NUCLEOTIDE-SEQUENCE ANALYSIS OF THE GENOMES OF THE MAV-PS1 AND P-PAV ISOLATES OF BARLEY YELLOW DWARF VIRUS

The MAV-PS1 and P-PAV isolates of barley yellow dwarf virus (BYDV) are serologically related, but not identical. Both are transmitted by the aphid Macrosiphum avenae, but P-PAV is also transmitted by Rhopalosiphum padi. To evaluate the basis for these and other differences, overlapping clones from cDNA libraries representing the genome of each isolate were characterized by restriction enzyme digestion and by hybridization, and subsequently sequenced. Each genome has six positive strand open reading frames (ORFs) which are similar to those identified from a BYDV isolate from Australia (Vic-PAV). The greatest diversity between MAV-PS1 and P-PAV sequences was found in ORFs located in the 3' half of the respective genomes, in particular ORFs 5 and 6, suggesting that these regions of the genome may be involved in the properties that differentiate MAV-PS1 and P-PAV. Sequence comparisons between P-PAV and Vic-PAV showed a high degree of identity in that all ORFs showed > 90% amino acid similarity, except ORF6 which had only 69% similarity.