THE HYPERSENSITIVITY OF EUROPEAN PLUM (PRUNUS DOMESTICA L.) AGAINST THE PLUM POX VIRUS

Six isolates of PPV were used for the inoculation of the hypersensitive cultivar ‘Jojo’, all of them elicitated the hypersensitive response in the ‘Jojo’ tissue. The higher the ratio between the viral doses used for inoculation and the size of the inoculated hypersensitive plant, the stronger were the visible symptoms of hypersensitivity. The transport of PPV from the point of artificial inoculation to the rootstock is possible, but it is not a sign of a breaking of the resistance. The cultivar ‘Topimmun’ was shown to be a host of PPV and therefore not to be immune. The hypersensitivity determined in the cultivar ‘Jojo’ seems to be an effective resistance mechanism which is, up to now, not overcome by any known PPV isolate.