Intracellular salivation is the aphid activity associated with inoculation of non-persistently transmitted viruses

Approximately 75 % of aphid-vectored viruses are transmitted in a non-persistent (non-circulative) manner. Localization studies indicate that such viruses are acquired via ingestion and retained in the food canal of the maxillary stylets, but the inoculation mechanism has remained unresolved. Electrical recording of stylet penetration activities reveals that inoculation is associated with the first intracellular activity (subphase II-1) following maxillary puncture of an epidermal cell. Subphase II-1 may represent virus inoculation via egestion (regurgitation of virions with food-canal contents) or salivation (saliva-mediated release of virions from the common food-salivary duct at the tips of the maxillary stylets). Here, inoculation of the circulatively transmitted Pea enation mosaic virus was used as a marker for intracellular salivation during epidermal cell punctures. The results confirmed that inoculation of non-persistently transmitted viruses (subphase II-1) is associated with active injection of saliva directly into the cytoplasm.