Salinity-tolerance related indices for screening rice (Oryza sativa L.) cultivars

Rice (Oryza sativa L.) serves as the main food for more than half of the world's population. Salinity is one of the most important factors which limits rice yield. Eleven rice cultivars were evaluated in a randomized complete block design with three replications under salinity stress and normal conditions. The stress tolerance and sensitivity indices, including the mean productivity (MP), the geometric mean (GMP), the stress tolerance index (STI), the yield index, the yield stability index, the harmonic mean (HM), the stress susceptibility index, the tolerance index and yield loss rate, and principal component analysis were used to evaluate the variation and response of rice cultivars under salinity stress conditions, and to identify the tolerant cultivars. A significant variation was observed among the cultivars for grain yield and stress indices. Principal component analysis using grain yield and stress tolerance indices identified two components including “salinity tolerance component” and “salinity sensitivity index component” with eigenvalues greater than 1, which described a cumulative explanation of 99.39 percent of the variance among the cultivars. MP, GMP, and STI were found to be considered as the most suitable indices for selecting rice cultivars tolerant to salinity. The cluster analysis and the distribution of the cultivars in the biplot diagram obtained based on grain yield, and stress tolerance indices introduced Lenjan Askari, Yasouj, and Kamfirouz as tolerant, and Loudab Champa, Gharib, and Mamassani Domsiah as sensitive cultivars. These tolerant cultivars can be used in breeding programs to improve the salinity tolerance of rice.