) population for root system architecture (RSA) and biomass related traits (BRT) in different P treatments at seedling stage using hydroponic culture, and to identify QTL using 660 K SNP array based high-density genetic map.ResultsAll traits showed significant variations among the DH lines with high heritabilities (0.76 to 0.91) and high correlations (r = 0.59 to 0.98) among all traits. Inclusive composite interval mapping (ICIM) identified 34 QTL with 4.64–20.41% of the phenotypic variances individually, and the log of odds (LOD) values ranging from 2.59 to 10.43. Seven QTL clusters (C1 to C7) were mapped on chromosomes 3DL, 4BS, 4DS, 6BL, 7AS, 7AL and 7BL, cluster C5 on chromosome 7AS (AX-109955164 - AX-109445593) with pleiotropic effect played key role in modulating root length (RL), root tips number (RTN) and root surface area (ROSA) under low P condition, with the favorable allele from Zhongmai 895.ConclusionsThis study carried out an imaging pipeline-based rapid phenotyping of RSA and BRT traits in hydroponic culture. It is an efficient approach for screening of large populations under different nutrient conditions. Four QTL on chromosomes 6BL (2) and 7AL (2) identified in low P treatment showed positive additive effects contributed by Zhongmai 895, indicating that Zhongmai 895 could be used as parent for P-deficient breeding. The most stable QTL QRRS.caas-4DS for ratio of root to shoot dry weight (RRS) harbored the stable genetic region with high phenotypic effect, and QTL clusters on 7A might be used for speedy selection of genotypes for P-uptake. SNPs closely linked to QTLs and clusters could be used to improve nutrient-use efficiency.

Impact of saline stress on the uptake of various macro and micronutrients and their associations with plant biomass and root traits in wheat

The associations among ion uptake, root development and biomass under salt stress have not been fully understood. To study this, a pot experiment was conducted with the objective to determine the concentrations of sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), zinc (Zn) and iron (Fe) and explore their associations with the biomass and root development by using eight wheat cultivars grown on control and salt stress treatments. About 6 folds increase Na&lt;sup&gt;+&lt;/sup&gt;/K&lt;sup&gt;+&lt;/sup&gt; ratio in root, while 10 folds in the shoot were detected in salt stress compared to that for control. Ca, Mg, Zn concentrations in both root and shoot, and Fe concentration in the shoot were significantly changed by salt stress, except Fe concentration in the root. Principal component analysis revealed significant associations of these ions with the aboveground biomass and root traits. On salt stress treatment, the Na&lt;sup&gt;+&lt;/sup&gt;/K&lt;sup&gt;+&lt;/sup&gt; ratio in shoot showed a significant negative correlation with root weight and aboveground biomass, while aboveground biomass correlated positively with lateral root length and root weight. A strategy towards manipulating the ion homeostasis, particularly Na&lt;sup&gt;+&lt;/sup&gt;/K&lt;sup&gt;+&lt;/sup&gt;, combined with selecting genotypes with better salt tolerance is of promise to alleviate the effects of salt stress.

Wheat root trait plasticity, nutrient acquisition and growth responses are dependent on specific arbuscular mycorrhizal fungus and plant genotype interactions

This study aimed to examine how interactions at both plant genotype and arbuscular mycorrhizal fungus species levels affected the expression of root traits and the subsequent effect on plant nutrition and growth. We used two wheat cultivars with contrasting phosphorus (P) acquisition efficiencies (Tukan and Crac) and two arbuscular mycorrhizal (AM) fungi (Rhizophagus intraradices and Claroideoglomus claroideum). Plant growth, as well as morphological and architectural root traits, were highly dependent on the myco-symbiotic partner in the case of the less P-acquisition efficient cultivar Tukan, with mycorrhizal responses ranging from -45 to 54 % with respect to non-mycorrhizal plants. Meanwhile, these responses were between only -7 and 5 % in the P-acquisition efficient cultivar Crac. The AM fungal species produced contrasting mechanisms in the improvement of plant nutrition and root trait responses. Colonization by R. intraradices increased Ca accumulation, regardless of the cultivar, but reduced root growth on Tukan plants. On the other hand, C. claroideum increased P content in both cultivars, with a concomitant increase in root growth and diffusion-based nutrient acquisition by Tukan. Moreover, plants in symbiosis with R. intraradices showed greater organic acid concentration in their rhizosphere compared to C. claroideum-colonized plants, especially Tukan (24 and 35 % more citrate and oxalate, respectively). Our results suggest that the responses in plant-AM fungal interactions related to nutrient dynamics are highly influenced at the fungus level and also by intra-specific variations in root traits at the genotype level, while growth responses related to improved nutrition depend on plant intrinsic acquisition efficiency.

