Susceptibility and Tolerance of New French <i>Prunus domestica</i> Cultivars to European Stone Fruit Yellows Phytoplasmas

Abstract

Five new cultivars of French prune (Prune d'Ente) and 11 cultivars or new clones of greengage (Reine Claude) were bud‐inoculated with European stone fruit yellows (ESFY) phytoplasmas and evaluated for their host response in the nursery over a period of 6 years. The ESFY infection was confirmed by specific polymerase chain reaction (PCR) detection and 4′,6‐diamidino‐2‐phenylindole (DAPI) staining in all Prunus domestica cultivars tested which were, thus, all susceptible to ESFY phytoplasmas. The new Prune d'Ente cultivars were more sensitive as they generally developed ESFY symptoms and showed a mortality of 19%. The fruit weight was significantly reduced. No mortality was observed with Reine Claude genotypes and only two cultivars exhibited weak ESFY symptoms. A new sensitive method was developed to measure the impact of ESFY phytoplasmas on the shoot growth. A significant growth reduction was found in all Prune d'Ente cultivars but only in four out of 11 Reine Claude genotypes. Therefore, the latter were found to be tolerant of ESFY infection.