Genetic and phenotypic associations between peduncle characteristics and spike productivity in wheat under drought and normal conditions

The peduncle stem plays an essential role in resource allocation and water transport to spike grains under normal conditions. Therefore, exploring peduncle traits and their relationships with spike production under drought stress may provide insights into the mechanisms that mitigate the effects of drought stress on grain yield in wheat. To address this challenge, a panel of 198 highly homozygous and diverse spring wheat varieties was evaluated under normal and drought conditions across two growing seasons. Peduncle traits, namely, length (PL), diameter (PD), and weight (PW), as well as spike traits, namely, spike length (SPL), number of spikelets/spike (NSPS), grain number/spike (GNPS), and grain yield per spike (GYPS), and thousand-kernel weight (TKW), were assessed. We revealed that PW and PD, unlike PL, were significantly and strongly associated with spike traits and grain weight under both conditions. Genome-wide association study (GWAS) revealed that spike and peduncle traits were controlled by different genetic mechanisms, as no stable markers were shared between these two groups. Distinct SNPs found between genotypes with contrasting peduncle traits led to the identification of a key SNP marker in a gene model encoding a protein highly expressed in the peduncle and spike of wheat. Comparing cultivars with low peduncle trait values to cultivars with high peduncle trait values, particularly PW and PD, high peduncle trait cultivars had greater yield-related trait values under both drought and normal conditions. The results of this study shed light on the importance of peduncle traits in enhancing wheat spike productivity under normal and drought stress conditions.