Abstract
Key messageAssessing adaptation to abiotic stresses such as high temperature conditions across multiple environments presents opportunities for breeders to target selection for broad adaptation and specific adaptation.Adaptation of wheat to heat stress is an important component of adaptation in variable climates such as the cereal producing areas of Australia. However, in variable climates stress conditions may not be present in every season or are present to varying degrees, at different times during the season. Such conditions complicate plant breeders’ ability to select for adaptation to abiotic stress. This study presents a framework for the assessment of the genetic basis of adaptation to heat stress conditions with improved relevance to breeders’ selection objectives. The framework was applied here with the evaluation of 1225 doubled haploid lines from five populations across six environments (three environments selected for contrasting temperature stress conditions during anthesis and grain fill periods, over two consecutive seasons), using regionally best practice planting times to evaluate the role of heat stress conditions in genotype adaptation. Temperature co-variates were determined for each genotype, in each environment, for the anthesis and grain fill periods. Genome-wide QTL analysis identified performance QTL for stable effects across all environments, and QTL that illustrated responsiveness to heat stress conditions across the sampled environments. A total of 199 QTL were identified, including 60 performance QTL, and 139 responsiveness QTL. Of the identified QTL, 99 occurred independent of the 21 anthesis date QTL identified. Assessing adaptation to heat stress conditions as the combination of performance and responsiveness offers breeders opportunities to select for grain yield stability across a range of environments, as well as genotypes with higher relative yield in stress conditions.
Highlights
Many regions throughout the world experience heat, drought, and frost stress that limit crop production
QTL were spread across all chromosomes except for chromosome 3D, as shown in Fig. 1
Grain yield QTL were not identified in the RG population, TWT QTL were not identified in the Scout/ Gladius (SG) population, while screenings QTL were not identified in the MG and SM populations
Summary
Many regions throughout the world experience heat, drought, and frost stress that limit crop production. In the Mediterranean-type climates of southern Australia, heat stress conditions during the sensitive crop development stages of anthesis and early grain filling are common (Zheng et al 2012), often co-occurring with other abiotic stresses such as drought and high wind (Machado and Paulsen 2001; Shah and Paulsen 2003). Stress conditions, like those described, impact negatively on a range of developmental stages and physiological processes (Wahid et al 2007). Heat stress results in reduced pollen viability and reduced seed set when it occurs during anthesis (Dolferus et al 2011; Saini et al 1999). Stress during grain filling leads to reduced starch and protein accumulation (Bhullar and Jenner 1985; Zahedi et al 2004), accelerated plant development, premature leaf senescence, and reduced photosynthetic rate and capacity (Stone and Nicolas 1995; Tewolde et al 2006), which reduces grain size (Sharma et al 2008; Stone and Nicolas 1995; Talukder et al 2014a; Wardlaw 1994) and grain yield (Talukder et al 2014a; Tewolde et al 2006)
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