Genetic polymorphism between and within Meloidogyne species detected with RAPD markers

Genetic analyses were conducted on root-knot nematode populations belonging to the four major species of the genus Meloidogyne and originating from many countries throughout the world. Discrete genetic markers used in this study were random genomic DNA sequences amplified by the polymerase chain reaction (RAPD). Primers of 17-30 nucleotides with 30-55% G + C content were tested. Five of them generated a total of 74 scorable markers that provided reliable polymorphisms both between and within species. Using RAPD patterns alone or in combination, all the Meloidogyne species and populations studied could be unambiguously discriminated. Based on the presence or absence of bands, maximum-parsimony analysis of the data resulted in clustering of species and populations congruent with previous isoenzymatic and molecular data. The resulting tree confirmed the early divergence of M. hapla from the other species and also that M. arenaria is closer to M. javanica than it is to M. incognita. The boot-strap analysis significantly supported most of the specific branching observed in the topology but did not identify the three M. arenaria populations as a monophyletic group.