Abstract:
Saline soil is a major problem that decreases growth and yield of rice, a salt sensitive crop. For sustainable food production, several rice genotypes with improved tolerance to salt were developed. The present study aimed to determine and differentiate the primary salinity tolerance mechanisms of selected tolerant genotypes through (1) the measurement of Na+ concentration, chlorophyll content, biomass, and visual SES (Standard Evaluation System) injury scores and (2) examination of the dynamics of these physiological traits under different salinity levels over time. This study observed the tolerant genotypes Pokkali, Capsule, Gundang, Anbarloo Sadri, Eratio, Daw Hawm and the pyramid lines DawxFL #1 and #2 at different salinity levels (0mM, 60mM, 120mM, 180mM) over time (5 weeks). Pokkali, Capsule, Gundang and Anbarloo Sadri showed Na+ exclusion as its primary salt tolerance mechanism whereas Eratio, Daw Hawm and the pyramid lines showed tissue tolerance. However, although Eratio is highly tolerant, it is not overall tolerant. On the other hand, the pyramid lines DawxFL #1 and #2 showed combined aspects of tolerance from both parents, Daw and FL478 and are even more salt tolerant. These indicate that the tolerance mechanisms of Daw Hawm and FL478 are different from each other and that pyramiding these contrasting genotypes was effective in improving salinity tolerance.
