Identification of two novel powdery mildew resistance loci, Ren6 and Ren7, from the wild Chinese grape species Vitis piasezkii

Descriptive statistics of the phenotypic scores within the base mapping population 11-373. Powdery mildew symptoms in the field were evaluated in two subsequent years. Greenhouse, in vitro experiments and the qPCR-based molecular assay were carried out with three to four biological replicates of each seedling plant in 2014. (DOCX 14ย�kb

Use of beneficial bacteria and their secondary metabolites to control grapevine pathogen diseases

Grapevine is one of the most important economic crops yielding berries, wine products as well as derivates. However, due to the large array of pathogens inducing diseases on this plant, considerable amounts of pesticides—with possible negative impact on the environment and health—have been used and are currently used in viticulture. To avoid negative impacts of such products and to ensure product quality, a substantial fraction of pesticides needs to be replaced in the near future. One solution can be related to the use of beneficial bacteria inhabiting the rhizo- and/or the endosphere of plants. These biocontrol bacteria and their secondary metabolites can reduce directly or indirectly pathogen diseases by affecting pathogen performance by antibiosis, competition for niches and nutrients, interference with pathogen signaling or by stimulation of host plant defenses. Due to the large demand for biocontrol of grapevine diseases, such biopesticides, their modes of actions and putative consequences of their uses need to be described. Moreover, the current knowledge on new strains from the rhizo- and endosphere and their metabolites that can be used on grapevine plants to counteract pathogen attack needs to be discussed. This is in particular with regard to the control of root rot, grey mould, trunk diseases, powdery and downy mildews, pierce’s disease, grapevine yellows as well as crown gall. Future prospects on specific beneficial microbes and their secondary metabolites that can be used as elicitors of plant defenses and/or as biocontrol agents with potential use in a more sustainable viticulture will be further discussed

Identification and distribution of mating-type idiomorphs in populations of Podosphaera macularis and development of chasmothecia of the fungus

Podosphaera macularis, the causal agent of hop powdery mildew, is known to produce chasmothecia (formerly cleistothecia) in eastern North America and Europe. Ascocarps have not yet been reported from the Pacific Northwestern region of North America. Reasons for the apparent absence of chasmothecia in the Pacific Northwest were unknown. This study established that P. macularis is heterothallic and ascocarp ontogeny, maturation, dehiscence and ascospore infection proceed similarly to other powdery mildew fungi. Genome sequencing of a MAT1-1 isolate revealed the structure of the MAT1 locus and presence of MAT1-1-3, demonstrating further similarities to other powdery mildew fungi. PCR assays with primers designed from conserved domains of the MAT1 idiomorphs were developed to characterize the frequency of idiomorphs in populations of P. macularis. Amongst 317 samples of P. macularis collected during 2012 and 2013 from the Pacific Northwest only the MAT1-1 idiomorph was found. In contrast, among 56 samples from the eastern United States and Europe, MAT1-1 and MAT1-2 idiomorphs were detected at equivalent frequencies. At temperatures representative of late season conditions in the Pacific Northwest, chasmothecia formed readily when a Pacific Northwest MAT1-1 isolate was paired with a MAT1-2 isolate collected from outside the region. Although these findings do not encompass all climatic, geographic or temporal barriers that could inhibit the formation of chasmothecia, the current absence of the ascigerious stage of P. macularis in the Pacific Northwest could be explained by the absence of the MAT1-2 mating type idiomorph.Keywords: Humulus lupulus, powdery mildew, Podosphaera macularis, chasmothecia, cleistothecia, ho

Spatio-temporal distribution of Erysiphe necator genetic groups and their relationship with disease levels in vineyards

