Chromosome Study in Five Endemic Kniphofia Species (Asphodelaceae) of Ethiopia
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Date
2009-09
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Addis Ababa University
Abstract
The karyotype of five endemic Kniphofia species of Ethiopia were studied. The studied species
are: K. foliosa, K. schimperi, K. hildebrandtii, K. isoetifolia, and K. insignis. Somatic
chromosomes were prepared from the root tip meristem using colchicines, 8-hydroxyquinoline
or ice-cold pretreatment, followed by fixation (3:1, ethanol:acetic acid) and then enzyme
maceration in pectinase-cellulase solution at 37°C for about 1 hr. Air-dry slides were prepared
and stained in Giemsa stain in Sorensons phosphate buffer (pH = 6.8). The karyotype analysis
has shown that K. foliosa, K. schimperi, K. hildebrandtii and K. isoetifolia are diploid with 2n =
12, where as K. insignis has 2n = 22 chromosomes which is assumed to be a polyploid on the
basis of x = 6 for the genus. Polyploidy is the first report for the species. Morphologically, the
chromosomes showed a gradual decrease in size in all the species with only small differences
between the longest and the shortest chromosomes of each species. The size differences are
relatively more pronounced in K. insignis. The karyotype formula was found to be 2m + 8sm+
2st in K. foliosa, K. schimperi and K. hildebrandtii; 2m + 2m/sm + 8sm for K. isoetifolia and
4m + 12sm + 1sm/st + 5st for K. insignis. Generally, there is only a minor degree of
differentiation observed among the karyotypes of the diploid species. One pair of small
satellites were observed on the tip of short arms in K. foliosa and K. hildebrandtii, two pairs in
K. schimperii and K. isoetifolia and in K. insignis, the secondary constriction is located in the
middle of the long arm of a pair of chromosomes and thus delineated two large satellites.
Kniphofia foliosa from ‘Laga Shore’, about 10 kms from Gedo town, west of Addis Ababa,
was found to have a B-chromosome. This is the first report of B-chromosome for the species as
well as the genus. In spite of the fact that samples were collected from only a limited
number of sites, the cytogenetical information reported here would create only the basis
for further cytological investigation of Kniphofia species. It is, thus, recommended that
further cytological and molecular studies including specimens from a wider geographic
area should be carried out.
Key words: B-chromosome, Chromosome, Endemic Kniphofia species, Ethiopia,
Karyotype, Polyploidy.
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Keywords
B-chromosome, Chromosome, Endemic Kniphofia species, Ethiopia, Karyotype, Polyploidy