Impact of Chemical and Alternative Fungicides Applied to Grapevine cv Nebbiolo on Microbial Ecology and Chemical-Physical Grape Characteristics at Harvest

Yeast communities of a North American hybrid wine grape differ between organic and conventional vineyards

AIMS

To compare the species diversity and composition of indigenous yeast communities of hybrid grapes from conventionally and organically cultivated vineyards of an emerging cool-climate wine producing region.

METHODS AND RESULTS

Illumina MiSeq sequences from L'Acadie blanc grape musts were processed and filtered to characterize indigenous yeast communities in organic and conventional vineyards of the Annapolis Valley wine region in Nova Scotia, Canada. While cultivation practice was not associated with yeast diversity or species richness, there was a strong effect on yeast community composition, with conventional vineyards characterized by higher proportions of Sporidiobolales and Filobasidium magnum, and organic vineyards supporting Filobasidium species other than F. magnum and higher proportions of Symmetrospora. There was also variation in yeast community composition among individual vineyards, and from year to year.

CONCLUSIONS

This is the first comprehensive assessment of yeasts associated with hybrid grapes grown using different cultivation practices in a North American cool climate wine region. Communities were dominated by basidiomycete yeasts and species composition of these yeasts differed significantly between vineyards employing organic and conventional cultivation practices. The role of basidiomycete yeasts in winemaking is not well understood, but some species may influence wine characteristics.

A comparison of microbiota isolation methods reveals habitat preferences for fermentative yeasts and plant pathogenic fungi in the grape berry

The methodologies for profiling the grape berry microbiota have exponentially evolved in the past 25 years. Recently, concerns arose regarding the homogeneity in the protocols of grape harvesting, sequencing and bioinformatic analyses, but the bias introduced by the microbiota isolation method is still unexplored. This study followed a simple approach of comparing two most used methods of microbiota collection from grape berries (washing vs crushing), hypothesizing a significant impact in the outcome of the microbiota profiles analyzed by NGS metabarcoding. Experiments conducted in fruits of three cultivars of the Douro wine region showed that only 52 % of OTUs were common to both surface and juice microbiota, suggesting specific microbial niches. Thirteen fungal genera were abundantly detected in the fruit surface, including Alternaria, Aureobasidium, Cladosporium, Didymella and Bipolaris. Fermentative yeasts including Meyerozyma and Saccharomyces cerevisiae were exclusively detected in the juice, together with several Penicillium species. Distinct habitat preferences of species within the genera Alternaria, Sporobolomyces and Rhodotorula were also revealed. The study showed that the microbiota isolation method is crucial in the detection of certain plant pathogenic/saprophytic fungi and yeasts with biotechnological and oenological interest, adding novelty to the globally accepted assumption that S. cerevisiae in musts originates primarily from the cellar.

Effects of fungicide application on physiological and molecular responses of grapevine (Vitis vinifera L.): a comparison between copper and sulfur fungicides applied alone and in combination with novel fungicides

BACKGROUND

Chemical products against fungi and oomycetes pose serious environmental issues. In the last decade, the use of less impacting active ingredients was encouraged to reduce chemical inputs in viticulture. In this study, the effect of different antifungal compounds on grapevine agronomic, physiological, and molecular responses in the vineyard was evaluated in addition to protection against powdery and downy mildews.

RESULTS

In 2 years and in two Vitis vinifera cultivars (Nebbiolo and Arneis), a conventional crop protection approach, based on traditional fungicides (sulfur and copper), was compared to combined strategies. A well-known resistance inducer (potassium phosphonate), Bacillus pumilus strain QST 2808 and calcium oxide, both active ingredients whose biological interaction with grapevine is poorly characterized, were applied in the combined strategies in association with chemical fungicides. Despite a genotype effect occurred, all treatments optimally controlled powdery and downy mildews, with minimal variations in physiological and molecular responses. Gas exchange, chlorophyll content and photosystem II efficiency increased in treated plants at the end of season, along with a slight improvement in the agronomic performances, and an activation of molecular defense processes linked to stilbene and jasmonate pathways.

