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Chromosome numbers, karyotypes and meiotic behavior of populations of some Trifolium(Leguminosae) species

Maria Teresa Schifino-Wittmann^I; Maria Irene B. Moraes-Fernandes^II

^ISetor de Plantas Forrageiras e Agrometeorologia, Departamento de Fitotecnia, Faculdade de Agronomia, Universidade Federal do Rio Grande do Sul, Caixa Postal 776, 90001 Porto Alegre, RS, Brasil. Send correspondence to M.T.S.-W.
^IICentro Nacional de Pesquisa do Trigo/EMBRAPA, Caixa Postal 569, 99001, Passo Fundo, RS, Brasil

ABSTRACT

Plants from different populations of Trifolium riograndense Burkart, T. polymorphum Poir and T. repens L. were cytogenetically studied in terms of chromosome numbers, karyotypes and meiotic behavior. No intraspecific variability in chromosome number was detected for the three species. The karyotypes of T. riograndense (2n = 16) and T. polymorphum (2n = 16), two species native to Rio Grande do Sul, differed by the relative position and centromeric index of the satellited (SAT) pair. One plant of T. riograndense presented two SAT pairs. The chromosomes of T. repens (2n = 32), an exotic species cultivated in the State, were smaller than those of the native species, probably reflecting less DNA content per chromosome. The meiotic behavior of T. repens and T. riograndense was regular with only bivalents being formed during metaphase 1. The presence of quadrivalentes in one individual of T. riograndense was probably due to translocation heterozygoxis. In T. polymorphum, however, 50% of the individuals from different populations presented quadrivalents, an unusual occurrence for a diploid inbreeding species. Other phases of meiosis were regular. All plants of the three species were considered meiotically stable, with meiotic indexes higher than 90%. Pollen viability varied among individuals of the same species and the low values obtained suggested the action of factors other than meiotic behavior.

Keywords: chromosome; karyotypes; meiotic; populations; Trifolium.

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