Durum Wheat Heat Tolerance Loci Defined via a North-South Gradient

Abstract

The global production of durum wheat (Triticum durumDesf.) is hindered by a constant rise in the frequency of severe heat stress. Three different germplasm panels were investigated under a range of heat stress to identify tolerant germplasm. The ‘discovery panel’ was field tested in the south of Morocco and along the Senegal River implementing a mild-to-strong North-South heat stress gradient. A subset of this same panel was also exposed to simulated terminal heat stress by applying plastic tunnels at the time of flowering. The ‘investigation panel’ and a ‘validation panel’ were field tested along the Senegal River under >32°C temperature throughout the season. Grain yield and its components were recorded at each site and a heat stress susceptibility index (HSI) was calculated. A total of 7,652 polymorphic single nucleotide polymorphisms (SNPs) defined the diversity of the first panel, while 5,642 SNPs defined the ‘investigation panel’. Genome-wide association study revealed that 36 quantitative trat loci were associated with the target traits in the ‘discovery’ panel, of which five were confirmed in the ‘subset’ tested with plastic tunnels and in the ‘investigation panel’. A haplotype study confirmed that Q.icd.Heat.003-1A, Q.icd.Heat.007-1B and Q.icd.Heat.016-3B are additive in nature and carrying the positive alleles at all three loci resulted in a 17% higher grain yield under heat stress. The underlying SNPs were converted into Kompetitive Allele Specific PCR (KASP) markers and tested on the ‘validation’ panel, confirming that each explained 4 to 9% of the phenotypic variation for grain yield under heat stress.

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

“…Genetic analysis of heat tolerance in wheat is a hot topic in recent years, and many studies have been performed for heat stress tolerance at flowering and reproductive stages [65][66][67][68][69][70][71]. However, there is limited empirical studies focusing on HST at the seedling stage in wheat [1,36,72,73].…”

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“…Temperature-related variables that affected yield under HS were generally those calculated based on temperatures at grain fill (post anthesis), confirming what has been observed in several small-grains species, that some of the most important yield-limiting effects of heat on the present durum panel were related to high temperatures from flowering through grain filling stages, which affects several reproductive and/or physiological processes (Cossani and Reynolds, 2012;Fabian et al, 2019), or grain metabolic pathways (Wahid et al, 2007;Farooq et al, 2011;Gautam et al, 2014;Sharma et al, 2017). However, HS prior to anthesis and grain fill is also critically detrimental, affecting final yield consequent to a reduced source capacity and/or biomass available to support grain filling, particularly in its final stages (Xu et al, 2022;Barratt et al, 2024;Sall et al, 2024). In the current study, a substantial reduction was observed in biomass accumulated up to shortly after anthesis (NDVI), averaging 52%, second only to the effect on final GY.…”

“…The study of structural models, and in particular of GSEM, lays a foundation for the next steps in elucidating the physiological response to heat by mapping QTLs controlling the trait (Igolkina et al, 2020) and to implement either marker-assisted selection, if large effects QTLs are identified, or genomic prediction tailored to heat tolerance improvement of durum wheat . Most importantly, we believe that meaningful tools to link genetic knowledge and environmental specificity, such as those employed in the present study, can be part of the most needed translational research aimed at actually improving crop cultivars (Kole et al, 2015;Millet et al, 2019;Reynolds et al, 2021;Welcker et al, 2022;Della Coletta et al, 2023;Sall et al, 2024).…”