Symptomatological and serological evaluation of peach cultivars for resistance to plum pox virus

Thirty four peach and two nectarine cultivars naturally infected with plum pox virus (PPV) in an orchard were evaluated for viral leaf and fruit symptoms, and also indexed for virus infection by ELISA. Relative concentration of PPV protein was determined by ELISA in flowers and found in most cultivars to be positively correlated with the intensity of leaf and fruit symptoms. None of the investigated peach cultivars was immune to PPV. Leaf and fruit symptoms appeared in all cultivars but with different intensity. Both relative concentration of PPV protein in flowers and intensity of the symptom response were used to characterize the degree of resistance of the peach cultivars. They were rated as medium resistant (cultivars Candor, Envoy, Favorita Morettini, Flamencrest, Harcrest, Harmony, Maycrest, Spring Lady, Triestina and Velvet), tolerant, medium susceptible and highly susceptible to PPV.