Satellite DNA as a target for PCR-specific detection of the plant-parasitic nematode Meloidogyne hapla.

The polymerase chain reaction was evaluated for its ability to amplify DNA sequences specific for the root-knot nematode Meloidogyne hapla, using oligonucleotides whose sequence was deduced from the satellite DNA previously cloned in this species as primers. As expected, ladder patterns of monomers and multimers of an approximate 150-170-bp repeat were amplified from purified genomic DNA of all the M. hapla isolates studied, while no amplification was detected with the five other Meloidogyne species tested. Moreover, the satellite DNA nature of the amplification products was confirmed through Southern-blot hybridization with the previously cloned monomeric unit. In further experiments, DNA was extracted from single females, males, juveniles, or eggs according to a simple procedure, and used as a template in PCR assays. Amplification products were obtained, whose electrophoretic patterns were always very similar to those from M. hapla genomic DNA, thus demonstrating the high sensitivity of the method. This satellite DNA-based strategy can be exploited to develop species-specific primer sets for use on a routine basis as a diagnostic tool for unambiguous nematode identification procedures.