Differential fine-regulation of enzyme driven ROS detoxification network imparts salt tolerance in contrasting peanut genotypes

Abstract

The present study was aimed to identify the major ROS detoxification pathway in peanut under salinity stress. Pot experiment was conducted with six peanut genotypes (differing in salt-sensitivity) and four levels of salt stress. Higher level of salt stress led to severe plant mortality and reduction in membrane stability especially in sensitive genotypes. Higher ROS accumulation in sensitive genotypes (NRCG 357 and TMV 2) as compared to the tolerant ones (Somnath, TPG 41, CS 240) was confirmed by both spectrometry and in situ histo-chemical staining. Salinity stress changed the cellular antioxidant pool, where the levels of total ascorbate and proline increased in all the genotypes, but the total glutathione content showed significant reduction with more pronounced effect in sensitive genotypes. Major changes in POD and CAT activities was observed in response to salt stress, indicating POD as the major H2O2 detoxifying enzyme in tolerant genotypes. The POD activity was supplemented by CAT activity in sensitive genotypes, where there was relatively higher ROS load. The SOD showed minimal up-regulation under salt stress with undistinguishable difference between tolerant and sensitive genotypes, while APX and GR showed almost no induction, suggesting nominal association of these enzymes with overall salt tolerance in peanut.