THE TRANSMISSIBILITY OF A POTYVIRUS BY AN APHID VECTOR - RELIABILITY OF MEASUREMENTS UNDER CONTROLLED CONDITIONS

Reproducibility of measurements of the transmission rate of a given potyvirus by a given aphid vector was assessed using a standardised transmission procedure. The plant-virus-vector system studied was: Cucurbita pepo - Papaya ringspot virus - Aphis gossypii. Several elements concerning the rearing and handling of the aphids were analysed. One of these, the climatic conditions under which the aphids were reared, influenced the transmission rate of the virus. Six trials were carried out to measure the rate of transmission of the virus from a defined leaf surface area. The measurements appeared to be reliable. A two year experiment was carried out to compare transmission rates at different dates. Although strong variations were observed in some source plants, the transmission rates obtained for samples of 10 source plants were stable, with a 10% coefficient of variation. The results show that transmissibility of the virus is a stable property which is independent of the trial date. They are discussed in relation to standardised elements of the transmission process.