LIBRO-CONGRESO-CITRUS

calcofluor white (CFW) or congo red (CR), but remarkably resistance to reactive oxygen species (ROS). Conidia
of the mutant were also resistant to the fungicidal activity of PAF26, confirming that protein glycosylation
also determines the sensitivity to antimicrobial peptides in filamentous fungi. None of the overexpressors
displayed variations in susceptibility against the antifungal compounds analyzed. In bioassays of controlled
inoculation, we confirmed that PMT2 is required for full virulence of P. digitatum to citrus fruit.
S09O06
PdCYP51B, a new sterol 14α-demethylase gene of Penicillium digitatum involved in resistance to
imazalil and other fungicides inhibiting ergosterol synthesis
Sun X.P., Wang J.Y., Feng D., and Li H.Y.
Institute of Biotechnology, Zhejiang University, China. hyli@zju.edu.cn
The phenotypes and genotypes of 403 isolates of Penicillium digitatum, collected from packing houses and
supermarkets in Zhejiang, China, during 2000 to 2010, were characterized in terms of their imazalil sensitivity.
The frequency of detected imazalil-resistant (IMZ-R) isolates increased from 2.1% in 2000 to 60–84% during
2005–2010. Only 6.5% and 4.5% of the collected IMZ-R isolates belong to the previously described IMZ-R1
and IMZ-R2 genotypes, respectively. A homolog (PdCYP51B) of PdCYP51, which encodes the target of imazalil,
was revealed from genomic database of P. digitatum. Sequence analysis of PdCYP51B from six IMZ-R3 and
eight imazalil-sensitive (IMZ-S) isolates indicated that a unique 199-bp insertion was presented in the
promoter region of PdCYP51B in all IMZ-R3 isolates but absent in all IMZ-S isolates. Transcription levels of
PdCYP51B in IMZ-R3 isolates were 7.5- to 13.6-fold higher than that in two IMZ-S isolates. Introduction of
another copy of PdCYP51Bs (from IMZ-S) into an IMZ-S isolate increased the resistance of P. digitatum to
demethylase inhibitors (DMIs) only to a small extent, but introduction of a copy of PdCYP51BR (from IMZ-R3)
dramatically increased the resistance level of P. digitatum to DMIs. Based on these results, we concluded
that (1) the CYP51 family of P. digitatum contains another member PdCYP51B, in addition to the known gene
PdCYP51A (previously PdCYP51); (2) PdCYP51B is involved in DMI fungicide resistance; and (3) overexpression
of PdCYP51B resulting from a 199-bp insertion mutation in the promoter region of PdCYP51B is responsible
for the IMZ-R3 type of DMI resistance in P. digitatum.
S09O07
Current and emerging strategies for Sour Rot management of citrus in Australia
Taverner P.D., and Cunningham N.M.
South Australian Research and Development Institute (SARDI), Sustainable Systems, Australia. Peter.Taverner@sa.gov.au
In Australia, Green Mould (Penicillium digitatum) and Blue Mould (P. italicum) are serious diseases affecting
citrus fruits. Sour Rot (Geotrichum citri-aurantii) is sporadic but control options are more limited. Sour Rot, or
rather a complex of Sour Rot with Mould, is an intractable problem for Australian citrus exports. Researchers
work closely with citrus packers to integrate control measures for sour rot into existing treatments for mould
control. This usually involves combining chemical fungicides with sanitisers &/or generally regarded as safe
compounds (GRAS). Careful evaluation is necessary because chemical mixtures can be neutral, additive,
synergistic or antagonistic. Generally, research adheres to two main aims; sour rot spore control in water
suspensions, and sour rot control on fruit. The first approach uses sanitisers in water washes and fungicide
applications. Sanitisers added to fungicide dips can reduce sour rot spore loads but chemical incompatibility
is common. The response varies with sanitiser active, fungicide active and fungicide formulation. The second
approach aims to enhance sour rot control on fruit by combining fungicides and GRAS compounds. Various
mineral and organic salts have demonstrated enhance sour rot control. Sanitising these mixed solutions is
problematic, with the choice of fungicide, salt and sanitiser influencing compatibility and efficacy. Increased
worldwide concern in Sour Rot has lead to productive research, which may lead to new approaches for
control of this disease. The studies used to develop current strategies and possible future research directions
are discussed.
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S09