Abstract:
Brenneria nigrifluens, the
cause of shallow bark canker of Persian
walnut trees (Juglans regia L.), has become
fairly widespread in Iran in recent years. It
is regarded as a great threat to walnut
production. To determine the diversity of B.
nigrifluens strains, sixty strains of the causal
bacterium were isolated from bark samples
of infected walnut trees collected from
Mazandaran, Guilan and Golestan provinces
and were studied. The physiological and
biochemical characteristics, electrophoretic
patterns of total cell proteins and rep-PCR
generated DNA fingerprints of B.
nigrifluens strains were compared. Strains
appeared to be more or less similar in
phenotypic characteristics. Less than 15% of
the strains differed in a few phenotypic
features such as the ability in production of
H2S from peptone, hydrolysis of esculin,
levan production, arginine dehydrolase,
nitrate reduction, indol production and
methyl red reaction. These differences did
not show any special distribution and
therefore was not suitable for classifying the
strains into distinct groups. The
electrophoretic patterns of cell proteins of
the strains were different from each other
and were only useful for preliminary
grouping of the isolates. The groups of
strains were differentiated by their rep-PCR
fingerprints and on which basis they were
placed in six groups in similarity level 95%.
Cluster analysis was performed using
NTSYSpd software. The results of these
studies demonstrated that the populations of
B. nigrifluens in North of Iran are
genetically heterogeneous. The results can
be used in selection of disease management
strategies.
