Expression of stay‐green drought tolerance in dhurrin‐free sorghum

Abstract

AbstractSorghum (Sorghum bicolor (L) Moench) is naturally adapted to water‐limited environments. Dhurrin is a secondary metabolite that is proposed to play a key role in the expression of stay‐green drought tolerance of sorghum. In this study, a genetic mutation in CYP79A1, the first enzyme in the biosynthetic pathway of dhurrin, was used to study the role of dhurrin accumulation in stay‐green drought tolerance of sorghum. The cyp79a1 mutation inhibits the production of dhurrin. Near‐isogenic lines (NILs), near‐isogenic backcross (NIBC) populations, and near‐isogenic hybrids (NIHs) were evaluated for variation in stay‐green drought tolerance in controlled environments and field trials. Chlorophyll concentration (CC) and normalized difference vegetation index (NDVI) were measured to quantify variation in stay‐green among genotypes. Comparisons of NILs of Tx623 bmr6 and NIBC progeny from the stay‐green donor Tx642 indicated differences in CC and NDVI between plants in the drought and irrigated treatments but no significant differences between NILs and NIBC within treatments (p < 0.05). Analyses of NIHs in a controlled environment and field trials demonstrated similar patterns although there was one set of NIHs that exhibited variation in the field trials. The NIHs carrying the cyp79a1 mutation exhibited reduced CC in comparison to the wild‐type plants in the drought treatments (p < 0.05). These studies indicated that dhurrin production may contribute to the expression of stay‐green, but the effects are generally small and genotype specific.