Pea seed-borne mosaic virus pathotypes isolated from Australian pea (Pisum sativum) seed

Pea seed lots (144) from Australian farms and research trials were assessed for pea seed-borne mosaic virus (PSbMV) seed transmission rates. High infection rates (up to 40%) were detected, particularly in the widely grown and highly PSbMV susceptible variety ‘Kaspa’, with only 12 out of 54 seed lots found to be free of the virus. PSbMV strains were isolated from 15 infected seed lots, and were pathotyped on a set of homogeneous Pisum sativum PSbMV differentials. Of the four pathotypes identified, P1 and P4 (eight and 20 isolates, respectively) were earlier reported in Australia. Pathotype P3, as yet unreported in Australia, was the most frequently identified pathotype (42 isolates). One PSbMV isolate was identified as the P2 pathotype, which has previously been isolated only from lentil seed. None of the isolated pathotypes could overcome the PSbMV resistance gene sbm1. The relevance of these findings for field pea breeding programmes and genomic studies of PSbMV are discussed.