Full text in pdf format

Sources of genetic variability in a neotropical cleistogamous species, Relbunium hypocarpium, Rubiaceae

Loreta Brandão de Freitas; Suzana Cavalli-Molina; Helga Winge

Departamento de Genética, Universidade Federal do Rio Grande do Sul-UFRGS, Caixa Postal 15053, 91501-970 Porto Alegre, RS, Brasil. Send correspondence to L.B.F.

ABSTRACT

Twenty-two strains of Relbunlum hypocarpium collected from four localities in Rio Grande do Sul (Brazil) and one in Argentina were studied for glutamate oxaloacetate transaminase (GOT, EC 2.6.1.1) isoenzyme patterns by horizontal gel electrophoresis in order to obtain more precise data on their reproductive system and on the origin of the variability observed in this cleistogamous species. The study was conducted on adult F₁ and F₂ of plants from nature, and seedlings of their progenies. When some variation was observed in the progeny, the same or sib seedlings were also analyzed for isoesterases (EST, EC 3.1.1). The results showed that R. hypocarpium, a cleistogamous species, and reproduces mostly by self-fertilization, although at least one event of cross-fertilization that occurred in nature, was detected in one strain out of 22 An additional source of variability observed in 14% to 18% of the strains, in the GOT system, was found to be the occurrence of isoenzyme modifiers, possibly involving post-synthesis modifications, the adaptive significance of which we are not yet able to explain.

Keywords: genetic variability; neotropical; cleistogamous; Relbunium hypocarpium; Rubiaceae.

REFERENCES

Barrett, S.C.H. and Eckert, C.G. (1990). Variation and evolution of mating systems in seed plants. In: Biological Approaches and Evolutionary Trends in Plants (Kawano, S., ed.). Academic Press, London, pp. 229-254.

Cavalli-Molina, S. and Winge, H. (1988). Phenetic relationships among populations of the autogamous plant Relbunium hypocarpium (Rubiaceae). Rev. Brasil. Genet. 11: 401-418.

Cavalli-Molina, S., Motta, V.E.P., Schiengold, M. and Winge, H. (1989). Identical isoenzyme patterns in sib plants of Relbunium hypocarpium (Rubiaceae). Rev. Brasil. Genet. 12: 361-368.

Ehrendorfer, F. (1955). Revision of the genus Relbunium (Endl.) Benth. et Hook f. (Rubiaceae-Galieae). Bot. Jb. 76: 516-533.

Harris, H. and Hopkinson, D.A. (1976). Handbook of Enzyme Electrophoresis in Human Genetics. Amsterdam, North Holland.

Hickenbick, M.C.M., Flores, A.I.P., Cavalli-Molina, S., Souza-Chies, T.T. and Albarus, M.H. (1992). Mode of reproduction and seed production in Paspalum dilatatum poir virasoro biotype-Dilatata group (Gramineae). Rev. Brasil. Genet. 15: 85-102.

MacDonald, T. and Brewbaker, J.L. (1974). Isozyme polymorphism in flowering plants. IX. The E5-E10 esterase loci of maize. J. Hered. 65: 37-42.

Mariath, J.E.A. (1990). Ontogenia, embriologia e biologia floral de Relbunium hypocarpium (Rubieae-Rubiaceae). Doctoral Thesis. Universidade de São Paulo, São Paulo, SP.

Mariath, J.E.A., Cavalli-Molina, S., Schiengold, M., Motta, V.E.P., Freitas, L.B., Winge, H. and Venturelli, M. (1987). Estudos morfológicos e genéticos em Relbunium hypocarpium (Rubiaceae): biologia floral, variabilidade isoenzimática e regulatória. XXXVIII Congresso Nacional de Botânica. Resumos (Soc. Botânica do Brasil e Univ. de São Paulo, eds.), pp. 344.

Motta, V.E.P. (1981). Desenvolvimento ontogenético e modifica-cães dos padrões isoesterásicos de Relbunium hypocarpium (Rubiaceae). Master's Thesis. Universidade Federal do Rio Grande do Sul, Porto Alegre, RS.

Motten, A.F. and Antonovics, J. (1992). Determinants of outcrossing rate in a predominantly self-fertilizing weed, Datura stramonium (Solanaceae). Amer. J. Bot. 79: 419-427.

Poulik, M.D. (1957). Starch gel electrophoresis in discontinuous system of buffers. Nature 180: 1477-1479.

Richards, A.J. (1986). Plant Breeding Systems. G. Allen & Unwin, London, XIV + 529 pp.

Rick, C.M., Tanksley, S.D. and Fobes, J.F. (1979). A pseudoduplication in Licopersicuin pimpinelifolium. Proc. Natl. Acad. Sci. USA 76: 3435-3439.

Scandalios, J.G. (1969). Genetic control of multiple molecular forms of enzymes in plants: a review. Biochem. Genet. 3: 37-79.

Scandalios, J.G. (1983). Molecular varieties of isozymes and their role in studies of gene Iegulation and expression during eukaryote development. Isozymes Current Topics in Biological and Medical Research, gene expression and development 9: 1-31.

Schiengold, M. (1985). Efeito da regulação gênica na variabilidade isoesterásica de Relbunium hypocarpium (Rubiaceae). Mater's Thesis. Universidade Federal do Rio Grande do Sul, Porto Alegre, RS.

Schiengold, M. and Winge, H. (1990). Methodology: a similarity coefficient of gene regulation. Rev. Brasil. Genet. 13: 855-860.

Stebbins, G.L. (1957). Self-fertilization and population variability in the higher plants. The Amer. Natur. 91: 337-354.

Tyson, H., Taylor, S.A. and Fields, M.F. (1978). Segregation of the environmentally induced mobility shifts in flax genotroph peroxidase isozymes. Heredity 40: 281-290.