Marion Schilling

Bio: Marion Schilling is an academic researcher from University of Lorraine. The author has contributed to research in topics: Fomitiporia mediterranea. The author has an hindex of 1, co-authored 2 publications receiving 5 citations.

Fomitiporia mediterranea M. Fisch., the historical Esca agent: a comprehensive review on the main grapevine wood rot agent in Europe

Abstract: Fomitiporia mediterranea M. Fisch. (Fmed) is a basidiomycete first described in 2002, and was considered up to then as part of Fomitiporia punctata (P. Karst) Murrill. This fungus can degrade lignocellulosic biomass, causing white rot and leaving bleached fibrous host residues. In Europe Fmed is considered the main grapevine wood rot (Esca) agent within the Esca disease complex, which includes some of the most economically important Grapevine Trunk Diseases (GTDs). This review summarises and evaluates published research on Fmed, on white rot elimination by curettage or management by treatments with specific products applied to diseased grapevines, and on the relationship between wood symptoms and Grapevine Leaf Stripe Disease (GLSD) in the Esca disease complex. Information is also reviewed on the fungus biology, mechanisms of pathogenicity, and their possible relationships with external foliar symptoms of the Esca disease complex. Information on Fmed control strategies is also reviewed.

Wood degradation in grapevine diseases

Abstract: The major Grapevine Trunk Diseases (GTD) gather diseases associated with either one particular fungal species, e.g., eutypiose, or with fungal species complexes, e.g., Botryosphaeriae dieback. GTD-associated fungi are part of different fungal classes, depending on their substrate degradation mechanisms or on their lifestyles. They are identified in grapevine wood and they lead to wood typical symptoms. They are sometimes associated to foliar symptoms too, despite not found in aerial parts, probably acting through fungal toxins or through physiological disorders, such as non-functional wood vessels. Grapevine is a liana, and as such shows structural and chemical differences compared to forest tree wood. However, knowledge on wood-degrading fungi growing on tree wood can contribute to a better understanding of grapevine wood adaptation mechanisms to fungal attack. For example, wood density, xylem vessels size and number, or lignin content and composition can play a role in wood sensitivity to fungi. Also, some fungal detoxification mechanisms against wood extractibles are host-specific. In a first part of this chapter, structure and chemical composition of grapevine wood are described, pointing out properties that might play a role in fungal growth. In a second part, GTD main associated fungi and their known mechanisms for wood degradation or wood chemical detoxification are discussed. Extracellular and intracellular enzymatic and non-enzymatic mechanisms are considered. These mechanisms, well described for their role in fungal adaptation to tree wood, have been much less studied for GTD associated fungi. Further studies about those mechanisms would contribute to understand fungal adaptation to grapevine.

Phenolic compounds have a role in the defence mechanism protecting grapevine against the fungi involved in Petri disease [Vitis vinifera L.]

Abstract: Scanning electron microscopy of stems and roots of vine plants affected by Petri disease demonstrated that the obstruction of xylem vessels and reduction in the flow of xylem sap, two symptoms of this disease, were mainly caused by tyloses forming in the vessels, and, to a lesser extent, by the accumulation of aggregates. Fungal hyphae were also found in the xylem. These hyphae propagated via the xylem and invaded other vessels or adjacent parenchymatic cells through the pit. Analysis of lignin peroxidase, manganese peroxidase and laccase activity (all of which are involved in lignin degradation) in different fungi isolated from Petri-disease-infected grapevines found that Phaeoacremonium aleophilum expressed low specific activity for manganese peroxidase and high specific activity for both lignin peroxidase and laccase, while Phaeomoniella chlamydospora showed no activity for any of these enzymes. All these enzyme activities were inhibited by the phenolic compounds in grapevine: p-coumaric acid, catechin, caffeic acid and tannins. The phenolic compounds also had a direct effect on fungal growth and sporulation. When SO4 vines affected by Petri disease were treated with Brotomax (a product that stimulates synthesis of phenolic compounds) plants showed an increase in growth and a reduction in Petri-disease symptoms. Any new shoots and roots formed after Brotomax treatment did not show any sign of obstruction or tyloses formation.

Compartmentalization: a conceptual framework for understanding how trees grow and defend themselves [Wood compartmentation and boundary zones]

Abstract: The purpose of this chapter is to describe a conceptual framework for understanding how trees grow and how they and other perennial plants defend themselves. The concept of compartmentalization has developed over many years, a synthesis of ideas from a number of investigators. It is derived from detailed studies of the gross morphology and cellular anatomy of the wood and bark of roots and stems in healthy angiosperms and gymnosperms. It is based on research in tree physiology and the chemistry of wood and bark. It is founded on observations of trees injured in the field by wind, snow, ice, fire, animals, and insects, as well as during pruning, coppicing, sugaring, and other forest and orchard management practices. It is based on experimental studies of natural and artificial wounds with and without controlled inoculations with selected pathogenic and saprophytic microorganisms. These microbes have included wood-decaying Basidiomycetes and Ascomycetes, wood-staining Ascomycetes and Fungi Imperfecti, canker fungi, and a myriad of woodinhabiting bacteria. The end result of all these studies is an integrating concept that involves defenses laid down by trees prior to injury and defenses laid down by trees after injury.

