Serological detection and antigenic variation of two whitefly‐transmitted geminiviruses: tobacco leaf curl and croton yellow vein mosaic viruses

Abstract

SummaryA panel of 25 monoclonal antibodies (MAbs) raised against particles of two heterologous whitefly‐transmitted geminiviruses (begomoviruses) was used in triple antibody‐sandwich ELISA (TAS‐ELISA) to determine the detectability and epitope profiles of 26 Indian isolates of tobacco leaf curl virus (TLCV) and 13 of croton yellow vein mosaic virus (CYVMV). Stock cultures of the two viruses had indistinguishable epitope profiles although they differ in symptomatology and particle stability. Their epitope profiles also strongly resembled those of Indian isolates of bhendi (okra) yellow vein mosaic and Indian cassava mosaic (ICMV) viruses. TLCV isolates from Andhra Pradesh, Gujarat and Karnataka States differed slightly in epitope profile: they reacted with at least eight out of 10 MAbs raised to ICMV but only one to four out of 15 MAbs raised to African cassava mosaic virus (ACMV). Virus isolates serologically indistinguishable from TLCV were detected in symptom‐bearing weeds (Acanthospermum hispidum, Ageratum conyzoides, Euphorbia geniculata, Parthenium hysterophorus) found in leaf curl‐affected tobacco fields and shown previously to be experimental hosts of TLCV. Indian TLCV isolates had small, consistent differences in epitope profile from Pakistani isolates but large differences from isolates from Burkina Faso, Malawi or Uganda. Isolates from the three African countries reacted with four or five of the ACMV MAbs but only one or two of the ICMV MAbs, and there were small but consistent inter‐country differences. CYVMV isolates from three Indian States showed less epitope variation than did Indian isolates of TLCV. TAS‐ELISA with MAb SCR 18 was a more sensitive test for detecting Indian TLCV isolates than was double antibody‐sandwich ELISA with polyclonal antibodies.