Association of the Nucleic Acid of Squash Leaf Curl Geminivirus with the WhiteflyBemisia tabaci

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Abstract
Squash leaf curl geminivirus (SLCV) was detected in its whitefly vector, Bemisia tabaci, using full-length cDNA clones of the SLCV genome in a nuclei acid spot hybridization assay. Viral DNA was detected more readily in individual whitelifes ground in buffer and spotted onto membranes than in whiteflies squashed onto membranes. Amounts of viral DNA from 3.2 to 926 pg were detected in individual whiteflies reared on SLCV-infected squash plants. No significant differences were found in the detection rates (number of insects with detectable amount of viral nucleic acid/number of insects tested) of male and femlae adults, but male insects contained more viral DNA/.mu.g of body weight than females. Viral nucleic acid was detected infrequently in immature stages of B. tabaci that developed on infected plants, and this corresponded with low virus transmission rates by adults emerging from tested populations of immature whiteflies. Viral nucleic acid was detected in adult whiteflies for at least 120 hr after 12- and 24-hr acquistion access periods on infected plants. Detection rates and mean amounts of detectable viral nucleic acid remained constant over the 120-hr period, while the whiteflies fed on a nonhost plant. Viral nuclei acid was detected in Trialeurodes vaporariorum, a nonvector whitefly species. Longer acquisition access periods resulted in a higher rates of detection in adults of B. tabaci and in increased rates of transmission. SLCV coat protein was detected in individual adults of B. tabaci using an enzyme-linked immunosorbent assay (ELISA). Detection rates, either by ELISA or nucleic acid spot hybridization, did not necessarily reflect transmission rates of individual whiteflies.