'Two in one' stress-tolerant rice: salinity and submergence

Coastal saline areas invariably experience frequent submergence for short periods with saline or freshwater in wet season (WS). Here, rice is the major crop owing to its suitability to the coastal areas as it can withstand temporary water logging. The ideal rice genotype for coastal areas needs dual tolerance for salinity and submergence for better adaptability. In this study qSALTOL and SUB1, a quantitative trait locus conferring vegetative stage tolerance to salinity and, a gene conferring tolerance to 1-2 weeks flooding, respectively, were combined using marker-aided selection (MAS), to develop rice varieties that can tolerate saline and submerged conditions. Progenies of crosses made between the donors of salinity tolerance (IR66946-3R-178-1-1 'FL478' and Cheriviruppu) and submergence (IR82809-237 and IR82810-407) which were tolerant to salinity at EC 12 ds/m were subjected to 14 days of submergence. (IR82809-237 and IR82810-407) which were tolerant to salinity at EC 12 dS;/m were subjected to 14 days of submergence. Survivors were then genotyped for both the Saltol and SUB1 loci, and individuals showing homozygosity for both loci were advanced until the F6 generation. The selected lines IR84645-34-9-1-B, IR84645-311-22-1B, and IR84649-81-4-B-B were subjected to submergence of 14 days, and respectively, exhibited 38%, 78% and 88% survival, with a mean of 63% (IRRI field, 2009 WS). Yields under submergence stress were 1.98, 3.29 and 3.80 t/ha, respectively. Submergence sensitive check Swarna had yield of 1.82 t/ha (25% survival), while Swarna-Sub1(submerence tolerance check) had 4.43 t/ha (84% survival). Combining Saltol and SUB1 in one genetic background seems feasible with no apparent negative impacts on agronomic traits and this will help develop more resilient varieties adopted to coastal zones.