Diversity of luteoviruses infecting faba bean (Vicia faba L) in Morocco, and their detection by the polymerase chain reaction

When surveying faba bean (Vicia faba L) for viruses in Morocco, members of the luteovirus group were found to be economically important. In order to further identify them, a number of faba bean samples showing symptoms indicative of luteovirus infection were serologically tested using polyclonal antisera for bean leafroll virus (BLRV), beet western yellows virus (BWYV), and subterranean clover red leaf virus (SCRLV), and two monoclonal antibodies which discriminate between BWYV and BLRV. Several serological reaction patterns were obtained which pointed towards a large variation in the luteovirus isolates studied. None of these isolates could be clearly identified as one of the luteoviruses known to infect legumes, although a number of them behaved like BWYV serologically. The potential of the polymerase chain reaction in detecting these luteoviruses was investigated, and a set of oligonucleotide primers was designed which specifically amplified a 535 bp fragment of the coat protein gene of known luteoviruses and of all the Moroccan isolates tested. In nucleic acid hybridization tests, the field isolates showed homology in nucleotide sequence among the Moroccan isolates and with BLRV, but not wih BWYV. In polyacrylamide gel electrophoresis, a purified Moroccan isolate was found to be different from BLRV and BWYV in coat-protein migration.