Surveys reveal a complex association of phytoplasmas and viruses with the blueberry stunt disease on Canadian blueberry farms

• Published in: Annals of applied biology 2019-03, Vol.174 (2), p.142-152
• Main Authors: Arocha‐Rosete, Yaima, Lambert, Liette, Joly‐Séguin, Violaine, Michelutti, Roberto, Schilder, Annemiek, Bertaccini, Assunta
• Format: Article
• Language: English
• Subjects: 16S rRNA gene; 16SrI phytoplasma; Blueberries; blueberry stunt; BRRV; Bushes; Candidatus Phytoplasma; Candidatus Phytoplasma asteris; Clustering; Cultivars; Deoxyribonucleic acid; DNA; Epidemiology; Farms; Gene polymorphism; Graphocephala fennahi; Phylogeny; Phytoplasma; Plant viruses; Polls & surveys; Polymerase chain reaction; Polymorphism; Primers; RFLP; Ribonucleic acid; RNA; rRNA 16S; secA gene; SecY gene; Signs and symptoms; Single-nucleotide polymorphism; Strains (organisms); Stunt; Subgroups; TRSV; Vaccinium corymbosum; Viruses; Yellowing
• ISSN: 0003-4746; 1744-7348
• DOI: 10.1111/aab.12481

Surveys for phytoplasmas and viruses were conducted during September 2014 and 2015 on highbush blueberry farms in the Région Montérégie, Quebec. Total DNA and RNA were extracted from blueberry bushes showing blueberry stunt (BBS) symptoms and from symptomless blueberry bushes, and utilised as templates for PCR and RT‐PCR assays, respectively. Phytoplasma DNA was amplified with universal phytoplasma primers that target the 16S rRNA, secA and secY genes from 12 out of 40 (30%) plants tested. Based on 16S rRNA, secA and secY gene sequence identity, phylogenetic clustering, actual and in silico RFLP analyses, phytoplasma strains associated with BBS disease in Quebec were identified as ‘Candidatus Phytoplasma asteris’‐related strains, closely related to the BBS Michigan phytoplasma strain (16SrI‐E). The secY gene sequence‐based single nucleotide polymorphism analysis revealed that one of the BBS phytoplasma strains associated with a leaf marginal yellowing is a secY‐I RFLP variant of the subgroup 16SrI‐E. Two viruses were detected in blueberry bushes. The Blueberry Red Ringspot Virus (BRRV) was found in a single infection in the cultivar Bluecrop with no apparent typical BRRV symptoms. The Tobacco Ringspot Virus (TRSV) was found singly infecting blueberry plants and co‐infecting a BBS phytoplasma‐infected blueberry cv. Bluecrop plant. This is the first report of TRSV in the cv. Bluecrop in Quebec. The Quebec BBS phytoplasma strain was identified in the leafhopper Graphocephala fennahi, which suggests that G. fennahi may be a potential vector for the BBS phytoplasma. The BBS disease shows a complex aetiology and epidemiology; therefore, prompt actions must be developed to support focused BBS integrated management strategies. Phytoplasma strains associated with BBS disease in the Région Montérégie, Quebec are “Candidatus Phytoplasma asteris”‐related strains, closely related to the BBS Michigan phytoplasma strain (16SrI‐E). One of the BBS phytoplasma strains is a secY‐I RFLP variant of the subgroup 16SrI‐E. The Blueberry Red Ringspot Virus (BRRV) was identified in the cultivar Bluecrop and the Tobacco Ringspot Virus (TRSV) co‐infecting a BBS phytoplasma‐infected blueberry plant cv. Bluecrop. Graphocephala fennahi was identified as a potential vector for the BBS phytoplasma. BBS shows a complex etiology and epidemiology; therefore, prompt actions must be developed to support focused BBS integrated management strategies.