CONCLUSION

The disease control strategies based on potassium phosphonate, Bacillus pumilus strain QST 2808 or calcium oxide combined with traditional chemical compounds did not cause severe limitations in plant ecophysiology, grape quality, and productive yields. The combination of potassium phosphonate and calcium oxide with traditional fungicides can represent a valuable strategy for reducing copper and sulfur inputs in the vineyards, including those organically managed. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The Impact of a Commercial Biostimulant on the Grape Mycobiota of Vitis vinifera cv. Barbera

Reducing the use of fungicides, insecticides, and herbicides in order to limit environmental pollution and health risks for agricultural operators and consumers is one of the goals of European regulations. In fact, the European Commission developed a package of measures (the European Green Deal) to promote the sustainable use of natural resources and strengthen the resilience of European agri-food systems. As a consequence, new plant protection products, such as biostimulants, have been proposed as alternatives to agrochemicals. Their application in agroecosystems could potentially open new scenarios regarding the microbiota. In particular, the vineyard microbiota and the microbiota on the grape surface can be affected by biostimulants and lead to different wine features. The aim of this work was to assess the occurrence of a possible variation in the mycobiota due to the biostimulant application. Therefore, our attention has been focused on the yeast community of grape bunches from vines subjected to the phytostimulant BION®50WG treatment. This work was carried out in the CREA-VE experimental vineyard of Vitis vinifera cv. Barbera in Asti (Piedmont, Italy). The composition of fungal communities on grapes from three experimental conditions such as IPM (integrated pest management), IPM+BION®50WG, and IPM+water foliar nebulization was compared by a metabarcoding approach. Our results revealed the magnitude of alpha and beta diversity, and the microbial biodiversity index and specific fungal signatures were highlighted by comparing the abundance of yeast and filamentous fungi in IPM and BION®50WG treatments. No significant differences in the mycobiota of grapevines subjected to the three treatments were detected.

Fungicides Cuprozin Progress and SWITCH Modulate Primary and Specialized Metabolites of Strawberry Fruits

Numerous pesticides, including fungicides, are applied every year to crop plants. However, such application may affect the plant metabolism and thus crop quality. Strawberry is an economically important crop, but the fruits are highly susceptible, especially to fungal diseases. In the present study, the effects of two fungicides, Cuprozin progress and SWITCH, on the metabolism of two cultivars and the wild strawberry were tested, focusing on primary (amino acids, (in)organic acids, sugars, total phenolics) and specialized metabolites (aroma volatiles), which determine the fruit flavor. The fungicide treatment significantly affected 11 out of 57 metabolites, while 20 of those differed between strawberry types and 27 were affected by the interaction of both factors. Given these modifications in metabolites in response to the treatments, the taste and quality of the strawberries may pronouncedly change when plants are treated with fungicides.

A Review of Cultural Practices for Botrytis Bunch Rot Management in New Zealand Vineyards

Botrytis bunch rot of grapes (BBR) causes substantial crop and wine quality issues globally. Past and present foundations for BBR control are based upon synthetic fungicides and varying forms of canopy management. Many authors regard the continued dependence on fungicides as unsustainable and have urged greater deployment of cultural, biological and nutritional strategies. However, in contrast to organic wine production, the uptake of alternative strategies in conventional vineyards has been slow based on cost and perceived reliability issues. This review summarises research from many different wine growing regions in New Zealand with the aim of demonstrating how traditional and newly developed cultural control practices have cost-effectively reduced BBR. In addition to reviewing traditional cultural practices (e.g., leaf removal), mechanical tools are described that remove floral trash and mechanically shake the vines. Multi-omics has improved our knowledge of the underlying changes to grape berries after mechanical shaking. Exogenous applications of calcium may correct calcium deficiencies in the berry skin and reduce BBR but the outcome varies between cultivar and regions. Nitrogen aids in grapevine defence against BBR but remains a complex and difficult nutrient to manage. The sustainable growth of organics and The European Green Deal will stimulate researchers to evaluate new combinations of non-chemical BBR strategies in the next decade.

