Reduction in the transmissibility of a greenhouse-maintained isolate of aster yellows agent

Abstract

A celery-infecting isolate of aster yellows agent (isolate A), maintained in the greenhouse since its isolation from the field in 1958, was found to be significantly less transmissible by the aster leafhopper. Macrosteles fascifrons (Stål) than a similar isolate (isolate B) obtained from the same area in 1972. The difference in transmissibility was greatest in male insects, especially those given acquisition access periods as adults. Transmission of isolate A was increased to equal that of isolate B when leafhoppers were injected with inocula prepared from inoculative leafhoppers. No differences were found between isolates in their incubation periods in plants and insects or in their ability to infect asters. On the basis of earlier data and present findings, it is suggested that isolate A has undergone a change in transmissibility during its maintenance in plants grown under artificial conditions.