Faculté des sciences

Isolation and identification of secondary metabolites from the fungus Phomopsis spp., a pathogen responsible for vine excoriosis = Isolement et identification de métabolites secondaires du champignon Phomosis spp., un pathogène responsable de l’excoriose de la vigne

Mottier, Nicolas ; Tabacchi, Raffaele (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2005 ; 1841.

Grapevine diseases are of great importance as they affect production and harvesting causing serious yield loss. The amount of damage or loss is often dependant on the climate of the region and the cultural practices of the grape growers. Control of these diseases is generally done using fungicide sprays and management techniques such as leaf plucking, pruning, etc. Epidemics do occur from time to... More

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    Summary
    Grapevine diseases are of great importance as they affect production and harvesting causing serious yield loss. The amount of damage or loss is often dependant on the climate of the region and the cultural practices of the grape growers. Control of these diseases is generally done using fungicide sprays and management techniques such as leaf plucking, pruning, etc. Epidemics do occur from time to time when even the most rigorous management cannot control the disease because of favourable weather conditions. One usually differentiates trunk and root diseases, e.g. Eutypa dieback and esca, from fruit and foliar diseases such as downy mildew, powdery mildew and grey rot. Grapevine trunk diseases are responsible for significant economic losses to the wine industry worldwide. Symptoms of these diseases include dead spurs, arms and shoots and eventual vine death due to canker formation in the vascular tissue. In Eutypa dieback, deformed leaves and shoots occur as the pathogen invades the ramifications. As cankers develop, yield reductions occur due to the loss of productive wood. The impact of grapevine wood diseases usually becomes more severe as vineyards get older until they weaken and eventually kill vines. Foliage and developing bunches must also be protected from attack by various pests, especially fungal pathogens, for the production of satisfactory yields of good-quality grapes, and especially for adequate vinification. To maintain economic production it is essential to use specific fungicides and correct application of plant protection products. However, the chemicals used can be non specific or used on a large scale at the wrong time either in the absence of the inoculum of the pathogen or under conditions that are not favourable for the disease development. Thus, the inappropriate use of these products with the increased realisation of environmental issues has lead to the need for growers and managers to adopt responsible and intelligent disease management systems. Understanding of grapevine diseases and their causal agents is vital as it can bring precious information for alternative pathways in management of the pathogens. Since 1986, grapevine diseases have been one of the main fields of research of the group of Professor R. Tabacchi with works published on esca, eutypa dieback, gray rot and downy mildew. The following project is the continuation of this research with the study of a worldwide spread disease, excoriosis or Phomopsis cane and leaf spot. This disease is caused by a fungus called Phomopsis viticola which can cause serious damage when weather conditions are suitable. The main symptoms are necrotic lesions on canes and shoots, black spots on leaves and, rarely, fruits. In collaboration with the group of Professor G. Défago of the Swiss Federal Institute of Technology, twelve strains of the fungus were collected from a grapevine field in Ticino, Switzerland. After growing the fungi on an artificial media, chemical metabolites were profiled using high-performance liquid chromatography and biological assays against grapevine leaf disks were performed. We decided to upscale the culture and study further three of the strains. Using the modern current separation and identification techniques, such as HPLC-UV and 1D and 2D NMR, we isolated several secondary metabolites produced by the fungus. Furthermore, the fungus was grown on grapevine wood pruned after harvest in order to have culture conditions as close to reality as possible. As detection of the metabolites in the wood must allow for low detection limits, LC-(API)-MS was the method of choice for this research.