Tobacco ringspot virus

Tobacco ringspot virus is a Nepovirus known to cause ringspots in a wide range of hosts including Solanum spp, grapes and mint species.

Soyabean
Plants are most severely affected when they are infected young (less than 5 weeks old or from seed), the virus spreading systemically in the plant. The terminal bud is curved to form a crook (bud blight), and other buds become brown, necrotic and brittle. Brown streaks can be seen in the pith of stems and branches, and occasionally on petioles and leaf veins. Leaflets are dwarfed and rolled. Pods develop poorly and late.

Tobacco
TRSV causes ring and line patterns on the foliage and stunting.

Cucurbits
Leaves are mottled and stunted, and fruits are deformed.

Grape
Plants show symptoms of decline, exactly as with Tomato ringspot virus, i.e. new growth is weak and sparse, internodes are shortened, leaves are small and distorted, and plants are stunted. Berries are sparse and develop unevenly.

Blueberry
Plant shows stem dieback and stunting. On a susceptible cultivar such as Pemberton, leaves are deformed and somewhat thickened, become chlorotic and show necrotic spots, and may drop giving a shothole or tattered effect.

Cherry
In cherry, in which the disease has only ever been seen in a few individual trees, young leaves show irregular chlorotic blotching over the whole leaf blade, and the leaf margins are deformed and lobed. These symptoms are seen in scattered leaves throughout the crown. Fruits mature late on infected trees.

Control
For soyabeans, disease-free seeds should be used. For fruit crops, it is relatively easy to test for TRSV in potential mother plants and establish virus-free nuclear stock, to be propagataed and distributed through a certification scheme. In the areas where the American dagger nematode (Xiphinema americanum) vector does not occur, the problem of re-infection does not then arise. In North America, it may be necessary to test soil for vector nematodes, and if necessary treat with nematicides, before replanting with healthy stock, e.g. for blueberry. For most of the fruit crops, however, TRSV infection is so rare that no special measures are needed to prevent reinfection of healthy planting material.