Lachenalia is a small bulbous geophyte of the family Hyacinthaceae, endemic to South
Africa and first described in 1787 by Jacquin. There is a large degree of variation in the genus
and some species overlap morphologically with other genera such as Polyxena and Massonia ,
and it is very difficult to delimit the species. There are currently approximately 120 species
described, but new species are frequently described. Several authors attempted to subdivide the
genus (Baker, 1897; Crosby, 1986; Duncan, 1988 & 2002). Lachenalia has a tremendous
cultivation potential, and 25 new cultivars have been introduced since 1966.
A cytogenetic, as well as a molecular study, was conducted to try and solve problems with
the classification in the genus, and to provide answers to the breeders regarding infertility
problems between interspecific crosses. The chromosome numbers of a few species were
determined by examining meiotic and mitotic chromosomes in order to guide the breeders in
their hybridisation studies. The numbers obtained during this study were combined with results
of previously studies to try and determine the original basic chromosome number(s) in the genus.
Several basic chromosome numbers have been reported in the genus, i.e. x = 5/10, 7, 8, 9,
11 and 13. The majority species have a basic chromosome number of x = 7, followed by x = 8
and then x = 11. Polyploidy is common, occurring in 40% of the species in the genus. The
number x = 7 has mainly diploids, 28.6% tetraploids and a few hexa - and octaploids and,
therefore, represents a young mature polyploid complex. The numbers x = 8 and x = 11 both
forms young polyploid complexes. According to this information, it can be concluded that x = 7
were the original basic number, from which x = 8 and x = 11 evolved. The hypothesis on the
evolution of the chromosome numbers were tested by sequencing the trnL-F region of the
chloroplast genome.
This region was also sequenced to try and provide answers for the taxonomists on the
difficult task of classifying and delimiting the genus. The phylogenetic position of the genus in
relation to other liliaceous plants also needed to be determined.
The basic chromosome numbers were superimposed on the cladogram, and a definite
correlation between chromosome numbers and monophyletic groups were obtained. Several
monophyletic clades formed, dividing the cladogram into four distictive groups: the
âL. juncifoliaâ, âLachenalia 1â, âLachenalia 2â and âL. zebrinaâ groups, and several subgroups.
The position of these groups and subgroups confirms the hypothesis that x = 8 evolved from x =
7. It also indicated that several hybrids prevail within the genus, explaining the delimitation
problems and the variation in basic chromosome numbers.
The genus Polyxena are included within the Lachanalia clade, indicating that this genus
should either be included in the genus, or Lachenalia should be split into several genera. Polyxena could also have introduced new chromosome numbers and variation in the genus by
hybridisation. The cladogram confirms that Polyxena is the closest relative of Lachenalia ,
followed by Massonia and Whiteheadia .
This study indicated that the cytogenetic and molecular data support one another. The trnL-F
region is useful to study phylogenetic relationships on genus or higher taxonomic levels, but
the addition of other genes will probably provide more answers for the classification and
evolution of the genus.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-08232005-113408 |
| Date | 23 August 2005 |
| Creators | Spies, Paula |
| Contributors | Prof JJ Spies |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-08232005-113408/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
Page generated in 0.0018 seconds