Serological detection and antigenic variation of two whitefly-transmitted geminiviruses: tobacco leaf curl and croton yellow vein mosaic viruses.
A panel of 25 monoclonal antibodies (MAbs) raised against particles of 2 heterologous whitefly-transmitted geminiviruses (begomoviruses) was used in TAS-ELISA to determine the detectability and epitope profiles of 26 Indian isolates of tobacco leaf curl bigeminivirus (TLCV) and 13 of croton yellow vein mosaic bigeminivirus (CYVMV). Stock cultures of the 2 viruses had indistinguishable epitope profiles, although they differed in symptomatology and particle stability. Their epitope profiles strongly resembled those of Indian isolates of bhendi (okra) yellow vein mosaic and cassava Indian mosaic (ICMV) bigeminiviruses. TLCV isolates from Andhra Pradesh, Gujarat and Karnataka, India, differed slightly in their epitope profiles. They reacted with at least 8 of 10 MAbs raised to ICMV, but with only 1-4 of the 15 MAbs raised ACMV. Virus isolates serologically indistinguishable from TLCV were detected in symptom-bearing weeds (Acanthospermum hispidum, Ageratum conyzoides, Euphorbia geniculata and Parthenium hysterophorus) growing in leaf curl-affected tobacco fields, and shown previously to be experimental hosts of TLCV. Indian TLCV isolates had small consistent differences in epitope profiles from Pakistani isolates, and large differences from isolates from Burkina Faso, Malawi or Uganda. These African isolates reacted with 4 or 5 of the ACMV MAbs, but with only 1 or 2 of the ICMV MAbs, and there were small but consistent inter-country differences. CYVMV isolates from the Indian States showed less epitope variation than Indian isolates of TLCV. TAS-ELISA with MAb SCR18 was a more sensitive test for detecting Indian TLCV isolates than DAS-ELISA with polyclonal antibodies.