Browsing by Author "Temesgen, Tezera"

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    Chromosome Study of Eleven Endemic Aloes Species of Ethiopia with Emphasis on the Satellites and Nucleoli
    (Addis Ababa University, 2008-07) Temesgen, Tezera; Dagne, Kifle (PhD)
    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