Biology subjects

Deliere, L.

Publications and source records attributed to Deliere, L..

5 recordsLinked to original sources

bioRxiv2025

A multivirulent Plasmopara viticola strain from Cilaos on Reunion Island breaks down Rpv1, Rpv3.1 and Rpv10 mediated resistance of grapevine

AbstractGrapevine downy mildew, caused by Plasmopara viticola, is one of the most destructive diseases in viticulture. Resistance-based management strategies rely on grapevine varieties carrying major resistance loci (Rpv). Although breakdown of several loci has been reported, Rpv1 had remained effective until now. Here, we provide the first evidence of Rpv1 breakdown by P. viticola in Cilaos on Reunion Island (France) and the first case of a strain simultaneously overcoming three resistances of grapevine. We combined pathogenicity assays with whole-genome sequencing to characterize a P. viticola strain collected in Cilaos in 2023, alongside a panel of eight reference strains of known virulence. Hypersensitive response and sporulation were assessed for each strain on Chardonnay (susceptible variety) and four resistant varieties carrying Rpv1, Rpv3.1, Rpv10, or Rpv12. The strain collected in Cilaos was able to overcome not only Rpv1 but also Rpv3.1 and Rpv10. On Rpv1, we observed a complete loss of host recognition with high sporulation. On Rpv3.1, the phenotype was consistent with previous breakdowns, and the strain carried the vir1 allele previously described in France. By contrast, the breakdown of Rpv10 differed from that reported in European populations: whereas European strains displayed only partial breakdown of resistance, the strain of Cilaos showed complete loss of host recognition with high sporulation. Moreover, genomic analyses revealed a novel mutation, a large homozygous deletion in the corresponding avr locus. Our genomic data analyses further suggests that this P. viticola strain shares a genetic background with populations from mainland France, raising serious concerns about the potential emergence and spread of multivirulent lineages in Europe. These findings highlight the need for large-scale virulence monitoring of P. viticola and improved strategies for the sustainable management of grapevine resistance in Europe.

plant biology↗

bioRxiv2025

Multiple geographic breakdown events of the Rpv1/Rpv3.1 pyramided resistance in grapevine by Plasmopara viticola.

In 2024, three vineyard sites located within a radius of 40 km in southeastern France, each planted with Artaban, a grapevine variety carrying pyramided resistance (Rpv1 and Rpv3.1), exhibited severe downy mildew symptoms following climatic conditions highly conducive to disease development. Twenty-one Plasmopara viticola isolates were collected from these vineyards and, after monosporangium isolation, tested under controlled conditions on a panel of susceptible and resistant grapevine varieties to assess their virulence. Among the 21 tested field strains, 19 overcame Rpv3.1 mediated resistance, 10 overcame Rpv1 alone, and four genetically distinct strains from two separate vineyards were overcoming the pyramided Rpv1-Rpv3.1 combination. The genetic characterization of the strains suggests that this adaptation likely resulted from convergent evolution. To our knowledge, these represent the first documented cases in Europe of a breakdown in resistance conferred by Rpv1, whether deployed alone or in combination with Rpv3.1.

plant biology↗

bioRxiv2024

Quantitative assessment and spatial distribution of Plasmopara viticola oospores in vineyard soil

