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International Journal of Botany

Year: 2007  |  Volume: 3  |  Issue: 2  |  Page No.: 147 - 159

Karyotype Analysis and Systematic Relationships in the Egyptian Astragalus L. (Fabaceae)

Abdelfattah Badr and Sherif M. Sharawy

Abstract

In this study the karyotype criteria of 35 taxa representing 24 species of Egyptian Astragalus have been analyzed and their impact on the systematic delimitation of the studied species is discussed. Chromosome numbers, based on x = 8 have been found in the majority of Astragalus species in Egypt. A diploid number (2n = 16) was recorded in 22 taxa representing 17 species and polyploid numbers are recorded in six taxa representing three species. Numbers based on x = 7 were recorded in four taxa of which three counts are tetraploid with 2n = 28 representing A. annularis, A. mareoticus and A. vogelii. In addition, numbers based on x = 6 were encountered in A. trimestris (2n = 12 and 2n = 24) and A. boeticus (2n = 30). The chromosomes in the studied species of Astragalus are generally small with a mean size ranging between 0.82 and 1.59 μm. Short chromosomes were particularly found in A. vogelii (MCL = 0.82 μm) and A. boeticus (MCL = 0.87 μm), whereas longer chromosomes were scored in A. sinaicus (MCL = 1.59 μm). The karyotype in the studied taxa is mostly comprised of metacentric to submetacentric chromosomes as indicated by their mean arm ratio that ranges between 1.35 in A. vogelii and 2.03 in A. asterias. The degree of karyotype asymmetry is indicated by high values of TF% that ranges between 36.11% in A. asterias and 47.48% in A. tribuloides. The A1 value ranges between 0.40 in A. vogelii and 0.90-0.92 in samples of A. asterias. Distance trees illustrating the relationships of the studied taxa, based on the analyses of karyotype features, have been constructed using Dice and Jaccard similarity coefficients. The grouping of the examined species, in these trees, is discussed in the light of their previous systematic treatments.

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