Waterlogging is associated with poor soil drainage. As a consequence oxygen levels decrease in the root environment inducing root asphyxia and affecting plant growth. Some plants can survive under these conditions triggering complex anatomical and biochemical adaptations, mostly in the roots. Long- and short-term responses to waterlogging stress were compared in two trials using a set of two myrobalans (Prunus cerasifera Erhr), 'P.2175' and 'P.2980', as tolerant rootstocks and two almond × peach [Prunus amygdalus Batsch ×Prunus persica (L.) Batsch] interspecific hybrids, 'Garnem' and 'Felinem', as sensitive ones in two consecutive years. Stomatal conductance and chlorophyll content were measured in the long-term trials to assess survival performance, while the enzyme activities of superoxide dismutase (SOD, EC 1.15.1.1), guaiacol peroxidase (POD, EC 1.11.1.7), and catalase (CAT, EC 1.11.1.6) were measured in the short-term trials to study early antioxidant response. The incidence of the stress in the root environment was different as a result of the different plant development at the moment of the treatment, as a consequence of different environmental conditions both before and during the treatment between the 2 years. The activity of the different enzymes was higher in the sensitive genotype 'Felinem' than in the tolerant 'P.2175'. This result shows an activation of the antioxidant system and has been observed to depend of the different nature of the roots between the 2 years. As the antioxidant enzymes seem to work more efficiently when roots are more aerated, we cannot conclude that they are responsible for the higher tolerance observed in the myrobalan plums.

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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 namé 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. The second method was a direct PCR with specific primers for 'Ca P. prunorum' (Eca1/Eca2). In the most symptomatic trees the 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.