EVIDENCE FOR LACK OF PROPAGATION OF POTATO LEAF ROLL VIRUS IN ITS S HID VECTOR, MYZUS-PERSICAE

Two isolates of potato leaf roll virus (PLRV) were used in serial passage tests with the green peach aphid, M. persicae. Initial characterization of the transmission pattern indicated that at 25.degree. C individual 1st instar larvae efficiently (92%) acquired and transmitted virus from infected Physalis floridana. When transferred to a sequence of P. floridana test seedlings, infective single aphids lived 18-24 days. After a 30-49 h median latent period, they inoculated an average of 6-8 seedlings and remained infective for an average of 9-11 days. Estimates varied with the length of the acquisition access period. Approximately 14% of late instar larvae injected with hemolymph from infective aphids transmitted PLRV. Injected insects survived about 16 days and inoculated an average of 1 plant/insect after a median latent period of approximately 85 h. They remained infective for approximately 5 days. In a series of serial passage trials, infectivity of aphids was not maintained beyond the 1st transfer. About 20% of larvae injected with hemolymph from aphids reared on infected Physalis transmitted PLRV (1st passage). No further passage occurred, regardless of whether aphids were kept on immune or susceptible test plants. Evidence suggests that these isolates of PLRV were circulative, but not propagative, in 2 clones of M. persicae.