Viruses occurring in white clover (Trifolium repens L.) from permanent pastures in Britain

SUMMARY Twenty‐five white clover plants were collected along a transect in each of twenty‐six old permanent pastures in Britain and tested for sap‐transmissible viruses. Viruses were identified by the symptoms they caused, by electron microscopy and by serological tests. Of the 683 plants tested 23 % were infected. In order of decreasing incidence the viruses found were: red clover vein mosaic (in 12% of all the plants tested, and in sixteen of the fields); clover yellow vein (9 % of plants, eighteen fields); white clover mosaic (4 % of plants, eleven fields); arabis mosaic (4 % of plants, eight fields); strawberry latent ringspot (1 % of plants, two fields); and tomato black ring (0.1 % of plants, one field). The three most common viruses occurred in all parts of Britain, and were most prevalent in fields where white clover was most abundant; white clover mosaic seemed more prevalent in fields that were both cut and grazed than in those only grazed. Arabis mosaic virus was obtained only from plants in the west and north of Britain.