Physiological Response to Salinity Stress of Japonica/Indica Lines Tolerant to Salt at Seedling Stage

Physiological responses to salinity stress were evaluated in six rice genotypes differing in their tolerance to salinity at the seedling stage. Susceptible genotypes ( Dongjingbyeo , Hwayeongbyeo , and IR29 ) showed salt injury symptoms (mean 8.8) and higher visual score under salt stress than that of tolerant ones ( Pokkali , IR74009 , and IR73571 ). As salinity affects growth and physiological parameters, the six genotypes thus showed significant reduction because of salt stress. Tolerant Japonica/Indica bred lines ( IR74009 , IR73571 ) showed lower reduction, 33.9%, 34.5%, and 50%, respectively, in plant seedling height, dry shoot weight and dry root weight than those of the susceptible Japonica varieties ( Dongjingbyeo , Hwayeongbyeo ), and the highest reduction under salt stress was observed in dry root weight, followed by dry shoot weight and seedling height, respectively. Shoot Na+ concentration of IR74099 and IR73571 was lower than that of the susceptible varieties, Dongjinbyeo and Hwayeongbyeo . There were no significant differences among genotypes in root Na+ concentration. Shoot K+ concentration showed a reverse tendency compared to shoot Na+ concentration. IR74009 and IR73571 had considerably lower ratio compared to Dongjinbyeo and Hwayeongbyeo in Na+/K+ ratio of their shoot and was not different the tolerant check, Pokkali .