The molecular characterization of the causal agent of diseases associated with several symptoms such as decline, yellowing,leaf roll and off-season growth in stone fruits made it possible to determine a common etiology, and the name ´European stone fruit yellows´ phytoplasma was proposed. Recently, the new taxonomical species description within the genus is 'Candidatus Phytoplasma prunorum'.A 2-yr survey was carried out in two different Prunus collections of the Centro de Investigación y Tecnología Agroalimentaria de Aragón (CITA) including European and Japanese plum genotypes of various species and several interspecific hybrids used as rootstocks. Both off-season growth in winter and decline were observed. In order to identify the phytoplasma suspected as a causal agent, two different PCR methods were applied to all inspected trees. The first method was a nested PCR with 16Sr X group-specific primers followed by RFLP analysis. Thesecond method was a direct PCR with specific primers for 'Ca P. prunorum' (Eca1/Eca2). In the most symptomatic treesthe presence of this phytoplasma was confirmed by at least one of the methods; negative results were obtained in asymptomatic trees. The nested PCR-RFLPs analysis was confirmed as a reliable method for routinary diagnosis rather than direct PCR.