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Title: First report of ‘Candidatus Phytoplasma asteris’ subgroup 16SrI-A associated with a disease of potato (Solanum tuberosum) in Lithuania

item IVANAUSKAS, ALGIRDAS - Nature Research Centre
item URBONAITE, IRENA - Nature Research Centre
item JOMANTIENE, RASA - Nature Research Centre
item VALIUNAS, DEIVIDAS - Nature Research Centre
item Davis, Robert

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2015
Publication Date: 1/1/2016
Citation: Ivanauskas, A., Urbonaite, I., Jomantiene, R., Valiunas, D., Davis, R.E. 2016. First report of ‘Candidatus Phytoplasma asteris’ subgroup 16SrI-A associated with a disease of potato (Solanum tuberosum) in Lithuania. Plant Disease. 100:207.

Interpretive Summary: Potato is a highly important food crop in many regions of the world, but potato harvests are threatened in some regions by damaging diseases that reduce the quantity and/or quality of potato production. In order to manage a potato disease effectively, and minimize damage from the disease, it is important to know the identity of the pathogen (germ) that causes the disease, and to understand how it can be spread. It this work, we discovered a serious disease of potato in the country of Lithuania, but the cause of the disease was unknown. By using molecular tools to diagnose the disease, we found that it is caused by a phytoplasma. Phytoplasmas are very small bacteria that are spread by insects and cause diseases that damage food crops and other plants around the world, including potato. We found that this potato-infecting phytoplasma is closely related to a phytoplasma that causes diseases in a wide range of vegetable and other plants. Our work identified molecular targets that can be used to monitor the presence and spread of this phytoplasma. The findings will be of interest to growers of potato and other crops, diagnostics laboratories, producers of disease-free potato planting stock, and international plant quarantine agencies. Because potato is a major food crop in Lithuania and surrounding countries, the disease could have serious economic and societal implications. This work provides a molecular tools that form a basis for intensified efforts to stem the spread of the disease.

Technical Abstract: Symptoms of little leaf, witches’-broom, and abnormally small and deformed potatoes, suggestive of possible phytoplasmal infection, were observed in diseased potato (Solanum tuberosum var. Hannibal arba Kestrel) in the Vilnius region of Lithuania. DNA extracted from symptomatic leaves and shoots were used as template in polymerase chain reactions (PCRs) for amplification of phytoplasmal 16S rRNA gene sequences (rDNA). Restriction fragment length polymorphism (RFLP) analysis of the amplified rDNA revealed that all diseased plants tested were infected by a phytoplasma (designated strain potWB-LT1) belonging to group 16SrI (‘Candidatus Phytoplasma asteris’ group), subgroup A (16SrI-A). Strain potWB-LT1 was further genotyped by analyses of ribosomal protein (rp) and secY protein translocase gene sequences; these DNA fragments were cloned, sequenced, and their nucleotide sequences and deduced amino acid sequences were analyzed. The results confirmed that strain potWB-LT1 is closely related to AY-WB phytoplasma. We further cloned and sequenced a 1 kbp DNA fragment characteristic of phytoplasmal sequence variable mosaics (SVMs) that we found to contain a 309-base open reading frame (ORF) that encodes a putative protein identical in amino acid sequence to a protein encoded by the genome of Italian clover phyllody phytoplasma, a member of group16SrIII (‘Ca. Phytoplasma pruni’ group). The discovery of diseased potatoes infected by a subgroup 16SrI-A phytoplasma in Lithuania could have serious implications, because potato is a major food crop in the country.