Enhancement of seedling emergence in sweet corn by marker-assisted backcrossing of beneficial QTL

Seedling emergence is an important trait that can limit commercialization of sweet corn hybrids. This study was designed to test what effect beneficial QTL alleles that enhance seedling emergence exert when introgressed, using marker-assisted backcrossing, into sweet corn commercial germplasm. Three RFLP marker alleles linked to QTL that enhanced seedling emergence were identified in an F_2:3 sweet corn mapping population. A recombinant inbred line (RIL, F₈) derived from this population was used as a donor parent to backcross the marker-QTL alleles into three elite commercial sweet corn inbreds. Plants in the three segregating BC₂ populations were crossed to the non-recurrent commercial inbreds to produce three BC₂F₁ populations with families either segregating or lacking the marker donor allele(s). These three populations were evaluated for seedling emergence under field conditions in two successive years. Across the three populations, BC₂F₁ families segregating for the donor QTL allele linked to the marker umc139 (on chromosome 2), bnl9.08 (on chromosome 8), or php200689 (on chromosome 1) displayed 40.8, 30.2, and 28.2% increases in seedling emergence, respectively, over the unmodified F₁s. The introgressed QTL alleles were observed to enhance seedling emergence in the BC₂F₁ generation as was observed in the original F_2:3 mapping population. Marker-QTL associated effects were reproducible across generations and populations indicating that QTL identified in one population can exert similar effects in different genetic backgrounds. Results suggest that using DNA marker technology can help to identify and introgress beneficial QTL alleles, shortening the time and resources required to develop improved germplasm.