CROSS-ABILITY IN THE GENUS LACHENALIA

Lachenalia is a bulbous genus endemic to southern Africa. The genus has been utilized in a breeding program with the aim to develop a new pot plant product for the international floriculture market. The genus has approximately 120 described species and is unusually variable. The variation in terms of flower-form, -colour, -length and -posture opens up a range of possibilities in terms of pot plant types as well as cut flower potential. The extent of the variation, however, also causes several natural crossing barriers influencing the cross-ability among species. The genus is just as varied in chromosome number as in phenotype. The basic chromosome numbers present in the genus are x=5, 6, 7, 8, 9, 10, 11 and 13. Ploidy levels range from diploid to octoploid and polyploidy is present in several species. A large number of interspecies crosses have been made. The results of these and the implication on the cross-ability of different species are discussed. Cross-ability between species with the same basic chromosome number is fairly successful. Cross-ability between species with different basic chromosome numbers is, however, low. The crossing data are compared to results from studies on the phylogeny of the genus as determined using sequencing of the transfer RNA intergenic spacer (trnL-F) sequencing and chromosome numbers. The same tendency can be observed if the inter-species crosses are linked to the phylogenetic groups identified within the genus. Within groups cross-ability is fairly successful, whilst between groups cross-ability is low. The crossing data thus, in most cases, correlate with the phylogenetic data. Where discrepancies occur further phylogenetic analysis is required.