Innovative strategies based on the use of biostimulants to manage plant diseases and minimize the application of synthetic fungicides in grapevine and stone fruits

Plant diseases can severely affect the grapevine and stone fruit production, contributing to food losses and food waste. The ordinary way to control plant diseases consists in the use of synthetic fungicides. However, restrictions due to legislation and the request from consumers of food free from pesticide residues triggered the investigation on natural alternatives. Among these, there is a biopolymer extracted from crab shell called chitosan that is able to produce a film on treated commodities. This biopolymer has antimicrobial, eliciting and film-forming activities, contributing for about 40%, 35% and 25%, respectively, to its control of plant diseases. When applied to grapevine canopy, chitosan reduced downy mildew, caused by Plasmopara viticola, at the same magnitude of copper widely used in organic agriculture, but it accumulates in the soil being phytotoxic and harming soil microbiota. Chitosan application on stone fruit decreases the development of brown rot on sweet cherries cold stored and exposed to shelf life. Since consumers are worried about the presence of fungicide residues in fruit, retailers impose to the growers a reduction on the pesticide residues far below the legal threshold. Moreover, copper is a candidate to the substitution, then, in few years, its application in agriculture can be banned in the EU. Therefore, the use of a biostimulants as chitosan, that is a natural compound used in slimming diets then safe for humans and the environment, is a strategy welcomed by organic growers, and applied in several wineries to manage grapevine downy mildew

Special Issue: “Biological Control of Pre- and Postharvest Fungal Diseases”

The 2030 Agenda for Sustainable Development planned 17 Sustainable Development Goals (SDGs) to ensure a better present and future for our planet and the people that are living on it. The European Union joined Agenda 2030 and included some of them in the Farm to Fork strategy of European Green Deal, which plans a list of measures within 2030, including reaching 25% of organic agriculture, halving food waste (often ascribed to the postharvest decay of fruit and vegetables) and halving the use of synthetic pesticides. Therefore, the need to find environmentally friendly and safe solutions and strategies for the management of pre- and postharvest diseases can meet some of these requirements. The Special Issue “Biological Control of Pre- and Postharvest Fungal Diseases” included nine research articles and two reviews. All contributions provided potential alternatives to synthetic pesticides by reporting innovative results about the use of alternative strategies to synthetic pesticides, involving the use of biocontrol agents (BCAs), essential oils (EOs), basic substances, and plant extracts to manage some of the most important pre- and postharvest diseases of fresh fruit and vegetables.info:eu-repo/semantics/publishedVersio

Antifungal activity of volatile organic compounds from essential oils against the postharvest pathogens Botrytis cinerea, Monilinia fructicola, Monilinia fructigena, and Monilinia laxa

[EN] Gray mold and brown rot, caused respectively by Botrytis cinerea and Monilinia spp., are fungal diseases responsible for significant losses during the storage of fruit and vegetables. Nowadays, the control of postharvest diseases is shifting towards more sustainable strategies, including the use of plant secondary metabolites. In this study, the antifungal activity of Origanum vulgare, Thymus vulgaris, Thymus serpyllum, Melaleuca alternifolia, Lavandula officinalis, Lavandula hybrida, Citrus bergamia, Rosmarinus officinalis, Cinnamomum zeylanicum essential oils (EOs) in vapor phase was tested in vitro against B. cinerea, Monilinia fructicola, Monilinia fructigena, and Monilinia laxa. For the experiments, a protocol using a volatile organic compounds (VOC) chamber was designed. Results indicate a dose-dependent inhibitory activity of all the tested EOs, with O. vulgare, T. vulgaris, and T. serpyllum being the most active ones, with minimum inhibitory concentrations (MIC) of 22.73, 45.45, and 22.73 μl/L, respectively, against B. cinerea and a range between 5.64 and 22.73 μl/L against the three Monilinia spp. Overall, B. cinerea presented lower sensitivity to vaporphase EOs than any of the Monilinia strains, except for the C. zeylanicum EO, which consistently showed higher inhibition against B. cinerea. Among the three Monilinia spp., M. fructicola was the least sensitive, while M. fructigena was the most sensitive. The use of VOC chambers proved to be a reliable protocol for the assessment of antimicrobial activities of EOs. These results suggest that the VOC emitted by the tested EOs are effective towards important decay-causing fungi, and that they could be used for the control of gray mold and brown rot in in vivo trials.SIThis work was conducted within PRIMA StopMedWaste “Innovative Sustainable technologies TO extend the shelf-life of Perishable MEDiterranean fresh fruit, vegetables and aromatic plants and to reduce WASTE”, which was funded by the Partnership for Research and Innovation in the Mediterranean Area (PRIMA), Project ID: 1556, a program supported by the European Union, and Euphresco BasicS “Basic substances as an environmentally friendly alternative to synthetic pesticides for plant protection” projects, and by Italy-China bilateral project “Biosynthesis regulation of metabolic markers and correlation with quality safety during fruit decay (BioQuaSa)”, funded by Italian Ministry of Foreign Affairs and International Cooperation. We acknowledge the Margarita Salas postdoctoral grant awarded to SÁ-G (Ministerio deUniversidades; Plan de Recuperación, Transformación y Resiliencia; Universidad de León; Spain) financed by the EU-NextGenerationEU

