Plant Virus Transmission by Insects

Abstract Most plant viruses depend on vectors for their survival and spread. Most vectors are piercing‐sucking insects that transmit plant viruses in either the circulative virus (CV) or noncirculative virus (NCV). NCV are carried on the lining cuticle of vectors stylets. CVs cross the vectors’ gut, move internally to the salivary glands (SG), cross the SG membranes to be ejected upon feeding. Transmissibility of NCVs depends on motifs of coat protein and for Potyviruses and Caulimoviruses also on helper proteins (encoded by the virus). NCV proteins were found to associate with vectors’ cuticle proteins. Transmissibility of CVs depends on proteins comprising the virus capsid (the coat protein and the read‐through protein) and on symbionin (produced by vectors’ symbionts). Passage of CV through the gut has been also associated with vectors’ proteins. To suppress plant virus epidemics, several control measures that interfere with vector landing or feeding are proposed. Key concepts Plants are rooted; therefore, plant viruses depend for their spread on insect vectors Epidemics occur when a new virus or a new vector invade a new ecological niche. Specificity between viruses and vector species may reflect the preference of the vector to the plant species. Viruses that lost the ability to be transmitted by vectors serve to identify protein motifs that are associated with transmission. Noncirculative viruses are transmitted by aphids during intracellular stylet penetrations whereas circulative viruses are transmitted during committed phloem ingestion. Proteins encoded by the potyviruses and caulimoviruses are essential for assisting transmission by aphids. Heteroencapsidation is responsible for expanding the vector range of luteoviruses. Vector proteins were found to associate with viral proteins (for potyviruses, caulimoviruses and luteoviruses). Insecticide are inefficient in preventing noncirculative plant viruses spread by vectors (the time needed to kill the vector is longer than the time needed to inoculate the host). Control measures that affect vector landing or feeding are efficient in suppressing virus spread.