4 DNA-A VARIANTS AMONG PAKISTANI ISOLATES OF COTTON LEAF CURL VIRUS AND THEIR AFFINITIES TO DNA-A OF GEMINIVIRUS ISOLATES FROM OKRA

Complete DNA-A sequences of nine Pakistani geminivirus isolates from l eaf curl-affected cotton (CLCuV-PK) or from okra, and the partial sequ ences of several additional isolates were determined, Sequences of iso lates from cotton were of four types, Isolates from leaf curl-affected okra had virtually the same sequences as those from cotton, isolates from yellow vein mosaic-affected okra were of two types (OYVMV types 2 01 and 301), both distinct from but closely related to the virus isola tes from cotton, Of these six types, two types of CLCuV-PK are the mos t closely related but another (CLCuV-PK type 72b) is the most distinct , Of the encoded proteins, coat protein (CP) is the most strongly cons erved (92-100 % amino acid sequence identity), and AC4 protein the mos t variable (41-87%). The 5' and 3' halves of the intergenic region of some isolates had different affinities and occurred in seven combinati ons, suggesting that recombination had occurred and that the origin of replication was a favoured recombination site, Similarly, the first 1 520 nt of CLCuV-PK type 804a DNA resembled those of OYVMV type 301 DNA but the remaining 1224 nt were very different, The AC1 (Rep) gene and 5' part of the intergenic region of CLCuV-PK type 72b closely resembl ed those of OYVMV type 301, whereas the rest of the sequence did not, The cotton leaf curl epidemic in Pakistan is caused by several distinc t variants, with recombination events involving OYVMV and other unspec ified geminiviruses having probably been involved in their evolution.