Cytological observations inAlbuca, including a survey of polymorphic variation in the Sat-chromosome pair

Abstract

Chromosome numbers for 14 South African species ofAlbucaL. (Liliaceae) have been determined. Ten of these are first reports, including counts for three new species. Members of all three sections of the genus are represented in this study, and all have a diploid number of 2n = 18. No polyploids or dysploids were encountered in this survey. There is no evidence that the sectional subdivisions ofAlbucacan be readily distinguished on differences in basic chromosome number or karyotype, for all taxa are characterized by a common basic number of x = 9 and by a remarkably uniform, strongly asymmetric and bimodal complement of three long chromosomes and six markedly shorter ones. Special attention is focused on the hitherto largely overlooked variability of the longest chromosome pair which, in a large proportion of the species examined, shows heterozygous variation in the size, morphology and stainability of its satellite and in some cases, also in the short chromosome arm that bears it. This unusually high incidence of polymorphism, and the diversity of form observed in this satellited (Sat-chromosome) pair is discussed in relation to similar patterns reported elsewhere.