Book of Abstracts (PDF) - International Mycological Association

IMC7 Friday August 16th Lectures
in mode. However, gene flow between widely isolated
locations is also evident, and repeated dispersal to distant
provenances may provide opportunities for
biodiversification through repeated rounds of allopatric
speciation. Older lineages may also be more likely to have
broader distributions than recently evolved ones. This
presentation will review recent advances in understanding
diversification in fungi through phylogeographic studies.
358 - In vitro fruiting of Cordyceps militaris
J.M. Sung * & B. Shrestha
Kangwon National University, Hyoja 2 Dong, Chuncheon,
200-701, Korea. - E-mail: jmsung@kangwon.ac.kr
Every year, 200-400 specimens of C. militaris are collected
mainly from Kangwon Province of Korea and their isolates
preserved in EFCC, KNU, Korea. Cordyceps species are
highly regarded as medicinal mushrooms in East Asia,
including Korea. Stromata of C. militaris could be
produced in vitro when its liquid suspensions were
inoculated in brown rice medium supplemented with
silkworm pupae and incubated in 20-25 °C under light and
high humidity conditions. But, the isolates showed unstable
variation in fruiting. Most of the isolates failed to produce
stromata or produced only few deformed stromata. Other
isolates, which produced good fruiting, could not produce
the same quality of fruiting when their subcultures were
used, while other few isolates produced good fruiting when
their subcultures were used. This was the main problem in
commercial cultivation of C. militaris. In order to
understand the fruiting character of C. militaris, several
single ascospore strains were crossed with each other and
observed for their fruiting. Out of eighteen strains, ten
strains produced stromata profusely with the remaining
eight strains in all the combinations, but not among
themselves and vice versa. When two opposite strains were
repeatedly inoculated together in large scale, they produced
good quality of fruiting continuously. This paper intends to
report that C. militaris is a bipolar heterothallic fungus and
crossing between two opposite types is a good method of
fruit body production.
359 - Breeding of mushroom by using cell fusion
techniques
T. Morinaga
School of Bioresources, Hiroshima Prefectural University,
Nanatsuka 562, Shobara-city, Hiroshima Prefecture 727-
0023, Japan. - E-mail: tmorina@bio.hiroshima-pu.ac.jp
Twenty-two homokaryons were isolated from one
commercial fruiting body of P. ostreatus. Then, all
homokaryons were crossed each other. In crossing tests of
homokaryotic mycelia, only two sexual phenomena were
observed: clamp formation and "Barrage" reaction, in
contrast with Schizophyllum commune (Raper 1966). We
determined the mating type of P. ostreatus by this two
reactions. As a result, P. ostreatus was determined to have
a bifactorial incompatibility; KM 4 (A1B1), KM 7 (A2B2),
KM 18 (A1B2) and KM 22 (A2B1). All compatible
dikaryons formed their fruiting bodies on commercial
sawdust media. By means of UV-irradiation to protoplasts
of these homokaryons, five strains of auxotrophic mutant
were obtained. The ratio of regeneration to mycelia from
protoplasts of homokaryons was about 0.1%. Reversion
rate of each mutant to prototroph was calculated from the
number of colonies that appeared on the complete medium
and that on the minimal medium against the number of
protoplasts or regenerated protoplasts. And then, protoplast
fusion between strain KM 4-1 (wet-) and KM 4-34 (ade-)
was done in the same mating type. Fifteen strains which
could grow on the minimal medium and possessed one
nucleus per each cell obseved by fluorescent microscopy,
were obtained with this fusion treatment. These strains
were inoculated to MYA medium containing methyl - 1 -
(butylcarbamoyl) - 2 - benzimidazole carbomate
(benomyl). Benomyl is known as a regent of
haploidization. Two strains (KM D-4-1 and KM D-4-2)
occurred sector on this medium. Therefore, these strains
were found to have one diploid nucleus per each cell. On
the other hand, the other diploid strains having the opposite
mating type were made by the same cell fusion technique.
After getting the strains, crossing were done among the
diploid strains. Finally, tetraploid mycelium were gotten.
The growth rate of these strains became about two times of
diloid strains and their fruiting also became faster than
normal commercial strains.
360 - The genus Pleurotus as a bioremediation tool
E. Sanjust
Cattedra di Chimica Biologica, Università di Cagliari,
Complesso Universitario, 09042 Monserrato (CA), Italy. -
E-mail: sanjust@unica.it
The genus Pleurotus belongs to the white rot fungi, capable
of rapid growth on lignocellulosics and with a preference
for lignin. It lacks lignin peroxidase, but actively excretes
other oxidative enzymes upon proper induction. Oxidised
products arising from extracellular enzyme action are
recycled by mycelium-bound reductases; enzymatic and/or
non-enzymatic re-oxidation of such reduced molecules
results in hydrogen peroxide production in the growth
media. Some details of this particular mechanism have
been recently elucidated whereas others are under study.
Pleurotus acts as a biochemical hydrogen peroxide factory
by means of quinone/polyphenol and benzyl
alcohol/benzaldehyde redox cycles. The bleaching power
of hydrogen peroxide as well as its production in
autoxidation reactions could be enhanced by the ability of
the fungus to raise the pH of culture media when stressed
by xenobiotics. Hydrogen peroxide and excreted enzymes
co-operate in the breakdown of a wide range of different
molecules. Therefore the fungus efficiently grows on a
variety of substrates. Chemicals that are toxic for other
fungi are bleached by Pleurotus just out of the hyphae and
cannot accumulate within the fungal cells. So safe and
valuable sporocarps could be obtained when starting from
Book of Abstracts 113