© Benaki Phytopathological Institute
Abstracts - 16th Hellenic Phytopathological Congress
83
Succinate dehydrogenase inhibitors (SDHIs)
are a fungicide class with increasing rele-
vance in grey mould control. However, they
are also a fungicide class at high risk for re-
sistance development. Recent studies have
shown that resistance of
B. cinerea
to SDHIs
is associated with mutations in the
sdh
gene.
The objective of the current study was to in-
vestigate the effect of the H272Y/R/L, N230I
and P225F mutations in the respiratory ac-
tivity, the fitness, and the competitive-
ness of
B. cinerea
isolates. Fitness parame-
ters measured were: i) mycelial growth and
conidial germination
in vitro
, ii) aggressive-
ness and sporulation capacity
in vivo
and iii)
sclerotia production
in vitro
and sclerotia vi-
ability under different storage conditions.
The competitive ability of the resistant iso-
lates was measured both in the absence and
in the presence of boscalid and fluopyram.
Measurements of oxygen uptake showed
that N230I mutants had the lowest respi-
ratory activity, followed by the H272Y mu-
tants. In contrast no differences in respi-
ratory activity were observed among the
H272R/L, P225F mutants and the wild-type
isolates. The measurements revealed sig-
nificant differences in most of the parame-
ters measured. In terms of fitness, the H272R
isolates most closely resembled the sensi-
tive isolates. In contrast, the H272Y/L, N230I
and P225F isolates showed reduced fitness
values when compared to the sensitive iso-
lates. In the competition experiments it was
found that, in the absence of fungicide se-
lection pressure, after 4 disease cycles the
sensitive isolates dominated the population
in all the mixtures tested. In contrast, when
the competition experiment was conduct-
ed under the selective pressure of boscalid,
a gradual decrease in the frequency of sen-
sitive isolates was observed while the fre-
quency of H272L and P225F isolates in-
creased. When the competition experiment
was conducted in the presence of fluopy-
ram the sensitive isolates were eliminated,
in some cases after a single disease cycle,
and the P225F mutants dominated the pop-
ulation. These results indicate that the
sdh
B
mutations adversely affect the mutants. The
observed dominance of sensitive isolates in
the competition experiments conducted in
the absence of fungicides suggest that the
application of SDHIs in alternation schemes
may delay the selection or reduce the fre-
quency of SDHI-resistant mutants.
Phytopathological and molecular characterization of
Penicillium
expansum
mutant strains resistant to new succinate dyhydrogenase
inhibitors
K.N. V
ATTIS
1
, G.S. K
ARAOGLANIDIS
2
and A.N. M
ARKOGLOU
1
1
Pesticide Science Laboratory, Agricultural University of Athens, 75 Iera Odos Str.,
GR-118 55 Athens, Greece.
2
Plant Pathology Laboratory, Faculty of Agriculture,
Aristotle University of Thessaloniki, POB 269, GR-541 24 Thessaloniki, Greece
Mutants of
Penicillium expansum
highly re-
sistant (RF: >300, based on EC
50s
) to the new
succinate dehydrogenase inhibitors (SDHIs)
were isolated at a mutation frequency of
2.3×10
-6
after UV-mutagenesis and selec-
tion on media containing boscalid. Cross
resistance studies with other fungicides
showed that themutation(s) for resistance to
boscalid also reduced the sensitivity of mu-
tant strains to isopyrazam, fluopyram, thiflu-
zamide and carboxin, but not to fungicides
affecting other cellular pathways or process-
es, such as the triazole flusilazole, the phe-
nylpyrrole fludixonil, the anilinopyrimidine
cyprodinil and the benzimidazole benomyl.
An increased sensitivity of most boscalid-re-
sistant mutant strains to fluopyram and pyr-
aclostrobin was observed. Studies of fitness-
determining parameters showed that the
mutation(s) for resistance to boscalid may
or may not affect the mycelial growth rate,
but had no adverse effect on sporulation,
conidial germination or pathogenicity. Anal-
ysis of mycelial extracts from the wild types
