Transmission of Pea Enation Mosaic Virus by the Pea Aphid, Acyrthosiphon pisum, following Virus Acquisition by Injection

Acyrthosiphon pisum (Harris) became highly inoculative after partially purified and density gradient-purified preparations of pea enation mosaic virus (PEMV) were injected into them as young nymphs. The aphids' mean rate of transmission, Vo , and mean (weighted) period of inoculativity, Tt , increased linearly as the dosage of injected virus increased, whereas the median latent period, LP50, decreased as dosage increased. When late 1st to early 2nd instars were inoculated with partially purified virus preparations at a concentration of A260nm = 30, a Vo of 21 transmissions per aphid per generation, a Tt of 9.35 days, and an LP50 as short as 3.0 hours were realized. All attempts to maintain inoculativity among aphid lines by the serial hemolymph-passage method failed after the 2nd passage, even though young nymphs were used as recipients in each passage. Inoculativity was maintained in over 60% of the aphid lines after the 1st passage. Aphid nymphs became inoculative when injected with hemolymph collected from aphids 4, 7, and 10 days after a 24-hour acquisition-access period on PEMV-infected plants but not when injected with hemolymph collected on the 13th day.