Quantity of Virus Required for Aphid Transmission of a Potyvirus

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Abstract
Aphids (Myzus persicae) were allowed a 10-min acquisition access, through a membrane, to solutions that contained helper component and 1 ng/.mu.l of tobacco etch virus or tobacco vein mottling virus the presence of 125I. Individual aphids were then placed in a gamma counter to determine 125I content and transferred to a tobacco seedling to test for transmission. Volumes of feeding solution acquired by aphids, calculated from their 125I content, typically ranged from approximately 300 pl to approximately 1 pl. Similar volumes were calculated when 125I-labeled virus was used to determine volumes acquired by aphids, indicating that there was not selective uptake of either the isotope or the virus. The number of virus particles in these volumes was calculated to be from approximately 4,000 to approximately 10. From 5 to 17% of the aphids transmitted virus, and there was no correlation between the number of particles acquired and the ability to transmit. The amount of virus required for transmission in these experiments was in the femtogram range and thus well below the limits of detection for currently available systems; this is of significance for attempts to detect viruliferous aphids for epidemiological studies or for predictive schemes.