Karyotype analysis of A. indica and B. nitida and their taxonomic relationship (Published)
Chromosome characters of two indigenous medicinal plants of high repute were studied. Variation in chromosome features is believed to have accompanied evolutionary divergence of many plant and animal species. This aspect of the research investigated the karyomorphological details of four species of medicinal plants (A. indica and B. nitida) from different families and their possible taxonomic relations using actively dividing root meristems and a high-resolution image-based cytogenetic system. The conventional squashing in aceto-orcein of root tissues after heating was used. The tissues were photographed under Nikon Universal Microscope, equipped with an MC 100 camera. The chromosomes were then measured under x400 magnification using a micrometer. The results revealed that the mitotic phases varied with species. Similarly, the arm ratio, r-value, centromeric index, coefficient of variation, total form, intra-chromosomal index and inter-chromosomal index varied with the accessions. All examined cells displayed a varied chromosome number and karyotype formula. The highest long arm chromosome was recorded in B. nitida with a mean value of 37.25± 0.88 µm while while A. indica registered the minimum (9.64±0.33 μm). The mean Arm Ratio of the chromosomes was highest in A. indica (2.048± 0.12 µm) while the least was recorded from B. nitida (1.450± 0.13 µm). A parallel pattern was observed for the Total length dimension, in which B. nitida attained the highest value (62.95 ± 1.43 μm) and A. indica the lowest (29.39 ± 1.57 μm). From the perspective of the centromeric index, the B. nitida population manifested the highest magnitude of this parameter (26.389± 0.05 μm), whereas A. indica presented the lowest value (10.128± 0.08 μm). These differences could be explored for the improvement of the medicinal plants cultivated in Nigeria.
Keywords: A. indica, B. nitida, Karyotype analysis, taxonomic relationship