Unravelling the genetic basis of terminal heat tolerance and yield related traits in bread wheat (Triticum aestivum L.)

Terminal heat stress is a critical abiotic stress in arid and semi-arid regions, causing substantial reductions in wheat productivity. Quantitative trait loci identification can aid marker-assisted selection in terminal heat tolerance wheat breeding by determining complex grain yield and its component traits. The present study reports the genetic dissection and QTL mapping for yield attributes and morpho-physiological traits using 200 recombinant inbred lines population, derived from WH711 (heat sensitive)/WH1021 (heat tolerant) grown under timely sown and late sown conditions during rabi 2018-19. Phenotyping was performed over 31 parameters, including morphological, physiological and yield attributes. Under heat stress conditions, a significant reduction was recorded in grain yield per plot and its component traits, viz. biological yield per plot, number of effective tillers per meter and gaseous parameters (photosynthetic rate, stomatal conductance and water use efficiency), whereas a reverse trend was observed in canopy temperature depression at anthesis and 15 days after anthesis stage based on total antioxidant activity and malondialdehyde content. Genetic diversity was assessed with the help of cluster analysis using 24 SSR markers data and 2-D and 3-D. PCA scaling broadly categorized the whole RIL population into two groups i.e., heat tolerant and heat susceptible. Seven novel QTLs were identified through composite interval mapping on chromosomes 1B, 3B, and 7A, associated with two key yield attributes, two morphological traits, and a physiological trait under terminal heat stress conditions. The SSR marker Xwmc 596 was found to be linked with grain yield per plot, biological yield per plot and NDVI, that can be utilized as a good source of gene deployment and enhancement of heat tolerance in future breeding.