An assessment of molecular variability and recombination patterns in South African isolates of Potato virus Y

The coat protein (CP) gene of 75 South African Potato virus Y (PVY) isolates was amplified using reverse-transcriptase polymerase chain reaction (RT-PCR). The resulting cDNA products were cloned and sequenced. These sequences were used to identify the strains to which the isolates belonged. Some, when compared to reference sequences, belonged to the PVY(N) and PVY(O) strains. A number of isolates were found to demonstrate significant homology to PVY(N) strains from China. A large number of South African isolates possessed CP sequences showing evidence of recombination between PVY(N) and PVY(O) strains, similar to those of PVY(NTN) isolates. Multiplex RT-PCR analysis allowed further differentiation of PVY(O) isolates and revealed that the majority were of the PVY(N)-Wilga strain. It was deduced that the most likely way in which these isolates reached South Africa was via the importation of infected material.