RAPD analysis of genetic diversity among and within Portuguese landraces of common white bean (Phaseolus vulgaris L.)

Seventeen landraces of common beans (Phaseolus vulgaris L.) sampled in the North and Centre of Portugal were analyzed at population level for 689 RAPD loci amplified by using forty random primers. The two different parameters used to estimate the genetic variability in and between samples indicate that the inter-population component of the genetic variability is mainly responsible for the diversity found, since only about a 10% would be of an intra-population nature. In addition, the gametic disequilibrium was estimated and reached an average value of 40% for the different combinations of pairs in the 689 loci studied taking the 17 samples as a whole population. Self-pollination, genetic drift and adaptation would thus be favouring the formation of multilocus associations. In addition, the fingerprinting study suggests that each landrace produced unique amplification products allowing it to be distinguished from the other tested genotypes, but, nevertheless, the landraces show a considerable genetic similarity (56% and 70.5% using two different methods). The Neighbour-Joining dendrogram did not show any relation between the geographical distribution of landraces and genetic distance. The results suggest that these Portuguese landraces conserved an important genetic diversity that can be useful to widen the genetic base of currently cultivated beans.