Mechanisms of the formation of acquired drought tolerance in wheat: insights from combining high-throughput phenotyping and genome-wide association study

Drought priming represents a potential strategy to bolster wheat yields in the face of recurring droughts, and there is a need to identify responsive cultivars and decipher the underlying mechanisms of priming. Here, the responses of 157 wheat cultivars to drought-priming were phenotyped using a high-throughput phenotyping (HTP) platform across two growing seasons, and a drought priming index (DPI) was devised to assess the priming sensitivity for each cultivar. A DPI comprehensive score (DPICS) was derived from 13 sensitive traits identified by principal component analysis, and significant variations in this score led to the classification of the cultivars into two distinct groups, one sensitive to drought priming and one not. The sensitive group contained 58 cultivars that had higher DPI values for traits including yield components, harvest index, post-anthesis assimilation, photochemical efficiency, canopy coverage, and normalized difference vegetation index, and lower DPI values for traits including remobilization of dry matter stored pre-anthesis, non-photochemical quenching, plant senescence reflectance index, and canopy temperature. A genome-wide association study (GWAS) based on the DPI identified 499 significant markers related to drought priming using a commercially Wheat660 SNP array. Notably, one marker situated on chromosome 5B consistently appeared in both the growing seasons that were studied. This marker resides within a 261.2 kb genomic block containing seven genes, including the candidate gene TraesCS5B03G1259700, which exhibited distinct transcriptional memory related to drought priming. Our results suggest that integrating HTP and GWAS has great potential for deciphering the genetic basis of acquired drought tolerance induced by priming and could facilitate the breeding of improved wheat varieties that can respond to recurring drought events.