Morpho-physiological Traits Associated with Tolerance of Salinity During Seedling Stage in Rice (Oryza sativa L.)

Contrasting rice genotypes were evaluated for morpho-physiological traits that contribute to salinity tolerance. Sixteen rice genotypes were subjected to 12 dS m(-1) salt stress during seedling stage. Relative vigor was measured prior to salinization while visual evaluation of salinity stress symptoms, leaf chlorophyll concentration, shoot and root growth, and sodium and potassium concentrations were measured 25 days after salinization. These parameters were found to vary among the rice genotypes. Pokkali, Cheriviruppu, FL478, and IR651 consistently expressed salt tolerance characters, such as higher vigor, lower standard evaluation system (SES) scores, higher total chlorophyll concentration, higher shoot and root biomass, lower shoot Na+ accumulation, and lower shoot Na+/K+ ratio compared to the salt-sensitive genotypes. These morpho-physiological traits were strongly correlated with one another. Cultivars IR29, CSR11, IR74, Kalimekri, and Bhirpala had high shoot Na+ concentration, high shoot Na+/K+ ratio, high SES scores, low shoot and root biomass, low leaf chlorophyll concentration, and low vigor, indicating sensitivity to salt stress. On the other hand, IR4630, Mushkan 41, Kalarata, TKM6, Kajalsail, IR72, and IR70, showed morpho-physiological traits that were intermediate between the two other groups. Though seemingly discrete in terms of groupings, variation in the expression of these traits within each group was also observed. These findings have substantial Implications for breeding, wherein strategies are needed to ensure the proper choice of donor parents with the best particular tolerance trait, and multiple donors are required to ensure the best trait combinations for genotypes with high tolerance to salt stress.