Evaluation of Genetic Resistance to Bacterial Dieback (Pseudomonas mors prunorum f. sp persicae) of Some Peach and Nectarine Cultivars in South East Romania

Bacterial dieback of peach caused by Pseudomonas mors prunorum f. sp. persicae is a relatively new disease of this fruit crop (Vigouroux and Blance, 1967). This disease has very important consequences for tree and orchard longevity; it can cause the death of young trees in a year and in 2 to 4 years the death of older ones (Luisetti, 1973). From the time it was first reported in 1965 this disease has not been controlled, and new outbreaks have occurred. In 1980 and 1992 it was detected in Romania. Disease spread was related to the susceptibility of cultivars that are grown, e. g., 'Cardinal', 'Southland', 'Collins', and 'I.H. Halle'. For this reason, the research carried in this study focused on resistance evaluation of some peach and nectarine genotypes from the national germplasm collection. For this reason the knowledge and the description of the details of the disease symptoms was neccesary in all seasons. The cultivars were divided into five (5) classes based upon their response to this disease (tolerant, less susceptible, medium susceptible, susceptible and very susceptible) depending of frequency (F%) and size (mm) of typical lesion. The results show that, the peach and nectarine cultivars with genetic resistance to this pathogen are: 'Dixired', 'Redhaven', 'Redskin', 'Sunhaven', 'Catherine Sel.1', 'Raluca', 'Florin', 'Cecilia' and 'Costin'.