Genetic Variability and Mating System in Three Species of the Genus Centrosema

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Abstract
The genus Centrosema includes several species both potentially and currently useful as pasture and fodder crops in tropical and subtropical areas. Genetic variability, population genetic structure, and the mating systems of three species of this genus, C. acutifolium, C. brasilianum, and C. pubescens have been studied using isozyme (17 loci) and DNA markers (random amplified polymorphic DNA and rDNA intergenic spacer length polymorphism). Both kinds of markers discriminate populations belonging to different species. Outcrossing rates and other experimental parameters have been determined in populations of an active germplasm collection outside the species native habitat. Populations of all three species showed relatively high polymorphism and heterozygosity, and total genetic diversity was higher within than between populations. The mating system parameters indicated that outcrossing was higher than expected in the three species, previously considered as being predominantly selfers. The multllocus analysis carried out in C. acutifolium provided estimations of the outcrossing rate ranging from 0.27 to 0.41 among populations; estimations carried out from the fixation Index in the other two species also suggested relatively high outcrossing rates. These species should be considered species with mixed mating systems, and this fact should be taken into consideration in further breeding programs and germplasm conservation.

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