Development of Drought Tolerant Rice Breeding Lines of an Elite Indian Rice (Oryza sativa L.) Variety Improved White Ponni through Molecular Breeding

Changes in climatic conditions especially unpredictable drought occurrences are challenging for food security. The present investigation was carried out to improve the grain yield in Improved White Ponni (IWP) rice under reproductive stage drought stress. This variety is well known for its grain quality. Physiological changes, grain yield and related traits under drought were evaluated in the advanced breeding lines of Improved White Ponni X Apo containing qDTY 3.1. The experiment was conducted at the Department of Rice, Centre for Plant Breeding and Genetics, Tamil Nadu Agricultural university, Coimbatore during 2020. Two superior backcross inbred lines of IWP X Apo, donor parent and recipient parent were raised under water stress in rain out shelter as well as in well irrigated conditions in replications. Soil moisture content was reduced to 12.7% in drought field showing the stress severity. Physiological parameters such as photosynthetic rate, transpiration rate, stomatal conductance, chlorophyll content and relative water content, Yield and related traits such as days to fifty percent flowering, productive tillers, spikelet fertility, grain yield and grain weight were recorded in the BILs and parents during flowering stages. Reduction was observed in all these traits under water stress. However, in comparison with IWP (94.6%) which lacks qDTY 3.1, BILs with qDTY 3.1 showed less reduction in grain yield (63%) and other traits. Earliness was also observed in qDTY 3.1 containing BILs under drought stress (BILs - 106 days, IWP-117 days) and controlled conditions (BILs- 83 days, IWP-107 days) when compared to IWP. Grain quality estimates in the BILs showed similarity to IWP. These BILs need to be evaluated further for confirmation of drought tolerance and they are effective resources for utilisation in drought breeding programmes.