Recessive Winter Growth Habit Allele on 5B Chromosome, vrn-B1, Improves Earliness and Grain Yield of Bread Wheat

Drought escape is an important wheat mechanism that triggers rapid growth development to complete the life cycle before drought occurrence. Earliness could reduce the risk of dehydration during heading date to physiological maturity. Three gene groups including vernalization (Vrn), photoperiod (Ppd), and earliness per se (Eps) control heading time in bread wheat. In the present research, isogenic lines for Vrn-B1 and Vrn-D1 were developed to assess the precise effect of Vrn genes on days to heading, grain yield, and important agronomic traits under well-watered and rain-fed conditions. It was assumed that spring habit alleles improve earliness in bread wheat. Here we showed for the first time that a winter growth habit allele on the B genome, vrn-B1, reduced days to heading by 5.47 days. The mentioned allele, significantly increased grain yield under well-watered conditions by 0.36 t/ha. Spring growth habit allele of the D genome, Vrn-D1a, decreased days to heading by 4.89 days and significantly improved grain yield under both well-watered and rain-fed conditions. This allele improved grain yield by 0.88 t/ha and 0.14 t/ha under well-watered and rain-fed conditions, respectively. The combination of vrn-B1 and Vrn-D1a decreased days to heading by 9.87 days and significantly increased grain yield by 1.24 and 0.15 t/ha under well-watered and rain-fed conditions, respectively.