DETECTION AND RELATIONSHIPS OF COTTON LEAF CURL VIRUS AND ALLIED WHITEFLY-TRANSMITTED GEMINIVIRUSES OCCURRING IN PAKISTAN

A stock culture of cotton leaf curl virus from Pakistan (CLCuV-PK), wa s transmitted by whiteflies (Bemisia tabaci) to seven plane species, i ncluding French bean, okra, tobacco and tomato, and caused vein thicke ning and leaf curl symptoms. It was readily detected in triple antibod y sandwich ELISA (TAS-ELISA) by 11 out of 31 monoclonal antibodies rai sed against the particles of three other geminiviruses: African cassav a mosaic, Indian cassava mosaic and okra leaf curl viruses. Reaction s trength was enhanced when the tissue extraction fluid contained sodium sulphite. Minor variations in epitope profile were found among virus isolates from cotton (Gossypium hirsutum) collected from different dis tricts in Pakistan over a 5-year period. These epitope profiles were d istinguishable from that of cotton leaf curl virus from G. barbadense in southern India but indistinguishable from the profiles of viruses c ausing yellow vein disease of okra in India or Pakistan, or leaf curl of okra (Abelmoschus esculentus), Hibiscus tiliaceus, radish or sunflo wer in Pakistan, suggesting that these plants are putative natural hos ts of CLCuV-PK. The viruses in cotton, and in okra with leaf curl or y ellow vein symptoms, were also detected by PCR with three pairs of CLC uV-PK-specific primers. Five additional whitefly-transmitted geminivir uses were found among isolates from 11 other naturally-infected specie s in Pakistan, and were distinguished by their epitope profiles, These viruses were associated, respectively, with tobacco leaf curl, squash yellow blotch, tomato yellow leaf curl, watermelon leaf crinkle and s oybean yellow mosaic diseases. The first four of these viruses were de tected readily by PCR with geminivirus general primers but only weakly , if at all, with two pairs of CLCuV-PK-specific primers. Pakistani cr ops are infected with a range of distinguishable but relatively closel y related whitefly-transmitted geminiviruses, some of which resemble t hose found in India.