Virus Tolerance, Plant Performance of Transgenic Tomato Plants Expressing Coat Protein from Tobacco Mosaic Virus

Two transgenic tomato plants that express the coat protein (CP) of the common (U 1 ) strain of tobacco mosaic virus (TMV) were produced from cultivar VF36 using gene transfer techniques. CP–expressing plants were partially resistant to infection and symptom development caused by TMV and tomato mosaic virus (ToMV) strains L, 2, or 2 2 . Strains 2 and 2 2 normally overcome the natural resistance genes present in many commercial tomato cultivars. In the field, no more than 5% of the CP–expressing plants inoculated with TMV exhibited visual systemic disease symptoms by fruit harvest compared with 99% of the VF36 plants. Lack of visual symptoms was associated with lack of virus accumulation in the CP–expressing plants. In terms of agronomic traits, leaf and stem dry weight accumulation in greenhouse–grown uninoculated CP–expressing (line 306) and nonexpressing plants were essentially equal. In field analyses, tomato fruit yields of the VF36 plants decreased 26–35% due to virus infection, whereas yields of the CP–expressing plants were unaffected. Yields from one CP–expressing line were equal to that of the uninoculated VF36 plants suggesting that expression of the CP gene does not intrinsically cause yield depression. The results from these growth chamber, greenhouse and field experiments indicate the potential for use of genetically engineered protection in agriculture.