First report of Leucostoma cinctum on sweet cherry and European plum in Italy

Leucostoma cinctum and L. persoonii are the two species involved in Leucostoma canker, a disease that causes dieback of twigs and branches, bark cankers, gummosis, and tree decline of stone fruit. The aim of this study was to identify the causal agent of Leucostoma canker in Italian stone fruit orchards. More than 200 isolates of Leucostoma spp. were obtained from branches and twigs of sweet and sour cherry, apricot, and European plum trees that showed typical symptoms of Leucostoma canker. These trees were in commercial orchards of two Italian regions, Marche and Apulia, in central-eastern and south-eastern Italy, respectively. Soon after isolation, all of the colonies that grew on potato dextrose agar were white in colour, and after about 10 d they became olive-green. Growth was not observed at 33°C, and the pycnidia were larger than 1 mm diam. This information led to the identification of L. cinctum as the causal agent of these Leucostoma cankers. To our knowledge, this is the first report of L. cinctum on sweet cherry and European plum in Italy

A review on the management of postharvest anthracnose in dragon fruits caused by Colletotrichum spp

none5Colletotrichum spp is one of the major cosmopolitan phytopathogens that cause postharvest anthracnose in dragon fruits. The pathogen attacks fruits on the field, during long-distance transport, and cold storage, leading to shorter shelf life. Traditionally, the plants are sprayed with synthetic fungicides, which is a strategic approach to control diseases in general and anthracnose in particular for dragon fruit production. Due to the demand for safe storage methods for consumers and the concerns about the use of synthetic fungicides, their use is restricted to control dragon fruits anthracnose after harvest. Despite "Umikai" (natural Calcium) is the commonly used preservative by some exporters of dragon fruits in Vietnam, recent reports indicated that Sodium nitroprusside (a Nitric oxide donor) markedly controlled anthracnose in dragon fruit at recommended levels. However, due to detrimental effect of these nitric oxide donors and other synthetic chemicals on human health, concerns are raised by the governments and other stakeholders to abolish, if not regulate the use of these synthetic chemicals in pre- and postharvest management of anthracnose. Consequently, several alternative methods have been developed to control postharvest decay, but with little success. This review summarizes the findings published within the last decade on current management practices on postharvest anthracnose in dragon fruit. We conclude that hot air/vapor heat treatment, water treatment, modified and controlled atmosphere packaging are commercially practiced and effective in reducing postharvest decay in dragon fruits while, X-ray irradiation is still under experimentation, Additionally, natural products (propolis and chitosan) shows promising effect without leaving residual harmful effect and could be adopted on a commercial scale to reduce postharvest losses after further commercial trials.Paa K. Bordoh; Asgar Ali; Matthew Dickinson; Yasmeen Siddiqui; Gianfranco RomanazziBordoh, Paa K.; Ali, Asgar; Dickinson, Matthew; Siddiqui, Yasmeen; Romanazzi, Gianfranc

