Abstract
Key messageThe response of a large panel of European elite wheat varieties to post-anthesis heat stress is influenced by 17 QTL linked to grain weight or the stay-green phenotype.Heat stress is a critical abiotic stress for winter bread wheat (Triticum aestivum L.) especially at the flowering and grain filling stages, limiting its growth and productivity in Europe and elsewhere. The breeding of new high-yield and stress-tolerant wheat varieties requires improved understanding of the physiological and genetic bases of heat tolerance. To identify genomic areas associated with plant and grain characteristics under heat stress, a panel of elite European wheat varieties (N = 199) was evaluated under controlled conditions in 2016 and 2017. A split-plot design was used to test the effects of high temperature for ten days after flowering. Flowering time, leaf chlorophyll content, the number of productive spikes, grain number, grain weight and grain size were measured, and the senescence process was modeled. Using genotyping data from a 280 K SNP chip, a genome-wide association study was carried out to test the main effect of each SNP and the effect of SNP × treatment interaction. Genotype × treatment interactions were mainly observed for grain traits measured on the main shoots and tillers. We identified 10 QTLs associated with the main effect of at least one trait and seven QTLs associated with the response to post-anthesis heat stress. Of these, two main QTLs associated with the heat tolerance of thousand-kernel weight were identified on chromosomes 4B and 6B. These QTLs will be useful for breeders to improve grain yield in environments where terminal heat stress is likely to occur.
Highlights
As one of the most important crops in the world, wheat (Triticum aestivum L.) has seen a steady growth in yields since the late 1960s in many areas (Calderini and Slafer 1998)
Vapor pressure deficit (VPD) was calculated from the temperature and relative humidity measurements and though slightly higher in 2016 than in 2017, in both years of the experiment there was a clear difference in VPD between S and NS conditions
The second data cleaning step were found to be essential to ensure the shape of the curves corresponded to a normal biological process, for example, the total chlorophyll content at the end of senescence could have been estimated at around 40 μg cm−3 or −10 μg cm−3, which does not reflect the real distribution for this trait
Summary
As one of the most important crops in the world, wheat (Triticum aestivum L.) has seen a steady growth in yields since the late 1960s in many areas (Calderini and Slafer 1998). A reversal of this trend has been observed in several countries over the last two decades (e.g., PeltonenSainio et al 2009; Brisson et al 2010; Rife et al 2019). Lower yields in France have mainly been explained by climate variability causing drought stress during booting and high temperatures during grain filling (Brisson et al 2010). It has been estimated on a world scale that climatic variations such as precipitation and heat stress may have led to a 5.5% reduction in grain yield since 1980, which corresponds to a loss of 35 M tonnes, equivalent to the annual wheat harvest of a country like France (Lobell et al 2011).
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