COS-OGA Applications in Organic Vineyard Manage Major Airborne Diseases and Maintain Postharvest Quality of Wine Grapes

In most wine-growing countries of the world the interest for organic viticulture and eco-friendly grape production processes increased significantly in the last decade. Organic viticulture is currently dependent on the availability of Cu and S compounds, but their massive use over time has led to negative effects on environment health. Consequently, the purpose of this study was to evaluate the effectiveness of alternative and sustainable treatments against powdery mildew, gray mold and sour rot under the field conditions on Nero d’Avola and Inzolia Sicilian cultivars. In detail, the efficacy of COS-OGA, composed by a complex of oligochitosans and oligopectates, and its effects in combination with arbuscular mycorrhizal fungi (AMF) were evaluated to reduce airborne disease infections of grape. COS-OGA combined with AMF induced a significant reduction in powdery mildew severity both on Nero d’Avola and Inzolia with a mean percentage decrease of about 15% and 33%, respectively. Moreover, COS-OGA alone and combined with AMF gave a good protection against gray mold and sour rot with results similar to the Cu–S complex (performance in disease reduction ranging from 65 to 100%) on tested cultivars. Similarly, the COS-OGA and AMF integration provided good performances in enhancing average yield and did not negatively impact quality and microbial communities of wine grape. Overall, COS-OGA alone and in combination could be proposed as a valid and safer option for the sustainable management of the main grapevine pathogens in organic agroecosystems.

Novel sustainable strategies to control Plasmopara viticola in grapevine unveil new insights on priming responses and arthropods ecology

BACKGROUND

Reduction of fungicide consumption in agriculture is globally recognized as a priority. Government authorities are fostering research to achieve a reduction of risks associated with conventional pesticides and promoting the development of sustainable alternatives. To address these issues, in the present study, alternative protocols for the control of downy mildew infection in grapevine were compared to the standard protocol. In the first protocol, only resistance inducers were used, comprising a single formulation with Acibenzolar S-methyl, laminarin and disodium-phosphonate. The second and third protocols followed the standard protocol but substituted phosphonates with phosphorus pentoxide and Ecklonia maxima extract.

RESULTS

The results showed that at veraison downy mildew incidence and severity in all tested protocols were significantly reduced compared to nontreated controls on both canopy and bunches. Expression analysis of key genes involved in plant stress response, indicated that the two protocols for phosphites substitution induced a remodulation of salicylic acid (SA) and jasmonic acid (JA), with positive impact on yields. Analysis of the first protocol revealed that the primed state induced a short delay in bunch ripening, with a shift of carbohydrate metabolism to boost the plant defences, involving an upregulation of defence related-gene, SAR response and a decreased ROS detoxification. Additionally, analysis on the arthropods populations, in parallel with the positive results achieved using alternatives to conventional fungicides, were enriched by those showing the potential of naturally occurring predators of spider mites.

CONCLUSION

This study provides practical solutions to reduce the environmental impact of treatments for the control downy mildew in viticulture. © 2022 Society of Chemical Industry.

A Laminarin-Based Formulation Protects Wheat Against Zymoseptoria tritici via Direct Antifungal Activity and Elicitation of Host Defense-Related Genes

The present study aimed to evaluate the potential of the laminarin-based formulation Vacciplant to protect and induce resistance in wheat against Zymoseptoria tritici, a major pathogen on this crop. Under greenhouse conditions, a single foliar spraying of the product 2 days before inoculation with Z. tritici reduced disease severity and pycnidium density by 42 and 45%, respectively. Vacciplant exhibited a direct antifungal activity on Z. tritici conidial germination both in vitro and in planta. Moreover, it reduced in planta substomatal colonization as well as pycnidium formation on treated leaves. Molecular investigations revealed that Vacciplant elicits but did not prime the expression of several wheat genes related to defense pathways, including phenylpropanoids (phenylalanine ammonia-lyase and chalcone synthase), octadecanoids (lipoxygenase and allene oxide synthase), and pathogenesis-related proteins (β-1,3-endoglucanase and chitinase). By contrast, it did not modulate the expression of oxalate oxidase gene involved in the reactive oxygen species metabolism. Ultrahigh-performance liquid chromatography-mass spectrometry analysis indicated limited changes in leaf metabolome after product application in both noninoculated and inoculated conditions, suggesting a low metabolic cost associated with induction of plant resistance. This study provides evidence that the laminarin-based formulation confers protection to wheat against Z. tritici through direct antifungal activity and elicitation of plant defense-associated genes.

