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 four diseases of crop plants in Burkina Faso: cassava mosaic, okra leaf curl, tobacco leaf curl and tomato yellow leaf curl. Tomato yellow leaf curl is an economically serious disease, reaching a high incidence in March, following a peak population of the vector whitefly, Bemisia tabaci, 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 period of okra production in the rainy season. The geminiviruses causing these four diseases, African cassava mosaic (ACMV), okra leaf curl (OLCV), tobacco leaf curl (TobLCV) and tomato yellow leaf curl (TYLCV) viruses, were each detected in field-collected samples by triple antibody sand-wich-ELISA with cross-reacting monoclonal antibodies (MAbs) to ACMV. Epitope profiles obtained by testing each virus isolate with panels of MAbs to ACMV, OLCV and Indian cassava mosaic virus enabled four viruses to be distinguished. ACMV and OLCV had similar but distinguishable profiles. The epitope profile of TobLCV was the same as that of one form of TYLCV (which may be the same virus) and was close to the profile of TYLCV from Sardinia. The other form of TYLCV reacted with several 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 Faso. Sida acuta is a wild host of OLCV.