Abstract
Genome-wide association study (GWAS) was performed for stomata- and yield-related attributes with high-density Illumina 90 K Infinium SNP (single nucleotide polymorphism) array in bread wheat to determine genetic potential of germplasm for scarce water resources with sustainable yield potential. Major yield and stomata attributes were phenotyped on a panel of Pakistani and foreign accessions grown in non-stressed and water shortage environments during two seasons. Highly significant variations were shown among accessions in both conditions for examined characteristics. Water shortage conditions reduced the overall wheat yield and strong positive correlation existed among stomatal frequency, leaf venation and grain yield per plant. Population structure analyses based on 90,000 SNP data classified the accessions into four sub-populations which indicated the presence of genetic variability. Marker-trait association (MTA) analyses revealed that 422 significant SNPs at p ≤ 10−3, after crossing the false discovery rate (FDR) <0.05 threshold, were linked with examined attributes. Pleiotropic loci (wsnp_Ex_c8913_14881924 and Tdurum_contig10598_304) were associated with flag leaf area (FLA), stomata size (SS), stomata frequency (SF), leaf venation (LV), number of grain per spike (NGS) and grain yield per plant (GYP), which were located on chromosome 4B and 6B at the positions 173.63cM and 229.64cM, respectively, under water shortage conditions. Pleotropic loci wsnp_Ex_c24167_33416760, wsnp_Ex_c5412_9564046 and Tdurum_contig81797_369 on chromosomes 7A, 2A and 4B at the positions 148.26cM, 261.05cM and 173.63cM, respectively, were significantly linked with stomata and yield indices such as FLA, SS, SF, LV, NGS and GYP under normal and water shortage conditions. The current experiment not only validated several MTAs for studied indices reported in other studies but also discovered novel MTAs significant under water shortage environments. Associated and significant SNPs will be useful in discovering novel genes underpinning water shortage tolerance in bread wheat for producing high-yielding and drought tolerant wheat varieties to fulfill the wheat demand for growing populations.
Highlights
Bread wheat (Triticum aestivum L.) is one of the earliest cereals ever domesticated and is currently one of the major sources of food and feed in the world
A panel of 96 Pakistani and foreign bread wheat accessions preserved at the department of Plant Breeding and Genetics (PBG), Faculty of Agriculture and Environment, The Islamia University of Bahawalpur, Pakistan was used in this study
For grain yield per plant (GYP), 31 markers were highly associated in non-stressed conditions which were found at chromosomes 1A, 1B, 2A, 2B, 2D, 3B, 3D, 4B, 5A, 5B, 6B, 7A, 7B and 7D (Figure 6A)
Summary
Bread wheat (Triticum aestivum L.) is one of the earliest cereals ever domesticated and is currently one of the major sources of food and feed in the world. The mechanisms of drought tolerance are very complicated, enhancing drought tolerance selection for productivity must be utilized together with all the unidentified factors that are necessary for the increasing drought tolerance [13] Approaches to decrease this gap include the advancement of genetics for water shortage environments by recognizing causes of water shortage tolerance and subsequent introgression of genes for associated specific characteristics to domesticated wheat genotypes. Stomatal size and number of stomata contribute to adequate water consumption, these traits can be selected for when developing normal and drought resistant wheat varieties Producing maximum yield and water shortage tolerant genotypes has been a slow process, since yield and water shortage tolerance-related genes are complex and polygenic in nature. Favorable alleles controlling grain yield and drought-related traits were of vital importance, and incorporation of these alleles after validation through marker assisted selection and fine mapping could be helpful in wheat yield improvement under stress and non-stress conditions
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