The Role of Biostimulants as Alleviators of Biotic and Abiotic Stresses in Grapevine: A Review

The viticulture and wine industry contribute to the economy and reputation of many countries all over the world. With the predicted climate change, a negative impact on grapevine physiology, growth, production, and quality of berries is expected. On the other hand, the impact of these changes in phytopathogenic fungi development, survival rates, and host susceptibility is unpredictable. Grapevine fungal diseases control has been a great challenge to winegrowers worldwide. The use of chemicals in viticulture is high, which can result in the development of pathogen resistance, increasingly raising concerns regarding residues in wine and effects on human and environmental health. Promoting sustainable patterns of production is one of the overarching objectives and essential requirements for sustainable development. Alternative holistic approaches, such as those making use of biostimulants, are emerging in order to reduce the consequences of biotic and abiotic stresses in the grapevine, namely preventing grape fungal diseases, improving grapevine resistance to water stress, and increasing yield and berry quality.

Yeast and Filamentous Fungi Microbial Communities in Organic Red Grape Juice: Effect of Vintage, Maturity Stage, SO2, and Bioprotection

Changes are currently being made to winemaking processes to reduce chemical inputs [particularly sulfur dioxide (SO₂)] and adapt to consumer demand. In this study, yeast growth and fungal diversity were investigated in merlot during the prefermentary stages of a winemaking process without addition of SO₂. Different factors were considered, in a two-year study: vintage, maturity level and bioprotection by the adding yeast as an alternative to SO₂. The population of the target species was monitored by quantitative-PCR, and yeast and filamentous fungi diversity was determined by 18S rDNA metabarcoding. A gradual decrease of the α-diversity during the maceration process was highlighted. Maturity level played a significant role in yeast and fungal abundance, which was lower at advanced maturity, while vintage had a strong impact on Hanseniaspora spp. population level and abundance. The presence of SO₂ altered the abundance of yeast and filamentous fungi, but not their nature. The absence of sulfiting led to an unexpected reduction in diversity compared to the presence of SO₂, which might result from the occupation of the niche by certain dominant species, namely Hanseniaspora spp. Inoculation of the grape juice with non-Saccharomyces yeast resulted in a decrease in the abundance of filamentous fungi generally associated with a decline in grape must quality. Lower abundance and niche occupation by bioprotection agents were observed at the overripened stage, thus suggesting that doses applied should be reconsidered at advanced maturity. Our study confirmed the bioprotective role of Metschnikowia pulcherrima and Torulaspora delbrueckii in a context of vinification without sulfites.

The use of a microbiological preparation based on Bacillus subtilis in organic viticulture

In organic farming, microbiological preparations are an alternative to chemical pesticides and mineral fertilizers. The article summarizes the experience of a three-year use of the biofungicide Extrasol in combination with colloidal sulfur in the vineyards of the Crimea. The use of the biofungicides makes it possible to control the development of powdery mildew of grape at the level of chemical plant protection products, including during the years of epiphytoties: on the cv. Bastardo magarachskiy grapes – 7.1–14.7 %, on the Italy grape cultivar – up to 5.2%. The degree of influence of the biofungicide Extrasol on the phenolic and oxidase complex of grapes depends on the background level of development of Uncinula necator and the biological effectiveness of the treatment. In comparison with chemical means of protection, the smallest effect of processing cv. Bastardo magarachskiy grapes with a biological product in relation to the accumulation of phenolic compounds was observed at a level of powdery mildew development of 30-50 %; the maximum increase in the technological reserve of phenolic compounds was 59 %, anthocyanins – 12 %; the activity of polyphenol oxidase increased 1.1–3.3 times. The use of the biofungicide Extrasol on Italian grape cultivar led to an increase in the weight of the bunch by an average of 11 %, yield – by 25.6 %, titratable acids – by 9.6 % relative to chemicals; improved the aroma, taste and texture of the berry.

The development of phytosanitary monitoring methods – creating of a schematic scale for as-sessing the development of Alternariosis on grape leaves

To ensure consistent good quality grape yields it is necessary to minimize losses associated with affection of grape plants by various dis-eases. One of the main conditions to ensure the effective control of phyto-pathogens is a timely monitoring, revealing and assessing of harmful or-ganisms development intensity. In modern research, in order to improve the accuracy and reliability of quantitative characteristics of disease devel-opment intensity, as well as comparability of the results obtained, it is pro-posed to use a “set of standard diagrams” or a “schematic scale” - a set of illustrations depicting an increasing percentage of damage to the surface of one or another plant organ. To date, similar "sets of standard diagrams" were proposed for such grape diseases as mildew, anthracnose and grape leave rust. The article presents the results of creating a new "schematic scale" for assessing the development intensity of grape Alternariosis as a disease with the recorded increasing importance at a recent time of climate change. The scale was developed using colored and black–and-white pho-tographs of grape leaves affected by Alternariosis to varying degrees to de-termine the real intensity of the disease in digital form. Scale levels were established in accordance with minimum and maximum values of damage degree. Validation was carried out by two groups of assessors with differ-ent experience in accounting. The determination coefficient (R2) of regres-sion line and the absolute error variance demonstrated an increase in accu-racy, repeatability and reproducibility of estimates using the developed “schematic scale”. Using of the developed scale made it possible to in-crease the accuracy of quantitative assessment of intensity of Alternariosis damage to grape leaves.

