Evidence for persistent, symptomless infection of some potato cultivars with tobacco rattle virus

Infection with an M-type (particle producing) isolate of tobacco rattle vir us (TRV) was detected in leaves and/or roots of some plants from 11 of 13 p otato cultivars grown in soil containing viruliferous trichodorid nematodes . Virus was detected in tubers of 8 of 13 cultivars, although only two (Pen tland Dell and Maris Bard) developed spraing symptoms. Six cultivars (Arran Consul, Home Guard, King Edward, Romano, Sante and Wilja) were infected wi th TRV without developing spraing symptoms. Plants grown from virus-contain ing, symptomless tubers became systemically infected with M-type TRV and pr oduced symptomless infected daughter tubers. Virus was maintained through t hree generations of vegetative propagation, and the plants were sources for acquisition of the virus by trichodorid nematodes. Distribution of virus i n both spraing-affected and symptomless tubers was erratic. Movement of sym ptomlessly infected seed tubers may be a means of dissemination of the viru s and of its introduction to previously unaffected sites.