sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

SDÜ ORMAN FAKÜLTESİ DERGİSİ
The frequency of necroses formation was changing depending on from the
poplar genotype. At some susceptible genotypes, single shoots showed up to 10
necroses. Some shoots with lesions that did not crack, dried above the damaged
spots.
Above and below the smaller necroses and lesions a wound periderm had
developed, varying in thickness with the poplar genotype (fig. 1-3). Inside the
shoots, tissue showed a hypertrophic ring-shaped zone with dark discolorations.
2. METHODS AND RESULTS
2.1. Bacteria identification
During the search for the cause of losses, no indication for fungal pathogens or
phytophagous insects could be found. Rather, investigations of damaged and
broken shoots resulted in a range of bacterial strains, which were isolated directly
from the margin of necrotic tissues and discoloured zones in winter season. The
isolations followed a standard protocol using Yeast extract-Mannitol Agar (YMA)
(Elkan and Bunn, 1992). The plates were incubated at 28 °C for three days. The
most frequent type could be identified by means of 16S rDNA sequence analysis
(primer pairs: fd1/ 926r and 799f/1492r, resp.) as Pseudomonas syringae pv.
syringae. This species could be found only in the damaged annular areas with inner
brown discolorations. The shoot segments between the lesions were free of P.
syringae. Further species like Rahnella sp., Pantoea agglomerans,
Pseudoclavibacter helvolus, Cellulomonas sp., and Microbacterium oxydans were
found with lower frequency. Only one strain could be isolated from Xanthomonas
sp. and X. campestris, resp., Curtobacterium flaccumfaciens, as well as some
unspecified isolates.
Figure 1, 2: Ring-shaped necrosis with wound periderm (left) and cracking of shoot
(right)
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