Book of Abstracts (PDF) - International Mycological Association

IMC7 Main Congress Theme II: SYSTEMATICS, PHYLOGENY AND EVOLUTION Posters
sequences of the cerato-ulmin gene and the colony type
gene of this unusual isolate were also identical to those of
O. novo-ulmi ssp. americana. The unusual colony
morphology of this Ophiostoma isolate and its female
sterility gives suspicion that it could have been arisen from
hybridization between O. ulmi and O. novo-ulmi or from
introgression of O. ulmi into O. novo-ulmi. Examination of
this isolate is continuing in order to prove its possible
interspecies hybrid origin.
710 - Hybridization between the subspecies of
Ophiostoma novo-ulmi in Austria, Central Europe
H. Konrad * , C. Stauffer, E. Halmschlager & T. Kirisits
Institute of Forest Entomology, Forest Pathology and
Forest Protection (IFFF), Universität für Bodenkultur
Wien, Hasenauerstrasse 38, A-1190 Vienna, Austria. - Email:
hkonrad@ento.boku.ac.at
The second epidemic of Dutch elm disease has been caused
by the ascomycete fungus Ophiostoma novo-ulmi. O. novoulmi
is separated into the subspecies novo-ulmi and
americana, both of which occur in Europe. We have
recently presented evidence for recombination between two
genes in isolates of O. novo-ulmi from Central Europe,
indicating hybridization between O. novo-ulmi ssp. novoulmi
and O. novo-ulmi ssp. americana (Konrad et al., Plant
Pathology 51, 78-84). In the present study a geographically
diverse population of 99 isolates of O. novo-ulmi from
Austria was investigated. Isolates were examined for their
fertility response as donor (male) to authenticated strains of
O. novo-ulmi spp. novo-ulmi and ssp. americana. They
were also studied by PCR-RFLP of the cerato-ulmin (cu)
gene and the colony type (col1) gene. In 71 isolates fertility
tests, as well as PCR-RFLP of cu and col1 gave consistent
results. 49 and 22 isolates were identified as ssp. novo-ulmi
and ssp. americana, respectively. 23 isolates showed
recombination between cu and col1 and were thus
identified as hybrids between ssp. novo-ulmi and ssp.
americana. In further 5 isolates the fertility tests and the
molecular analyses gave conflicting results and these
isolates are suggested to be subspecies hybrids as well.
This study has shown that a large portion of isolates of O.
novo-ulmi from Austria consists of hybrids between ssp.
novo-ulmi and ssp. americana.
711 - Analysis of pathogenicity and molecular markers
in sexual hybrids of Phytophthora infestans and P.
mirabilis
L.P.N.M. Kroon * & W.G. Flier
Plant Research International, P.O. Box 16 6700AA
Wageningen, The Netherlands. - E-mail:
l.p.n.m.kroon@plant.wag-ur.nl
Isolates of Phytophthora infestans and P. mirabilis,
originating from the presumed centre of origin of P.
infestans (Toluca valley, Mexico), were crossed in vitro.
Both species are heterothallic, and can act both as male and
female partners in the cross. Viable offspring was obtained
with an increased in vitro growth rate and abundant
sporulation. DNA-fingerprinting (AFLP) showed that the
F1 progeny consisted of true sexual hybrids. The offspring
was (mildly) pathogenic on potato and Mirabilis jalapa, the
respective hosts of P. infestans and P. mirabilis, and on
tomato. F1 isolates were successfully crossed to obtain F2
and back-cross offspring. In F2 and BC populations,
pathogenicity on tomato and potato (and possibly on M.
jalapa) was a segregating trait. Mitochondrial DNA
haplotype was checked for all offspring and almost all
isolates contained the P. mirabilis type mitochondrial
DNA, indicating that P. mirabilis acts preferably as the
maternal partner. By analysing the molecular make-up and
host specificity of P. infestans/P. mirabilis F1, F2 and BC
hybrids, the possible role of hybridisation in the speciation
process of Phytophthora species in Toluca valley could be
assessed.
712 - Lewia teleomorph of Alternaria triticicola from oat
grain in Norway is now described
H. Kwasna 1* & B. Kosiak 2
1 Department of Forest Pathology, Agricultural University,
ul. Wojska Polskiegio 71 c, Poland. - 2 National Veterinary
Institute, Department of Feed and Food Hygiene, P. O. Box
8156 Dept., N-OO33 Oslo, Norway. - E-mail:
barbara.kosiak@vetinst.no
Lewia triticicola Kosiak & Kwaúna ined., the teleomorph
of Alternaria triticicola isolated from oat grain in Norway,
has recently been described. During a survey of Fusarium
and Alternaria species in Norwegian grains of reduced
quality, a fungus with characteristics of Alternaria
triticicola Vasant Rao isolated from surface disinfected oat
(Avena sativa L.) kernels has been identified. The oat
sample was collected from Volden in Trøndelag, Norway
in September 1998. Stored on slant agar at 4 °C in darkness
for a year, the fungus produced ascomata. The ascomata
were single or often gathered in groups, 2-3 mm in
diameter, submerged mainly in the surface layer of the
medium. Single-ascospore cultures produced anamorphic
and teleomorphic states by the same isolate. This is the first
report on the production of a teleomorph by A. triticicola.
The teleomorph of A. triticicola was named Lewia
triticicola Kosiak & Kwaúna ined. Although the fungus
originated from Avena and not Triticum, the specific name
triticicola is retained to conform with that of the anamorph,
as is conventional for Lewia / Alternaria relationships.
Lewia Barr & Simmons species are known as teleomorphs
of Alternaria Nees: Fries. Including this new species, five
species of Lewia connected with Alternaria anamorphs
have been described so far. Apart from L. infectoria, which
is a common inhabitant of Gramineae, no other Lewia
species have been described from cereals.
Book of Abstracts 215