Pyramiding of Multiple QTL for Drought and Submergence Tolerance for Infusing Climate-Resilience in Rice Variety Samba Mahsuri

Water-deficit under drought and anoxia under flash flooding in the same field are recurring problems limiting rice production in rainfed lowland Agri-ecosystem. Hence, there is need to develop high-yielding rice varieties with inbuilt drought and submergence tolerance. Samba Mahsuri (SM) is a high-yielding mega variety of rice which is popular among the farmers due to its excellent eating quality despite long duration and sensitivity to drought and submergence. The objective of present study was to pyramid major QTL for drought and submergence tolerance in the genetic background of SM. A population of 990 F₂ plants from a cross between SM-Sub1-DTY2.1 (DRR Dhan 50) and SM-Sub1-DTY3.2 was analysed using SSR markers linked to drought tolerance QTL qDTY2.1 and qDTY3.2 to select homozygous QTL-pyramided lines (QPL) in SM-Sub1 background. Sixty-two such lines were identified and advanced to F₃ generation. Since both the parents matured earlier than SM, the QPL segregated for time to maturity, and only those showing uniform maturity were advanced to F₄₋₆ generation. Of these, four lines were evaluated for agronomic and physiological performance under control and drought stress. The QPL showed significantly lower loss of grain yield under drought than SM and single-QTL parental lines. QPL 62 showed the least reduction in grain yield and was 16 days earlier in maturity than SM. It has over 95% genetic background similarity and similar grain and cooking quality to SM. Hence, it can be taken forward for multi-location QTL-NIL trials for commercial release as a climate-resilient version of SM.