Enhancing taxonomic resolution: distribution dependent genetic diversity in populations of Meloidogyne

Abstract

AbstractRoot-knot nematodes (Meloidogyne) are one of the most damaging agricultural pests. The polyploid apomictic M. arenaria, M. javanica and M. incognita are particularly ubiquitous and exhibit an extreme polyphagy. The taxonomic position of these three species remains unclear, as does the phylogenetic relationships between them. To characterise phenotype variants among these three species, allozyme electrophoresis (α-EST, MDH, CAT, GPI, DIA, GOT, and SOD) was performed in populations from the Iberian Peninsula. A total of 50 multilocus enzyme electrophoresis (MLEE) phenotype variants were detected of which, according to the esterase pattern, 24 corresponded to M. arenaria, 15 to M. javanica and 11 to M. incognita. The phylogenetic relationships of these 50 MLEE variants were studied following the Neighbour-Joining (NJ) distance method based on an allelic frequencies matrix built using two different methodologies. In addition, Maximum-Parsimony (MP) and Maximum-Likelihood (ML) phylogenetic methods were done in order to corroborate the phylogenies obtained. Our results showed a great disparity in the NJ trees obtained, thus indicating that the monophyly of the parthenogenetic Meloidogyne spp. would seem to depend on the methodology used. Evolutionary and epidemiological implications of the recovered phylogenies are discussed.