Development of early maturing submergence-tolerant rice varieties for Bangladesh

Flash flooding imparts adverse effect on rice production worldwide. Because of the needs for multiple cropping and to avoid incidences of cold and diseases later in the season, early maturing submergence tolerant varieties have been urgently needed in some rice producing areas. Marker-assisted backcrossing (MABC) was used to introgress the submergence-tolerance SUB1 QTL from BRRI dhan52 into a short-duration rice variety, BRRI dhan33. In this particular study, a combination of foreground and phenotypic selection was performed during the BC1F1-BC4F1 stages, while the whole set of foreground, recombinant and background markers were used at the BC4F2 stage. At the final stage, the recovery of recipient parent genome ranged from 90.7 to 95.2% in 15 BC4F3 promising lines. The introgression sizes of the different Sub1 lines were estimated to be around 2.4 to 5.6 Mb. The submergence tolerance of line BR9157-12-2-37-13-15-40 was found to be the best, having 87.7% survival. The grain yield of the Sub1 lines was also significantly higher compared with that of the original variety, BRRI dhan33, under both flooded and non-flooded conditions in on-station and on-farm trials. The maximum grain yield obtained from a BRRI dhan33-Sub1 line was 4.8 t/ha under on-farm non-flooded conditions and 3.8 t/ha under on-farm flooded conditions. The best selected Sub1 line may be released in the future as a short-duration, submergence-tolerant high-yielding variety for flood-prone rainfed areas in Bangladesh.