Photosynthetic and yield traits identified through multivariate analysis in mungbean exhibiting tolerance to the combined stresses of low phosphorus and drought

Experiments were conducted to study the genotypic variability for tolerance to combined stresses of low availability of phosphorus (P) and drought in 14 mungbean [Vigna radiata (L.) R. Wilczek] accessions. The accessions were evaluated under four conditions viz., control (sufficient P, irrigated), low P (without P, irrigated), drought (sufficient P, withholding irrigation) and combined stresses (low P, withholding irrigation). The relative stress tolerance was estimated for 22 agro-physiological traits. The principal component analysis (PCA) and relative stress indices (RSIs) of traits exhibited significant variation among the treatments and accessions. Based on RSIs, the PCA ranking analysis showed that the accessions IC 280489, PDM 139 and IC 76491 were highly ranked and tolerant to low P, drought and combined stresses. The relative increase in component traits such as photosynthetic parameters, relative water content, above-ground biomass, seed P content and number of pods plant⁻¹ were higher while canopy temperature and water use efficiency were reduced in tolerant accessions. In contrast, IPM 2-3 was found to be relatively sensitive to all three treatments. Tolerant accessions may be either included in the breeding program or used directly as cultivar that can be grown under low P and drought.