Breeding for submergence tolerance on rice for rainfed lowland environments

Early generation backcross population (BC1F3) derived from a cross involving Huang Hua Zhan (HHZ) as female recurrent parent with OM1723 (as male donor parent) was first separately raised under irrigated, drought, and salinity stress conditions. The selected survivors were then collectively subjected to submergence stress to introgress abiotic tolerant alleles from OM1723 into widely adapted background i.e(HHZ) a high yielding indica variety in China. A total of 115 BC1F4 progenies, composed of 36 lines previously selected from irrigated, 51 from drought and 28 from salinity were screened for submergence in a concrete tank, during the 2009 WS. Germinated seeds of each line were sown on trays, grown for two weeks and submerged for 14 days. IR49830 and IR42 served as tolerant and susceptible check, respectively. Percentage survival and submergence tolerant lines were identified and characterized from BC1F4 population. Variation in response to submergence stress was observed among the 115 lines. Lines selected from irrigated condition gave 38% survival rate as compared to lines selected from drought and salinity with only 15% each. From the irrigated selection, nine lines were identified to have higher survival rate than the tolerant check. Characterization was done using 60 polymorphic markers from a total of 555 SSR markers that were used for this study. These markers had determined the introgression of the favorable segments from OM 1723 regions using GGT software. With this breeding approach, the authors have also identified lines that were showing multiple abiotic tolerances. However, such lines will be carefully used in designed QTL pyramiding approach of pooling more of the favorable chromosomal segments into elite high yielding backgrounds. By doing so, breeding of varieties for rainfed lowlands that are not only submergence tolerant but also exhibit drought and salinity tolerance can be done.