TOBACCO ETCH VIRUS IN ONTARIO

Abstract

Tobacco etch is one of the most widespread and injurious viruses on burley tobacco in Ontario. Three strains of this virus were obtained from tobacco collections. Their symptoms and behavior on tobacco and other hosts are described. Tobacco varieties were divided into two groups on the basis of their reaction to the etch virus. The group comprising all burley varieties tested showed severe symptoms while the other, comprising flue cured, dark, and cigar varieties, developed mild symptoms. The F1 from severe-symptom varieties × mild-symptom varieties exhibit mild symptoms while the F2 has segregated into severe- and mild-symptom types. The widespread occurrence of etch is attributed to the prevalence on tobacco of the vector Myzus persicae. A mixture of potato virus X (ringspot strain) and etch causes a more severe disease on burley tobacco than either virus by itself.