Studies on the relationships of cucumber vein yellowing Ipomovirus with its whitefly vector Bemisia tabaci

Cucumber vein yellowing virus (CVYV), a tentative member of the genus Ipomovirus (Potyviridae) with host-range restricted to Cucurbitaceae, was first described in Israel in the Sixties and has been recently reported in Spain. We have studied the relationships of CVYV with its whitefly vector Bemisia tabaci Genn. B biotype, by means of experimental transmissions from melon to melon (cv Vedrantais) with groups of insects of variable size, under controlled conditions. CVYV was transmitted in a semi-persistent manner by B. tabaci. The maximum estimated proportion of transmission by single insect was quite variable in different experiments ranging from 7 to 21%, but in all cases it attained a maximum between 4 and 8 h of acquisition access. The vectoring efficiency had a significant reduction when the acquisition access was extended to 8-16 h, and a new increase when prolonged further. After an acquisition access of 7 h on infected melons, the transmission efficiency of vectors increased exponentially with the time of inoculation access, approaching the maximum after 12 h. The maximum retention of infectivity was between 12 and 15 h, from the end of an acquisition access of 7 h. The transmission efficiency decreased exponentially with time, with a half-life of about 3 h 45 min. Mathematical models of the transmission kinetics are proposed.