Genetic and Phenotypic Associations between Peduncle Characteristics and Spike Productivity in Wheat Under Drought and Normal Conditions

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 (PUL), diameter (PUD), and weight (PUW), as well as spike traits (spike length, number of spikelets/spike, grain number/spike, and grain yield per spike, and thousand kernel weight), were assessed. We revealed that PUW and PUD, unlike PUL, were significantly and strongly associated with spike traits and grain weight under all conditions. GWAS revealed that spike and peduncle traits were controlled by different genetic mechanisms, as no stable markers were shared between these two groups. The identification of distinct SNPs between genotypes with two contrasting peduncle traits revealed a key SNP marker located within a gene model that encodes a protein highly expressed in the peduncle and spike traits of wheat. Comparing cultivars with low peduncle trait values to cultivars with high peduncle trait values, particularly PUW and PUD, high peduncle trait cultivars had greater yield-related trait values under both drought and normal conditions. This study proposes to investigate the distinct SNPs between the selected genotypes, with contrasting target traits, to address the limitations of GWASs in detecting important marker-trait associations.