KARYOTYPE ANALYSIS IN SOME GENERA OF COMPOSITAE. VIII. FURTHER STUDIES ON THE CHROMOSOMES OF ASTER

HUZIWARA, Y. (Kobe U., Mikage, Kobe, Japan.) Karyotype analysis in some genera of Compositae. VIII. Further studies on the chromosomes of Aster. Amer. Jour. Bot. 49(2): 116-119. Illus. 1962. -The karyotypes of 3 Asiatic and 3 American taxa of Aster are reported here for the first time. These are: A. ageratoides subsp. sugimotoi (Kitamura) Kitamura 2n = 36, A. ageratoides subsp. (Taxon AIII) 2n = 72, A. himalaicus C. B. Clarke 2n = 18, A. ericoides L. 2n = 32, A. meritus A. Nels. 2n = 27, A. umbellatus Mill. 2n = 18. Two American taxa, namely, A. meritus and A. -umbellatus, are considered to be ancestral taxa which have retained primitive karyotypes similar to those of Asiatic species of Aster. IN THE PREVIOUS papers of this series, the writer (Huziwara, 1957a,b, 1958) has reported chromosome numbers and karyotypes for 58 taxa of Aster. There were some cytological differences observed between those of Asiatic and American origin. In strong contrast to the symmetrical karyotypes found in the Asiatic species, there was a marked increase in asymmetry in the American species. In addition, the somatic chromosomes of the Asiatic species are large, whereas those of the American species are very small. The Asiatic species all have a single basic chromosome number of 9. In contrast, the American species have 3 basic chromosome numbers, namely, 5, 8 and 9. In this paper the karyotypes of 6 additional taxa are reported. MATERIALS AND METHODS-Seed samples of Aster ericoides and A. umbellatus were obtained from the Montreal Botanical Garden. Those of A. meritus were received from the Lund Botanical Garden. Specimens of A. ageratoides were collected in their natural habitats in Japan. The plants of A. himalaicus were obtained from the Nikko Botanical Garden, Tokyo University. The cytological methods used are the same as those described in previous papers of this series (Huziwara, 1957a,b). Herbarium specimens of the taxa studied have been deposited in the herbarium of Kobe University. OBSERVATIONS-Aster ageratoides subsp. sugimotoi (Kitamura) Kitamura (2n-36; Fig. 1, 7) is a tetraploid with a somatic chromosome number of 36. The plant from which karyological studies were made was collected at Mt. Kiyozumi, Chiba-pref. The 36 somatic chromosomes vary in length from 6.6,u to 3.6 ,. Size difference within the complement is not so marked as in the ovatus group of A. ageratoides (Huziwara, 1957b). One pair of chro1 Received for publication June 14, 1961. The writer is indebted to Dr. W. F. Grant, Department of Genetics, Macdonald College of McGill University, for a constructive criticism of the manuscript. He is also grateful to Dr. A. L6ve and Dr. A. Lima-de-Faria for the kindness he received from them. mosomes has subterminal centromeres, 2 pairs have median, and the rest have submedian ones. The 2 homologues of the largest pair of chromosomes have each a secondary constriction in the short arm and are designated L2E-chromosomes (Shimotomai and Huziwara, 1942). The karyotype of this subspecies is similar to that of the tetraploid race of A. ageratoides subsp. leiophyllus (Huziwara, 1957b). This taxon has been treated as distinct species, A. sugimotoi Kitamura (Kitamura, 1937). Aster ageratoides subsp. is an undescribed taxon (Taxon AIII) (2n=72; Fig. 2, 8). The plant from which cytological observations were made was collected at Tainogo, Yakushima, Kagoshima-pref. by Dr. Tagawa of Kyoto University. It is an octoploid with a somatic chromosome number of 72, which represents a new number for the A. ageratoides group. This octoploid is clearly distinguished from other races of A. ageratoides by its brighter, fleshy leaves. The 72 chromosomes vary in length from 5.4 ju to 1.8 ft. Size difference within the complement is marked. One pair of chromosomes has subterminal centromeres, 6 pairs have median, and the rest have submedian ones. The karyotype representative of this plant is similar to those found in the ovatus group of A. ageratoides (Huziwara, 1957b). Only 2, rather than the expected 8, L2E_ chromosomes were found in this octoploid. Aster himalcicus C. B. Clarke (2n=18; Fig. 3) is a species native to Himalaya. The plants of this species were kindly supplied by Mr. Kubota, Nikko Botanical Garden, Tokyo University. The 18 somatic chromosomes vary in length from 7.6 f to 4.2 ju. Two pairs of chromosomes have median centro. meres, the remainder have submedian ones. The 2 homologues of the largest pair of chromosomes have a secondary constriction in the short arm. Aster ericoides L. (2n=32; Fig. 4) is a tetraploid with a basic chromosome number of 8. Besides the typical A. ericoides studied here, Fernald (1950) recognized 4 forms, i.e., f. prostratus, f. exiguus, f. caeruleus, and f. gramsii, in this species. The seeds were collected at Saint-Jean, Quebec, by Drs Kucyniak, Raymond, Gousy and Gougeon of the Montreal