Genotypic differences in plant growth, osmotic and antioxidative defence of Cajanus cajan (L.) Millsp. modulated by salt stress

Abstract

Two pigeonpea genotypes – PUSA2002-2 (salt tolerant) and RG-01-73N (salt sensitive) – were recognized after analyzing the salt tolerance index (STI) of nine genotypes (PUSA2002-2, HPM-1, RC01-69N, PUSA2001-7, PUSA2002-1, AK2000-3N3, AL1455, RG01-73N and PUSA2004-1) grown in the greenhouse under saline environment. The effects of salinity on plant biomass, membrane stability index (MSI), thiobarbituric acid reactive substances, osmolyte accumulation, antioxidant enzyme activities were studied. Genotype PUSA2002-2 showed smallest declines and RG01-73N exhibited maximum decline in plant biomass. Salinity led to lipid peroxidation (TBARS) in the leaves as well as in roots which resulted in significant reductions in the membrane stability index (MSI) and ionic imbalance (K+/Na+, Ca2+/Na+ ratios) of all genotypes. The accumulation of organic solutes such as proline, glycine betaine, total free amino acids, proteins and soluble sugars induced under salt stress and the level of these osmolytes were correlated with the degree of tolerance of the genotype to stress. The activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APOX) and glutathione reductase (GR) increased in all the genotypes. The results indicated that pigeonpea genotypes tolerant of salt stress (PUSA2002-2, HPM-1, RC01-69N, PUSA2001-7 and PUSA2002-1) had better growth and supported higher levels of MSI, ionic ratios, osmoprotectants and antioxidant enzyme activities as compared to RG01-73N, AK2000-3N3, AL1455 and PUSA2004-1.