Identification and genetic diversity of Meloidogyne spp. (Tylenchida: Meloidogynidae) on coffee from Brazil, Central America and Hawaii

The present study was based on 18 populations of Meloidogyne spp. originating from different coffee fields in Brazil, Central America and the USA (Hawaii). The identification of the main species and an outline of the diversity of root-knot nematodes parasitising coffee in these countries with respect to esterase phenotypes, morphology and molecular polymorphism, are provided. With the present electrophoretic procedure, esterase phenotypes were demonstrated to be species-specific and constitute a good tool for identifying root-knot species from coffee, viz., M. incognita (Est 11, 12), M. paranaensis (Est P1, P2), M. arenaria (Est A2), M. arabicida (Est AR2), M. exigua (Est E1), M. mayaguensis (Est M2) and two unknown populations that probably represent new species (Est SA2, SA4). The perineal pattern is often an unreliable character when used alone for making diagnostic conclusions but, when used as a complementary tool together with enzyme characterisation, is essential for checking the morphological consistency of the identification. Male characters are important for confirming the diagnosis of some species, such as M. paranaensis, M. konaensis and M. incognita. The results showed that the RAPD markers produced are consistent with other approaches (esterase phenotypes and morphological features) for confirming species identification and for estimating genetic relationships among species and isolates. Phylogenetic analyses showed that M. mayaguensis and M. exigua are more closely related to one another than they are to the other species. This was also true for M. javanica, M. arenaria and Meloidogyne spp. Low levels of intraspecific polymorphism were detected in M. exigua (8.6%), M. incognita (11.2%) and M. paranaensis (20.3%). Conversely, M. arenaria and the two unknown Meloidogyne spp. exhibited higher levels of intra- or interspecific variability (34.9 and 29.9%, respectively). (Résumé d'auteur