Serological relationships and epitope profiles of isolates of okra leaf curl geminivirus from Africa and the Middle East

A panel of seven murine monoclonal antibodies (mAbs) was raised against particles of okra leaf curl virus (OLCV), a whitefly-transmitted geminivirus which is prevalent in West Africa. The mAbs detected at least six distinguishable epitopes, two continuous and four discontinuous. In tests with these mAbs, relatively little antigenic variation was found among 24 OLCV isolates from Burkina Faso, Chad, Ghana, Ivory Coast, Nigeria, Oman and Saudi Arabia, each virus isolate reacting with at least five of them. However, on the basis of their reactions with 17 mAbs raised against particles of a group A isolate of African cassava mosaic virus (ACMV), the OLCV isolates could be assigned to two groups, which have geographical distributions that overlap in West Africa. A network of antigenic relationships was revealed by reactions between the OLCV mAbs and other whitefly-transmitted geminiviruses from six plant species in 12 countries. OLCV shared the most epitopes with tobacco leaf curl (African isolates) virus, ACMV, Indian cassava mosaic virus and bean golden mosaic virus. Selected OLCV mAbs are suitable for routine detection of OLCV, and a panel of three mAbs can be used to identify it.