Allelic differences at enzyme loci and hybrid performance in maize

Evaluation of hybrids to identify lines with superior combining ability is a time-consuming and expensive phase of hybrid breeding programs. Techniques that would allow the breeder to screen lines for combining ability before evaluation in hybrid combinations are desirable. Twenty-four high-yielding and 21 low-yielding lines selected for their relative yield from a group of 247 inbred lines derived by single-seed descent from the ‘lowa Stiff Stalk Synthetic’ maize (Zea mays L.) population were assayed electrophoretically. High X high, high X low, and low X low hybrids of the high-and low-yielding lines were evaluated, and the genotypes at 11 enzyme marker loci of the lines were used to determine the genotypes of the hybrids. The objective was to determine if allelic differences at the enzyme loci could be used to predict hybrid performance of maize. Two enzyme loci (Est4 and Pgd2) were nearly fixed, leaving nine enzyme loci, which represented five of the 10 maize chromosomes. The results indicated that allelic differences at enzyme loci are not indicative of the performance of hybrids made from unselected lines derived from random mating populations. Our results and those of others suggest that enzyme loci are of limited usefulness in predicting combining ability in maize