Marker-assisted pyramiding of qDTY QTLs and assessment of their performance under varied moisture-stress environments

Context Traditional breeding methods have achieved limited success in improving drought tolerance in rice due to the complex quantitative nature of the trait. However, modern approaches such as marker-assisted breeding (MAB) have enabled the development of drought-resilient varieties. Aim Given the popularity of ADT (R) 45 and its susceptibility to drought, this study aimed to introgress three drought-yield quantitative trait loci (QTLs) of qDTY1.1, qDTY3.1, and qDTY12.1 into ADT (R) 45 by using marker-assisted backcross breeding, and to identify promising drought-tolerant versions through both genotyping and phenotyping. Methods Backcrossing was conducted using F1s of ADT (R) 45 crossed with Apo and Way Rarem. Resulting BC3F1 and intermated populations (BC2F1 of ADT (R) 45/Way Rarem//BC2F1 of ADT (R) 45/Apo) were advanced to BC3F2 and intermated F2, followed by BC3F3 and intermated F3 generations. Marker-assisted selection (MAS) was applied in BC3F2 and intermated F2 to identify superior backcross inbred lines (BILs). Key results Sixteen BILs showed more than 10% yield gain under both moderate and severe stress. BILs I85 and W61 showed superior physiological traits such as higher relative water content, soil plant analysis development (SPAD) value, proline content, and better recovery under drought. Conclusions BIL I85 showed best score for leaf rolling, leaf drying, drought recovery as well as higher SPAD value and proline content. Whereas BIL W61 exhibited higher values for SPAD, relative water content, proline content and leaf drying score. These two BILs were also found to possess more than 10% single plant yield over recurrent parent ADT (R) 45. Implications These two BILS are therefore considered for further trials at the national and state levels, and the most promising one will be selected for release as a high-yielding drought-tolerant variety.