Book of Abstracts (PDF) - International Mycological Association

IMC7 Main Congress Theme III: PATHOGENS AND NUISANCES, FOOD AND MEDICINE Posters
like ours, because its high average annual temperature (25
centigrades) and relative humidity (50% or more). Among
suggestions were a much more frequent filter change,
sealing of all porous surfaces and a tight control of relative
humidity inside the production zone.
849 - A new Phytophthora infestans molecular marker
O.I. Lavrova * & Y.T. Dyakov
Moscow Lomonosov State University, 119899, Vorob'evy
gory, MSU, Biology Faculty, Mycology and Algology
Department, Russia. - E-mail: ilinir@mail.ru
Short interspersed elements (SINEs) or short retroposons
are 80-400 bp repetitive DNA sequences that proliferate in
eukaryotic genomes via transcription followed by reverse
trancription. Recently SINEs have been used as molecular
markers for intraspecies differentiation. Most SINEs have
an internal promoter for RNA polymerase III composed of
two boxes (A and B) spaced by 30-35 bp similar to tRNA
genes. To detect and clone novel tRNA-derived SINEs in
Phytophthora infestans genome we have used PCRamplified
total genomic DNA as a template and primers
specific to boxes A and B for PCR amplification. This
reaction, designated A-B PCR, amplifies the region
between boxes. The resulting DNA fragments have been
cloned and sequenced. The sequences obtained of 8
fragments (45-51 bp) are similar but not identical
suggesting that they may have been amplified from
individual copies of a single SINE famile. All 8 fragments
have 24 bp conservative sequence. On the basis of this
sequence we constructed one primer to use it as a marker
for P. infestans intraspecies differentiation. This marker is
more reliable than RAPD because it is specific sequence
and it gives the same results in the several experiment
repeatings. Acknowledgements: This work was supported
by the grant from the International Science and Technology
Center No. 1640.
850 - Plant and microorganisms interactions mediated
by Pythium oligandrum
G. Le Floch 1* , P. Rey 1 , N. Benhamou 3 , M.I. Salerno 2 & Y.
Tirilly 1
1 Laboratoire de Microbiologie et Sécurité Alimentaire,
ESMISAB technopôle Brest Iroise 29 280 Plouzane,
France. - 2 Laboratorio de Proteccion Forestral, CISAUA-
Facultad de Ciencias Agrarias y Forestales UNLP 60 y
119 CC31 (1900) La Plata, Argentina. - 3 Département
Recherche en Sciences de la Vie et de la Santé, Pav. Ch.E.
Marchand, Université Laval Sainte-Foy Québec GIK7P4,
Canada. - E-mail: gaetan.lefloch@univ-brest.fr
Over the past few years, experiments performed by our
group have demonstrated that the role played by antagonist
fungus, Pythium oligandrum, on plant development and
protection involves a tripartite interaction between the
biocontrol microorganism, the pathogen agent and the
plant. Such a complex process includes indirect effects
through the control of pathogens in the rhizosphere and/or
direct effects mediated by plant-induced resistance.
Interaction of P. oligandrum with soil-borne pathogens to
control their development in the rhizosphere and even in
planta consists in a series of events involving mainly
mycoparasitism and/or antibiosis. However, antagonism is
a multifaceted process dependent on the involved target
host; for example, by forming a thicken wall barrier
Rhizoctonia solani and Phytophthora cinnamomi limit P.
oligandrum antagonistic activity. We also showed
hyperparasitism on various sclerotia. Plant-induced
resistance mediated by P. oligandrum is a key event in this
kind of fungus-plant interaction. Evidence of plant
sensitisation by P. oligandrum to respond more rapidly and
efficiently to pathogen attacks was also provided. It can
protect plants from B. cinerea, Fusarium oxysporum f.sp.
radicis lycopersici, Phytophthora parasitica, P. ultimum
attacks by either inducing local protection or triggering
systemic resistance.
851 - Selection of baiting materials for Phytophthora
palmivora (Butler) Butler., the causal agent of coconut
nut falling disease
S. Likhitekaraj * & W. Ouvanich
Plant Pathology and Microbiology Division, Department of
Agriculture, Chatuchuk, Bangkok 10900, Thailand.
Coconut nut falling disease is caused by Phytophthora
palmivora (Butler) Butler. A serious outbreak of this
disease was found on 'Yellow Dwarf' cultivar of coconut
grown at Surat Thani Rubber Research Center. Since P.
palmivora is a soil-borne fungus, to isolate the fungus
needs to apply baiting techniques to trap the fungus from
the soil. Leaves of nine crop plant species, namely
pararubber, cacao, citrus, durian, coffee. Black pepper, oil
palm, and coconut cvs. 'yellow Dwarf' and F1 Hybrid
Sawee I. The leaves were immersed in the zoospore
suspension for 1, 3, 6 and 24 hours. It was found the leaves
of all tested plant species excluding pararubber could trap
up to 95% of the fungal spores when immersed in the
zoospore suspension for 24 hr. An experiment was
conducted to study on the optimum duration of fungal
existiance in the soil to be best baited by using cacao
leaves. Among 1, 15, 30, 45, and 60 days of the durations,
it was found that 90% of the fungus could be trapped from
the soil at 60-days duration. Suitable methods in using
leaves of nine plant species to bait P. palmivora from the
soil was also performed. The three methods include placing
the leaves on the soil surface, placing the leaves one inch
below the soil surface, and immersing the leaves in the
infected soil suspension. The results revealed that
immersing the leaves in the infected soil suspension was
best in baiting the fungus from the soil.
Book of Abstracts 255