Permanent translocation heterozygosity in dioecious Baccharis coridifolia DC. (Asteraceae)

En:

Hereditas 2002;137(2):132-139

Fecha:

2002

Formato:

application/pdf

Tipo de documento:

info:eu-repo/semantics/article
info:ar-repo/semantics/artículo
info:eu-repo/semantics/publishedVersion

Descriptores:

allele -  article -  Asteraceae -  centromere -  chromosome -  chromosome bivalent -  chromosome translocation -  controlled study -  diploidy

Descripción:

The karyotype of Baccharis coridifolia DC., a dioecious diploid species consists of 16 chromosomes with median (m) and 2 with submedian centromeric positions (sm) (2n = 18). Meiotic analyses of 219 male plants belonging to 12 populations showed across a wide geographical range one quadrivalent and seven bivalents in all of them. The quadrivalent involves the four biggest m chromosomes and probably constitutes a sex multivalent carrying in tight linkage the sex genes and provides a mechanism whereby permanent translocation heterozygosity is maintained. In metaphase I alternate orientation of the quadrivalent was predominant (85.71 %). Fourteen megaspore mother cells were analyzed and did not show the quadrivalent. A model for the origin and maintenance of the sexual translocation system is presented. It is assumed that there are two non-allelic factors M and n; M would be a dominant female suppresor and n a recessive male-suppresor. The excess of male plants observed in several populations at different localities might result from heterotic effects of some gene complexes carried by the translocation. This excess probably ensures a good supply of pollen for the vagaries of insect pollination at flowering time.
Fil:Wulff, A.F. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Identificador(es):

http://hdl.handle.net/20.500.12110/paper_00180661_v137_n2_p132_Hunziker

Derechos:

info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by/2.5/ar