Screening salt-tolerant rice at the seedling and reproductive stages: An effective and reliable approach

Screening salt-tolerant rice genotypes is important to develop salt-tolerant high-yielding cultivars. To categorize salt-tolerant genotypes, we used a comprehensive collection of morpho-physiological parameters, yield-contributing characteristics, and molecular and biochemical markers with multivariate analysis in this study. A total of 20 rice genotypes were screened at seedling stages in a hydroponic system at three different salinity levels (8, 10, and 12 dS m(-1)). Furthermore, at the reproductive stage, 12 genotypes were evaluated at 4 and 6 dS m(-1) salinity conditions. The seedlings growth of the most rice genotypes were severely reduced by salinity stress, however, some genotypes (M-12, M-20, IR-10, IR-8, and M-19) showed the lowest growth reduction. Total salt stress response index revealed that the genotypes M-12 was the most salt-tolerant. Though the genotype M-12 acquired the highest position in seedling stage screening but unfortunately failed to show sufficient yield po-tential at reproductive stage, in which M-19 was qualified with highest yield response. Therefore, only seedling stage screening may provide misleading results. M-19 also showed the highest antioxidant activity with lower Na+/ K+ ratio, hydrogen peroxide, and malondialdehyde content, indicating a strong defense mechanism against salt-induced oxidative and osmotic stress. Overall, M-19 was selected as the most appropriate candidate geno-types for salinity tolerance. The accuracy and reliability of these methods were superbly assured by principal component analysis and seedling stage molecular assay. Therefore, the identified salt-tolerant genotypes could be further utilized as a source of appropriate donor parents in breeding of salt-tolerant high-yielding rice varieties.