Screening for Sodium-Salt Tolerance at the Seedling Stage of Rice (Oryza sativa L.) Genotypes from Sudan and South Sudan

Morpho-physiological and genetic studies of salinity are important in understanding the mechanism of plant adaptation to stressful environment. Eighteen rice genotypes collected from Sudan and South Sudan, which were never tested for salt tolerance, as well as two genotypes (FL478 as tolerant check and IR29 as sensitive check) from the International Rice Research Institute (IRRI), were subjected to salinity stress at seedling stage. Test was carried out in hydroponic system applying electrical conductivity (EC) 12 dS/m NaCl using randomized complete block design with three replicates. Most of the genotypes showed sensitivity to salt stress; one genotype PIPANFARY RED2 was moderately sensitive and three genotypes MASURY1, MASURY2 and FL478 were tolerant. Salinity significantly reduced leaf dry weight, shoot dry weight, root dry weigh and biomass production (biomass/plant) by 31%, 42%, 60% and 47%, respectively. Tolerant genotypes accumulated low amount (2.52 g/100 g dry weight (dwt)) of Na in the root, whereas highly sensitive genotypes accumulated high amount (3.87 g/100 g dwt) of Na. Tolerant genotypes showed less reduction in K concentration than the sensitive genotypes. Therefore, they maintained lowest Na/K ratio in the shoot (1.47%) than in the root (3.69%) compared to the intolerant genotypes (7.49% and 8.49%). The genotypes that showed tolerance to salinity stress can be used as a source of resistance/tolerance in a breeding program for rice improvement in uplands areas in semi-arid condition.