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Time vs drought : leaf age rather than drought drives osmotic adjustment in V. vinifera cv. Pinot Noir
Elena Farolfi, Jan Reščič, 2023, published scientific conference contribution abstract

Abstract: Global warming and increased frequency and/or severity of drought events are among the most threatening consequences of climate change for agricultural crops. In response to drought, grapevine (as many other plants) exhibits osmotic adjustment through active accumulation of osmolytes which in turn shift the leaf turgor loss point (TLP) to more negative values, allowing to maintain stomata opened at lower water potentials1. We investigated the capacity of Pinot noir leaves to modulate their osmotic potential as a function of: (i) time (seasonal osmoregulation), (ii) growing temperatures, and (iii) drought events, to enhance comprehension of the resilience of grapevines in drought conditions. We performed trails under semi-controlled field conditions, and in two different greenhouse chambers (20/15 °C vs 25/20 °C day/night). For two consecutive vegetative seasons, grafted potted grapevines (Pinot noir/SO4) were subjected to two different water regimes for at least 30 days: well-watered (WW) and water deficit (WD). Via pressure-volume (PV) curves and osmometer measurements we derived the leaf osmotic adjustment capability and TLP, while monitoring the plant gas exchange and water potential. Surprisingly, lower water potentials in WD vines throughout the season and in all situations (field and greenhouse) did not trigger osmoregulation, changes in TLP nor a modification of the modulus of elasticity. PV curves provided clear evidence that both temperature and water availability do not stimulate active osmotic adjustment in Vitis vinifera cv. Pinot Noir. Conversely, there is a clear impact of seasonal osmoregulation throughout the growing season2, decreasing the osmotic potential at full turgor by an average of 0.46 MPa in 90 days. Lack of osmotic adjustment in response to drought observed in this cultivar suggests Vitis genotypes have a broad spectrum of responses to drought and the strategy adopted to cope with it is highly dependent on the cultivar under analysis.
Keywords: grapevine, drought, osmotic adjustment, osmoregulation, turgor loss point
Published in RUNG: 21.11.2023; Views: 501; Downloads: 1
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Exploration of yeast biodiversity potential for development of alternative biofungicides in viticulture : dissertation
Rowland Adesida, 2022, doctoral dissertation

Abstract: 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.
Keywords: sustainable viticulture, Botrytis cinerea, gray mould, yeasts, biocontrol, canopy microclimate manipulation, grapevine metabolite, dissertations
Published in RUNG: 07.07.2022; Views: 1756; Downloads: 132
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Facilitating green care improvements in viticulture
Melita Sternad Lemut, Lorena Butinar, Adesida Rowland, Urban Česnik, Tjaša Jug, Paolo Sivilotti, Urška Vrhovšek, 2019, published scientific conference contribution

Abstract: The growing demand of consumers for environment-friendly and safe food products already forced many winemakers to restrict the application of synthetic fungicides to earlier season, trying to reduce the risk of residues being detected in wines. Main risk for infection by B. cinerea, however, occurs later in the season. To support an improvement in whole-season B. cinerea green care, the potential of yeasts as biocontrol agent (PBA) was studied. Selected yeasts were tested for their antifungal activities. Furthermore, a field experiment in Pinot noir and Pinot gris vineyards was designed to study different combinations of optimized canopy microclimate manipulation (CMM) techniques and PBA application. In experimental conditions, PBA's ability to maintain appropriate population density for disease prevention was observed. Grape and wine quality parameters were evaluated. Analytical approach of metabolomics was applied to upgrade the understanding of potentially induced changes in plant metabolism. Based on yeasts testing results, biocontrol yeast P. guilliermondii ZIM 624 was selected and after its field application, we were able to detect its suitable density on grapes until harvest. In case of early defoliation for both varieties smaller grape compactness was confirmed together with lower yield. Among grape basic quality parameters, optimized techniques showed positive effect on sugar content, but unexpectedly, in the treatments with biocontrol yeasts the trends toward higher acidity were noticed in Pinot gris. CMM and PBA introduction indicated some effects on grapevine biosynthetic behaviour but the differences in content of these metabolites compared to control were poorly detected in final wines with exception of mainly some flavonols, stilbenes and flavan-3-ols (and consequently total phenolic content).
Keywords: sustainable viticulture, Botrytis cinerea, yeasts, biocontrol, canopy microclimate manipulation, metabolomics, grapevine metabolites
Published in RUNG: 28.02.2020; Views: 3724; Downloads: 0
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Biological role of Grapevine fanleaf virus (GFLV) in winegrowing region of Northern Primorska
Anastazija Jež Krebelj, 2015, doctoral dissertation

