Drought resilience in CIMMYT maize lines adapted to Africa resulting from transpiration sensitivity to vapor pressure deficit and soil drying

Low rainfall limits crop yield, particularly for maize (Zea mays L.) in southern Africa. Consequently, there is a need to identify genetic sources of specific drought-related traits that can contribute to soil water conservation and increased yields under water-limited conditions. In this study, maize genotypes released for production in southern Africa were tested for expression of two soil water-conservation traits: limited transpiration under elevated vapor pressure deficit (VPD) and decreased transpiration rate at high soil water contents earlier in the soil drying cycle. Two genotypes, CML 590 and CML 593, were identified and confirmed to initiate expression of limited-transpiration rate at VPD above about 1.9 kPa. In the soil-drying experiment, Umbelu 8923 and Umbelu 8930 closed their stomata earliest in the soil drying cycle as compared to other tested genotypes. These four genotypes with specific physiological traits for superior response to water deficit are genetic resources for further study to improve maize drought resilience.