Tomato ringspot nepovirus (TomRSV)
Tobacco ringspot No. 2 and several other synonyms
English names: Tomato ringspot virus
Nordic names: Tomatringpletvirus (DK), Rengaslaikka (FI), Tomat ringflekkvirus (NO)
Major host plants
In nature, different strains of TomRSV occur mostly in a wide range of woody plants, rather than in herbaceous hosts. Host plants include raspberries, grapes, peaches, cherries and other Prunus spp., blueberries, black currants, gooseberries, strawberries, Pelargonium, Hydrangea, Gladiolus and Fraxinus americana. Many weeds such as Taraxacum officinale and Stellaria media can constitute reservoirs for the disease.
Symptom development is variable but canes are stunted and both fruit size and yield are reduced. Chlorotic ringspot markings may be evident on leaves of young plants. In subsequent years foliar symptoms are few, but they can show epinasty and early abscission. Later 10-80% of fruiting canes may die.
Infected leaves are malformed with circular spots 2-5 mm in diameter. Necrotic spots can also occur on canes. Symptoms are variable within the same plant. Infected plants may be defoliated by mid-harvest. Oval-shaped patches of weak or dying plants develop over several years.
Symptoms are difficult to diagnose early in the season unless vines are severely affected. Leaves develop ringspots and mottling, are reduced in size and rosetted due to the shortening of internodes. Fruit clusters are reduced in size and many berries fall. Removal of bark from trunks and stems of diseased vines may reveal thickened, spongy phloem tissue with numerous necrotic pits.
Pale yellow-green, oblong, feather-edged blotches develop along the main vein or large lateral veins of the leaves. Buds either produce rosettes of small and often distorted leaves, with or without mottling, or are pale yellow and later die. Fruit may be dwarfed and malformed. Some strains of TomRSV cause stem-pitting symptoms in peach and other Prunus spp.
Young leaves may develop ringspot symptoms or faint, chlorotic flecks and a mottle with slight leaf distortion. Older leaves may show chlorotic bands in an oak-leaf pattern, or symptoms may fade, so that plants show only a slight dwarfing compared with healthy ones. Flowers show no definite colour break, but may be uneven and distorted.
TomRSV is present on several continents but has a very restricted distribution in the EPPO region.
A map can be downloaded from EPPO’s website. See instructions here.
Virus transmission varies within the different host plants. The virus is readily transmissible by grafting and by sap inoculation. TomRSV is also seed-transmitted in several hosts and can be spread by pollen in Pelargonium. In nature, TomRSV is transmitted by nematodes within the complex Xiphinema americanum sensu lato of which only few species are present in Europe.
Long-range dispersal of infected plants happens in trade. Accompanying soil may harbour infective seeds and the nematode vector.
Detection and inspection
Visual symptoms cannot be taken as proof of the presence of the virus, therefore, serological or molecular tests are essential for positive identification.
Pest status and importance
The virus is of some economic importance in those EPPO countries where it occurs.
Source of information
See further information here:
Author: Christiane Scheel and Elise T. Yamamoto Buch
Editor: Dorthe Vestergaard