Relative salinity tolerance of rice cultivars native to North East India: a physiological, biochemical and molecular perspective.

Salinity is the second most prevalent abiotic stress faced by plants, and rice is not an exception. Through this study, it has been tried upon, to study the relative salinity tolerance of eight local varieties of North East India. Preliminary screening was based on their dose- and time-dependent physiological responses to salinity stress. Among the cultivars, Tampha was found to be relatively more tolerant, whereas MSE9 the most sensitive. To further ascertain their tolerance capacity, MDA and H2O2 content was determined, which also confirmed the tolerance level of the two cultivars. Histochemical assays for root plasma membrane integrity and leaf and root H2O2 and O2- content also showed more damage in Tampha in comparison to MSE9. Finally, gene expression analysis for Na+/K+ co-transporters, OsHKT2;1, OsHKT2;3 and OsHKT2;4, was performed to observe how the expression level of these transporters varies with the tolerance capacity of these two cultivars in leaves and roots under different time frames. The study reveals Tampha to be the most tolerant and MSE9 the most sensitive when compared to the other six screened cultivars for salinity stress.