Biology subjects

Schnee, S.

Publications and source records attributed to Schnee, S..

4 recordsLinked to original sources

bioRxiv2025

Rpv2 is part of a cluster of NLRs specific to Vitis rotundifolia and confers extreme resistance to grapevine downy mildew.

Downy mildew caused by the oomycete Plasmopara viticola is one of the most important diseases affecting grapevine. Resistant varieties are an environmentally-friendly tool to control grapevine downy mildew. Efficient breeding for durable resistance requires knowledge of the underlying mechanisms. Here we aimed at identifying the molecular basis of Rpv2, a gene for extreme resistance to downy mildew derived from Vitis rotundifolia, and at characterizing its effect on pathogen development. Individuals from two populations segregating for Rpv2 were evaluated for resistance to downy mildew and genotyped. Following genetic mapping, markers flanking Rpv2 were used to screen new populations and identify recombinant individuals. Sequencing of recombinants and in silico chromosome painting was used to reduce the interval containing Rpv2. Comparative genomics inside the Vitaceae, involving de novo assembly of the V. rotundifolia Regale genome, allowed narrowing-down the list of candidate genes. We restrict Rpv2 to a 250 kb genomic region that contains two resistance genes of the NLR type. Comparative genomics analyses could not find orthologs of both NLRs in the other Vitis species studied. We also show that Rpv2-mediated resistance leads to pathogen arrest early in the infection cycle. Our results show that Rpv2 belongs to the NLR family of resistance genes, contributing thus to understand the potential and risks of its use in breeding programs and suggesting that combining NLR-type genes may lead to durable resistance KEY MESSAGEThe Rpv2 locus for extreme resistance to grapevine downy mildew is mapped to a 250 kb genomic region containing two NLR-type genes specific to V. rotundifolia.

plant biology↗

bioRxiv2025

Phyllosphere microbiome-based biocontrol solution against the filamentous pathogens Botrytis cinerea and Plasmopara viticola in grapevine

Plants harbor different microbial communities in their different organs. This difference is due to the various conditions to which the different parts of the plant are subjected. Consequently, the phyllosphere microbiota can differ strongly from root-associated communities. We hypothesize that the grapevine phyllosphere is a valuable source of biocontrol bacteria, whose adaptation to the aerial plant environment may enable them to reach their full protective potential against foliar pathogens. In previous work, we isolated phyllosphere bacteria and showed that many strains were very effective against such pathogens in vitro, inhibiting their mycelial and spore development. This work investigates the biocontrol ability of these phyllosphere bacteria in leaf disc assays against two foliar pathogens: Botrytis cinerea (gray mold) and Plasmopara viticola (downy mildew). Our results show that 40 strains out of 46 affected at least one pathogen by altering their spore physiology and/or reducing disease progression. Among these strains, 27 strains could impact both pathogens and 20 were also capable of stimulating plant defenses. Because bacterial consortia might perform better than single strains, we also compared the protection conferred by individual bacteria and associations of up to three strains. When combined, bacteria showed improved efficacy in vitro against B. cinerea and in planta against P. viticola, resulting in a much stronger protection than that obtained by the application of the strains alone. These data suggest that phyllosphere bacteria could be a promising tool to help winegrowers manage grapevine diseases by providing an effective and sustainable protection of their crops.

plant biology↗

bioRxiv2025

Potato Late Blight Control with a Botanical Product and Reduced Copper Applications

Potato late blight (PLB), due to the pathogenic oomycete, Phytophthora infestans, can cause extensive economic damage, particularly in organic potato production. Although copper is used to combat PLB in organic production, it is banned in some countries, and its reduction or elimination as a plant protection product is an increasing priority in Europe. Alternative control strategies, including botanicals, could potentially reduce copper and control PLB. We investigated the application of Frangula alnus bark, its sequential use with a reduced copper application, and a reduced copper application alone in field and lab experiments. The influence of different dosages and preparations on efficacy and the quantity of the posited active ingredients were examined. Frangula alnus treatments decreased disease severity compared to a water control but showed differences in efficacy depending on dosage and disease pressure. Through in vitro and in planta experiments, we investigated whether F. alnus directly or indirectly controlled PLB. A bacterium (Erwinia spp.), originating from the F. alnus extract, colonized the media and accounted for most of the direct inhibition in vitro, but removing microorganisms through filtration had no effect on the extracts efficacy in planta. The contribution of extract-associated microorganisms to PLB control is unclear and requires additional experimentation to assess. The presence of measured anthraquinones likely contributed to the effect of F. alnus. In field experiments, copper consistently and F. alnus generally (except for one year) reduced disease severity compared to a water control. No difference was observed in disease severity between the full and reduced copper treatments. Potato variety more consistently drove differences in total and marketable yields compared to the applied treatment. The relative stability of the yield suggests that treatment effectiveness is intertwined with the timing of disease development and environmental conditions.

plant biology↗

bioRxiv2023

New viruses of Cladosporium sp. expand considerably the taxonomic structure of Gammapartitivirus genus

Despite the fact that Cladosporium sp. are ubiquitous fungi, their viromes have been little studied. By analysing a collection of Cladosporium fungi, two new partitiviruses named Cladosporium cladosporioides partitivirus 1 (CcPV1) and Cladosporium cladosporioides partitivirus 2 (CcPV2) co-infecting a strain of Cladosporium cladosporioides were identified. Their complete genome consists in two monocistronic dsRNA segments (RNA1 and RNA2) with a high percentage of pairwise identity on 5 and 3 end. The RNA dependant RNA polymerase (RdRp) of both viruses and the capsid protein (CP) of CcPV1 display the classic characteristics required for their assignment to the Gammapartitivirus genus. In contrast, CcPV2 RNA2 encodes for a 41 KDa CP that is unusually small with a low percentage of amino acid identity as compared to CPs of other viruses classified in this genus. This sequence was used to annotate fifteen similar viral sequences with unconfirmed function. The phylogeny of the CP was highly consistent with the phylogeny of their corresponding RdRp, supporting the organization of gammapartitiviruses into three distinct clades despite stretching the current demarcation criteria.

microbiology↗