Exploration of yeast biodiversity potential for development of alternative biofungicides in viticulture : dissertationRowland Adesida
, 2022, doktorska disertacija
Opis: Botrytis cinerea Pers., the fungal plant pathogen and the causal agent of gray mould diseases in grapevine, is vastly responsible for substantial economic losses in table and wine grapes production worldwide by negatively affecting plant growth and causing the
reduction of grape and wine quality. The conventional approach for pathogen control has been up to date based on synthetic fungicides with good effectiveness against pathogens but a negative impact on the environment. The growing level of harmful residues in the environment and some also detected in wines have led the European
Union and many winemakers to limit the application of synthetic fungicides to earlier season. However, with a high risk of disease also late in the season, the need for other solutions is clear. Consequently, more and more research is focused on finding potential alternatives in the form of effective biological control agents. Although there are several reports of yeast’s biocontrol activity, they are up to date still poorly commercialized for such purposes. As
the yeasts represent an important part of the grape microflora, competing with other microorganisms (including pathogens) for nutrients and space, we decided to examine the potential of autochthonous yeasts as "green" alternatives in fighting against
phytopathogens such as B. cinerea in viticulture. With this aim, we tested the biocontrol activity of 119 different indigenous yeasts belonging to 30 different species of 17 genera against filamentous fungus B. cinerea, the causal agent of grey mould or botrytis
bunch rot in grape. The yeasts were screened for putative multidimensional modes of action such as antifungal volatiles (VOC), in vitro inhibition of fungal mycelial growth, competition for nutrients, hydrolytic enzyme activities, and yeast tolerance to fungicides like copper, iprodione and cyprodinil/fludioxonil combination. With a qualitative detection of the hydrolysis activity by using screening methods based on solid medium with chitin or βD-glucosides as substrates, we found that many tested yeasts were capable of producing lytic enzymes with the ability to degrade the cell wall of phytopathogenic fungi and are potentially also able to produce VOCs via hydrolysis of grape glycosides as a result of β-glucosidase presence. Furthermore, we observed the capability of tested yeast to inhibit fungal mycelia growth on plate and assimilation of a wide variety of carbon sources; however, no siderophore producers were detected. In general, the yeasts under observation were tolerant to the tested fungicides. Their fungicide resistance can indeed be regarded as a beneficial trait for potential biofungicide agent (PBA) candidates due to open possibilities of applications and combinations within low input pest management strategies in the vineyard. Finally, a field experiment in Pinot noir and Pinot gris vineyards was designed to study different combinations of optimized canopy microclimate manipulation (CMM) techniques and potential biocontrol agent (PBA) application. In experimental
conditions, the ability of PBA’s to maintain appropriate population density for disease prevention was observed. In addition, the grape and wine quality parameters were analysed to observe the possible impact of implemented biocontrol yeast on final products.
The biocontrol yeast Pichia guilliermondii ZIM 624 was selected and applied in experimental vineyards based on yeast testing results. We were able to detect and confirm PBA yeast’s suitable density on grapes until harvest. In the case of early defoliation for both varieties lower grape compactness was observed together with lower yield/ plant, regardless of PBA yeast/ no yeast application. Among grape basic quality parameters, the optimized techniques showed a positive effect on sugar content. Still, unexpectedly, in the treatments with biocontrol yeasts some trends toward higher
acidity were noticed in Pinot gris.
Ključne besede: sustainable viticulture, Botrytis cinerea, gray mould, yeasts, biocontrol, canopy microclimate manipulation, grapevine metabolite, dissertations
Objavljeno v RUNG: 07.07.2022; Ogledov: 1645; Prenosov: 128
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