MORPHOLOGICAL CHARACTERIZATION AND CLASSIFICATION OF OPEN-POLLINATED SWEET CORN CULTIVARS

Sweet corn is one of the most important vegetable crops in the United States, however the morphology and phylogeny of open-pollinated sweet corn cultivars has not been studied. Fifty eight open-pollinated sweet corn cultivars were characterized with thirty-four descriptors to pro vide information for breeders interested in broadening the genetic bas e of sweet corn. Principal component analysis and cluster analysis wer e performed to classify sw eet corn cultivars based on morphology. Als o, relationships among morphological variables in this set of cultivar s were determined. The general ordination of cultivars followed an axi s representing earliness, and plant, leaf, and tassel size, while ear and kernel attributes were less variable. The morphological variabilit y among all of the widely used sweet corn cultivars, except ''Country Gentleman'', was not greater than the variability found among the ''Go lden Bantam'' strains. Based on morphology, 52 of the cultivars could be considered as one race, which we propose be called ''Northeastern S weets''. These may be a subset of the race ''Northern Flint''. Five of the remaining cultivars are from the north-central or southwestern Un ited States and may represent races from those areas. The sixth cultiv ar is ''Country Gentleman'', a commercially important sweet corn culti var. Due to the importance of ''Country Gentleman'' and the introgress ion of nonsweet germplasm into modern sweet corn, we believe that swee t corn should be defined based on its use as a vegetable and on the pr esence of one or more genes that increase sugar levels in the endosper m.