Estudios cromosómicos en dos especies de Senecio (Asteraceae)

DEMATTEIS, M.; FERNÁNDEZ, A.

BOLETíN DE LA SOCIEDAD ARGENTINA DE BOTáNICA

Sociedad Argentina de Botánica

Lugar: Buenos Aires; Año: 1998 vol. 33 p. 181 - 184

0373-580X

Chromosomes in two species of Senecio (Compositae). The karyotypes of S. bonariensis Hook. et Arn. and S. grisebachii Baker var. leptotus Cabrera are analyzed for the first time. The chromosome study has showed 2n=40= 24m + 4sm + 12st in S. bonariensis and 2n=40 + 0-1B=30m + 10sm in S. grisebachii var. leptotus. Meiotic behavior was regular in the latter species, it presented 20 bivalents and 0 or 1B univalent. The B chromosome has a small size (1,39 µm) and it is metacentric/submetacentric. At meiosis, MPCs with and without B chromosome were observed, fact which suggests mitotic instability of the B chromosome during microsporocite ontogeny. Both species may be considered octoploids with a basic chromosome number x=5.