Molecular stacking of wide compatibility gene, S5 n and elongated uppermost internode (eui) gene into IR 58025B, an elite maintainer line of rice

Abstract

One of the most widely used and stable wild-abortive cytoplasmic male sterile (WA-CMS) line is IR 58025A. We had earlier transferred the gene (eui1) for elongated uppermost internode into the elite WA-CMS line named IR 58025eB with the help of markers. To overcome incomplete panicle exsertion in the WA-CMS line and better exploitation of indica/japonica heterosis, we have stacked a major gene for wide-compatibility (S5 n ) into IR 58025eB through marker-assisted breeding. SSR markers (RM5970) tightly linked to eui1 gene and (S5-InDel) functional maker of S5 n gene were used for foreground selection, while ninety-one microsatellite markers polymorphic between IR 58025eB and donor Dular (S5 n ) were utilized for background selection at each backcross generation and backcrossing was continued till BC3 generation. Phenotypic observation previous to background selection at each generation provided supplementary information for identifying the novel recombinants and the fast-tracked recurrent parent genome recovery which ranged from 94.50 to 96.70% in selected BC3F4 plants. At BC3F5 generation, seven stable, backcross-derived lines possessing S5 n and eui genes, high yield, and long-slender grain type have been identified; their maintainer ability was confirmed through test crosses. These improved lines are being converted to CMS lines by marker-assisted backcrossing.