Chlorophyll Fluorescence to Evaluate Pigeonpea Breeding Lines and Mungbean for Drought Tolerance

Crops with increased biomass production and yield under suboptimal water availability are vital for sustainable production under abiotic stress. We identified drought tolerance in pigeonpea and mungbean cultivars by measuring chlorophyll florescence, an indicator to evaluate the efficiency of PSII photochemistry. Significant variation (p < 0.05) observed among cultivars and crops with high quantum yields (Fv/Fm) in Mungbean (Texas sprout) and Pigeonpea (W1, W3, G1) and were highly drought tolerant. Pigeonpea (Fv/Fm = 0.7933) and mungbean (Fv/Fm = 0.7993) were equally potential and significantly (p < 0.05) more tolerant to water stress (50% field capacity) during early vegetative growth stage compared to soybean (Fv/Fm = 0.7870). The quantum yields were high (0.79-0.81) during early growth stage indicating high water use efficiency and low (0.71, pigeonpea; 0.77, mungbean) during podding and flowering stages respectively indicating distribution of photosynthetic assimilates. Among all the growth stages evaluated, the podding and maturity stages were with less water use efficiency as indicated by relatively less values of Fv/Fm in both crops requiring relatively less amount of water compared to active vegetative growth stage. The cultivars with shortest plant height and tan seed coat were observed with drought tolerance in pigeonpea. Among the six food legumes studied for mean comparisons, the chickpea, pigeonpea and mungbean were highly tolerant followed by soybean, mothbean and tepary bean while fababean was less tolerant to drought stress.