Selection of Salt Tolerant Cowpea Genotypes Based on Salt Tolerant Indices of Morpho-biochemical Traits

Soil salinity is one of the abiotic factors affecting crop production worldwide. Introducing salt tolerant genotypes is considered as an economical strategy for increasing the production of agricultural crops in salt affected soils. In this study, morphological and biochemical changes of twenty three cowpea genotypes from India were evaluated for salt tolerance using seven days old seedlings treated with 0 and 75mM sodium chloride solutions. Chlorophyll, sugar, proline, soluble protein, sodium (Na⁺), potassium (K⁺), K⁺/Na⁺ ratio, shoot length, root length and fresh weight were determined and all observations were converted to salt tolerance indices (STI). Chlorophyll content, K⁺/Na⁺ ratio, and growth parameters decreased on exposure to salt stress; whereas sugar, proline and soluble protein contents increased. To improve the selection efficiency of salt tolerant genotypes, STI values of all parameters were subjected to hierarchical clustering and the 23 genotypes were grouped into three clusters. Nine salt tolerant genotypes (KBC2, IVT-VCP-09-013, VBN1, VBN2, CO(CP)7, VCP-09-001, DC15, PGCP5 and VCP-09-030) were identified by hierarchical clustering. Correlation studies showed that soluble protein content and K⁺/Na⁺ ratio positively correlated with all the growth parameters indicating their major contribution towards salt tolerance.