Abstract: Grapevines (Vitis vinifera L.) represent one of the most important crops in the world in terms of both production and economic importance. Grapevines are exposed to many types of abiotic stresses (e.g., drought, flooding, low and high temperature, salinity) and biotic stresses (e.g., viruses, bacteria, phytoplasma, fungal disease) during their life-cycle. Therefore, grapevines elicit the appropriate defence mechanisms. In the first part of this study, we monitored the occurrence of Grapevine fanleaf virus (GFLV) infection, which causes progressive decline of infected grapevines and lowers their yield. Grapevines were also tested for the presence of other viruses important for grapevines: Arabis mosaic virus (ArMV), Grapevine leafroll associated virus (GLRaV)-1, -2, -3, -4, -9, Grapevine virus A (GVA), Grapevine fleck virus (GFkV) in this study; and by Cigoj (2015): Grapevine virus B (GVB), Tomato black ring virus (TBRV), Grapevine chrome mosaic virus (GCMV), Tomato ringspot virus (ToRSV), Raspberry ringspot virus (RpRSV), Strawberry latent ringspot virus (SLRSV), and Tobacco ringspot virus (TRSV). Using ELISA, the presence of the following grapevine viruses were detected: GFLV, (GFkV), (GVA), and Grapevine leafroll associated viruses- 1, -2, -3,. A wide range of GFLV symptoms caused by grapevine fanleaf disease in naturally infected vineyards were observed, including leaf, shoot and cluster malformations and leaf yellowing. GFLV is disseminated by its biological vector X. index, and through vegetative propagation of virus-infected material. The spread of GFLV in the vineyards was investigated here. We constructed a spatio-temporal study of the GFLV titres during the seasons and throughout the grapevine, for its distribution in different grapevine organs through the season. This study shows that young leaves have high virus titres through the whole vegetative period, while mature leaves, tendrils and flower/ berry clusters only have high titres at the beginning of the vegetative period. The seeds retain high virus titres after berry colouring. Phloem scrapings were shown to contain lower virus titres during the vegetative period, with an increase outside and at the beginning of the vegetative period. In flower/ berry clusters, mature leaves and tendrils, the GFLV titres decrease significantly over the vegetative period. Additionally, different GFLV titres were shown in five different cultivars, and different combinations of mixed infections with other grapevine viruses influenced the GFLV titre differently. Finally, correlation between the magnitude of symptom appearance and GFLV titres was analysed. Grapevines adapt to abiotic stresses and biotic stresses by the expression of a wide range of stress-responsive genes, which are thought to have key roles in stress tolerance and survival. SWP of the infected grapevines through the season was lower than SWP measured for healthy grapevines. For both seasons, there were significant differences in SWP measurements between healthy and GFLV-infected grapevines of ‘Schioppettino’ trained using the single Guyot training system. SWP and RHC of the GFLV-infected grapevines were reduced compared to the healthy controls. The water deficit triggered the production of ABA, which induced the expression of the stress-related gene RD22. Additionally, this study shows that the WRKY gene that is involved in the ABA signalling network is regulated by water deficit. Plant defence responses to water stress also included up-regulation of the F3H2 and LDOX genes, which are involved in anthocyanins synthesis. GFLV infection significant impacted upon the expression of genes involves in ABA biosynthesis, as NCED1 and NCED2, and upon two genes involved in the early stages of anthocyanins synthesis, as CHS2 and F3H1. We also showed that the combination of grapevine cultivar, training system, and environmental conditions impacts on gene expression
Keywords: Vitis vinifera L., grapevine, Grapevine fanleaf virus, GFLV, grapevine disease, virus titre, distribution, fluctuation, ELISA, qPCR, ABA, drought, water status, water deficit, SWP, RHC, anthocyanins, gene expression
Published in RUNG: 27.07.2015; Views: 8312; Downloads: 415
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