Cucumber mosaic virus groups IA and II are represented among isolates from naturally infected lilies

Four cucumber mosaic virus isolates (named Cas, CB, P26 and Simp2) found in naturally infected lily plants were characterized on the basis of their serological properties and the results of analysis of RNA3 sequence fragments containing coat protein and movement protein genes. The properties of lily isolates were compared with those of eight other virus isolates originating from dahlia, delphinium, impatiens, honeysuckle, cucumber and redcurrant plants. On the basis of the reaction with group-specific monoclonal antibodies and RNA3 sequence analysis, two lily isolates (Cas and CB) were classified to group I of CMV, similarly to all previously reported virus isolates found in lily plants. Surprisingly, sequences of coat protein and movement protein genes of two other lily isolates (P26 and Simp2) showed more than 98% similarity to CMV group II isolates, and only 77% similarity to group I isolates. Results of ELISA with CMV group II-specific monoclonal antibodies confirmed the classification of isolate Simp2 as a member of group II. Isolate P26 reacted neither with CMV group I nor with group II-specific monoclonal antibodies. In order to explain the lack of reaction of P26 isolate with monoclonal antibodies, comparative analysis of predicted amino acid sequence of the coat protein was done. This revealed a mutation—change from alanine at position 138 to threonine, probably responsible for particular serological properties of isolate P26.