Phosphate Solubilizing Rhizobacteria Could Have a Stronger Influence on Wheat Root Traits and Aboveground Physiology Than Rhizosphere P Solubilization.

Limited P availability in several agricultural areas is one of the key challenges facing current agriculture. Exploiting P-solubilizing bacteria (PSB) has been an emerging bio-solution for a higher rhizosphere P-availability, meanwhile the above- and below-ground interactions that PSB would trigger remain unclear over plant growing stages. We hypothesized that PSB effects on plant growth may be greater on root traits that positively links with aboveground physiology more than the commonly believed rhizosphere P bio-solubilization. In this study, five contrasting PSB (Pseudomonas spp.) isolates (low “PSB1”, moderate “PSB2 and PSB4” and high “PSB3 and PSB5” P-solubilizing capacity “PSC”) were used to investigate above- and below-ground responses in wheat fertilized with rock P (RP) under controlled conditions. Our findings show that all PSB isolates increased wheat root traits, particularly PSB5 which increased root biomass and PSB3 that had greater effect on root diameter in 7-, 15- and 42-day old plants. The length, surface and volume of roots significantly increased along with higher rhizosphere available P in 15- and 42-day old plants inoculated with PSB4 and PSB2. Shoot biomass significantly increased with both PSB2 and PSB5. Root and shoot physiology significantly improved with PSB1 (lowest PSC) and PSB4 (moderate PSC), notably shoot total P (78.38%) and root phosphatase activity (390%). Moreover, nutrients acquisition and chlorophyll content increased in inoculated plants and was stimulated (PSB2, PSB4) more than rhizosphere P-solubilization, which was also revealed by the significant above- and below-ground inter-correlations, mainly chlorophyll and both total (R = 0.75, p = 0.001**) and intracellular (R = 0.7, p = 0.000114*) P contents. These findings demonstrate the necessity to timely monitor the plant-rhizosphere continuum responses, which may be a relevant approach to accurately evaluate PSB through considering below- and above-ground relationships; thus enabling unbiased interpretations prior to field applications.

Effects of organic inputs derived from pea and wheat root functional traits on soil protease activities

Legume-derived organic inputs such as crop residues or compounds derived from rhizodeposition can influence soil microbial activities implicated in the degradation of organic N. Crops succeeding legumes can also be important drivers of such microbial activities, and trait-based approaches can be employed to better understand the influence of plants on soil microbial activities. The objective of this study was to examine the effects of organic inputs (rhizodeposits and crop residues) of previously planted pea together with wheat root traits on soil protease activities. We measured soil protease activities, soil variables describing C and N availability and microbial biomass N and wheat root functional traits related to resource acquisition and rhizodeposition at 5 wheat developmental stages. Soil protease activities were significantly increased by the addition of pea crop residues, whereas previous pea cropping (i.e., soil containing organic inputs derived from pea rhizodeposition) did not influence these activities. The percentage of fine roots < 0.1 mm in diameter was the only root trait that contributed to variation in soil protease activities. Other belowground traits related to plant nutrient competitive abilities (specific root length, root N uptake, root biomass, and hot water-extractable root N) did not influence soil protease activities. We showed that pea crop residues, acting as substrates, are the main drivers of soil protease activities. However, our results highlight the importance of considering fine roots to understand the effects of plants on soil microbial activities implicated in N mineralization.

Burying Your Head in the Sand: Heading Belowground to Find Future Targets of Selection in Roots.

