QUANTITATION OVER TIME OF TOMATO YELLOW LEAF CURL GEMINIVIRUS DNA IN ITS WHITEFLY VECTOR

The amount of tomato yellow leaf curl geminivirus (TYLCV) DNA that acc umulated in the vector Bemisia tabaci was studied by quantitative chem iluminescent dot-blot assay, using digoxigenin-labeled specific DNA pr obes. Large groups of female whiteflies were allowed to feed for 4, 12 , 24, or 48 h on TYLCV-infected tomato plants and then were transferre d to TYLCV-immune cucumber plants. Insects were sampled at different t imes during and after acquisition access and tested for TYLCV-DNA cont ent. TYLCV-DNA assays were done either on whole insects or on the head plus prothorax (to include salivary glands) and abdomen separately. T he maximum amount of TYLCV DNA, averaging from 0.5 to 1.6 ng per insec t, was always attained at the end of the acquisition period. The mean amount then decreased by about 1 to 2% per day, remaining clearly dete ctable up to 20 days after the end of the acquisition period. Only som e whiteflies that were TYLCV-positive in the abdomen were positive for head plus prothorax. In both parts of the body, TYLCV DNA remained de tectable up to 18 days after the end of the acquisition period, showin g that TYLCV DNA remains in insect tissues much longer than infectivit y indicates.