Heat inactivation and interactions of four aster yellows virus strains in their vector, Macrosteles fascifrons (Stål)

Macrosteles fascifrons (Stål) leafhopper colonies were infected with four strains of aster yellows virus (AYV); eastern AYV, western AYV, AYV 2, and AYV 6. Infective leafhopper colonies were given heat treatments. Exposure for 10 days at 36°C, or 5 days at 40°, resulted in inconsistent transmission, but no permanent loss of virus. Exposure for 7 days at 40° rendered leafhoppers infected with eastern (noncelery-infecting) AYV noninfective for at least 19 days, but western (celery-infecting) strains of AYV regained their ability to transmit the virus in 3–5 days. Thus, the eastern strain of AYV is more sensitive to heat than three western-type strains. Cross protection tests in individual insects showed that eastern AYV failed to protect against infection by the celery-infecting strains AYV 2 and western AYV. However, three celery-infecting strains protected insects from infection by eastern AYV.