sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

SDÜ ORMAN FAKÜLTESİ DERGİSİ
medium is necessary for obtaining synnemata and perithecia, essentially important
for classifying into mating type (A or B), vegetative compatibility groups and
fertility tests (identification of subspecies).
2.5. Infection tests: Isolate M3 was inoculated into sapwood of 10 living elms
which represents in vitro cloned progenies of two elm hybrids – ´Groeneveld´ and
´Dodoens´ (Krajnakova and Longauer, 1996). The experimental plot is situated
near to Banská Štiavnica (coordinates: N 48°28´ E 18°58´, 590 m a. s. l.) 5
representative trees per each hybrid were inoculated and observed according to
Solla et al. (2005).
3. RESULTS
3.1. Ratios of O. novo-ulmi subspecies: Altogether 58 isolates were achieved
from nearly the entire area of the Czech Republic. The isolated strains were
identified as O. novo-ulmi and both subspecies novo-ulmi (29) and americana (5)
were found, as well as their hybrids (24). Decreasing trend in occurrence of
Ophiostoma ulmi confirms the results of other authors (Brasier, 1991; Hoegger et
al., 1996; Konrad et al., 2002). They suppose that Ophiostoma ulmi disappeared by
the end of the 1970's.
3.2. Production of cerato-ulmin: Absorbances of the samples were very
variable. Dilution with most variable results was 1:4. Statistical analysis (z-test)
did not show any differences in cerato-ulmin production between subspecies and
hybrids. Interesting exception is M9, which produces no cerato-ulmin, although it
was isolated from infected branch. Culture of M9 seems to be d-infected.
3.3. Mating type, vc-type and fertility response variability: Among 13
isolates investigated both mating types occur; 9 isolates are of B type, 4 of A type.
Vc-tests showed on high diversity of strains. Any isolate was not compatible with
any other, although two of them were collected from the same tree. Fertility tests
revealed 3 subspecies americana and 10 ssp. novo-ulmi. In comparison with
identification by molecular tools there is some relation with cu-region, isolate M10
is the only exception.
3.4. Infection tests: Isolate M3 caused extremely high defoliation on resistant
elm hybrid ´Groeneveld´ and low defoliation on the hybrid ´Dodoens´.
4. DISCUSSION AND CONCLUSION
Methods which have been used proved to be useful in the recognition of
diversity in DED causal agent populations. From the distribution of isolates is
evident that we cannot draw any borders between areas which are occupied only by
ssp. novo-ulmi or by ssp. americana. In many cases such areas were observed
where both subspecies and their hybrids are overlapping and where more than one
strain of pathogen is responsible for dying of a tree. This phenomenon was
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