OCCURRENCE OF WHITEFLY-TRANSMITTED GEMINIVIRUSES IN CROPS IN BURKINA-FASO, AND THEIR SEROLOGICAL DETECTION AND DIFFERENTIATION

Whitefly-transmitted geminiviruses were found to be associated with fo ur diseases of crop plants in Burkina Faso: cassava mosaic, okra leaf curl, tobacco leaf curl and tomato yellow leaf curl. Tomato yellow lea f curl is an economically serious disease, reaching a high incidence i n March, following a peak population of the vector whitefly, Bemisia t abaci, in December. Okra leaf curl is also a problem in the small area of okra grown in the dry season but is not important in the main peri od of okra production in the rainy season. The geminiviruses causing t hese four diseases, African cassava mosaic (ACMV), okra leaf curl (OLC V), tobacco leaf curl (TobLCV) and tomato yellow leaf curl (TYLCV) vir uses, were each detected in field-collected samples by triple antibody sandwich-ELISA with cross-reacting monoclonal antibodies (MAbs) to AC MV. Epitope profiles obtained by testing each virus isolate with panel s of MAbs to ACMV, OLCV and Indian cassava mosaic virus enabled four v iruses to be distinguished. ACMV and OLCV had similar but distinguisha ble profiles. The epitope profile of TobLCV was the same as that of on e form of TYLCV (which may be the same virus) and was close to the pro file of TYLCV from Sardinia. The other form of TYLCV reacted with seve ral additional MAbs and had an epitope profile close to that of TYLCV from Senegal. Only minor variations within each of these four types of epitope profile were found among geminivirus isolates from Burkina Fa so. Sida acuta is a wild host of OLCV.