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Acquisition, Interference, and Retention of Cucurbit Leaf Curl Viruses in Whiteflies. S. Cohen, Visiting scientist, Volcani Institute of Agricultural Research, Bet-Dagan, Israel; J. E. Duffus, and H. Y. Liu. Plant pathologists, USDA-ARS, 1636 E. Alisal St., Salinas, CA 93905. Phytopathology 79:109-113. Accepted for publication 28 July 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-109.

Squash leaf curl virus (SLCV) antigens could be detected by enzyme-linked immunosorbent assay (ELISA) in Bemisia tabaci extracts when batches of at least 20 females previously fed for 48 hr or more on a SLCV source were tested. ELISA reaction intensity of extracts depended on the age of the squash source plants and the position of the leaves on which B. tabaci fed. ELISA detectable virus antigen and transmission rate were higher with a longer acquisition access period. SLCV antigen detected by ELISA decreased rapidly with time after acquisition feeding, but the insects remained inoculative for many more days. As long as SLCV antigen could be detected in B. tabaci, no significant decrease in transmission efficiency was observed. A reduction in transmission efficiency of melon leaf curl virus (MLCV; closely related to SLCV) by B. tabaci was demonstrated when insects were first allowed to acquire SLCV. A higher SLCV antigen titer per unit weight was found to accumulate in the nonvector whitefly, Trialeurodes abutilonea, than in B. tabaci. These findings are compatible with a model described for luteoviruses, in which the virus in the haemocoele serves as a reservoir for the salivary gland system where virus specific sites exist. It appears, however, that once the SLCV becomes attached to these sites, it remains infectious, but can no longer be detected by ELISA. In the case of T. abutilonea, the inability of the virus to pass through the salivary glands is possibly the reason for its failure to transmit SLCV.