‘Candidatus Phytoplasma pruni’ detected in apple (Malus domestica)
During a study conducted from 2013 to 2015 in Pennsylvania (US), more than 40 blocks of apple (Malus domestica) orchards from 9 counties were surveyed for phytoplasmas. Out of 218 tested samples, results showed that 3 mature apple trees belonging to different varieties and from 2 farms were infected by phytoplasmas. Affected trees showed abnormally small fruits, clumps of small leaves, leaf curling, and premature reddening. Molecular tests (PCR tests, sequencing, RFLP) revealed the presence of ‘Candidatus Phytoplasma pruni’ (associated with X-disease - EPPO A1 List). This is the first time that ‘Ca. P. pruni’ is detected in M. domestica. It is noted that with a set of only 3 positive trees, the extent of the disease on apple trees remains undetermined. However, the detection of ‘Ca. P. pruni’ in apple might have important epidemiological and quarantine consequences for the fruit tree industry.
Sources
Nikolaeva EV, Welliver R, Rosa C, Jones T, Peter K, Costanzo S, Davis RE (2017) First report of apple (Malus domestica) as a host of ‘Candidatus Phytoplasma pruni’ in the United States. Plant Disease 101(2), p 378.