Cytogenetic Studies in the Genus Iris: Subsection Evansia, Benth

Abstract

The karyotype analyses of the Evansia species did not suggest any simple explanation for the origin of the progressional series of chromosome numbers of 2n=26, 28, 30, 32, 34, 36, 42, 44 and 54. A comparison of the karyotypes of geographically adjacent species showed that an increase in chromosome number was accompanied by a decrease in chromosome size. Karyotype differnces did not always suggest lack of affinity between species as was shown between I. japonica and I. confusa which formed fertile hybrids although their karyotypes were very different. The hybrids between I. japonica and I. confusa vary in their chromosome numbers from 2n=39 to 2n=43. The karyotypes of I. wattii and I. confusa showed greater similarities, a correspondence paralleled by their successful hybridization to form F₁ hybrids. I. wattii could represent a subspecies of I. confusa. Meiotic divisions in the available clones of I. wattii and I. japonica showed that these 2 species were atypical in that the latter was possibly a triploid and the former the product of a chromosomal interchange.