In vitro Biological Activity Associated with the Aphid Transmission Factor of Cauliflower Mosaic Virus

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Abstract
Summary An assay system was developed to enable cauliflower mosaic virus (CaMV) isolate Cabb B-JI to be acquired by Myzus persicae feeding through membranes on crude extracts and subcellular fractions of infected turnip plants. Optimum transmission of the virus was from solutions containing 200 mm-Tris-HCl pH 7.6, 100 mm-EGTA and 50 mm-MgCl2. The rates of transmission by single aphids from such extracts were similar to or higher than those of single aphids from injected plants to healthy plants. Similar transmission efficiencies following feeds lasting 1 min, 15 min or 3 h show that the aphid-virus association is not diminished by long acquisition feeds. Subcellular fractionation showed that transmission was related to the presence of virus particles and aphid transmission factor (ATF) but not to the inclusion body protein. It is suggested that the transmitted agents were virus particles linked to ATF. Although figwort mosaic virus (FMV) was not transmitted by aphids from extracts of infected plants it became aphid-transmissible when the extracts were mixed with similar extracts of plants infected with CaMV-Cabb B-JI, perhaps because CaMV ATF assists in the transmission of FMV.