Modifications of Grapevine Berry Composition Induced by Main Viral and Fungal Pathogens in a Climate Change Scenario

The grapevine is subject to high number of fungal and viral diseases, which are responsible for important economic losses in the global wine sector every year. These pathogens deteriorate grapevine berry quality either directly via the modulation of fruit metabolic pathways and the production of endogenous compounds associated with bad taste and/or flavor, or indirectly via their impact on vine physiology. The most common and devastating fungal diseases in viticulture are gray mold, downy mildew (DM), and powdery mildew (PM), caused, respectively by Botrytis cinerea, Plasmopara viticola, and Erysiphe necator. Whereas B. cinerea mainly infects and deteriorates the ripening fruit directly, deteriorations by DM and PM are mostly indirect via a reduction of photosynthetic leaf area. Nevertheless, mildews can also infect berries at certain developmental stages and directly alter fruit quality via the biosynthesis of unpleasant flavor compounds that impair ultimate wine quality. The grapevine is furthermore host of a wide range of viruses that reduce vine longevity, productivity and berry quality in different ways. The most widespread virus-related diseases, that are known nowadays, are Grapevine Leafroll Disease (GLRD), Grapevine Fanleaf Disease (GFLD), and the more recently characterized grapevine red blotch disease (GRBD). Future climatic conditions are creating a more favorable environment for the proliferation of most virus-insect vectors, so the spread of virus-related diseases is expected to increase in most wine-growing regions. However, the impact of climate change on the evolution of fungal disease pressure will be variable and depending on region and pathogen, with mildews remaining certainly the major phytosanitary threat in most regions because their development rate is to a large extent temperature-driven. This paper aims to provide a review of published literature on most important grapevine fungal and viral pathogens and their impact on grape berry physiology and quality. Our overview of the published literature highlights gaps in our understanding of plant-pathogen interactions, which are valuable for conceiving future research programs dealing with the different pathogens and their impacts on grapevine berry quality and metabolism.

Grapevine Powdery Mildew: Fungicides for Its Management and Advances in Molecular Detection of Markers Associated with Resistance

Grapevine powdery mildew is a principal fungal disease of grapevine worldwide. Even though it usually does not cause plant death directly, heavy infections can lead to extensive yield losses, and even low levels of the disease can negatively affect the quality of the wine. Therefore, intensive spraying programs are commonly applied to control the disease, which often leads to the emergence and spread of powdery mildew strains resistant to different fungicides. In this review, we describe major fungicide classes used for grapevine powdery mildew management and the most common single nucleotide mutations in target genes known to confer resistance to different classes of fungicides. We searched the current literature to review the development of novel molecular methods for quick detection and monitoring of resistance to commonly used single-site fungicides against Erysiphe necator. We analyze and compare the developed methods. From our investigation it became evident that this research topic has been strongly neglected and we hope that effective molecular methods will be developed also for resistance monitoring in biotroph pathogens.

Impact of Application of Abscisic Acid, Benzothiadiazole and Chitosan on Berry Quality Characteristics and Plant Associated Microbial Communities of Vitis vinifera L var. Mouhtaro Plants

The phenolic profile of the grape berries is a key quality factor for the red grapevine varieties and several techniques have been applied to improve it. An innovative technique is the application of resistance elicitors and phytohormones. In the present study, leaves and berries of a Greek red indigenous variety (Mouhtaro) sprayed with two elicitors, benzothiadiazole and chitosan and a plant hormone abscisic acid, during veraison. Physicochemical and phenolic characteristics of the berries and microbial communities of rhizosphere, phyllosphere and carposphere were analyzed at harvest. Differences in the microbial communities on different plant compartments were observed after the application of the plant activators. Chitosan treatment increased the abundance of the beneficial lactic acid bacteria, while the abscisic acid treatment decreased the presence of spoilage fungi on the carposphere. Treatments differentiate total phenolics, anthocyanins and in the chemical characteristics of grape must with chitosan treated grapes had increased anthocyanins and skin-derived phenolics that correlated positively with the microbial taxa that was discriminant by LefSe analysis. This research provides an overview of the effect of plant activators on the microbial ecology and grape quality of the Greek variety Mouhtaro and presents the potential of new and innovative approaches in the field of sustainable viticulture.

