Chromosome Studies on the Genus Isostigma (Heliantheae, Asteraceae)

抄録

Chromosome information about the small South American genus Isostigma (Heliantheae, Asteraceae) is reported for the first time. The somatic chromosomes of two species were analyzed in detail : I. hoffmannii Kuntze and I. peucedanifolium (Spreng.) Less. The first taxa showed a somatic number of 2n=18, having the karyotype composed for 8 metacentric and 10 submetacentric chromosomes. While I. peucedanifolium, the type species of the genus, presented 2n=24 and a karyotype formula with 8 metacentric, 10 submetacentric and 6 subtelocentric chromosomes. In addition to the basic number, I. hoffmannii and I. peucedanifolium revealed substantial differences in karyotype formula, chromosome size and asymmetry level. The results are discussed in relation to earlier chromosome studies for the tribe.