A
Novel Bacteroidetes Symbiont Is Localized in Scaphoideus
titanus, the Insect Vector of Flavescence Doree in Vitis
vinifera
Massimo Marzorati,1 Alberto
Alma,2 Luciano Sacchi,3 Massimo Pajoro,2
Simona Palermo,2 Lorenzo Brusetti,1
Noura Raddadi,1 Annalisa Balloi,1 Rosemarie
Tedeschi,2
Emanuela Clementi,3 Silvia Corona,3
Fabio Quaglino,4 Piero Attilio Bianco,4
Tiziana Beninati,5 Claudio Bandi,5 and
Daniele Daffonchio1*
Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche,
Via Celoria 2, 20133 Milan,
Italy.
Abstract
Flavescence doree (FD) is a grapevine disease
that afflicts several wine production areas in Europe, from
Portugal to Serbia. FD is caused by a bacterium, “Candidatus
Phytoplasma vitis,” which is spread throughout the vineyards
by a leafhopper, Scaphoideus titanus (Cicadellidae).
After collection of S. titanus specimens from FD-contaminated
vineyards in three different areas in the Piedmont region
of Italy, we performed a survey to characterize the bacterial
microflora associated with this insect. Using length heterogeneity
PCR with universal primers for bacteria we identified a major
peak associated with almost all of the individuals examined
(both males and females). Characterization by denaturing gradient
gel electrophoresis confirmed the presence of a major band
that, after sequencing, showed a 97 to 99% identity with Bacteroidetes
symbionts of the “Candidatus Cardinium hertigii”
group. In addition, electron microscopy of tissues of S.
titanus fed for 3 months on phytoplasma-infected grapevine
plants showed bacterial cells with the typical morphology
of “Ca. Cardinium hertigii.” This endosymbiont,
tentatively designated ST1-C, was found in the cytoplasm of
previtellogenic and vitellogenic ovarian cells, in the follicle
cells, and in the fat body and salivary glands. In addition,
cell morphologies resembling those of “Ca.
Phytoplasma vitis” were detected in the midgut, and
specific PCR assays indicated the presence of the phytoplasma
in the gut, fat body and salivary glands. These results indicate
that ST1-C and “Ca. Phytoplasma vitis”
have a complex life cycle in the body of S. titanus
and are colocalized in different organs and tissues.
Keywords:Flavescence doree;Candidatus
Phytoplasma vitis;Rickettsia rickettsii;Scaphoideus
titanus;Bacteroidetes;Ca. Phytoplasma;Dermacentor
andersoni;plant pathogen phytoplasmas;taxonomy.
Corresponding author: Tel 39-0250316730;
Fax 39-0250316694
E-mail: daniele
.daffonchio@unimi.it |
