Genome wide association mapping for stem water soluble carbohydrates in bread wheat (Triticum aestivum L.) under terminal water stress
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Date
2020-11-26
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CCSHAU, Hisar
Abstract
Genomic assisted breeding is one way to improve drought stress tolerance in wheat. To uncover the genomic regions for grain yield, its attributing traits, water soluble carbohydrates (WSCs) and its components mainly fructans, a comprehensive multidisciplinary study was conducted with a diverse set of 302 bread wheat genotypes. All the genotypes were evaluated under complete irrigation, rainfed and complete water stressed condition for two consecutive crop seasons at three locations (Hisar, Karnal and Baramati). The study indicated significant effect of different water regimes and locations on the expression of traits and as much as 80% of yield reduction was reported under DT. Seven promising drought tolerant verities were identified on the basis of drought susceptibility index. In this study, correlation between yield and studied traits largely varied with environmental and water conditions. However, shorter plant height, longer grain filling duration, days to heading, thousand kernel weight (35-40 g) is the most favorable trait combination for obtaining high grain yield under studied conditions. Positive correlation of WSCs with grain yield was reported only for drought tolerant genotypes. High values of all the genetic components were reported for all the traits within environments, however in pooled over management these values ranged between low to moderate for most of the studied traits due to genotype x environment. Traits like plant height, peduncle length, spikelet per spike and thousand kernel weight were least influenced with genotype x environment interaction thus found suitable for selection of grain yield. Substantial genetic diversity was reported in the studied material which was attributed by each of the studied trait equally. With 35K Axiom array and applying compressed mixed linear model, 431 stable SNPs were identified for 20 studied traits in 1288986.92 cM genomic region of bread wheat. These SNPs explained ca. 30-53% of phenotypic variations. Of 431 stable SNPs 77 were showing pleiotropy for various traits. Five SNPs (AX-94583229, AX-94879209, AX-94759517, AX-94887053 and AX-94964616) for fructans and total non-structural carbohydrates, three (AX-94508292, AX-95257620 and AX-94456473) for days to heading and one (AX-94412521) for plant height were most significant. In functional analysis of significant SNPs, 249 genes were identified which were mainly involved in carbohydrate metabolism and repair mechanism. Only few were reported with direct involvement in stress responses. In an in silco study 104 genes (TaFruc) transcribing into stable protein associated with fructans metabolism were identified. All of these were involved in either hydrolase or transferase activities of glycosyl groups of soluble sugars. These genes were found expressive under different stress conditions, mainly water stress. To facilitate the future breeding programs a total of 189 SSR molecular markers and 60 micro RNAs have been predicted successfully for TaFruc genes.