Cytogenetic Study of Some Species of Swertia L. (Gentianaceae) from Ethiopia

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Addis Ababa,University


Chromosome data have contributed little towards resolving the problems of classification and phylogeny orthe Swertia species (Y uan, 1993). For many species of the genus the chromosome number as weJ[ as morphology were not stud ied (Yuan and KUpfer, 1993). In the present work, ch romosome numbers were documented for six species of Swerlia L. (Gentianaceae) from Ethiopia. S. fimbria/a, s. kiJill/wu/s charica, S. macrosepa/a subsp. microsperma and S. va/kensii var. baleellsis were found to be diploid with 2n=26. S. crassillscula subsp. robllsta was dip loid with 211=20. The above chromosome numbers were determined from mitotic chromosomes. Diploid (211=20, n"" I 0) and tetraploid (2n=40, n=20) chromosome numbers were found for S. abyssillica from meiot ic chromosome study. The chromosome numbers of S. crassilisclila subsp. robusta , S macrosepala subsp. microsperma, S volkellsii val'. baleensis and 211=40 cytotype of S. abyssil/ica were reported for the first time. Further, the present study confimled previous reports on the chromosome numbers of the remaining species and the basic chromosome number x= 13 and x=1 0 for the genus. Karyotypes of five species of SlI'ertia namely, S fimbria/a , S. kilimalltischarica, S. macrosepala subsp. microsperma. S. crassiuscula subsp. robusta and S. volkensii val'. baleellsis have been described and their similarities and differences were discussed. Even though tile chromosome morphology of these species is very similar, some variat ions in basic number, ploidy level, satell ite number and size of chromosomes were observed among the Swerlia species studied. The study revealed that the spec ies were heterogeneous. It is recommended that fu rther study of karyotype of all the species of the genus including chromosome banding is necessary to complete the cytotaxonomic knowledge of the genus as a whole.



Cytogenetic Study of Some Species of Swertia L.