Genomic relationships in the Lachenalia orchioides group

[摘要] English: The genus Lachenalia belongs to the family Hyacinthaceae and the order Asparagales. Lachenalia is commonly known as the 'Cape Cowslip' and this small bulbous geophyte is endemic to South Africa. The genus contains hundred and twenty species and is essentially a genus of the winter rainfall regions of southern Africa. In an attempt to produce new and better ornamentals, breeding-programmes were developed. The Roodeplaat Vegetable and Ornamental Plant Institute of the ARC (ARC-Roodeplaat) developed an economically viable breeding-programme in South Africa, for the genus Lachenalia. The exceptional morphological variation in the genus Lachenalia led to the initiation of this breeding-programme in which the genus was developed into an ideal pot plant and twenty-five cultivars have been registered since. Factors of importance in the breeding programme are flower size, genetic variation within the genus, as well as polyploidy. Different chromosome numbers as well as different basic chromosome numbers have been reported for more than fifty Lachenalia species. When Crosby (1986) reviewed the genus, chromosome studies [made by Moffett (1936) and Crosby (1986)] lead to the division of the genus into five provisional groups. Basic chromosome numbers were used as one of the criteria in the delimitation of these groups. These chromosome numbers can contribute enormously to the taxonomic classification of the Lachenalia species. Very little DNA sequencing has been done in the genus Lachenalia.During this study chromosome numbers (mitosis and meiosis) and DNA sequencing (trnL-F region) were used to evaluate the phylogenetic relationships of the species within the Lachenalia orchioides group. Clustal G was used to align the sequences and PAUP to determine the phylogenetic relationship.The somatic chromosome numbers of 2n = 12, 14, 24, 28, 42 were observed in the L. orchioides group. Different basic chromosome numbers (6 and 7) were observed within L. mutabilis, but within the rest of the group the basic chromosome number was 7. The basic chromosome number of x = 7 occurs most frequently throughout the L. orchioides group and thus seems to be the predominant basic chromosome number. DNA sequencing results supported x=7 as original basic chromosome number of the L. orchioides group. L. fistulosa has not been classified into a group yet. The strict consensus cladograms (Fig. 4.1-4.4) as well as the basic chromosome number of seven supports L. fistulosa as part of this group. These results support the monophyly of the L. orchioides group, which indicates close relationships.The phylogenetic analysis did not resolve the variation in chromosome numbers of L. mutabilis. Molecular cytogenetics (GISH and FISH) together with sequencing of more genes may help to resolve this relationship.

[发布机构] University of the Free State