Physiological traits reveal potential for identification of drought tolerant mungbean [Vigna radiata (L.) Wilczek] genotypes under moderate soil-moisture deficit

Canopy temperature is an important physiological trait used for screening drought tolerance in several crop plants. Mungbean being often exposed to post-flowering drought, we evaluated a set of 48 genotypes for variability in post-flowering canopy temperature and its association with root traits and other physiological parameters contributing to drought tolerance under soil-moisture deficit stress conditions. Overall, canopy temperature depression revealed significant association with seed yield. Root traits like number of lateral branches and dry root weight exhibited significant negative correlation with canopy temperature. Leaf SPAD readings were positively associated with grain yield and most of the high SPAD genotypes maintained hot canopies under drought. Some genotypes with contrasting variation in SPAD levels (DMG-1050 and SML-1628) maintained their photosystem PSII health at par. Moreover, cool canopy was no guarantee for better PSII health or vice versa. This study identified some cool canopy genotypes (VC-6173-C, IC-325770 and ML-2082) and a genotype (DMG-1050) with novel trait combinations like high SPAD and better PSII health despite high canopy temperature which can be used as donors in mungbean breeding programs. Present study explores genetic variation in these adaptation traits contributing to plant performance under soil-moisture deficit stress conditions and potential of physiological breeding approaches for genetic enhancement of this legume crop.