Cytological studies on wild Farfugium japonicum (Asteraceae)

Farfugium japonicum, Asteraceae, Japanese name: Tsuwabuki, is a traditional garden plant of Japan. At present more than 100 horticultural cultivars are known, and most of them have been selected from wild populations. In order to obtain cytological information on F. japonicum as horticultural resource, chromosome numbers, meiotic chromosome behaviors and pollen stainabilities were examined on wild plants from 70 collection sites selected from the whole range of distributional areas in Japan. Except for one aneuploid (2n=61) plant which has a common leaf morphology, all 177 individuals of var. japonicum were counted to be 2n=60. Meiotic division is normal and 30 bivalents were observed at metaphase I. The frequency of stainable pollen grains was high (93.9±8.8%, N=60). Other three taxa of this species, var. giganteum, var. luchuense and var. formosanum, were also observed to be 2n=60. From the cytogenetical viewpoint, F. japonicum is considered to be a stable diploid, although its chromosome number is relatively high.