Analysis of Genetic Diversity of Fusarium oxysporum f. sp. phaseoli Isolates, Pathogenic and Non-pathogenic to Common Bean (Phaseolus vulgaris L.)

Twenty isolates of Fusarium oxysporum from Brazil, pathogenic and non-pathogenic to common bean, were analysed using random amplified polymorphic DNA (RAPDs) to study the genetic diversity. RAPD analysis using 23 oligonucleotides resulted in the amplification of 229 polymorphic and 7 monomorphic DNA fragments ranging from 234 to 2590 bp. High genetic variability was observed among the isolates, with the distances varying between 8% and 76% among pathogenic, 2% and 63% among the non-pathogenic and 45% and 76% between pathogenic and non-pathogenic isolates. The analysis of genetic distance data showed that the pathogenic isolates tended to group in one group and the non-pathogenic in another. The genetic distance values of 30% among the pathogenic isolates in cluster A are compatible with the genetic distance values observed within the physiological races, but the distance values among the pathogenic isolates in clusters B and G are not compatible with the distance values observed within the race. Although our results are preliminary, it was not possible to exclude the existence of more than one race of this fungus in Brazil