Multilocus Genotyping of 'Candidatus Phytoplasma Solani' Associated with Grapevine Bois Noir in Iran

none5Simple Summary Understanding the epidemiological cycle of Bois noir (BN) associated with 'Candidatus Phytoplasma solani' is vital to managing the disease effectively. The genotyping of 'Ca. P. solani' strains, according to tuf, vmp1, and stamp genes, contributes to a better knowledge of the geographical distribution of BN. In this study, we provide information on the molecular variants of 'Ca. P. solani' in Iranian vineyards. We observed six known vmp1 variants and discovered two new ones, V24 and V27. This information is useful for future investigations to more accurately understand the epidemiological cycle(s) of BN in Iranian vineyards, contributing to the management of the disease. Grapevine Bois noir (BN) is associated with 'Candidatus Phytoplasma solani'. It has been recorded in vineyards throughout Europe as well as in different countries in Asia, where it now constitutes a threat to Iranian viticulture. BN is strictly dependent on 'Ca. P. solani' strains, wild host plants, and insect vectors. The molecular typing of 'Ca. P. solani', based on the nonribosomal gene tuf and the two hypervariable markers vmp1 and stamp, is valuable for the reconstruction and clarification of the pathways of BN spread. In this study, an RFLP analysis was performed on the vmp1 gene, and a single-nucleotide polymorphism analysis confirmed new vmp types in 'Ca. P. solani'. A stamp gene phylogenetic analysis allowed us to distinguish between the new genotype infections in the grapevines and the 'weeds' Convolvulus arvensis and Erigeron bonariensis in Iranian vineyards, highlighting the close genetic relatedness of the strains of 'Ca. P. solani' found in Iran and Azerbaijan. The most common genotype in the grapevines was tuf b/V24/stamp III, which was associated with C. arvensis. This information contributes toward the identification of further routes of introduction of 'Ca. P. solani' in Iran to sustain the control measures for the management of BN.Jamshidi, Elham; Murolo, Sergio; Ravari, Sareh Baghaee; Salehi, Mohammad; Romanazzi, GianfrancoJamshidi, Elham; Murolo, Sergio; Ravari, Sareh Baghaee; Salehi, Mohammad; Romanazzi, Gianfranc

Basic Substances, a Sustainable Tool to Complement and Eventually Replace Synthetic Pesticides in the Management of Pre and Postharvest Diseases: Reviewed Instructions for Users

none5Synthetic pesticides are widely used to protect crops from pathogens and pests, especially for fruits and vegetables, and this may lead to the presence of residues on fresh produce. Improving the sustainability of agriculture and, at the same time, reducing the adverse effects of synthetic pesticides on human health requires effective alternatives that improve the productivity while maintaining the food quality and safety. Moreover, retailers increasingly request fresh produce with the amounts of pesticides largely below the official maximum residue levels. Basic substances are relatively novel compounds that can be used in plant protection without neurotoxic or immune-toxic effects and are still poorly known by phytosanitary consultants (plant doctors), researchers, growers, consumers, and decision makers. The focus of this review is to provide updated information about 24 basic substances currently approved in the EU and to summarize in a single document their properties and instructions for users. Most of these substances have a fungicidal activity (calcium hydroxide, chitosan, chitosan hydrochloride, Equisetum arvense L., hydrogen peroxide, lecithins, cow milk, mustard seed powder, Salix spp., sunflower oil, sodium chloride, sodium hydrogen carbonate, Urtica spp., vinegar, and whey). Considering the increasing requests from consumers of fruits and vegetables for high quality with no or a reduced amount of pesticide residues, basic substances can complement and, at times, replace the application of synthetic pesticides with benefits for users and for consumers. Large-scale trials are important to design the best dosage and strategies for the application of basic substances against pathogens and pests in different growing environments and contexts.Romanazzi, Gianfranco; Orçonneau, Yann; Moumni, Marwa; Davillerd, Yann; Marchand, Patrice AndréRomanazzi, Gianfranco; Orçonneau, Yann; Moumni, Marwa; Davillerd, Yann; Marchand, Patrice Andr

