Introgression of bacterial blight and blast resistance the elite rice variety, Akshayadhan through marker-assisted backcross breeding

Abstract

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 bacterial blight (BB) and blast diseases. In the present study, we attempted to improve Akshayadhan for resistance against BB and blast through marker-assisted backcross breeding (MABB). A breeding line in the genetic background of Samba Mahsuri, FBR1-15 possessing the bacterial blight resistance gene, Xa33 and C101A51 possessing the blast resistance gene, Pi2 served as donors and two sets of backcrosses were carried out to combine Xa33 and Pi2 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 Xa33 or Pi2 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 Xa33 and Pi2. Homozygous ICF2 plants were advanced further by pedigree method for further evaluation. At ICF4 selected lines were subjected for screening against BB and blast pathogens and all of them were observed to be resistant against the two diseases. Further, the selected lines also were observed to closely resemble Akshayadhan with respect to agromorphological traits and possessed long-slender grains.