Abstract
Twenty five accessions of tetraploid Ipomoea species that are closely related to sweetpotato were used for the analysis of morphological variation and evaluation of crossing ability. Based on the principal component analysis of 47 characters, the accessions were morphologically classified into four groups. One of the groups consisted of five accessions which had small, thick and leathery or membranous leaves and markedly different from other three groups. However, crossing rates were not significantly different in inter- and intra-group cross combinations, suggesting that there was no significant biological isolation. Morphological variation in the progeny resulting from inter-group crossing, covered almost all range of the variations of parental accessions. All the tetraploid accessions used in this study were considered to belong to one taxon, as indicated in the taxonomical studies carried out in U. S. A. Therefore these accessions should be designated as I. batatas.
