Multi-locus genotyping reveals new molecular markers for differentiating distinct genetic lineages among 'Candidatus Phytoplasma solani' strains associated with grapevine bois noir

Authors: PASSERA, ALESSANDRO - University Of Milan; Zhao, Yan; MUROLO, SERGIO - Polytechnic University Of Marche; PIERRO, ROBERTO - University Of Pisa; ARSOV, EMILIJA - University Goce Delcev; MORI, NICOLA - University Of Verona; MOUSSA, ABDELHAMEED - University Of Milan; SILLETTI, MARIA - Center For Research And Experimentation In Agriculture; CASATI, PAOLA - University Of Milan; PANATTONI, ALESSANDRA - University Of Pisa; Wei, Wei; MITREV, SASA - University Goce Delcev; MATERAZZI, ALBERTO - University Of Pisa; LUVISI, ANDREA - Universita Del Salento; ROMANAZZI, GIANFRANCO - Polytechnic University Of Marche; BIANCO, PIERO - University Of Milan; DAVIS, ROBERT - Retired ARS Employee; QUAGLINO, FABIO - University Of Milan

Submitted to: Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2020
Publication Date: 11/26/2020
Citation: Passera, A., Zhao, Y., Murolo, S., Pierro, R., Arsov, E., Mori, N., Moussa, A., Silletti, M.R., Casati, P., Panattoni, A., Wei, W., Mitrev, S., Materazzi, A., Luvisi, A., Romanazzi, G., Bianco, P.A., Davis, R.E., Quaglino, F. 2020. Multi-locus genotyping reveals new molecular markers for differentiating distinct genetic lineages among 'Candidatus Phytoplasma solani' strains associated with grapevine bois noir. Pathogens. 2020 9:(11)970 https://doi.org/10.3390/pathogens9110970.
DOI: https://doi.org/10.3390/pathogens9110970

Interpretive Summary: Bois noir is a grapevine disease associated with infection by a cell wall-less bacterium termed 'Candidatus Phytoplasma solani' (CaPsol). The disease is prevalent in many European countries and causes significant economic losses to the viticulture industry. In collaboration with scientists in Italy, ARS researchers at the Beltsville Agricultural Research Center conducted multi-gene comparative analysis on CaPsol strains identified from vineyards in Italy and North Macedonia. The study found presence of mutually distinct CaPsol lineages in the vineyards and identified new molecular markers that can tell the different lineages apart. Results from the study indicated that different CaPsol lineages may have been evolved from and adapted to different ecosystems of the vineyards. This article will be of interest to research scientists, plant disease diagnosticians, and extension personnel who are interested in phytoplasma genetic diversity and disease management. This information is also important to regulatory agencies for implementing control measures to prevent exotic phytoplasmas from coming into the U.S.

Technical Abstract: Grapevine bois noir (BN) disease is associated with infection by 'Candidatus Phytoplasma solani' (CaPsol). In this study, an array of CaPsol strains were identified from 142 symptomatic grapevines in vineyards of northern, central, and southern Italy, and North Macedonia. Molecular typing of the CaPsol strains was carried out by analysis of genes encoding 16S rRNA and translation elongation factor EF-Tu2 as well as other eight previously uncharacterized genomic fragments. Tuf-type a and b were found differentially distributed in the examined geographic regions in correlation with the prevalence of nettle- and bindweed-related pathosystem. Two sequence variants were identified in each of the four genomic segments that harbor hlyC, cbiQ-glyA, trxA-truB-rsuA, and rplS-tyrS-csdB, respectivly. Fifteen CaPsol lineages were identified based on didstinct combinations of sequence variations within these genetic loci. Each such CaPsol lineage exhibited a unique collective RFLP pattern and differed from each other in geographic distribution, in relation to the diverse ecological complexity of vineyards and their surroundings. This RFLP-based typing method can be a useful tool for investigating CaPsol ecology and epidemiology of the associated diseases. Phylogenetic analyses highlighted that the sequence variants of the gene hlyC, encoding a hemolysin III-like protein, separated into two clusters consistent with the separaration of two distinct lineages on the basis of tufB gene sequences. Alignments of deduced full protein sequences of Elongation Factor-Tu (tufB gene) and hemolysin III-like protein (hlyC gene) revealed the presence of critical amino acid substitutions distinguishing CaPsol lineages of tuf-type a and b. Findings from the present study provides new insights into genetic diversity and ecology of CaPsol populations in vineyards.