Abstract
The karyotypes of Lathyrus nervosus Lam., L. pubescens Hook. et Arn., L. paranensis Burk. and L. crassipes Gill ap. Hook et Arn., native to Rio Grande do Sul (southern Brazil), are described in detail for the first time. All taxa have 2n = 14 chromosomes. The karyotypic formulae were 2 m + 12 sm for L. nervosus, L. pubescens and L. paranensis and 4 m + 10 sm for L. crassipes. In all species, the smallest chromosome pair bore a secondary constriction with a satellite in the long arm. Intraspecific variability in the position and number of secondary constrictions was observed in L. nervosus and L. pubescens. All of the species had a conservative and similar karyotype morphology, but differed in total complement size by as much as 20% between the highest (L. nervosus) and lowest (L. crassipes) values. These results suggest that changes in chromosome size during evolution have been similar for all the chromosomes of the complement. Together with data on the life cycle and mode of reproduction, these results also indicate that L. crassipes is a derived taxon, if an evolutionary trend towards a decrease in chromosome size is accepted.
Highlights
The genus Lathyrus (Fabaceae, Papilionoideae, Vicieae) comprises nearly 150 species of annual and perennial, autogamous and allogamous herbaceous creeping plants, which occur throughout the temperate regions of the Northern Hemisphere and South America
Seeds from 12 accessions of L. nervosus, 10 of L. pubescens, 6 of L. paranensis and 10 of L. crassipes were collected in several regions of Rio Grande do Sul and one accession each of L. nervosus and L. pubescens from Uruguay (28-35o latitude South)
This agrees with previous studies of Lathyrus species, including South American taxa (Federov, 1969; Kupicha, 1983; Yamamoto et al, 1984; Broich, 1989; Battistin and Fernandez, 1994; Schifino-Wittmann et al, 1994)
Summary
The genus Lathyrus (Fabaceae, Papilionoideae, Vicieae) comprises nearly 150 species of annual and perennial, autogamous and allogamous herbaceous creeping plants, which occur throughout the temperate regions of the Northern Hemisphere and South America. In this paper we present a detailed karyotypic study of several populations of four Lathyrus species native to Rio Grande do Sul. This information is useful for germplasm characterization and for plant breeding and may improve our understanding of the evolution of the genus. Seeds from 12 accessions of L. nervosus, 10 of L. pubescens, 6 of L. paranensis and 10 of L. crassipes were collected in several regions of Rio Grande do Sul and one accession each of L. nervosus and L. pubescens from Uruguay (28-35o latitude South).
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