Purpan Engineering School

The hyperdiverse wood-inhabiting fungi play a crucial role in the global carbon cycle, but often are threatened by deadwood removal, particularly in temperate forests dominated by European beech (Fagus sylvatica) and Oriental beech (Fagus orientalis). To study the impact of abiotic drivers, deadwood factors, forest management and biogeographical patterns in forests of both beech species on fungal composition and diversity, we collected 215 deadwood-drilling samples in 18 forests from France to Armenia and identified fungi by meta-barcoding. In our analyses, we distinguished the patterns driven by rare, common, and dominant species using Hill numbers. Despite a broad overlap in species, the fungal composition with focus on rare species was determined by Fagus species, deadwood type, deadwood diameter, precipitation, temperature, and management status in decreasing order. Shifting the focus on common and dominant species, only Fagus species, both climate variables and deadwood type remained. The richness of species within the deadwood objects increased significantly only with decay stage. Gamma diversity in European beech forests was higher than in Oriental beech forests. We revealed the highest gamma diversity for old-growth forests of European beech when focusing on dominant species. Our results implicate that deadwood retention efforts, focusing on dominant fungi species, critical for the decay process, should be distributed across precipitation and temperature gradients and both Fagus species. Strategies focusing on rare species should additionally focus on different diameters and on the conservation of old-growth forests.

National audience

Vitis vinifera is affected by many diseases every year, depending on causal agents, susceptibility of cultivars, and climate region. Some are caused by a single agent, such as gray mold caused by Botrytis cinerea or powdery mildew caused by Erysiphe necator. Others result from the actions of a complex of pathogens such as grapevine trunk diseases (GTDs). GTDs are presently among the most devastating diseases in viticulture worldwide because both the economic losses and the long-term sustainability of vineyards are strongly affected. The complexity of GTDs results from the diversity of associated fungi, the undetermined period of latency within the vine (asymptomatic status), the erratic foliar symptom expression from one year to the next, and, probably correlated with all of these points, the lack of efficient strategies to control them. Distinct methods can be beneficial to improve our knowledge of GTDs. In vitro bioassays with cell suspensions, calli, foliar discs, full leaves, or plantlets, and in vivo natural bioassays with cuttings, grafted plants in the greenhouse, or artificially infected ones in the vineyard, can be applied by using progressive integrative levels of in vitro and in vivo, depending on the information searched. In this review, the methods available to understand GTDs are described in terms of experimental procedures, main obtained results, and deliverable prospects. The advantages and disadvantages of each model are also discussed.

National audience

National audience

International audience

A large network of field experiments has been conducted over several years across France to identify combinations of winter wheat cultivars and management leading to achieve the double objective of ecological sustainability and economic viability. Little information is available to document the variation in multiple disease levels, a necessary step towards a chemical extensification process, in wheat networked experiments. This article provides a description of disease intensities in a set of 101 experiments totalling 3525 individual wheat plots over eight successive years (2003–2010). The diseases considered are brown rust (BR, Puccinia triticina), yellow rust (YR, Puccinia striiformis), fusarium head blight (FHB, Fusarium graminearum, F. culmorum, and F. avenaceum), powdery mildew (PM, Blumeria graminis), and septoria tritici blotch (STB, Zymoseptoria tritici). Disease intensities were represented by binary variables (epidemic vs non-epidemic), and three disease syndromes were identified, which correspond to different disease profiles. Three variety groups were also identified, according to their responses to diseases. The results indicate that climatic years, wheat varieties, and crop management, in this decreasing order, define disease epidemic risk in the multiple wheat-diseases pathosystem. The associations between climate variables and epidemic risks identified here conform to disease-specific knowledge of climate effects on the components of the pathosystem. This report emphasises the value of large scale data in crop health assessment and the usefulness of a risk factor approach for both tactical and strategic decisions for crop health management.

National audience

National audience