Modified backcross breeding method for rapid conversion of field corn line to shrunken2 (sh2) gene-based sweet corn line

Abstract

The non-availability of superior and diverse inbred parents is one of the major bottlenecks to develop high yielding sweet corn hybrids. The sh2, one of the promising recessive mutant alleles, has been used in sweet corn development however its transfer to superior field corn lines may require extra inbreeding to identify heterozygous carrier plants. The use of molecular markers linked with sh2 requires a well-equipped laboratory and skilled person to carry the marker assisted backcross breeding (MABB). Considering the above constraints, a modified backcross breeding method was used taking advantage of shrunken kernel of sweet corn for foreground selection coupled with phenotypic comparison with recurrent parent (RP). The BC1F1 plants were grown and plants having high phenotypic similarity with RP were selfed as well as backcrossed as pollen parent. The BC2F1 kernels of BC1F1 plants having high similarity with RP and segregation in BC1F2 kernels were harvested. The BC2F1 plants phenotypically most similar to recomment parameter (RP) were selfed and the shrunken kernels were selected from the segregating BC2F2. The shrunken kernels were homozygous (sh2sh2) at Sh2 locus, which were validated upon inbreeding based on nonsegregating kernels in BC2F3. The modified backcross method used is rapid, cost effective and can be used by maize breeder with limited resources for conversion as well diversification of sweet corn germplasm.