White Rot Fungi (Hymenochaetales) and Esca of Grapevine: Insights from Recent Microbiome Studies

Abstract: Esca is a major grapevine trunk disease that heavily affects vineyards in the Northern hemisphere. The etiology and epidemiology of this disease have been subject of dispute ever since the earliest disease reports. The reason behind such debate is the presence of multiple internal and external symptoms, as well as several putative and confirmed wood pathogens. While the role of pathogenic fungi, as causal agents of wood symptoms, has been thoroughly assessed, their role in the expression of leaf symptoms remains to be fully elucidated. In this review, we analyzed etiological and epidemiological data, with a special focus on the microbiological aspect of esca and the involvement of Hymenochaetales (Basidiomycota). Vineyard studies have associated leaf symptoms with the presence of white rot, most frequently caused by Fomitiporia mediterranea (Hymenochaetales), while tracheomycotic fungi are commonly found, with similar abundance, in symptomatic and asymptomatic vines. Pathogenicity trials have excluded a direct effect of Hymenochaetales species in triggering leaf symptoms, while the data concerning the role of tracheomycotic fungi remains controversial. Recent microbiome studies confirmed that F. mediterranea is more abundant in leaf-symptomatic vines, and treatments that effectively control leaf symptoms, such as sodium arsenite spray and trunk surgery, act directly on the abundance of F. mediterranea or on the presence of white rot. This suggest that the simultaneous presence of Hymenochaetales and tracheomycotic fungi is a pre-requisite for leaf symptoms; however, the relation among fungal pathogens, grapevine and other biotic and abiotic factors needs further investigation.

Activity of Trichoderma asperellum Strain ICC 012 and Trichoderma gamsii Strain ICC 080 Toward Diseases of Esca Complex and Associated Pathogens

Abstract: Grapevine trunk diseases are widespread in all grape-growing countries. The diseases included in the Esca complex of diseases are particularly common in European vineyards. Their distinctive foliar symptoms are well known to be associated not only with losses in quantity, as with all grapevine wood diseases, but also with losses in the quality of the crop. Protection of pruning wounds is known to reduce infections in artificial inoculations and, to some extent, reduce the external leaf symptoms. The application of biological control agents in the field is typically started at the first appearance of symptoms. In this article, the two strains belonging to two different species, Trichoderma asperellum ICC 012 and T. gamsii ICC 080, which are present in a commercial formulation, were tested in vitro, in vivo in artificial inoculation, and in the field in long-term experiments where the wounds on four young asymptomatic vineyards were protected since 1 or 2 years after planting. The in vitro trials highlighted the different temperature requirements of the two strains, the direct mycoparasitizing activity of T. asperellum, and the indirect activity shown by both Trichoderma strains. The in vivo trials confirmed the ability of the two strains to reduce the colonization following artificial inoculations with the high, unnatural concentration of spores used in artificial infections, even if with variable efficacy, and with long persistence as they could be reisolated 7 months post-application. The preventive applications carried out over 9 years showed a very high reduction in symptom development in the treated vines, on annual and cumulated incidence and on the death of vines, with disease reduction varying from 66 to almost 90%. Early and annual application of protection to the pruning wounds appears to be the best method for reducing damages caused by grapevine leaf stripe disease (a disease of the Esca complex of diseases). Trichoderma appears to offer an efficient, environmentally friendly, and long-lasting protection in the presence of a natural inoculum concentration.

Metagenomic Assessment Unravels Fungal Microbiota Associated to Grapevine Trunk Diseases

Abstract: Grapevine trunk diseases (GTDs) are among the most important problems that affect the longevity and productivity of vineyards in all the major growing regions of the world. They are slow-progression diseases caused by several wood-inhabiting fungi with similar life cycles and epidemiology. The simultaneous presence of multiple trunk pathogens in a single plant together with the inconsistent GTDs symptoms expression, their isolation in asymptomatic plants, and the absence of effective treatments make these diseases extremely complex to identify and eradicate. Aiming to gain a better knowledge of GTDs and search sustainable alternatives to limit their development, the present work studied the fungal community structure associated with GTDs symptomatic and asymptomatic grapevines, following a metagenomic approach. Two important cultivars from the Alentejo region with different levels of susceptibility to GTDs were selected, namely, ‘Alicante Bouschet’ and ‘Trincadeira’. Deep sequencing of fungal-directed ITS1 amplicon led to the detection of 258 taxa, including 10 fungi previously described as responsible for GTDs. Symptomatic plants exhibited a lower abundance of GTDs-associated fungi, although with significantly higher diversity of those pathogens. Our results demonstrated that trunk diseases symptoms are intensified by a set of multiple GTDs-associated fungi on the same plant. The composition of fungal endophytic communities was significantly different according to the symptomatology and it was not affected by the cultivar. This study opens new perspectives in the study of GTDs-associated fungi and their relation to the symptomatology in grapevines.