Chitosan, a Biopolymer With Triple Action on Postharvest Decay of Fruit and Vegetables: Eliciting, Antimicrobial and Film-Forming Properties

Chitosan is a natural biopolymer from crab shells that is known for its biocompatibility, biodegradability, and bioactivity. In human medicine, chitosan is used as a stabilizer for active ingredients in tablets, and is popular in slimming diets. Due to its low toxicity, it was the first basic substance approved by the European Union for plant protection (Reg. EU 2014/563), for both organic agriculture and integrated pest management. When applied to plants, chitosan shows triple activity: (i) elicitation of host defenses; (ii) antimicrobial activity; and (iii) film formation on the treated surface. The eliciting activity of chitosan has been studied since the 1990’s, which started with monitoring of enzyme activities linked to defense mechanisms (e.g., chitinase, β-1,3 glucanase, phenylalanine ammonia-lyase) in different fruit (e.g., strawberry, other berries, citrus fruit, table grapes). This continued with investigations with qRT-PCR (Quantitative Real-Time Polymerase Chain Reaction), and more recently, with RNA-Seq. The antimicrobial activity of chitosan against a wide range of plant pathogens has been confirmed through many in-vitro and in-vivo studies. Once applied to a plant surface (e.g., dipping, spraying), chitosan forms an edible coating, the properties of which (e.g., thickness, viscosity, gas and water permeability) depend on the acid in which it is dissolved. Based on data in literature, we propose that overall, the eliciting represents 30 to 40% of the chitosan activity, its antimicrobial activity 35 to 45%, and its film-forming activity 20 to 30%, in terms of its effectiveness in the control of postharvest decay of fresh fruit. As well as being used alone, chitosan can be applied together with many other alternatives to synthetic fungicides, to boost its eliciting, antimicrobial and film-forming properties, with additive, and at times synergistic, interactions. Several commercial chitosan formulations are available as biopesticides, with their effectiveness due to the integrated combination of these three mechanisms of action of chitosan

Ethylene and Chitosan Affected the Seed Yield Components of Onion Depending More on the Dose than Timing of Application

(1) Background: the production of onion seeds is limited by the competition between seeds and the vegetative organs and by scape lodging. However, information on the effects of plant growth regulation on onion seed production is scarce. Aim of the present study was to evaluate the seed yield components and germination ability of onion seeds as affected by the timing and dose of an ethylene application, a plant growth regulator able to modulate shoot–flower competition; and chitosan, an elicitor of plant defense mechanisms able to increase its tolerance to various stresses. (2) Methods: Onion was treated with ethylene at the recommended dose (100% RD) of a commercial product, at 150% RD in two contrasting phenological phases or untreated (control), or ‘with’ or ‘without’ chitosan, and the seed yield components and germination trend were measured. (3) Results: 100% RD at an early phase of growth did not influence the seed yield and increased the thousand seed weight (TSW) by 3.2%. The application of 150% RD decreased the seed yield by 33.5%, and this occurred irrespective of the timing of application. Such decreases were due to a reduction in the number of seeds per flower. The application of chitosan did not affect the crop at 100% RD and increased the seed yield and slightly increased, but not significantly, the TSW under 150% RD. Germination of the fresh seed was 92%, and 17 months of aging reduced it by 14%, with no effects of the treatments on the germination pattern. (4) Conclusions: the ethylene application mostly affected TSW but not the yield, whereas high doses of ethylene reduced yields irrespective of the timing of application. Such a result may have been due to a delay in the flowering onset that occurred in a relatively dry month. Chitosan sustained its yield when the yield potential was reduced by 150% RD, and such a result was likely due to physical protection from the transpiration since the synthetic fungicides applied did not likely allow the pathogens to infections. These results have implications for establishing the timing and dose of application of plant growth regulators and elicitors in seed onions to sustain the seed quality