Biology subjects

Mugnai, L.

Publications and source records attributed to Mugnai, L..

3 recordsLinked to original sources

bioRxiv2026

Association between soil properties and Grapevine Leaf Stripe Disease (Esca Complex) symptom expression. Part I: soil physical, hydrological and chemical characteristics

This study is the first of two companion papers (Part II addresses rhizosphere microbial communities) and aims to investigate the influence of soil properties on GLSD foliar symptom expression by comparing high recurrence of symptomatic vines areas (HRSVAs) and low recurrence of symptomatic vines areas (LRSVAs). The research was conducted in an approximately 1.75-hectare Cabernet Sauvignon vineyard in Tuscany, Italy. Electromagnetic induction (EMI) proximal sensing was combined with kriging-based maps of grapevine leaf stripe disease (GLSD) symptom recurrence over a five-year period, allowing the identification of four vineyard sectors representing contrasting levels of symptom recurrence (high vs. low) and soil apparent electrical conductivity (ECa; medium vs. high). One soil profile was excavated in each sector and characterised through pedological description and physicochemical analysis. GLSD symptoms showed a heterogeneous yet spatially structured distribution, with distinct zones exhibiting contrasting recurrence. Soil properties differed markedly between HRSVAs and LRSVAs. LRSVAs were characterised by clay loam to silty clay loam textures, high lime content, alkaline pH, higher available water capacity (AWC), and lower available manganese concentrations (4.5-4.8 mg/kg). In contrast, HRSVAs had sandy loam to sandy clay loam textures, subalkaline pH, greater soil fertility (higher nitrogen and organic matter contents), deeper root distribution, and higher available manganese concentrations (14.7-14.8 mg/kg). These findings highlight the importance of investigating soil physicochemical properties in relation to GLSD symptom expression, as both macro- and micronutrient availability may be associated with disease dynamics. The higher manganese availability observed in HRSVAs, together with recent evidence that manganese can stimulate the wood-degrading activity of Fomitiporia mediterranea, warrants further investigation into the potential association between soil manganese bioavailability and disease expression. The spatial correspondence between soil heterogeneity and GLSD symptom recurrence highlights the value of high-resolution investigations of soil-plant interactions for improving our understanding of this complex disease.

plant biology↗

bioRxiv2026

Endophytic colonization pathways of Pseudomonas chlororaphis M71 and Trichoderma atroviride SC1 in grapevine following stem injection

Endophytic biocontrol agents may contribute to grapevine health, but their ability to establish, persist, and move within woody tissues remains poorly understood. In this study, a stem injection method was developed to introduce Pseudomonas chlororaphis M71 and Trichoderma atroviride SC1 into rooted and grafted grapevine plants, and their spatial and temporal colonization patterns were compared with the movement of a dye tracer. The dye tracer moved rapidly through xylem tissues, whereas both microorganisms showed more restricted early distribution. Over time, M71 and SC1 displayed distinct colonization patterns. M71 persisted after injection, but remained localized near the inoculation site, with limited movement toward roots or distal aerial tissues. In grafted plants, M71 recovery depended on the injection site and declined more markedly after rootstock injection than after scion injection. In contrast, SC1 showed broader and more persistent colonization. In rooted cuttings, SC1 was recovered from stem and root tissues up to 56 days post-injection, and in grafted plants it was recovered across the graft union, particularly after scion injection. Microscopy supported internal localization of both microorganisms. GFP-labelled M71 and SC1 hyphae were observed mainly within xylem vessels, and viable microorganisms were recovered from corresponding wood tissues. No contamination was observed in control plants. These results show that beneficial microorganisms can be introduced into grapevine tissues by stem injection and that bacterial and fungal biocontrol agents differ markedly in their internal movement and persistence. IMPORTANCEIntroducing beneficial microorganisms directly into plant tissues could help in establishing protective endophytic populations, but little is known about how such microorganisms move and persist inside grapevine. This study shows that stem injection can deliver Pseudomonas chlororaphis M71 and Trichoderma atroviride SC1 into grapevine tissues without visible phytotoxicity. The two microorganisms followed different colonization patterns. M71 remained mostly localized near the injection site, whereas SC1 spread more broadly and persisted in both rooted and grafted plants. These findings provide a basis for developing targeted endophytic biocontrol strategies in grapevine propagation and early plant establishment. This approach may be particularly relevant for grapevine trunk diseases and other vascular disorders, in which pathogens colonize internal woody tissues.

microbiology↗

bioRxiv2021

The Role of Low Molecular Weight Fungal Metabolites in Grapevine Trunk Disease Pathogenesis: Eutypa Dieback and Esca

Eutypa dieback and Esca are serious grapevine trunk diseases (GTDs) caused by fungal consortia causing large economic losses in vineyards. Depending on the disease the species involved include Eutypa lata, Phaeoacremonium minimum, and Phaeomoniella chlamydospora. There is a need to understand the complex pathogenesis mechanisms used by these causative fungi to develop treatments for the diseases they cause. Low molecular weight metabolites (LMW) are known to be involved in non-enzymatic oxygen radical generation in fungal degradation of wood by some Basidiomycota species, and as part of our work to explore the basis for fungal consortia pathogenesis, LMW metabolite involvement by the causal GTD fungi was explored. The GTD fungal pathogens examined, Eutypa lata, Phaeoacremonium minimum and Phaeomoniella chlamydospora, were found to produce low molecular weight iron binding metabolites that preferentially reduced iron or redox cycled to produce hydrogen peroxide. Uniquely, different LMW metabolites isolated from the GTD fungi promoted distinct chemistries that are important in a type of non-enzymatic catalysis known as chelator-mediated Fenton (CMF) reactions. CMF chemistry promoted by LMW metabolites from these fungi allowed for the generation of highly reactive hydroxyl radicals under conditions promoted by the fungi. We hypothesize that this new reported mechanism may help to explain the necrosis of woody grapevine tissue as a causal mechanism important in pathogenesis in these two grapevine trunk diseases. IMPORTANCEUnderstanding the pathogenesis of grape trunk diseases (GTDs) is the key to the development of disease control and treatment. While fungal extracellular enzyme systems are typically cited relative to their fungal mechanisms in pathogenesis, non-enzymatic mechanisms have been less studied in this regard and the role of low molecular weight (LMW) fungal metabolites in GTD development is quite limited. In this article, we demonstrate that GTD-causative fungal pathogens Eutypa lata, Phaeoacremonium minimum and Phaeomoniella chlamydospore produce LMW phenolic metabolites under iron-restricted conditions. These metabolites undergo a series of redox reactions, with different fungi producing metabolites that preferentially either reduce iron, or generate hydrogen peroxide, under conditions simulating grapevine woody tissue. These conditions have the potential to promote generation of highly damaging hydroxyl radicals through a mechanism that appears to be similar to non-enzymatic chelator-mediated Fenton (CMF) chemistry which is involved in fungal degradation of wood by non-related fungal orders. This is the first report of CMF chemistry promoted by GTD-causative fungi under laboratory conditions and the research suggests an alternate pathway that may contribute to pathogenesis in GTDs, and a potential target for vine protection.

microbiology↗