THE SUSCEPTIBILITY OF PEA CULTIVARS TO PEA SEED-BORNE MOSAIC-VIRUS INFECTION AND VIRUS SEED TRANSMISSION IN THE UK

The reaction of 25 UK pea cultivars to pea seedborne mosaic virus (PSbMV) was studied in the glasshouse. All cultivars proved to be susceptible. When leaf or tendril samples from inoculated plants were analysed, it was found that most combining cultivars had a lower virus content, as measured by A405 values in ELISA, than garden and vining cultivars, and that garden and vining cultivars had a similar virus content. Seed transmission of PSbMV in 20 cultivars ranged from 0% in cvs Maro, Princess and Progreta to 74% in cv. Vedette. There was no obvious relationship between virus content and the efficiency of seed transmission in different cultivars. Wide variation in percentage seed transmission between individuals of single cultivars was observed; for seven cvs (ST 2-49%) tested, all showed some plants escaping seed transmission altogether. Seedlings infected through the seed showed symptoms similar to those in the infected parent plants. Virus particles were readily detectable by immunosorbent electron microscopy in infected seedlings, and in elongated infected embryonic shoots produced 3 days after seed germination, by ELISA. An ELISA test of seed samples from cv. Waverex showed that virus was as readily detected 3 days after germination as after growth to symptomatic seedlings (4 weeks), and probably provides the most sensitive, accurate and time-saving assay for seed transmission of PSbMV.