Sucrose synthase activity and its association with phenological and yield-related traits under heat stress in wheat

Abstract

Rising temperatures associated with climate change pose a serious threat to wheat productivity, particularly through terminal heat stress during reproductive and grain-filling stages. Understanding the physiological and biochemical mechanisms underlying heat tolerance is therefore critical for sustaining yield stability. The present study evaluated the response of sucrose synthase (SuSy) activity and its association with phenological and yield traits under non-stress (timely sown) and heat-stress (late sown) conditions in a doubled haploid (DH) wheat population. A total of 23 DH lines representing extremes of maturity, along with their heat-tolerant and heat-susceptible parents, were evaluated over two thermal regimes using a randomized block design. Phenological traits, grain filling duration, thousand grain weight, grain yield, and SuSy activity at the soft dough stage were recorded. Heat stress significantly accelerated phenological development, shortened grain filling duration, and reduced grain yield and thousand grain weight, accompanied by an overall decline in SuSy activity. Substantial genotypic variation was observed for SuSy activity under both conditions. Several DH lines, notably DH 182, DH 154, DH 42, and DH 33, maintained higher SuSy activity under heat stress than the tolerant parent, indicating superior biochemical resilience. Correlation analysis revealed that under non-stress conditions, SuSy activity was positively associated with grain yield and thousand grain weight, whereas under heat stress, SuSy activity remained positively correlated with thousand grain weight but not with grain yield. These results highlight the importance of sucrose metabolism in sustaining grain filling under elevated temperatures and suggest that SuSy activity may serve as a useful biochemical indicator for selecting heat-tolerant wheat genotypes.