Specific diagnosis of two root-knot nematodes, Meloidogyne chitwoodi and M-fallax, with satellite DNA probes

Meloidogyne chitwoodi and M. fallax are serious pests of potato, and both s pecies have been recently designated as quarantine organisms in the Europea n Community and in Canada. The sympatric and less damaging species M. hapla is often found associated with both of them under temperate climates. Here , we describe the use of satellite DNA (satDNA) sequences previously isolat ed from these three root-knot nematode species for the development of speci fic diagnostic procedures. In dot-blot experiments, it was unambiguously po ssible to separate M. chitwoodi and M. fallax from M. hapla using satDNA mo nomers as probes. In squash-blot experiments, satDNAs allowed discriminatio n between single individuals of M. chitwoodi or M. fallax from M. hapla, ev en within root tissues, without the need for DNA purification. The same res ults were obtained with radioactive or digoxigenin-labeled probes with no l oss of sensitivity in detection. M. fallax and M. chitwoodi could not be di stinguished. From this study, it is concluded that such cloned satDNA seque nces may constitute a powerful tool for the identification and management o f Meloidogyne spp. populations in the field and for the implementation of q uarantine regulations against these pests.