B-chromosomes in some Lachenalia species and hybrids

Varying chromosome numbers within a species and a series of diploid, polyploid and basic numbers have been reported for the genus Lachenalia. In a cytogenetical study conducted on this genus, B-chromosomes were observed in somatic and meiotic material of some species and F1 hybrids. The size of the B-chromosomes in somatic material was found to be similar, or slightly smaller than the smallest chromosome of the normal complement. In pollen mother cells (PMCs), having univalent B-chromosomes, the B-chromosomes divided precociously during the first meiotic division. In a few PMCs of the hybrids where more than one B-chromosome was observed, the B-chromosomes associated to produce bivalents indicating that they are homologous or homoeologous. The B-chromosome bivalents tended to disjoin normally during the first meiotic division and the resulting chromosomes divided normally during the second meiotic division. The discovery of B-chromosomes in the genus helps to account for some of the variation in chromosome number that has been reported for the genus, and specifically for the species L. orchioides (L.) Ait