Burrowing nematodes from Colombia and their relationship with Radopholus similis populations, R. arabocoffeae and R. duriophilus

Two burrowing nematode populations from Colombia were characterised using morphological, morphometric and molecular criteria. The morphological and morphometric characters of the two populations did not differ from those of Radopholus similis. The phylogenetic analysis based on sequence comparison of 18S, D2D3 regions of these populations with those of Radopholus sp., R. similis and other Tylenchomorpha from GenBank confirmed the close molecular relationship between the genus Radopholus and the Hoplolaimidae. The consensus tree based on the comparison of ITS1-5.8-ITS2 rDNA sequences of the Colombian populations with R. similis (many sources), R. arabocoffeae and R. duriophilus from GenBank grouped the Colombian populations in a clade which also included R. similis from different localities. Other R. similis populations grouped in separated clades, which were closely related to the clade containing R. arabocoffeae and R. duriophilus. The high genetic variability among the R. similis populations was observed and confirmed by the high ITS1-5.8-ITS2 sequence divergence within the R. similis populations studied (5.4%) which was comparable to the divergence (4.2-6.9%) between the Radopholus species included in the analysis. These findings and the unresolved phylogenetic placement of R. arabocoffeae and R. duriophilus among R. similis suggests that the burrowing nematode could be a species complex. Limited information on the variability of the 18S and D2D3 region gives an indication of their possible value, besides ITS1-5.8-ITS, as molecular markers within Radopholus. No complete and comprehensible relation was found between the phylogenetic position of the Radopholus populations and their geographical origin or host.