Helicotylenchus microlobus is considered to be a junior synonym of H. pseudorobustus by several authors while others consider it as valid. To clarify the status of both species, 39 samples collected from various countries were subjected to statistical analyses that showed they could be grouped into six groups. Topotypes of H. pseudorobustus and H. microlobus belong to two different groups. However, samples in the other groups were morphologically intermediate between these two groups. Characters used in the past to uphold the validity of H. microlobus were variable and overlapping from group to group. The 28 samples studied are identified as H. pseudorobustus. Helicotylenchus microlobus, H. bradys and H. phalerus are confirmed as junior synonyms of H. pseudorobustus. There was no complete congruence between the morphological groups and molecular groups proposed by other authors. For these, two MOTU (Molecular Operational Taxonomic Unit) are accepted within H. pseudorobustus.
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