Comparative study of common bean (Phaseolus vulgaris L.) and mungbean (Vigna radiata (L.) Wilczek) response to seven watering regimes in a controlled environment

Legume crops are often grown in drought-prone areas, and subjected to water stress. Greater understanding of drought tolerance in legumes and the use of physiological traits in breeding programs would likely provide high returns. An experiment was conducted comparing the response of two legume crops, common bean (Phaseolus vulgaris L.) and mungbean (Vigna radiata (L.) Wilczek), to seven watering regimes, in order to identify traits and timing of observations that are inexpensive and relatively easy to phenotype. Gas exchange measurements were conducted before and after selected waterings, and plants were harvested at flowering for the determination of leaf area, biomass, relative water content, and water potential. Results demonstrated that mungbean exhibited a conservative use of water through lower leaf area and a limit to maximum transpiration under non-limiting soil moisture conditions, as well as a greater partitioning of biomass into stems rather than leaves. Mungbean also maintained higher photosynthesis than common bean in low soil moisture conditions, and maintained higher relative water content than common bean. We suggest investigations into stem water-soluble carbohydrates would be worthwhile.