Epiphytic Microbial Diversity of Vitis vinifera Fructosphere: Present Status and Potential Applications

Vineyard provides an apt environment for growth of different types of microorganisms. The microbial domain is greatly affected by changing climatic conditions, geographical region, water activity, agricultural practices, presence of different pathogens and various pests. Grapevine microbial diversity is also affected by different stages of plant growth. Epiphytic berry microflora is specifically influenced by developmental phases and plays an important role in winemaking which is studied extensively. However, very little information is available about microbial community associated with table grape berries, which are consumed as fresh fruits. Moreover, our knowledge about the important role played by these microbes is precise and their scope might be larger than what is existing in the public domain. A systematic study on effect of developmental stages of table grape berries on microbial diversity would provide new insights for exploring the applicability of these microbes in plant growth, crop protection and bioremediation. In this review, we propose an effort to relate the developmental stages of grape berry with microbial consortium present and at the same time discuss the possible applications of these microbes in plant protection and biodegradation.

Fungicides of biological and chemical origin to control grape alternariosis

At the modern stage of development, the support of sustainable viticulture is possible having an optimal set of methods and means of effective disease control. Currently, with distribution and development of grape leaf alternariosis, the issue of forming a zonal assortment of fungicides by replenishing with preparations that effectively regulate the causative agent of this grape disease in addition to basic diseases - mildew and oidium, is updated. The paper presents the results of laboratory and field studies aimed at finding effective means of biological and chemical origin to control the development of grape alternariosis. The maximum antifungal activity against Alternaria sp. for the period of 2016-2020 in vitro was showen by 2 biological preparations based on OPS and OST-713 strains of the bacterium Bacillus amyloliquefaciens, as well as by active agents from triazole and strobilurin chemical classes. Field studies of 2018-2020 found out that the minimum values of aternariosis development on leaves were obtained with three-fold application of fungicides Skor, EC (0.4 l/ha), Acrobat Top, WDG (1.5 kg/ha), Dynali, DC (0.6 l/ha), Quadris, SC (0.6 l/ha), Topaz, EC (0.4 l/ha), as well as when using the biological preparation Serenade ASO, SC (5.0 l/ha). The obtained results allow to conclude that fungicides of both biological and chemical origin, intended for protection of grapes from basic diseases, can be used to effectively control grape alternariosis.

Biological and molecular interplay between two viruses and powdery and downy mildews in two grapevine cultivars

Grapevine may be affected simultaneously by several pathogens whose complex interplay is largely unknown. We studied the effects of infection by two grapevine viruses on powdery mildew and downy mildew development and the molecular modifications induced in grapevines by their multiple interactions. Grapevine fanleaf virus (GFLV) and grapevine rupestris stem pitting-associated virus (GRSPaV) were transmitted by in vitro-grafting to Vitis vinifera cv Nebbiolo and Chardonnay virus-free plantlets regenerated by somatic embryogenesis. Grapevines were then artificially inoculated in the greenhouse with either Plasmopara viticola or Erysiphe necator spores. GFLV-infected plants showed a reduction in severity of the diseases caused by powdery and downy mildews in comparison to virus-free plants. GFLV induced the overexpression of stilbene synthase genes, pathogenesis-related proteins, and influenced the genes involved in carbohydrate metabolism in grapevine. These transcriptional changes suggest improved innate plant immunity, which makes the GFLV-infected grapevines less susceptible to other biotic attacks. This, however, cannot be extrapolated to GRSPaV as it was unable to promote protection against the fungal/oomycete pathogens. In these multiple interactions, the grapevine genotype seemed to have a crucial role: in 'Nebbiolo', the virus-induced molecular changes were different from those observed in 'Chardonnay', suggesting that different metabolic pathways may be involved in protection against fungal/oomycete pathogens. These results indicate that complex interactions do exist between grapevine and its different pathogens and represent the first study on a topic that still is largely unexplored.

