Effect of random mating on marker-QTL associations for grain quality traits in the cross of Illinois High Oil X Illinois Low Oil

Altered concentrations of oil, protein or starch in maize (Zea mays L.) kernels can provide value-added products. Progeny developed from the cross between the long-term divergently selected strains, Illinois High Oil OHO) and Illinois Low Oil (ILO), cycle 70, were used to detect quantitative trait loci (QTL) for protein, starch, and oil concentration, and kernel weight. Recombinant inbred lines (RIL) were derived from an F2 created from one cycle of random mating the F1 (RM1) or after four cycles of random mating the RM1 (R-N45). Both per se and corresponding testcrossed lines (TC1 and TC5) were evaluated in four environments. Genetic variance was lower in the testcrosses than in the per se progenies for all traits. Random mating was associated with a reduction in genetic variance for oil concentration between TC1 and TC5. Recombination maps constructed for the RM1 and RM5 revealed an expansion of 2.05 fold after random mating, close to the expected 1.83 fold expansion. Fewer loci were significant in the random mated generations, reflecting recombination between the markets and the quantitative trait loci (QTL) or between linked QTL. Using composite interval mapping (CIM), kernel oil concentration QTL were detected in chromosomal bins 2.09, 3.04, 6.04, 8.04, 8.05, and 8.07 of RM1 or TC1. The oil QTL detected in bin 6.04 in RM1 was also detected in TCI and in previous research, but not in RM5 or TC5. This may be due to break up of marker-QTL associations and/or recombination between QTL.