SEQUENCE ANALYSIS OF THE D2/D3 REGION OF THE LARGE SUBUNIT RDNA FROM DIFFERENT MELOIDOGYNE ISOLATES

Abstract

The phylogenetic relationships of eight Meloidogyne species and twelve isolates from Brazil and other countries were investigated using sequence data of the D2/D3 expansion segments of the large subunit of ribosomal DNA. The phylogenetic procedures used were maximum parsimony, maximum likelihood and neighbor-joining, using different mathematical alignment algorithms as implemented in TreeAlign and ClustalX, and different tree construction methods of TreeAlign and PAUP*. The results obtained with ClustalX alignments are robust and supported by high bootstrap values, suggesting a strong phylogenetic signal, as also supported by the obtained values of skewness parameter g1. Although the consensus topology of trees derived from TreeAlign alignments is more poorly resolved, the topologies obtained with different algorithms and software are congruent in dividing the species into two clusters: a heterogeneous grouping of M. chitwoodi, M. exigua (three isolates), M. graminicola and M. trifoliophila; and a much less divergent cluster with M. arenaria (race 2), M. incognita, M. konaensis and M. paranaensis (three isolates). The phylogenetic usefulness of the D2/D3 region clearly depends greatly on the evolutionary rates within the investigated lineages. For the Meloidogyne isolate study presented here, the D2/D3 region seems to be a more appropriate marker for relationships between species groups than between individual species.