Improvement of an elite maintainer line, DRR17B for bacterial blight and gall midge resistance through marker-assisted selection

Abstract

DRR 17A, a stable, wild abortive cytoplasmic male sterile line possessing fine grains and developed by Indian Institute of Rice Research(IIRR), Hyderabad. DRR17A and its maintainer line DRR17B and highly susceptible to bacterial blight (BB) disease and the insect pest, gall midge. In order to address this problem, we have introgressed two dominant genes, Xa21 (for BB resistance) and Gm4 (for gall midge resistance) in the genetic background of DRR17B through Marker-assisted backcross breeding (MABB). A breeding line in the background of Samba Mahsuri (RP Bio Ent-2) possessing Xa21 and Gm4 served as donor for both the genes. Molecular markers specific for target genes were used at each backcross generation to identify plants possessing the target genes and backcrossing was continued till BC3 generation. At BC3F2 generation, plants homozygous for both the genes and closely resembling DRR 17B were identified and advanced. At BC3F4 generation, five elite lines possessing both Xa21 and Gm4 were screened against bacterial blight under glass house condition; the lines were subjected to screening for resistance. All the five lines were observed to show high level of resistance against BB and possessed yield, grain quality and plant type similar to DRR17B and we are in the process of converting them to WA-CMS lines through marker-assisted breeding