Burying one’s head in the sand is usually synonymous with avoiding an issue, but in this volume of Plant Physiology , [Colombi et al. (2019)][1] delve belowground to tackle an important topic in the ongoing quest to improve crop productivity. The authors investigate root traits in wheat ( Triticum

Juvenile Root Traits Show Limited Correlation with Grain Yield, Yield Components and Grain Mineral Composition Traits in Indian Wheat under Hostile Soils

Correlations between juvenile wheat root traits, and grain yield and yield component traits under optimal field conditions have previously been reported in some conditions. The aim of this study was to test the hypothesis that juvenile wheat root traits correlate with yield, yield components and grain mineral composition traits under a range of soil environments in India. A diverse panel of 36 Indian wheat genotypes were grown for ten days in ‘pouch and wick’ high-throughput phenotyping (HTP) system (20 replicates). Correlations between juvenile root architecture traits, including primary and lateral root length, and grain yield, yield components and grain mineral composition traits were determined, using field data from previously published experiments at six sites in India. Only a limited number of juvenile root traits correlated with grain yield (GYD), yield components, and grain mineral composition traits. A narrow root angle, potentially representing a ‘steep’ phenotype, was associated with increased GYD and harvest index (HI) averaged across sites and years. Length related root traits were not correlated with GYD or HI at most sites, however, the total length of lateral roots and lateral root number correlated with GYD at a sodic site of pH 9.5. The total length of lateral roots (TLLR) correlated with grain zinc (Zn) concentration at one site. A wider root angle, representing a shallow root system, correlated with grain iron (Fe) concentration at most sites. The total length of all roots (TLAR) and total length of primary roots (TLPR) correlated with grain S concentration at most sites. Narrow root angle in juvenile plants could be a useful proxy trait for screening germplasm for improved grain yield. Lateral root and shallow root traits could potentially be used to improve grain mineral concentrations. The use of juvenile root traits should be explored further in wheat breeding for diverse environments.

Characterization of QTLs for Root Traits of Wheat Grown under Different Nitrogen and Phosphorus Supply Levels.

Root is important in acquiring nutrients from soils. Developing marker-assisted selection for wheat root traits can help wheat breeders to select roots desirable for efficient acquisition of nutrients. A recombinant inbred line (RIL) population derived from wheat varieties Xiaoyan 54 and Jing 411 was used to detect QTLs for maximum root length and root dry weight (RDW) under control, low nitrogen and low phosphorus conditions in hydrophobic culture (HC). We totally detected 17 QTLs for the investigated root traits located at 13 loci on 11 chromosomes. These loci differentially expressed under different nutrient supplying levels. The RILs simultaneously harboring positive alleles or negative alleles of the most significant three QTLs for RDW, qRDW.CK-2A, qRDW.CK-2D, and qRDW.CK-3B, were selected for soil column culture (SC) trial to verify the effects of these QTLs under soil conditions. The RILs pyramiding the positive alleles not only had significantly higher shoot dry weight, RDW, nitrogen and phosphorus uptake in all the three treatments of the HC trial, but also had significantly higher RDW distribution in both the top- and sub-soils in the SC trial than those pyramiding the negative alleles. These results suggested that QTL analysis based on hydroponic culture can provide useful information for molecular design of wheat with large and deep root system.

A strong root-specific expression system for stable transgene expression in bread wheat.

A strong, stable and root-specific expression system was developed from a rice root-specific GLYCINE - RICH PROTEIN 7 promoter for use as an enabling technology for genetic manipulation of wheat root traits. Root systems play an important role in wheat productivity. Genetic manipulation of wheat root traits often requires a root-specific or root-predominant expression system as an essential enabling technology. In this study, we investigated promoters from rice root-specific or root-predominant expressed genes for development of a root expression system in bread wheat. Transient expression analysis using a GREEN FLUORESCENT PROTEIN (GFP) reporter gene driven by rice promoters identified six promoters that were strongly expressed in wheat roots. Extensive organ specificity analysis of three rice promoters in transgenic wheat revealed that the promoter of rice GLYCINE-RICH PROTEIN 7 (OsGRP7) gene conferred a root-specific expression pattern in wheat. Strong GFP fluorescence in the seminal and branch roots of wheat expressing GFP reporter driven by the OsGRP7 promoter was detected in epidermal, cortical and endodermal cells in mature parts of the root. The GFP reporter driven by the promoter of rice METALLOTHIONEIN-LIKE PROTEIN 1 (OsMTL1) gene was mainly expressed in the roots with essentially no expression in the leaf, stem or seed. However, it was also expressed in floral organs including glume, lemma, palea and awn. In contrast, strong expression of rice RCg2 promoter-driven GFP was found in many tissues. The GFP expression driven by these three rice promoters was stable in transgenic wheat plants through three generations (T1-T3) examined. These data suggest that the OsGRP7 promoter can provide a strong, stable and root-specific expression system for use as an enabling technology for genetic manipulation of wheat root traits.

