Sub1 and qDTY.sub.3.1 improved tolerance of rice lines to drought and submergence stresses

Drought has had a significant impact on rice cultivation and production in Malaysia. Using the marker-assisted breeding technique, the current study was conducted to introgress the submergence tolerance QTL (Sub1) from IR64-Sub1 into UKM91 with drought yield QTL (qDTY.sub.3.1). The effects of Sub1 introgression on agro-morpho-physiological traits under reproductive stage drought stress (RSD) and non-stress (NS) conditions, as well as survival percentage under vegetative stage submergence stress (VS) are reported in this study. In both RSD and NS, the effect of Sub1 presence alone outperformed the effect of Sub1 + qDTY.sub.3.1 combination for grain yield (GY). Under RSD, lines with only Sub1 had a higher number of panicles and thousand-grain weight than lines with Sub1 + qDTY.sub.3.1 and qDTY.sub.3.1 only, indicating that Sub1 plays multiple roles in conferring drought tolerance. In RSD and NS, the best-performing lines achieved GY advantages of up to 1713 kg/ha and 1028 kg/ha over UKM91 respectively. After 14 days of VS, the selected lines from NS and RSD trials (GEN11, GEN19, GEN37, GEN49, GEN66 and GEN72) had a 100% survival rate while IR64-Sub1 had an 86.67% survival rate due to a low reduction in chlorophyll content and a low shoot elongation percentage. The developed lines have the potential to mitigate the effects of climate change and reduce yield loss while also serving as pre-breeding materials for breeding programmes.