Identification of quantitative trait loci and candidate genes underlying kernel traits of wheat (Triticum aestivum L.) in response to drought stress.

Fourteen environmentally stable QTLs for kernel traits were identified and shown to interact significantly with drought-stressed environments. Initial investigation of candidate genes from ten QTL clusters was undertaken, including a KASP marker for TaCYP71E1-A1 on chromosome 5A. Kernel traits, as critical yield components in wheat (Triticum aestivum L.), are governed by quantitative inheritance and are influenced by drought. The identification of quantitative trait loci (QTL) underlying wheat kernel traits in response to drought stress will help enhance breeding for dryland wheat yield. In this study, a hexaploid wheat population of 160 F recombinant inbred lines (RILs) derived from a cross between 'GW011' and 'Jinmai47' and genotyped using the Wheat 90 K Infinium Single Nucleotide Polymorphism (SNP) array were employed to identify QTLs for six kernel traits under drought-stressed and well-watered conditions across six environments. A total of 85 additive QTLs, including 16 for thousand-kernel weight (TKW), 14 for kernel length (KL), 16 for kernel width (KW), 11 for kernel thickness (KT), 18 for kernel size (KS), and 10 for kernel diameter ratio (KDR), were identified with significant additive and QTL × water environmental interaction (QEI) effects. Among them, 14 QTLs were identified as environmentally stable (being identified in five or more test environments), where 12 stable loci were further refined into ten QTL clusters on chromosomes 1B, 2B, 5A, 5B, 5D, 6D, 7A and 7D. A total of 3738 genes were extracted from the confidence intervals of these QTL clusters. A candidate gene, TraesCS5A02G288000 (TaCYP71E1-A1) involved in the cytochrome P450 pathway, was identified within the C3 QTL cluster interval which is associated with KL and KS on chromosome 5A. A Kompetitive Allele Specific PCR (KASP) marker for TaCYP71E1-A1 was developed and validated across 220 wheat varieties. These results provide insight into the genetic basis underlying kernel traits in response to drought stress and will facilitate the genetic improvement of dryland wheat productivity.