Field Screening for Drought Tolerance in Cotton

Drought is frequently encountered in cotton production across the Cotton Belt and causes significant yield loss in many states. Drought stress reduces photosynthesis and plant growth and prolonged field drought causes leaf desiccation, yellowing and wilting, and fruit abscission, leading to reduced fiber yield and quality. Currently, there are no commercial cotton cultivars developed for drought tolerance. The objectives of the present study were to evaluate cotton cultivars and breeding lines for drought tolerance under delayed field irrigation conditions; and (2) to evaluate the possibility of using a leaf chlorophyll SPAD meter for a quick and quantitative determination of field drought tolerance. Among 83 commercial cultivars from major seed companies and advanced breeding lines from most of the public cotton breeding programs, several cultivars and breeding lines exhibited some levels of drought tolerance with high drought tolerance index (DTI). A number of breeding lines developed from interspecific hybrids between Upland and Pima cotton at New Mexico State University displayed good drought tolerance, one of which did not show any drought stress in leaf morphology and plant growth under severe field water deficit conditions. DTI had moderate to high heritability and was significantly correlated with SPAD chlorophyll readings in one test but not in another, indicating a need for further studies.