International Congress BIOLOGICAL PRODUCTS - Gruppo di ...

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EFFICACY EVALUATION OF BIOLOGICAL CONTROL AGENTS AGAINST
PLASMOPARA VITICOLA
Ilaria Pertot, Federica De Luca, Antonella Vecchione, Luca Zulini
Istituto Agrario di San Michele all’Adige, via E. Mach 1, S. Michele all’Adige (TN)
ilaria.pertot@ismaa.it
Keywords
downy mildew, Plasmopara viticola, biological control agents, organic agriculture.
Introduction
Downy mildew causal agent, Plasmopara viticola (Berk. et Curt.) Berl. et De Toni, is one of the most important
grapevine pathogens, causing great losses if no protective treatments are applied (Kortekamp, 1997).
Nowadays consumer and farmer are much more concerned about food, health and environment safety (Butt,
2001). The conditions for using copper will be restricted by European Union by fixing a ceiling on use expressed
in terms of kilograms of copper per hectare per year in organic agriculture. Antagonist microorganisms could be
a possible alternative to copper in downy mildew controlling. Epidemiological characteristics of downy mildew
probably would not allow a complete field control based on a single biocontrol agent (BCA). A possible solution
for improving efficacy of BCA could be the integration of several micro-organisms with different action
mechanisms on specific stages of disease: i) during oospore overwintering and germination, for primary
inoculum reduction ii) and during sporangia germination for protection against secondary infections.
Materials and methods
Micro-organisms were isolated from grapevine leaf material and rhizosphere of 18 different vineyards located in
the north –east of Italy. Vineyards were abandoned and chemically untreated for at least three years. Microorganisms
were isolated on potato dextrose agar, malt agar and nutrient sucrose agar and grown at 20°C. Several
isolation methods were used: inocula were based on leaf washing water, necrotic leaf portions grounded in sterile
water with mortar and pestle, necrotic leaf pieces, infected leaf dish maintained in contact with naturally
degraded leaf material and root surface material. For each kind of material used, all morphologically different
colonies of fungi and bacteria were collected. A sample of 46 isolates was evaluated for sporangia germination
and infection inhibition activity. A sample of 33 isolates was evaluated for overwintering oospores inhibition
activity.
The evaluation methods used were:
i) oospore germination inhibition, based on a modified floating leaf disk method (Hill);
ii) inhibition of sporangia germination, based on reduction percentage of sporangia germination in a 1:1
water solution of the isolate culture broth and P. viticola sporangia;
iii) infection inhibition, based on the reduction of the number of sporangiophore developed on isolate
culture broth treated leaves.
Results and discussion
Several micro-organisms have induced a partial inhibition of sporangia germination (tab. 1), but the complete
control of infection on leaf can be achieved with only few of them.
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