SciELO - Scientific Electronic Library Online

 
vol.22 issue3Comparison of similarity coefficients based on RAPD markers in the common beanExpression of a methionine-rich storage albumin from the Brazil nut (Bertholletia excelsa H.B.K., Lecythidaceae) in transgenic bean plants (Phaseolus vulgaris L., Fabaceae) author indexsubject indexarticles search
Home Pagealphabetic serial listing  

Genetics and Molecular Biology

Print version ISSN 1415-4757

Abstract

MAFFEI, Eliane M.D. et al. Chromosomal polymorphism in 12 populations of Mikania micrantha (Compositae). Genet. Mol. Biol. [online]. 1999, vol.22, n.3, pp. 433-444. ISSN 1415-4757.  http://dx.doi.org/10.1590/S1415-47571999000300025.

Mikania micrantha is a climbing perennial weed of the family Asteraceae, with a vast distribution from South America to south of the United States. This species is widely distributed throughout Brazil, where it shows little morphological variation. Mitotic chromosomes of 12 populations of M. micrantha derived from several Brazilian sites were studied using Feulgen staining and C-banding. The populations included eight diploid (2n = 36 and 42) and four tetraploid (2n = 72) cytotypes. Chromosome numbers of 2n = 36 and 2n = 42 are reported for the first time for M. micrantha. These populations had a secondary constriction in the middle of the larger arm of chromosome pair 1, following the same pattern described for all Mikania species analyzed so far. Numerical and structural variation of the chromosomes was quite common among the karyotypes and nearly all cytotypes differed from each other in some aspect. Most of the chromosomal differentiation may be attributed to inversions and addition or deletion of DNA fragments. C-banding, applied to three of the 12 populations, also revealed polymorphism in the distribution of heterochromatin. Additionally, one to 14 supernumerary or B-chromosomes were observed. The Bs were detected in six of the 12 populations and varied in size, number, and structure among karyotypes and also among cells of the same root meristem. The B chromosomes were also heterochromatic, showing a C-banding pattern similar to the A chromosomes, and suggesting that they may be derived from the chromosomes of the A complement.

        · abstract in Portuguese     · text in English     · pdf in English