Evaluation location: , Australia
The molecular diversity of 14 isolates of Pea seed-borne mosaic virus (PSbMV) from southern Australia, 13 previously described isolates from Pakistan, and a reference isolate from the
United States have been studied to determine whether a relatively simple molecular diagnostic
assay and classification scheme could be developed for this virus. The Australian isolates were
placed into either pathotype P1 or pathotype P4 by bioassay on differential genotypes of Pisum
sativum. The Pakistani isolates represented pathotypes P1, P4, U1, and U2, and an undetermined
pathotype. The reference US isolate was pathotype P1. A reverse transcription?polymerase chain
reaction (RT-PCR) assay based on an amplicon from the variable HC-Pro coding region of potyviruses
was shown to distinguish PSbMV from seven other legume infecting potyviruses. Restriction
fragment length polymorphisms (RFLPs) generated from the HC-Pro RT-PCR products
of all 28 isolates using seven restriction endonucleases placed them into eight groups. A phylogenetic
tree based on a Bray-Curtis similarity comparison placed the groups into three clusters.
The groups and clusters had no clear association with either pathotype or geographic source. It is
concluded that within the range of viruses and isolates tested, the RT-PCR-RFLP method will
both specifically identify PSbMV and provide a simple, qualitative, and rapid means for placing
PSbMV isolates into groups. Applications could include mapping and tracking isolates in space and time.