Chromosome Study of Eleven Endemic Aloes Species of Ethiopia with Emphasis on the Satellites and Nucleoli
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Date
2008-07
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Addis Ababa University
Abstract
In the present work eleven endemic Aloe species of Ethiopia were cytologically studied.
These species include: A. friisii, A. otallensis, A. tewoldei, A. camperi, A. yavellana, A.
harlana, A. schelpei. A. trigonantha, Aloe species from Bale, A. debrana and A. kefaensis
Somatic chromosomes were prepared from the root tip meristem using colchcine solution
or ice-cold pretreatment, followed by fixation (3:1, ethanol: acetic acid) and enzyme
maceration in pectinase-cellulase solution. The air-dry slides so prepared were stained in
Giemsa stain for chromosome morphological study or stained in silver nitrate to study the
number of nucleoli. This is the first cytological study for A. friisii, A. otallensis, A.
tewoldei and A. camperi. Also all the eleven species were studied for silver staining were
for the first time.
The karyotype analysis has shown that all the species have 2n = 14 chromosomes,
consisting of four pairs of large and three pairs of small chromosomes which form a
bimodal karyotype. The maximum number of nucleoli observed varied among the species.
Two nucleoli per nucleus was observed in A. kefaensis; four in A. otallensis and A.
debrana; five in A. tewoldei and A. friisii; and six in A. schelpei, A. trigonantha, A.
yavellana; A. harlana , A. camperi and Aloe species from Bale. The number of satellite
chromosomes observed generally corresponded to the number of nucleoli. The satellites
were observed on the long arm of long chromosomes and on the short arm of short
chromosomes. These occurred in different combinations in different species. Thus, the
species were observed to possess all the three pairs, or two long pairs, or one long pair, or
one long plus one short pairs of chromosomes.
It was recommended to extend similar studies to the rest of the endemic species of Aloe
and to carry out other studies which involve biochemical and molecular investigations in
order to reveal more cytological and genetic variation which would help to elucidate the
phylogenetic and evolutionary relationship among species of Aloe.
Key words: Endemic Aloe, Ethiopia, karyotype, satellite, nucleoli
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Keywords
Endemic Aloe, Ethiopia, karyotype, satellite, nucleoli