Development of opaque-2 introgression line in maize using marker assisted backcross breeding

Two elite normal maize inbreds that produced heterotic experimental hybrid (OML 17-3 × OML 42-9) with 45% yield advantage over the standard check Vivek QPM 9, were used for conversion to QPM status using opaque-2 donors (CML 176 and CML 186) using marker assisted back cross breeding. Each of the normal maize parental inbreds was used as female parent in separate conversion programme using cross combination OML 17-3 × CML 176 and OML 42-9 × CML 186. Foreground selection (using opaque-2 specific marker phi 057) combined with phenotypic selection for recipient parent at early back cross generations (BC1 to BC3) was carried out for rapid recovery of recurrent parent genotype. The BC3F1 plants showing heterozygous status (O2o2) were selfed and advanced to BC3F2 to enable for identification of homozygous recessive opaque-2 segregants at seedling stage. The most promising BC3F3 introgression lines from either cross combinations were finally selected based on higher tryptophan and lysine content. The newly developed introgression lines (OQL 176-17-3 and OQL 186-42-9) were at par with the QPM donors (CML 176 and CML 186) and nearly double the lysine and tryptophan content as compared to respective normal inbreds (OML 17-3 and OML 42-9). These may serve as valuable breeding materials for development of QPM hybrids.