Introgrossion of brown planthopper (bph) and gall midge (gm) resistance genes into the elite rice variety, akshayadhan through marker-assisted backcross breeding

Marker assisted backcross breeding (MABB) is a promising strategy for improvement of elite crop varieties for one or more agronomical traits with minimal linkage drag. Akshayadhan is a high-yielding medium duration variety (135 days), whose yield is significantly limited by brown plant hopper (BPH) and gall midge (GM) insects. In the present study, we attempted to improve Akshayadhan for resistance against BPH and GM through marker-assisted backcross breeding (MABB). A rice line in the Abhaya, possessing the gall midge (GM) resistance gene, Gm4 and a rice line RP 2068 18-3-5 possessing the brown planthopper (BPH) resistance gene, Bph33 served as donors and two sets of backcrosses were carried out to combine Gm4 and Bph33 into Akshayadhan separately. Backcrossing was continued till BC2 generation, and gene-specific markers for the two resistance genes were used for marker-assisted selection at each stage of backcrossing in addition to phenotype-based selection for identification of plants closely resembling Akshayadhan. A single BC2F2 plant from each backcross possessing either Bph33 or Gm4 in homozygous condition and closely resembling Akshayadhan were intercrossed to generate inter-cross F1s (ICF1s) to combine the two traits. ‘True’ICF1s were identified using the gene-specific marker(s) and selfed to generate ICF2s, which were then subjected for marker-assisted selection to identify plants which are homozygous for both Bph33 and Gm4.. At ICF2 selected lines were subjected for screening against BPH and GM, all of them were observed to be resistant against the two insects and were advanced further by pedigree method for further evaluation. Further, the selected lines also were observed to closely resemble Akshayadhan with respect to agromorphological traits and possessed long-slender grains.