ADDITIONAL EVIDENCE OF MULTIPLICATION OF SOWTHISTLE YELLOW VEIN VIRUS IN AN APHID VECTOR-SERIAL PASSAGE

Beginning with an injected dose of an estimated 105 particles of the sowthistle yellow vein virus (SYVV) and approximately a 70-fold dilution at each subsequent injection, the inoculativity of an aphid vector, Hyperomyzus lactucae (L.), was maintained for 6 successive passages. The interval between the passages varied from 10 to 12 days, during which time individual insects were tested for inoculativity by transferring them to healthy sowthistle, Sonchus oleraceus L., plants every 48 hours. The insects were kept at 26 ± 1° in constant light of 600-800 foot candles at cage level. At each passage the virus underwent an incubation period in the aphids. The median length of the incubation period was approximately 6 days, and this was independent of the passage, indicating that the dose of inoculum remained constant. Some 77% of the insects in the hemolymph transfers survived the interval between injections. Successful virus passage, among the surviving insects, from infected donors to recipient aphids occurred in about 97% of the cases. There was evidence that the infection was associated with an increased mortality rate among the hemolymph-injected aphids. © 1969.