Potential of Field Corn Germplasm for the Improvement of Sweet Corn

In corn (Zea mays L.), sweet corn has not benefited from yield gains due to genetic improvement as field corn has. Possible reasons include the narrowness of the genetic base of sweet corn, the lack of defined heterotic groups, and the greater effort devoted to improving yield in field corn. The objectives of this study were to measure the combining ability of certain field and sweet inbreds, the potential contributions of field corn to sweet corn, and whether or not heterotic groups exist within sweet corn as in field corn. Seven adapted sweet inbreds of different genetic backgrounds were crossed with four Corn Belt Dent inbreds and were included in a diallel sweet corn series. Three of the inbreds were from the stiff stalk synthetic group; one was a Lancaster type. The experiment was grown in two years at Arlington, WI. Data were collected on ear weight, yield, number of usable ears, number of ear shoots, plant and ear height, tillers, ear diameter and length, maturity, ear shape, tipfill, and row configuration. The field-sweet hybrids resulted in high general combining ability effects for both field and sweet parents for all traits. The field-sweet hybrids had higher yields, more ears, taller plants, fewer tillers, longer ears, and better ear tipfill, shape, and row configuration than the diallel series of sweet hybrids. Specific combining ability was not important in the field-sweet hybrids. Although field corn inbreds offer a potential source of desirable genes for sweet corn improvement, no specificity of sweet inbreds for field corn heterotic groups was found. for the sweet hybrids in the diallel series, highly significant general and specific combining ability effects were observed for most traits, although, as for the field-sweet hybrids, no clear combining ability groups emerged based on ancestry. Contribution from Wisconsin Agric. Exp. Stn. Research supported by the College of Agric. and Life Sciences, University of Wisconsin-Madison.