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Cytogenetic analysis of species and hybrids of Leucaena(Leguminosae) in relation to acid soil tolerance

Liane Helena Cardoso de Freitas^I; Maria Teresa Schifino-Wittmann^I; E. Mark Hutton^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 de Pesquisa Agropecuária dos Cerrados - EMBRAPA, Caixa Postal 70.0023, 73300 Planaltina, DF, Brasil

ABSTRACT

Chromosome number and meiotic behavior were studied in L. leucocephala, L. diversifolia, L. pulverulenta, F₁, F₂ and F₃ hybrids of L. leucocephala x L. diversifolia and F₁ of L. leucocephala x L. esculenta and L. leucocephala x L. shannoni. Wide intraspecific variation in chromosome number was detected in L. leucocephala and L. diversifolia, probably due to natural hybridization. Low (close to the 2n = 52 of diploid L. diversifolia), intermediate and high (close to the 2n = 104 of L. leucocephala and tetraploid L. diversifolia) chromosome numbers were observed. The same applied to F ₁ hybrids between these two species. In F₂ and F₃ trees from L. leucocephala x diploid L. diversifolia crosses only intermediate and high chromosome numbers were detected, pointing to a tendency towards increasing chromosome numbers in advanced generations, selected for acid soil tolerance. Meiotic behavior was mainly regular in the species and hybrids, with predominance of pollen-mother-cells with only bivalents at metaphase I. It is suggested that only intraspecific homologous and homoeologous pairing occurs and consequently the genes of each species present in a particular chromosome are transmitted in blocks to the hybrids, with important theoretical and practical implications for the plant breeder.

Keywords: cytogenetic; analysis; species; hybrids; Leucaena; acid soil; tolerance.

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