International audienceThe discovery of genetically distinct Erysiphe necator groups (A or B), with high phenotypic similarities, raises important questions about their coexistence. For plant pathogens, niche partitioning, allowing the coexistence on the same host (i.e. the same resource), might result from separation in space and/or time. We used a landscape genetic approach to study the geographic distribution of genetic groups of E. necator (distinguished by a SNP in the β-tubulin gene) at the spatial scale of the Languedoc-Roussillon region (southern France) and to assess the temporal succession of groups along the course of the 2007 epidemic. Spatial distribution revealed a high heterogeneity between vineyards: from 100% B to 100% A, with 62% and 38% of vineyards showing a majority of A and B isolates, respectively. Temporal isolation seems to be the major mechanism in the coexistence of the two genetic groups: all isolates collected towards the end of the epidemic belonged to group B, whatever the initial frequency of genetic groups. Our results confirm that both A or B isolates can lead to flag-shoot symptoms, and showed that group A isolates tend to disappear during the course of the epidemic, whereas group B isolates may be active during the entire epidemic and involved in further production of cleistothecia, when recombination takes place. For the first time, the relationship between the frequency of genetic groups and disease levels on leaves and clusters at the end of the epidemic was evaluated. We showed a strong relationship between the disease severity and the genetic composition of E. necator populations: the damage was more important when the epidemic was initiated by B isolates

Programmable Attenuation of Antigenic Sensitivity for a Nanobody-Based EGFR Chimeric Antigen Receptor Through Hinge Domain Truncation

Epidermal growth factor family receptor (EGFR) is commonly overexpressed in many solid tumors and an attractive target for chimeric antigen receptor (CAR)-T therapy, but as EGFR is also expressed at lower levels in healthy tissues a therapeutic strategy must balance antigenic responsiveness against the risk of on-target off-tumor toxicity. Herein, we identify several camelid single-domain antibodies (also known as nanobodies) that are effective EGFR targeting moieties for CARs (EGFR-sdCARs) with very strong reactivity to EGFR-high and EGFR-low target cells. As a strategy to attenuate their potent antigenic sensitivity, we performed progressive truncation of the human CD8 hinge commonly used as a spacer domain in many CAR constructs. Single amino acid hinge-domain truncation progressively decreased both EGFR-sdCAR-Jurkat cell binding to EGFR-expressing targets and expression of the CD69 activation marker. Attenuated signaling in hinge-truncated EGFR-sdCAR constructs increased selectivity for antigen-dense EGFR-overexpressing cells over an EGFR-low tumor cell line or healthy donor derived EGFR-positive fibroblasts. We also provide evidence that epitope location is critical for determining hinge-domain requirement for CARs, as hinge truncation similarly decreased antigenic sensitivity of a membrane-proximal epitope targeting HER2-CAR but not a membrane-distal EGFRvIII-specific CAR. Hinge-modified EGFR-sdCAR cells showed clear functional attenuation in Jurkat-CAR-T cells and primary human CAR-T cells from multiple donors in vitro and in vivo. Overall, these results indicate that hinge length tuning provides a programmable strategy for throttling antigenic sensitivity in CARs targeting membrane-proximal epitopes, and could be employed for CAR-optimization and improved tumor selectivity

Sporulation rate in culture and mycoparasitic activity, but not mycohost specificity, are the key factors for selecting Ampelomyces strains for biocontrol of grapevine powdery mildew (Erysiphe necator)

To develop a new biofungicide product against grapevine powdery mildew, caused by Erysiphe necator, cultural characteristics and mycoparasitic activities of pre-selected strains of Ampelomyces spp. were compared in laboratory tests to the commercial strain AQ10. Then, a 2-year experiment was performed in five vineyards with a selected strain, RS1-a, and the AQ10 strain. This consisted of autumn sprays in vineyards as the goal was to reduce the number of chasmothecia of E. necator, and, thus, the amount of overwintering inocula, instead of targeting the conidial stage of the pathogen during spring and summer. This is a yet little explored strategy to manage E. necator in vineyards. Laboratory tests compared the growth and sporulation of colonies of a total of 33 strains in culture; among these, eight strains with superior characteristics were compared to the commercial product AQ10 Biofungicide® in terms of their intrahyphal spread, pycnidial production, and reduction of both asexual and sexual reproduction in E. necator colonies. Mycoparasitic activities of the eight strains isolated from six different powdery mildew species, including E. necator, did not depend on their mycohost species of origin. Strain RS1-a, isolated from rose powdery mildew, showed, togetherwith three strains from E. necator, the highest rate of parasitism of E. necator chasmothecia. In field experiments, each strain, AQ10 and RS1-a, applied twice in autumn, significantly delayed and reduced early-season development of grapevine powdery mildew in the next year. Therefore, instead of mycohost specificity of Ampelomyces presumed in some works, but not confirmed by this study, the high sporulation rate in culture and the mycoparasitic patterns became the key factors for proposing strain RS1-a for further development as a biocontrol agent of E. necator