KARYOTYPES OF IRIS SPECIES INDIGENOUS TO THE USSR

Abstract

Randolph, L. F., and Jyotirmay Mitra. (Cornell U., Ithaca, N. Y.) Karyotypes of Iris species indigenous to the USSR. Amer. Jour. Bot. 48(10): 862–870. Illus. 1961.—The present center of diversity of the more than 200 species of Iris is in the eastern Mediterranean area of the Balkans and western Asia, with extensions of several important sections of the genus northeastward into the USSR. Karyotype analyses by the authors, previously limited chiefly to European, western Asian and American species, in this study included 10 tall bearded, dwarf bearded, regelia and oncocyclus species obtained from the USSR. A higher number of metacentric chromosomes was found in I. albertii than in any Iris species studied previously, suggesting a primitive status for this species, according to the Lewitsky concept of karyotype evolution. The 24‐chromosome dwarfs, I. timofejewii and scariosa, also have more metacentric chromosomes than do Balkan dwarf species with the same chromosome number. Pumila dwarfs of the USSR have either 30, 31, or 32 chromosomes, and evidence of the mechanism concerned in this variation in number was obtained. A rare case of somatic translocation involving non‐homologous acrocentric chromosomes was observed, and its significance as a source of chromosomal mutants was considered. The regelia species, I. longiscapa, rarely seen in cultivation, was found to have 18 chromosomes, which is a new number for a regelia species. The oncocyclus species, I. elegantissima and paradoxa, have karyotypes similar to those of other oncocyclus species studied previously. The potential value of Russian species of Iris in the production of more winter‐hardy and otherwise desirable new kinds of garden hybrids is discussed.