Dissecting Salt-Induced growth and physiological responses in blackgram [Vigna mungo (L.) Hepper] via multivariate analysis

Salinity tolerance in blackgram is genotype- and growth stage-specific, and the crop is highly susceptible to salinity stress. Therefore, deciphering the tolerance mechanisms of available germplasm is crucial for breeding genotypes with multiple salinity tolerance traits. In this study, a fuzzy logic based comprehensive approach using membership function values (MFVs) was employed to integrate multiple traits involving morphology (root and shoot length and their fresh and dry weights), ion accumulation (sodium and potassium), physiology (SPAD, NDVI, chlorophyll fluorescence, electrolyte leakage, and relative water content), and biochemical parameters (superoxide dismutase, catalase, ascorbate peroxidase, malondialdehyde, chlorophyll, and proline) into a single comprehensive metric for evaluating salt tolerance and to identify promising genotypes. Salinity stress significantly reduced fresh and dry biomass, photosynthetic pigments and related traits, relative water content, and potassium levels, while increasing sodium accumulation, electrolyte leakage, antioxidant enzyme activity, and proline content. Salinity-sensitive genotypes exhibited increased root length and higher sodium ion accumulation across all plant parts. In contrast, tolerant genotypes showed greater photosynthetic efficiency, chlorophyll content, enzymatic activity, higher leaf biomass, and better ion homeostasis throughout the plant. On the basis of principal component analysis (PCA) and membership function values, tolerant (VBG 19010 and VBG 17007) and susceptible (VBG 13003 and ADT 3) genotypes were identified for further molecular dissection. These tolerant genotypes can be used to identify the possible genomic regions and metabolites responsible for salinity tolerance in black gram and serve as valuable resources for crop breeding programs.