# An ambrosia beetle recently introduced in Europe shows specific association with a yeast fungus

Cecile Robin, Pilar Fernandez-Conradi, Emilie Chancerel, Benjamin Penaud, Marie-Anne Auger-Rozenberg, Alain Roques

► To cite this version:

Cecile Robin, Pilar Fernandez-Conradi, Emilie Chancerel, Benjamin Penaud, Marie-Anne Auger-Rozenberg, et al. An ambrosia beetle recently introduced in Europe shows specific association with a yeast fungus. International Congress of Plant Pathology, Aug 2023, Lyon, France. hal-05302513

HAL Id: hal-05302513

https://hal.science/hal-05302513v1

Submitted on 7 Oct 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# An ambrosia beetle recently introduced in Europe shows specific association with a yeast fungus

Cécile Robin¹, Pilar Fernandez-Conradi², Emilie Chancerel¹, Benjamin Penaud¹, Marie-Anne Auger-Rozenberg³, Alain Roques³

¹ UMR BIOGECO, Bordeaux, ² URFM, Avignon, ³ URZF, Orléans, FRANCE

RÉPUBLIQUE
FRANÇAISE

INRAE

Agence
Agroalimentaire
France

Ambrosia beetles are wood boring insects which can become tree killers. They are also characterized by a high invasion success rate and by symbiotic and phoretic relationships with different fungi. Together, insects and their fungal communities cause important damages to forest and agricultural ecosystems worldwide. A better preparedness to this threat requires to identify the fungal communities associated with any newly introduced ambrosia beetle and a better knowledge of tree killing mechanisms operating in such complex associations.

We aimed to determine whether the fungi associated with the insects intercepted during a monitoring program were sufficiently stable to be characterized with a culture-independent method.

We initiated this study in the frame of the SAMFIX project, focused on *Xylosandrus* species in European Mediterranean countries, and during which we identified a newly introduced beetle species: *Amasa sp. near truncata* (Erichson). It was first detected in South-Eastern France in 2018 at Antibes, presumably attacking Eucalyptus spp. (Barnouin et al. 2020). This ambrosia beetle was used as a case study species.

<figure><img src="image_2.png" /></figure>

## Methods

### Insect sampling

* Ambrosia beetles were collected in south-Eastern France, using attractive traps baited with Eanol + α-pinene+α-copaene+ quercivorol and monitored weekly or bi-weekly

* Two studies were carried out :

* in 2018: mycobiomes of ambrosia beetles (*Amasa near truncata*, *Xylosandrus compactus*, *X. crassiusculus*) trapped in 3 sites (Antibes, Nice, Mont Boron) were analysed

* in 2021: mycobiomes of Amasa individuals collected in 7 sites

### Mycobiome analysis

* Total DNA from each sampled individual was extracted using Quiagen DNA extraction Kit

* Fungal ITS1 and ITS2 regions were amplified using respectively primer pairs ITS1F and ITS2, ITS3 and ITS4

* Library pool was sequenced on the Illumina MiSeq platform using the v2 kit to obtain 2 × 250 bp paired-end sequences

* OTUs were taxonomically assigned with the online BLAST web interface against the GenBank database

<figure><img src="image_3.png" /></figure>

### Mycobiomes varied with ambrosia species and sites

* Shannon diversity index of Amasa fungal communities was lower compared to fungal communities associated to one population of *X. crassiusculus* (*t* = 2.96; *P*< 0.018) but similar to mycobiomes of another one (*t* = 2.13; *P* = 0.066) and of *X. compactus* population (*t* = 1.067; *P* = 0.31)

<figure><img src="image_4.png" /></figure>

* Composition of fungal communities associated to the four ambrosia beetle species are well discriminated (PERMANOVA: *F* = 4.57; *R*2= 0.63; *P* < 0.0001)

<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /></figure>

* Composition of Amasa fungal communities?

* Stability in time and space?

## Results

<figure><img src="image_7.png" /></figure>

### Amasa mycobiomes

* We found 810 093 reads from 780 OTUs assigned to Fungi Kingdom.

* Most of these OTUs belong to Ascomycota phylum (93% of total fungal reads).

* Within the Ascomycota most of them belonged to Saccharomyces's Class (88% of total fungal reads).

* Fungal OTU richness and Shannon diversity were similar for all sites (*F-value* = 0.83, *P* = 0.553 and *F-value* = 0.52, *P* = 0.787).

<figure><img src="image_8.png" /></figure>

<figure><img src="image_9.png" /></figure>

<figure><img src="image_10.png" /></figure>

<figure><img src="image_11.png" /></figure>

<figure><img src="image_12.png" /></figure>

The most abundant species identified in the fungal communities were:

* Millerozyma petchabunensis (83% of fungal reads)

* Malassezia restricta (1%)

* Melassezia globosa (0.2%)

The core mycobiome of the Amasa individuals is dominated by a *Millerozyma* species belonging to a yeast family (Debaryomycetaceae, Saccharomycetales). Members of this family are reported in various substrates and environments. Several of them are known to have a xylose-fermenting ability and to be gut symbionts of wood boring insects, with which they establish a symbiotic interaction (Stefanini 2017). Debayomicetacea have not been reported as phytopathogens. The type of relationship, which appears to be as a rather specific and permanent one, between this fungus and the *Amasa* sp. near *truncata* introduced in France, needs to be investigated.

By contrast, *Dryadomyces amasae* gen. sp. nov., reported in galleries bored by *Amasa concitatus*, was not identified during our study (Gebhardt et al. 2005).