Genetic variation among cotton germplasm for water-use efficiency

Abstract

Cotton ( Gossypium spp.) genotypes including three species, five modern cultivars, one strain and 18 primitive race stocks were grown in two greenhouse experiments to determine differences in water-use efficiency (WUE). Water-use efficiency was defined as “the weight of total biomass (shoot and root) produced per unit of water transpired”. Plastic containers were filled with air-dried soil, and water was added until the soil reached field capacity. Plants were then grown (with further watering) until reaching the permanent wilting point. Data on plant biomass (shoot and root), water use, and days to permanent wilting were then collected. Differences occurred between the two experiments in water used prior to permanent wilting. No significant differences between genotypes were observed in the amount of water used, but differences did occur in biomass production and days to permanent wilting. Genotypes did not interact with environments for water used, biomass produced, or WUE. Differences did occur among genotypes between experiments for WUE. Genotypic means showed a 28% range in WUE between the highest vs the lowest entries and a 14% improvement above the best cultivar. G. herbaceum L. and G. barbadense L. fell within the distribution range for G. hirsutum L. Primitive race stocks of G. hirsutum were more efficient as a group in water use than were modern cultivars of the species.