Detection of phytoplasma by polymerase chain reaction of insect feeding medium and its use in determining vectoring ability

A polymerase chain reaction (PCR)-based method was developed for the detection of phytoplasma in insect feeding medium (sucrose). A correlation was established between the transmissibility of Flavescence doree phytoplasma in the experimental leafhopper vector Euscelidius variegatus and its detection by PCR in the insect feeding medium. However, phytoplasma were detected in the insects' bodies 3 weeks before they began to transmit. Hence, PCR assays of the sucrose medium reflected phytoplasma vectoring ability probably by detecting it in the insect saliva, whereas detection of phytoplasma in the insect's body did not identify it as a vector. The assay was applied to two field-collected leafhoppers suspected of being phytoplasma vectors in Israel (Orosius albicinctus and Anaceratagallia laevis). The presence of phytoplasma in the body of specimens of the latter species was assayed by PCR in 1999. Phytoplasmas were detected in insects' bodies throughout the year, with no specific seasonal pattern. In the sal...