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Title: Molecular identification of Phytoplasmas infecting diseased pine trees in the UNESCO-protected Curonian Spit of Lithuania

Author
item VALIUNAS, D - Nature Research Centre
item JOMANTIENE, R - Nature Research Centre
item IVANAUSKAS, A - Nature Research Centre
item URBONAITE, I - Nature Research Centre
item SNEIDERIS, D - Nature Research Centre
item Davis, Robert

Submitted to: Forests
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2015
Publication Date: 7/17/2015
Citation: Valiunas, D., Jomantiene, R., Ivanauskas, A., Urbonaite, I., Sneideris, D., Davis, R.E. 2015. Molecular identification of Phytoplasmas infecting diseased pine trees in the UNESCO-protected Curonian Spit of Lithuania. Forests. 6:2469:2483.

Interpretive Summary: Pine trees are some of the most important trees in natural and managed forests, but in recent years a disease began to seriously damage pine trees growing in forests of Europe. The diseased trees were found to be infected by a tiny germ, a bacterium called phytoplasma. In the present work, pine trees were studied in forests of Lithuania, particularly in a UNESCO-protected World Heritage site, the Curonian Spit, a narrow segment of land bordering the Baltic Sea. Of 300 diseased trees that were studied, we found that 80% were infected by a phytoplasma that had earlier been found affecting pine trees in Germany and Poland, although the observed incidence of diseased trees in the forests of the Curonian Spit was much greater than expected. This work draws attention to the apparently increasing problem caused by phytoplasma-caused disease in pine trees, raising awareness of the disease problem and alerting scientists, quarantine agencies, and diagnostics laboratories to the need for intensified efforts to prevent spread of the phytoplasma to geographic regions where it does not now occur.

Technical Abstract: Although mainly known as pathogens that affect angiosperms, phytoplasmas have recently been detected in diseased coniferous plants. In 2008-2014, we observed, in the Curonian Spit of western Lithuania and in forests of southern Lithuania (Varena district), diseased trees of Scots pine (Pinus sylvestris) and mountain pine (Pinus mugo) with unusual symptoms similar to those caused by phytoplasmas. Diseased trees exhibited excessive branching, dwarfed reddish or yellow needles, dried shoots and ball-like structures. RFLP and nucleotide sequence analysis of 16S rRNA gene fragments revealed that individual trees were infected by ‘Candidatus (Ca.) Phytoplasma pini‘-related strains (members of phytoplasma subgroup 16SrXXI-A) or by ‘Ca. Phytoplasma asteris‘-related strains (subgroup 16SrI-A). Of the nearly 300 trees that were sampled, 80% were infected by ‘Ca. Phytoplasma pini’-related strains. Strains belonging to subgroup 16SrI-A were identified from only few trees. Use of an additional molecular marker, secA, supported the findings. This study provides evidence of large scale infection of Pinus by ‘Ca. Phytoplasma pini’ in Lithuania, and it reveals that this phytoplasma is more widespread geographically than previously appreciated. This is also the first report of phytoplasma subgroup 16SrI-A in pine trees.