Grapevine downy mildew, caused by the oomycete Plasmopara viticola, is one of the most devastating diseases of grapevine worldwide. Primary inoculum (i.e. oospores) play a decisive role in downy mildew epidemics, but we still know very little about its abundance in vineyard soil. This study presents a novel molecular method for quantifying P. viticola oospore concentration in vineyard soil using digital droplet PCR (ddPCR). The development of this method enabled characterization of both the abundance and spatial distribution of oospores in a vineyard at the onset of the growing season. Following a regular grid, a total of 198 soil samples (0-15cm horizon) were collected in March 2022 in grapevine rows in a 0.22 ha vineyard planted with cv. Merlot and conducted according to French organic viticulture specifications. Additional samples were collected from the same field within five nested sampling plots with three distance levels, including samples collected in the inter-rows. Using ddPCR, we found P. viticola DNA in all soil samples except one, and we estimated that oospore concentration ranged from 0 to 1858 oospores per gram of soil (303 {+/-} 308 on average). The distribution of oospores at field scale was not random but characterized by 15 m-diameter patches of concentrically increasing oospore concentration. Oospores accumulated 5 times more below the vine stocks than in the inter-row. Using a leaf disc bioassay, we found that soil infectious potential significantly increased with oospore concentration assessed by ddPCR. However, the low coefficient of determination of the relationship indicated that DNA-based oospore quantification lacked clear epidemiological significance. Both ddPCR and bioassay methods are valuable tools that could be used to assess reservoirs of P. viticola primary inoculum across different agroclimatic contexts, thereby bringing greater genericity. Further methodological improvement will also help refine the accuracy of DNA-based assessment of primary inoculum reservoir and improve our understanding of the relationship between primary inoculum reservoir and epidemic dynamics. Ultimately, these data will be essential for improving epidemic risk models and evaluating new preventive disease management strategies targeting the primary inoculum. ImportanceGrapevine downy mildew caused by the oomycete Plasmopara viticola, affects leaves and bunches, and leads to important economic losses for viticulturists. Recently, evidences have accumulated that soilborne primary inoculum (i.e. oospores in the soil) importantly contributes to disease progress. The significance of our work is in presenting a direct and sensitive method for assessing soil oospore concentration, as well as quantitative and spatially-explicit data on downy mildew primary inoculum. This opens the way to new research, the evaluation of new disease control strategies based on primary inoculum management and the improvement of epidemic risk models, which will potentially contribute to lower fungicide use in viticulture in fine.

plant biology↗

bioRxiv2020

Europe as a bridgehead in the worldwide invasion history of grapevine downy mildew, Plasmopara viticola

Europe is the historical cradle of viticulture, but grapevines have been increasingly threatened by pathogens of American origin. The invasive oomycete Plasmopara viticola causes downy mildew, one of the most devastating grapevine diseases worldwide. Despite major economic consequences, its invasion history remains poorly understood. Comprehensive population genetic analyses of ~2000 samples from the most important wine-producing countries revealed very low genetic diversity in invasive downy mildew populations worldwide. All the populations originated from one of five native North American lineages, the one parasitizing wild summer grape. After an initial introduction into Europe, invasive European populations served as a secondary source of introduction into vineyards worldwide, including China, South Africa and, twice independently, Australia. Invasion of Argentina probably represents a tertiary introduction from Australia. Our findings provide a striking example of a global pathogen invasion resulting from secondary dispersal of a successful invasive population. It will help designing quarantine regulations and efficient breeding for resistance against grapevine downy mildew.

evolutionary biology↗

bioRxiv2019

Microbial networks inferred from metabarcoding data lack replicability: consequences for next-generation biomonitoring

Plant-associated microbial interaction networks protect plants against disease. There is, therefore, a need to monitor in real time their responses to environmental changes to predict disease risk and adjust crop protection strategies. Next-Generation Biomonitoring (NGB) proposes to reconstruct automatically these networks from metabarcoding data, to complement ecological community properties commonly used for ecosystem health assessment. This study aimed to evaluate the benefits and shortcomings of community-level and network-level properties for biomonitoring. We specifically investigated whether microbial networks inferred from metabarcoding data show robust responses to agricultural practices, using the grapevine microbiota as a study system. Our results demonstrate a strong footprint of the agricultural practice on the metabarcoding data, when analyzed at the community level. The richness, diversity and evenness of fungal communities were significantly higher in organic than conventional plots. The cropping system also affected the composition of grapevine foliar fungal communities significantly. Contrary to our expectations, microbial networks were less sensitive to changes in agricultural practices than microbial communities, confirming that NGB should not only consider network-level properties but also community-level properties. Moreover, we found that microbial networks lacked replicability within a cropping system but that consensus networks, built from several network replicates, could generate relevant hypotheses of microbial interactions. As things stand, community-level properties appear to be a more reliable and statistically powerful monitoring option than network-level properties. Future developments, especially in network inference methods, are likely to challenge our findings and help to improve the monitoring of the ecosystem services provided by the plant microbiota.

ecology↗