Tobacco plants infected with CMV-16
were allowed to become infested with
aphids, then transplanted to the field to
serve as a natural source of inoculum for
untreated melon test plants as well as vaccinated melon plants. The viruliferous
aphids carrying the severe CMV-16 strain
then infected the melon plants, simulating
a natural CMV-infection such as might
occur in cases of heavy infestation. The
fruit yield in vaccinated plants dropped
from 126 to 101% (approximately 20%
yield reduction) when viruliferous aphids
were the source for the challenge inoculation with CMV-16 (S/16 compared to
S/16A: Table 2). This reduced yield is
comparable to the yields of healthy control
plants or vaccinated plants. However, the
yield percentage was lowered to 40% when
nonvaccinated (unprotected) healthy plants
were exposed to viruliferous aphids and to
53% when mechanically challenged. This
indicates that viruliferous aphids may be
more efficient in transmitting the virus to
plant tissues than mechanical transmission.
Surprisingly, vaccinated and challenged
plants showed a higher yield percentage
(126%) than any of other treatment (Table
2). The average yield from vaccinated
plants was significantly higher than fruits
harvested from either nonvaccinated
plants, healthy plants challenged with
CMV-16 via aphids, or plants mechanically
inoculated with CMV-16 alone.