Genome-wide association for heat tolerance at seedling stage in historical spring wheat cultivars

Abstract

Increasing global temperature has adverse effects on crop health and productivity at both seedling and reproductivity stages. It is paramount to develop heat tolerant wheat cultivars able to sustain under high and fluctuating temperature conditions. An experiment was conducted to characterize 194 historical wheat cultivars of Pakistan under high temperature at seedling stage to identify loci associated with heat tolerance using genome-wide association studies (GWAS). A quantitative trait locus, TaHST1, on chr4A was also characterized to identify the haplotypes at this locus associated with heat tolerance in wheat from Pakistan. Initially, the diversity panel was planted under control conditions (25°C/20°C day and night temperature) in a glass house. At three leaf stage, plants were subjected to heat stress (HS) by increasing temperature (40°C/35°C day and night), while one treatment was kept at control condition. After 7 days of HS, data were collected for seedling morphology. Heat stress reduced these traits by 25% (root weight) to 40% (shoot weight), and shoot biomass was largely affected by heat stress. A GWAS model, fixed and random model circulating probability unification (FarmCPU), identified 43 quantitative trait nucleotides (QTNs) on all chromosomes, except chr7B, were associated under both HS and control conditions. Thirteen QTNs were identified in control, while 30 QTNs were identified in HS condition. In total, 24 haplotypes were identified at TaHST1 locus, and most of the heat tolerant genotypes were assigned to Hap-20 and Hap-21. Eleven QTNs were identified within 0.3–3.1 Mb proximity of heat shock protein (HSP). Conclusively, this study provided a detailed genetic framework of heat tolerance in wheat at the seedling stage and identify potential genetic regions associated with heat tolerance which can be used for marker assisted selection (MAS) in breeding for heat stress tolerance.

Genome-wide association study for seedling heat tolerance under two temperature conditions in bread wheat (Triticum aestivum L.)

“…QHST3 on Chr1D was found to associated with traits such as TRL-HS, MRL-HS, HSI-TRL, and HSI-MRL, which was also identified in previous research (Table 3 ) [ 1 ]. Two QTLs, QSRHS.nri-2 A and QSLHR.nri-7D , previously found at the seedling stage [ 36 ], were also detected in this study shown as QHST4 and QHST5 (Table 3 ).…”

“…The heat susceptible index (HSI) is widely used to evaluate HST for wheat [ 1 , 37 ]. The wheat varieties were considered to be high heat-resistance materials if HSI were less than 0.5 [ 1 ].…”

“…The heat susceptible index (HSI) is widely used to evaluate HST for wheat [ 1 , 37 ]. The wheat varieties were considered to be high heat-resistance materials if HSI were less than 0.5 [ 1 ]. Due to the strong relationship between HSI of seedling root length and heat tolerance at the adult stage [ 37 ], HSI of MRL (HSI-MRL) and TRL (HSI-TRL) were used as standards to identify HST varieties.…”

“…Bread wheat ( Triticum aestivum L.) is the most widely cultivated cereal crop and serves as a staple food for over 35% of the global population [ 1 , 2 ]. The ideal temperature range for wheat growth is around 22/14℃ (day/night) [ 3 ].…”

Co‐expression network analysis of diverse wheat landraces reveals markers of early thermotolerance and a candidate master regulator of thermotolerance genes

“…The present work is also distinct from much of the above published works, as it concerns heat stress exposure and thermotolerance at an early developmental stage. The study of the genetic governance of wheat seedling thermotolerance is fairly limited, with only a handful of published works identifying key genes or genomic regions associated with the trait (Abd El‐Daim et al., 2014 ; Khan et al., 2022 ; Khatun et al., 2018 ). Much of the study on the effect of heat stress on wheat concerns its effect at, or around, anthesis and grain filling, and its subsequent effect on yield, as these are the developmental stages when heat stress commonly occurs in some major wheat producing countries (Stone & Nicolas, 1994 , 1995 , 1996 ).…”