Further biochemical evidence showing that Meloidogyne hapla, M. chitwoodi and M. fallax are distinct species
Classical nematode species determination is based upon a relatively small number of morphological characters and does not always allow to differentiate between certain species. This was one of the reasons why no discrimination could be made between M. chitwoodi (EPPO A2 quarantine pest) and some populations of M. hapla or the recently described M. fallax. Despite this morphological similarity between, clear differences can be demonstrated between these three species by certain stable morphological traits, isozyme phenotypes, rDNA patterns of the ITS (internal transcribed spacer) regions, etc.
Two-dimensional gel electrophoresis of total soluble proteins has been used to study the similarity between various isolates of the three species. The results confirmed that Meloidogyne hapla, M. chitwoodi and M. fallax are distinct biological entities, as the intraspecific variation (within the three species) is much less than the interspecific variation. Although variation was limited, M. hapla shows more intraspecific variation than M. chitwoodi and M. fallax. The authors also referred to other studies on intraspecific variations in virulence (tests done on potato cultivars and wild Solanum species) which showed that no variation was found in M. chitwoodi and M. fallax whereas a remarkably large variation in virulence was found in M. hapla. They felt that the differences in intraspecific variation within these three Meloidogyne species can have important implications for crop protection based on the use of host-resistant plants, as breeding for resistant plants might be more promising for M. chitwoodi and M. fallax than for M. hapla.
van der Beek, J.G.; Folkertsma, R.; Poleij, L.M.; van Koert, P.H.G.; Bakker, J.; (1997) Molecular evidence that Meloidogyne hapla, M. chitwoodi and M. fallax are distinct biological entities.
Fundamental and applied Nematology, 20(5), 513-520.