Tobacco plants transformed with the potato virus YN coat protein gene are protected against different PVY isolates and against aphid-mediated infection

Tobacco plant lines transformed with the coat protein (CP) gene of the tobacco veinal necrosis strain of potato virus Y (PVY^N), and previously shown to be protected against mechanical inoculation with the virus, have now been tested for specificity and protection against virus infection mediated by viruliferous aphids. To determine the specificity of virus protection, two transgenic tobacco lines, A30 and A80, were challenged with several isolates of distinct PVY strains (PVY^N, PVY^O and PVY^C) by mechanical inoculation. Clear levels of protection against the PVY^O-isolates tested were maintained in the transgenic plants, although these levels were slightly lower than the protection against the homologous PVY^N strain from which the CP gene was derived. Interestingly, no protection against mechanical virus inoculation with the Gladblaadje isolate of PVY^C could be observed. To assess the levels of protection against aphid-mediated virus infection, two transgenic plant lines, A30 and D25, showing respective levels of protection of 95 and 80% against mechanical virus inoculation, were challenged using PVY^N viruliferousMyzus persicae. Virus inoculation using six aphids per plant, resulted in similar levels of protection in both transgenic lines as found previously for mechanical inoculation. Protection was maintained in both lines, even when as many as 60 viruliferous aphids were used per plant in the inoculation experiments.