GENETIC-RESOURCES OF CENTROSEMA SPP - GENETIC CHANGES ASSOCIATED TO THE HANDLING OF AN ACTIVE COLLECTION

The potentials of the species of Centrosema as pasture and fodder crop s in Tropical and Subtropical areas have promoted their germplasm coll ection and evaluation in Brazil and other countries of Central and Sou th America. The species C. acutifolium, C. pubescens and C. brasilianu m are of particular interest. Samples of the same accessions from wild materials collected in Brazil have been agronomically evaluated in Br azil and Colombia, and handled as self-pollinating species. Pairs of s amples (one from Brazil and the other from Colombia) of four accession s have been genetically analyzed using isozyme markers at 16 loci. A n oticeable genetic differentiation has occurred between members of each pair in few generations. Experimental evidences indicate that frequen cy of outcrossing are relatively high in these species. It is proposed that outcrossing between non-isolated neighboring accessions and gene tic drift in small size plantings are the causes of the genetic differ entiation between Brazilian and Colombian samples. Guides to evaluate and multiply Centrosema germplasm are suggested.