A plant virus lethal to its insect vector

Abstract

The peach yellow leaf roll strain of Western X-disease virus was shown to cause the premature death of its leafhopper vector, Colladonus montanus. Celery was used as virus source plants and as test plants. In one type of experiment, leafhoppers from a single colony were divided into two equal groups. One group was caged on diseased celery for 21 days while the control group fed only on healthy celery. Later, 15 insects from each group were tested singly for virus transmission and longevity. Twelve leafhoppers which transmitted virus had a mean longevity of 38 days compared to 82 days for the noninfective controls. The remaining insects from each of the two main groups were tested in groups of 10. The mean longevity of these infective and noninfective groups was 24 and 51 days, respectively. In other experiments all leafhoppers were caged on diseased plants and were subsequently tested individually for virus transmission and longevity. In fourteen such experiments the mean longevity of 116 leafhoppers that transmitted virus was 20 days compared to 51 days for the 64 nontransmitting individuals. These results indicate that the virus itself shortens the life of leafhoppers which acquire it and that the differences in longevity cannot be accounted for on the basis of altered physiology of diseased plants. This appears to be the first record of a virus that eventually kills its insect vector, and it adds to the plausibility of the theory that plant viruses may have evolved from arthropod viruses.