© Benaki Phytopathological Institute
Abstracts - 16th Hellenic Phytopathological Congress
33
*Present Address: The Sainsbury Laboratory, John Innes Centre, Norwich Research
Park, Norwich NR4 7UH, UK.
Recent taxonomic advances based on bio-
chemical as well as genotypic analysis have
demonstrated that plant pathogen species
Pseudomonas cichorii
consists of a cluster
of closely related genomic groups collec-
tively defined as the
P. cichorii
complex. Pri-
or to this study, three pathovar groups had
been described, all sharing common pheno-
typic and biochemical characters but pre-
senting variability regarding their DNA con-
tent. All entities of the complex can cause
disease in a variety of hosts, including let-
tuce, celery and chrysanthemum, among
others. In this study, we present the isola-
tion and biochemical and molecular charac-
terisation of
P. cichorii
isolates as the caus-
al agent of pith necrosis in tomato plants. A
detailed characterization of the genetic vari-
ability among strains belonging to
P. cichorii
was achieved using different molecular typ-
ing methods, including rep-PCR (BOX- and
ERIC), as well as Multilocus Sequence Typing
(MLST), utilizing the partial sequences of the
genes
gyrB
,
rpoB
and
rpoD
. Likewise, a num-
ber of biochemical tests were also used for
the biochemical identification of the toma-
to
P. cichorii
isolates. To our knowledge, this
is the first complete biochemical, molecular
and phylogenetic analysis of
P. cichorii
spe-
cies as the causal agent of tomato pith ne-
crosis. Our results clearly demonstrate the
emergence of a new genomic group in the
P. cichorii
complex, consisting of strains that
could consistently be separated from other
members of the complex. Finally, this is the
first record of
P. cichorii
as a pathogen of to-
mato pith necrosis in Greece.
Infection of watermelon, melon and cucumber plants by a
phytopathogenic bacterium of the genus
Acidovorax
in Greece
M.C. H
OLEVA
, P.E. G
LYNOS
and C.D. K
ARAFLA
Benaki Phytopathological Institute, Department of Phytopathology, Laboratory of
Bacteriology, 8 St. Delta Str., GR-145 61 Kifissia, Athens, Greece
During the period of March-May 2012, spec-
imens of young seedlings of watermelon,
melon and cucumber from a greenhouse
crop in the area of Thiva (Boeotia), exhibit-
ing necrotic, brown, irregular-shaped leaf
lesions, of variable size and most often sur-
rounded by a chlorotic halo, were examined
in the Laboratory of Bacteriology of the Insti-
tute. The lesions were observed on the coty-
ledons of watermelon, melon and cucumber
plants, as well as on a small number of true
leaves of the melon plants. The outbreak was
reported by the agronomist who supervised
the crops to have affected 10 to 100 % of the
plants. In all specimens, microscopic exam-
ination of affected leaves revealed bacteri-
al streaming from lesion margins. Bacterial
isolates obtained from the leaf lesions were
consistently identified on the basis of cul-
tural, biochemical and serological assays, as
well as a tobacco hypersensitivity test, as a
phytopathogenic species of the genus
Aci-
dovorax
. Sequencing of the 16S rDNA region
showed significant sequence identity of the
isolates to
A. valerianellae
, whereas PCR as-
says showed them to differ from reference
strains of
A. citrulli
. Studies are ongoing to
further characterize the isolates at the spe-
cies level. This is a preliminary report on the
presence of a phytopathogenic species of
Acidovorax
causing economically important
damage to crops of cucurbits in Greece.
First report of infection of sweet basil plantlets by the phytopathogenic
bacterium
Pseudomonas viridiflava
in Greece
