Chromosome associations of three interspecific, dibasic Lachenalia hybrids

Abstract

The ARC-Roodepiaat started to develop some endemic species as commercial pot plants and cut flowers several years ago. One of the genera selected for pot plant breeding was Lachenalia. For proper planning of the breeding programme the relationship between and within species is of utmost importance. Determining these relationships is an ongoing process at the ARC-Roodeplaat. The present study was done on three interspecific dibasic hybrids, that resulted from two crosses made between the species L. splendida (x = 8) and L. unicolor (x = 8) as female parents and L. aloides (x = 7) as male parent. Chromosome associations were used to draw conclusions on the relationship between species with different basic chromosome numbers. On morphological grounds the species L. aloides does not seem to be closely related to L. splendida and L. unicolor. Chromosome pairing in the interspecific hybrids, however, revealed that these species are more closely related than expected. The study further revealed homeology between two chromosomes of the x = 7 karyotype and three chromosomes of the x = 8 karyotype. It indicates that the x = 7 plants differ from the x = 8 plants by at least two exchanges of chromosome material and involves also the loss of one centromere from the x = 8 karyotype. It further indicates that the change in the basic chromosome number of Lachenalia involves a reduction in chromosome number. The process of change is, however, not straight forward, since the x = 8 karyotype has no acrocentric chromosomes, it was not just the result of simple centric fusion.