Study of Karyotype Variability and Genome Size in 13 Species of Cassia L. in Interpreting Interspecific Genetic Diversity
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Somatic chromosome number, karyotype and 4C DNA content was studied in 13 species of <i>Cassia</i> of the family Leguminosae obtained from Royal Botanic Gardens, Kew. Somatic chromosome number 2<i>n</i>=28 was observed in all the species except <i>C. lindheimariana</i> and <i>C. versicolor</i> with 2<i>n</i>=26 chromosomes. In addition, polyploid chromosomes were observed in <i>C. atomaria</i> and <i>C. hirsuta</i> (2<i>n</i>=56). Variations among the species were observed in their minute structural details of the karyotype. On the basis of centromeric index, 4 types (Type A, B, C and D) of chromosomes were found in different species. Significant variations in the chromosome length were observed among different species from 13.25 μm in <i>C. wislizenii</i> to 24.73 μm in <i>C. polyantha</i>. Total chromosome volume varied significantly from 6.93 μm<sup>3</sup> in <i>C. hirsuta</i> to 11.10 μm<sup>3</sup> in <i>C. lindheimariana</i>. Highest centromeric index percentage (43.69%) was noted in <i>C. italica</i> and that of lowest (34.12%) was found in <i>C. polyantha</i>. Significant variation in 4C nuclear DNA content was observed among the species that varied from 6.45 pg in <i>C. italica</i> to 15.77 pg in <i>C. spectabilis</i>. The correlation coefficients showed various chromosomal and nuclear parameters interdependent suggesting a interspecific relationship between structural and genetic changes of the genome architecture during evolution of speciation.
CYTOLOGIA 71(3), 261-267, 2006-09-25
Japan Mendel Society, International Society of Cytology