Persistence of European stone fruit yellows phytoplasma in the aerial parts of Prunus in winter
European stone fruit yellows phytoplasma (potential EPPO A2 quarantine pest, including the A2 pest apricot chlorotic leaf roll phytoplasma) affects several Prunus species: apricot (Prunus armeniaca), peach (P. persica), Japanese plum (P. salicina), European plum (P. domestica), almond (P. amygdalus), flowering cherry (P. serrulata) and other stone fruit species used as rootstocks. Fluorescence microscopy, PCR, and graft transmission experiments were used to study the persistence of European stone fruit yellows phytoplasma in the stem of various Prunus species (artificially inoculated or naturally infected) during the dormant season. Results showed that phytoplasmas are present in the stem during winter and are viable and transmissible.
European stone fruit phytoplasma is closely related to apple proliferation and pear decline phytoplasmas (both EPPO A2 quarantine pests) but these are known to be unable to persist in the aerial parts of the trees during winter (although they can survive in the roots). It is felt that these facts can probably be explained by physiological differences during the dormant season. It has been observed that sieve tubes of the stem phloem (on which phytoplasmas seem to depend) degenerate completely at the end of the growing season in apple and pear, and not in several Prunus species. The authors pointed out that the persistence of European stone fruit phytoplasma in aerial parts of Prunus in winter has implications for the epidemiology of the disease and also for plant quarantine, as there is a risk of dissemination with exchanges of dormant material.
Sources
Seemüller, E.; Stolz, H.; Kison, H. (1998) Persistence of the European stone fruit yellows phytoplasma in aerial parts of Prunus taxa during the dormant season.
Journal of Phytopathology, 146(8-9), 407-410.