Chloroanisoles occurrence in wine from grapes subjected to electrolyzed water treatments in the vineyard

Recently the use of electrolyzed water (EW) attracted much attention as a high-performance, new technology for its potential use in the food industry. The aim of this work was to investigate the impact of grape EW treatments, applied at different time intervals prior to harvest, on the indigenous yeast populations of grape surface (Chenin blanc and Cabernet franc) and the occurrence of 2,4,6-trichloroanisole (TCA) in Cabernet franc wine. In addition, the evolution of inoculated and spontaneous fermentations on treated and non-treated grapes was also considered. The yeast population present on grape berries surface was influenced in a grape variety and EW treatment time-dependent way, since only Chenin blanc grapes treated with EW 7 days prior to harvest had significantly lower yeast population levels, compared to the respective control. Concerning the yeast diversity in the grape samples, a dominance of Aureobasidium pullulans was observed in treated grapes, independently of the grape variety. At the end of alcoholic fermentation, 2,4,6-trichloroanisole was detected in wine when the EW solution was applied at one or two weeks before harvest time. After wine storage, 2,4,6-trichloroanisole and chlorophenols contents generally exhibited a loss relative to initial values. The results showed that EW treatments tended to slightly increase the TCA concentration in final wine and did not affect the fermentation performances and chromatic properties of resulting wine. On the other hand, absorption or desorption phenomena by wine lees could be involved in the change of 2,4,6-trichloroanisole concentration in wine during storage time.

The Molecular Priming of Defense Responses is Differently Regulated in Grapevine Genotypes Following Elicitor Application against Powdery Mildew

Molecular changes associated with response to powdery mildew (PM) caused by Erysiphe necator have been largely explored in Vitis vinifera cultivars, but little is known on transcriptional and metabolic modifications following application of resistance elicitors against this disease. In this study, the whole transcriptome sequencing, and hormone and metabolite analyses were combined to dissect long-term defense mechanisms induced by molecular reprogramming events in PM-infected ‘Moscato’ and ‘Nebbiolo’ leaves treated with three resistance inducers: acibenzolar-S-methyl, potassium phosphonate, and laminarin. Although all compounds were effective in counteracting the disease, acibenzolar-S-methyl caused the most intense transcriptional modifications in both cultivars. These involved a strong down-regulation of photosynthesis and energy metabolism and changes in carbohydrate accumulation and partitioning that most likely shifted the plant growth-defense trade-off towards the establishment of disease resistance processes. It was also shown that genotype-associated metabolic signals significantly affected the cultivar defense machinery. Indeed, ‘Nebbiolo’ and ‘Moscato’ built up different defense strategies, often enhanced by the application of a specific elicitor, which resulted in either reinforcement of early defense mechanisms (e.g., epicuticular wax deposition and overexpression of pathogenesis-related genes in ‘Nebbiolo’), or accumulation of endogenous hormones and antimicrobial compounds (e.g., high content of abscisic acid, jasmonic acid, and viniferin in ‘Moscato’).

Long-Term Impact of Chemical and Alternative Fungicides Applied to Grapevine cv Nebbiolo on Berry Transcriptome

Viticulture is one of the horticultural systems in which antifungal treatments can be extremely frequent, with substantial economic and environmental costs. New products, such as biofungicides, resistance inducers and biostimulants, may represent alternative crop protection strategies respectful of the environmental sustainability and food safety. Here, the main purpose was to evaluate the systemic molecular modifications induced by biocontrol products as laminarin, resistance inducers (i.e., fosetyl-Al and potassium phosphonate), electrolyzed water and a standard chemical fungicide (i.e., metiram), on the transcriptomic profile of ‘Nebbiolo’ grape berries at harvest. In addition to a validation of the sequencing data through real-time polymerase chain reaction (PCR), for the first-time the expression of some candidate genes in different cell-types of berry skin (i.e., epidermal and hypodermal layers) was evaluated using the laser microdissection approach. Results showed that several considered antifungal treatments do not strongly affect the berry transcriptome profile at the end of season. Although some treatments do not activate long lasting molecular defense priming features in berry, some compounds appear to be more active in long-term responses. In addition, genes differentially expressed in the two-cell type populations forming the berry skin were found, suggesting a different function for the two-cell type populations.