Cytogenetics Study of Vetiveria Germplasm in Thailand

摘要

A cytological technique was developed to display chromosome morphology of 15 Thai andrn5 introduced clones/ecotypes of vetiver from their root tip cells. They were classified as 13rnVetiveria zizaniodes and 7 V. nemoralis A. Camus. Humic acid solution was applied to obtainrnhealthy root tips used for conventional slide preparation. The appropriate period for cutting the rootrntips was around 11 a.m. to 1 p.m. for further fixation. Enzyme mixture treatment appeared to be arnpromising way to separate groups of cells and to clear the cytoplasm. It was found that allrnclones/ecotypes studied had the same chromosome number, 2n = 2x = 20. Three B-chromosomesrnwere observed only in one clone. The variation in satellite chromosomes in terms of number andrnmorphology was evident in six clones/ecotypes. The total chromosome length varied from 1.2-8.4rnμm. The karyotype consisted of metacentric and submetacentric chromosomes, all of which werernnearly symetrical. Localization of the heterochromatic regions on the chromosome of vetiver wasrnachieved by (a) modified C-band and (b) N-band. It was possible to characterize each pair of thernvetiver chromosome. All ten pairs of chromosome were identified by these banding patterns, alongrnwith their length and arm ratios. They can be used as the basis for reproducible karyotype and forrndetecting chromosome relationship among clones/ecotypes. Each clone/ecotype showed at leastrnone chromosome with a whole dark band, indicating a constitutive heterochromatin. The remainderrnindicated variation patterns from clone/ecotype to clone/ecotype of some faint and dark bands.