Phenotyping pipeline reveals major seedling root growth QTL in hexaploid wheat.

Seedling root traits of wheat (Triticum aestivum L.) have been shown to be important for efficient establishment and linked to mature plant traits such as height and yield. A root phenotyping pipeline, consisting of a germination paper-based screen combined with image segmentation and analysis software, was developed and used to characterize seedling traits in 94 doubled haploid progeny derived from a cross between the winter wheat cultivars Rialto and Savannah. Field experiments were conducted to measure mature plant height, grain yield, and nitrogen (N) uptake in three sites over 2 years. In total, 29 quantitative trait loci (QTLs) for seedling root traits were identified. Two QTLs for grain yield and N uptake co-localize with root QTLs on chromosomes 2B and 7D, respectively. Of the 29 root QTLs identified, 11 were found to co-localize on 6D, with four of these achieving highly significant logarithm of odds scores (>20). These results suggest the presence of a major-effect gene regulating seedling root vigour/growth on chromosome 6D.

High-throughput phenotyping of seminal root traits in wheat.

BackgroundWater availability is a major limiting factor for wheat (Triticum aestivum L.) production in rain-fed agricultural systems worldwide. Root system architecture has important functional implications for the timing and extent of soil water extraction, yet selection for root architectural traits in breeding programs has been limited by a lack of suitable phenotyping methods. The aim of this research was to develop low-cost high-throughput phenotyping methods to facilitate selection for desirable root architectural traits. Here, we report two methods, one using clear pots and the other using growth pouches, to assess the angle and the number of seminal roots in wheat seedlings– two proxy traits associated with the root architecture of mature wheat plants.ResultsBoth methods revealed genetic variation for seminal root angle and number in the panel of 24 wheat cultivars. The clear pot method provided higher heritability and higher genetic correlations across experiments compared to the growth pouch method. In addition, the clear pot method was more efficient – requiring less time, space, and labour compared to the growth pouch method. Therefore the clear pot method was considered the most suitable for large-scale and high-throughput screening of seedling root characteristics in crop improvement programs.ConclusionsThe clear-pot method could be easily integrated in breeding programs targeting drought tolerance to rapidly enrich breeding populations with desirable alleles. For instance, selection for narrow root angle and high number of seminal roots could lead to deeper root systems with higher branching at depth. Such root characteristics are highly desirable in wheat to cope with anticipated future climate conditions, particularly where crops rely heavily on stored soil moisture at depth, including some Australian, Indian, South American, and African cropping regions.

Genetic analysis of root morphological traits in wheat.

Traits related to root architecture are of great importance for yield performance of crop species, although they remain poorly understood. The present study is aimed at identifying the genomic regions involved in the control of root morphological traits in durum wheat (Triticum durum Desf.). A set of 123 recombinant inbred lines derived from the durum wheat cross of cvs. 'Creso'×'Pedroso' were grown hydroponically to two growth stages, and were phenotypically evaluated for a number of root traits. In addition, meta-(M)QTL analysis was performed that considered the results of other root traits studies in wheat, to compare with the 'Creso'×'Pedroso' cross and to increase the QTL detection power. Eight quantitative trait loci (QTL) for traits related to root morphology were identified on chromosomes 1A, 1B, 2A, 3A, 6A and 6B in the 'Creso'×'Pedroso' segregating population. Twenty-two MQTL that comprised from two to six individual QTL that had widely varying confidence intervals were found on 14 chromosomes. The data from the present study provide a detailed analysis of the genetic basis of morphological root traits in wheat. This study of the 'Creso'×'Pedroso' durum-wheat population has revealed some QTL that had not been previously identified.