Vegetable Viruses

From 67 of the about 200 vegetable crops used by man, about 200 viruses have been detected or isolated. Although most vegetables escape viruses, an average of 3-5% of overall vegetable production is lost to virus infections. Vegetable viruses display one or more features to ensure their success as parasites: high variability; transmission from host to host by specific vectors; transmission through seeds and pollen; high stability of virus particles for long persistence in the environment and mechanical transmission by man; and presence in plant parts used for vegetative propagation. Control of vegetable virus diseases is based on prevention of virus infection, using virus-free seeds and multiplication material, controlling virus reservoirs (weeds and volunteer plants) and vectors, and hygiene of operators and disinfecting implements. Damages can be reduced by inoculating plants with mild virus strains (cross-protection) or a satellite of a virus. Another method of avoiding virus diseases is resistance breeding: Natural resistance has been bred for various crop-virus combinations, and a few crop-vector combinations; other sources of resistances are available through genetic engineering techniques. A few examples of virus disease of vegetables are given among aphid-, thrips-, and whitefly-borne viruses, mechanically transmitted viruses, and vegetatively propagated viruses.