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# Action of Pythium oligandrum on Grapevine Trunk Diseases and its impact on microbial communities

Severine Lopez, Alexandre Chataigner, Jessica Vallance, Olivier Zekri, Ahmed Taïbi, Assia Dreux-Zigha, Marie-Cecile Dufour

► To cite this version:

Severine Lopez, Alexandre Chataigner, Jessica Vallance, Olivier Zekri, Ahmed Taïbi, et al. Action of Pythium oligandrum on Grapevine Trunk Diseases and its impact on microbial communities. Biosolutions 2025, RFE BIOV; Université Perpignan; Fondation UPVD; BESTIM, Sep 2025, Perpignan, France. hal-05329621

HAL Id: hal-05329621

https://hal.inrae.fr/hal-05329621v1

Submitted on 24 Oct 2025

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from September
23rd to 26th, 2025
Perpignan, FRANCE
# Action of *Pythium oligandrum* on Grapevine Trunk Diseases and its impact on microbial communities

Séverine Lopez¹, Alexandre Chataigner¹, Jessica Vallance¹, Olivier Zekri², Ahmed Taïbi³, Assia Dreux-Zigha³ and Marie-Cécile Dufour¹

(1) INRAE, Bordeaux Sciences Agro, ISVV, SAVE, 33140 Villenave d'Ornon, France

(2) Novatech - Groupe Mercier, les champs des Noëls, 85770 Le Gué de Velluire, France

(3) GreenCell Biopole, Clermont Limagne, 63360 St Beauzire, France.

Grapevine Trunk Diseases (GTDs) have become a major challenge for viticulture.

Since the ban of sodium arsenate in 2001, the need for alternative methods, such as biocontrol, has become increasingly urgent. One promising microorganism is the oomycete *Pythium oligandrum*, which is known to improve plant health by increasing natural defences and reducing disease incidence by up to 40%. In order to use this microorganism in vineyards, it need first to be formulated and tested to ensure its safety.

The aim of this study is to demonstrate the efficiency of the bio-fungicide at different spatial scales (from the greenhouse to the vineyard, including the nursery grapevine propagation) but also to better understand the effects of microorganism-based treatments on existing microbial communities, essential to ensure sustainable and safe vineyard management practices.

In a greenhouse under controlled conditions, the treatment applied showed reduced necrosis induced by the pathogens P. chlamydospora and N. parvum by 47% and 67% respectively.

In nursery, with commonly used cultivars, these solutions consistently demonstrated lower levels of natural contamination by GTD-plant pathogenic fungi monitored by qPCR analyses compared to the untreated control.

The *P. oligandrum* biopesticide had minimal effect on the total microbial community of the vine rhizosphere. However, the treatment appeared to enhance several beneficial taxa that play a role as plant growth promoting rhizobacteria (PGPR) or biocontrol agents (BCA).

In the vineyard, 3 years of treatments were managed (2021-2022 and 2023) with different formulations (solid or liquid). For one of the field trial (at Château Luchey), a diminution of Esca symptomes had taken place for the vines treated with the liquid biofungicide, while with the solid formulation, the disease has not progressed but on the contrary seems to reverse (vines went from symptomatic to healthy).

**Mots-clés / Key words:** Grapevine Trunk Diseases - biocontrol - biopesticide - *Pythium oligandrum* - microbial communities

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