Arthropod Transmission of Plant Viruses: a New Synthesis

This review focuses on the more important arthropod vectors of plant viruses, 4 families of homopterans (aphids, whiteflies, leafhoppers, and delphacid planthoppers), thrips, chrysomellid beetles, and, among the acarines, the eriophyid mites. More than 380 viruses from 27 plant virus genera are transmitted by the Homoptera. Two systems of terminology have been devised to describe and group homopteran-borne plant viruses. One is based on persistence of transmissible virus in the vector and the other on the mechanism of transmission or route of virus transport in the vector. Here the 2 systems are combined to create the following 4 transmission groups: (1) the nonpersistently transmitted, stylet-borne viruses; (2) the semi-persistently transmitted, foregut-borne viruses; (3) the persistently transmitted, circulative viruses; and (4) the persistently transmitted, propagative viruses. Homopteran transmitted viruses are characterized by the following 3 traits: (1) no virus is transmitted by vectors from >1 homopteran family; (2) most plant virus genera have vectors from 1 family of homopterans, although some are characterized by vectors from ≥2 families, usually from the same homopteran suborder; (3) the persistence and mode of transmission for all viruses within a virus genus is almost always the same and appears to be a stable evolutionary trait. Certain aspects of the feeding behavior and the morphology of the mouth parts and digestive systems of the Homoptera and other vectors covered in this review are discussed with respect to their relevance to vector transmission. The thrips-borne viruses are transmitted much in the same way as are the persistently transmitted, propagative viruses by the Homoptera. At least 42 plant viruses are transmitted by the Coleoptera. Their mode of transmission differs markedly from that described for the homopterans and thrips. So, too, does the transmission of plant viruses by eriophyid mites. Throughout this review, frequent mention is made as to how an understanding of virus transmission is important to interpreting virus epidemiology and in the control of virus disease.