Detection of Heterozygous o2O2 Allele in BC1F1 Progeny of QPM Versus Normal Cross in Maize Using Marker-Assisted Selection

Abstract

Marker assisted back crossing is reliable tool in selecting the heterozygotes in backcross generations. It quickens the selection process which would otherwise require an extra generation/season for raising the BCF2 seed for finding the recessive allele which needs to be phenotypically expressed. Therefore in the present study normal maize (BML-6and IML-187) and QPM donor lines (DQL-2029-1 and DQL-779-2-9) were genotyped at o2 locus using co-dominant SSR marker phi057. The marker allele size at 02 locus for normal parents was 155 bp in IML-187(P1) and 160 bp in BML-6(P2). 170bp in DQL-2029-1(P3) and DQL-779-2-9(P4) for QPM or donor parents. Based on this polymorphism crosses were made to generate F1 hybrids. IML-87 was crossed with DQL-2029-1 and BML-6 was crossed with DQL-779-2-9. Thus, based on polymorphism at the DNA level, biparental backcrosses were made to eventually combine o2 allele in the endosperm of normal maize. The two BC1F1 populations were genotyped at the opaque-2 locus using phi057 SSR marker. It was observed that out of 96 plants analyzed, 40 individuals were heterozygous at o2 locus in BC1F1 population derived from the cross BC1F1 (A) while 43 out of the 100 plant analyzed in cross BC1F1 (B) were heterozygous when screened with phi057 SSR marker. Marker Assisted backcrossing is a useful tool in trait introgression as it helps in pre-flowering elimination of negative plants as well as donor genome and need for selfing is eliminated in BCF1 s. SSR phi-057 was able to clearly distinguish between QPM and normal parents and detect heterozygous plants in the backcross progeny.