Morphological and physiological evaluation of Korean Rice genotypes for salt resistance

Salinity either in the soil or irrigation water hampers the profitable crop production. This study was conducted to evaluate the response of rice genotypes to salt stress. Four rice genotypes (IR29, CHIEH-KENG44, CHING-YIN1 and RYKUU15) were sown in germination trays filled with soil especially formulated for rice and were then transferred to iron containers. Salt stress (100 mM NaCl) was imposed in equal increments of 25 mM per day. Salt stress caused substantial decrease in plant height, shoot length, root and shoot fresh and dry weights, leaf area, and fresh and dry weight of seedlings of all rice genotypes. Although the genotypes responded to salt stress differently, however, root length of IR29 and RYKUU15 was increased under salt stress. Salt stress increased the polyphenol contents and antioxidant activity of all rice genotypes, but maximum polyphenol contents were observed in CHING-YYEH1. Salt stress caused substantial decrease in K⁺/Na⁺ ratio owing to significant rise in Na+ contents on the expense of K⁺, but genotypes behaved differently in this regard. Minimum decrease in seedling fresh and dry weights was observed in rice genotype CHING-YIN1 owing to less Na⁺ uptake under salt, which also helped in maintaining better K⁺/Na⁺ ratio. Although Na⁺ content indicated a strong negative correlation, whereas K⁺/Na⁺ ratio had strong positive correlation with seedling fresh and dry weights. In conclusion, although salt stress decreased the growth of tested rice genotypes; genotype CHING-YIN1 was more resistant to salinity amongst all the genotypes owing to reduced Na⁺content and greater K⁺/Na⁺ ratio. This study suggests that seedling fresh weight, tissue Na+ contents and tissue K⁺/Na⁺ ratio may be used as markers in screening rice genotypes resistant to salt stress.