ARTICLE | doi:10.20944/preprints202211.0473.v1
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: Biocontrol; fire blight; Erwinia amylovora
Online: 25 November 2022 (07:21:57 CET)
Erwinia amylovora, the causative agent of fire blight, leads to important economic losses of apple and pear crops worldwide. This study aimed to investigate the potential of the resident bacterial flora of the apple blossom in combatting plant disease-causing organisms, with a focus on strains that show potential for controlling fire blight. We collected samples of apple blossoms from dif-ferent sites around Canton Zurich, some grown with and some without the use of conventional pesticides, and isolated 538 strains which we tested for activity against Pectobacterium carotovorum and E. amylovora. We also tested the isolates against oomycete and fungal pathogens, to evaluate them for additional potential as biocontrol agents. Nine isolates showed activity against P. ca-rotovorum and eight of these against E. amylovora. Furthermore, 117 showed antifungal and 161 anti-oomycete activity. Five strains showed activity against all classes of pathogen and were tested in a detached apple model for anti-E. amylovora activity. Of these five strains, two were able to antagonise E. amylovora; Bacillus velezensis #124 and Pantoea agglomerans #378. We also show that B. velezensis #124 exhibits strong activity against three different fungi and two oomycetes in vitro, suggesting that this strain might have broad potential for biocontrol. Our results showcase the potential of the natural apple blossom flora. We isolated two candidate biocontrol strains from apple blossoms, suggesting that they can persist at the most common entry point for the causative agent of fire blight. Furthermore, they are probably already part of the human diet, suggesting they are safe for consumption and thus are promising candidates for biocontrol applications.
REVIEW | doi:10.20944/preprints202306.1851.v1
Subject: Biology And Life Sciences, Plant Sciences Keywords: medicinal plants; endophyte; biocontrol; medicinal components
Online: 27 June 2023 (05:37:48 CEST)
With the increasing demand for medicinal plants and the increasing shortage of resources, improving the quality and yield of medicinal plants and making more effective use of medicinal plants has become an urgent problem to be solved. In the process of growth and development of medicinal plants, due to the threat of various adversity, there are problems such as nutrient loss and yield decline. Using traditional chemical pesticides to control the stress resistance of plants will cause serious pollution to the environment and even endanger human health. Therefore, it is necessary to find suitable pesticide substitutes from natural ingredients. As an important part of the microecology of medicinal plants, endophytes can promote the growth of medicinal plants, improve the stress resistance of hosts, and promote the accumulation of active components of hosts. Because it has a more positive and direct impact on the host, and can metabolize rich medicinal ingredients, so researchers pay attention to it. This paper reviews the research in recent five years, aiming to provide ideas for improving the quality of medicinal plants, developing more microbial resources, exploring more medicinal natural products, and providing help for the development of the research on medicinal plants and endophytes.
REVIEW | doi:10.20944/preprints202204.0309.v1
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: bacteriophages; biocontrol; food production; bacterial resistance
Online: 29 April 2022 (15:49:21 CEST)
Bacteriophages have been recognized as potential biocontrol agents in the food industry. Bacteriophages have been proposed for a variety of applications within this industry including bio preservation, pathogen detection, and as an alternative treatment method to antibiotics in animal health. The potential applications of bacteriophages are widespread throughout the entire food production process and serve to enhance food quality, prevent foodborne illnesses, and enhance the efficiency of production. The ability of bacteriophages to lyse bacterial targets with high specificity and pose no threat to mammalian cells or natural microbiota is unique and relevant in terms of suitability for food safety. This review will outline potential and current applications of bacteriophages and their respective impacts on the field.
ARTICLE | doi:10.20944/preprints201909.0113.v1
Subject: Biology And Life Sciences, Agricultural Science And Agronomy Keywords: native yeast; biocontrol; fungal pathogens; VOCs
Online: 11 September 2019 (02:55:31 CEST)
Changes in consumer expectations have led to increasing demand for novel plant protection strategies, in order to reduce the application of chemical products, reduce the occurrence of new pests and the impact that all these actions generate in the environment. In recent years there have been numerous investigations related to biological control and the use of microorganisms as new control strategies. As part of integrated disease management, antagonistic microorganisms have been investigated lately and presented great interest. Such microorganisms can be applied in conventional and in organic farming as biological control agents (BCA). Many of these microorganisms are present in the microbial ecology generating interactive associations between surrounding microorganisms. For these reasons, it has become necessary to search new natural antimicrobial agents as alternatives to synthetic and chemical products. It has been discovered that there are microorganisms, particularly yeasts, that have antagonistic activity and different mechanisms of action, indicating that they could be interesting candidates for the development of BCA. Here, we evaluate the antagonist effect of four endophytic yeast, Cryptococcus antarcticus, Aureobasidium pullulans, Cryptococcus terrestris and Cryptococcus oeirensis over the growth of Botrytis cinerea, Monilinia laxa, Penicillium expansum and Geotrichum candidum in in vitro assays (inhibition zone diameter assay and confrontation assay).The results revealed that the four yeast strains evaluated showed antagonistic activity against the phytopathogens tested, suggesting that these yeasts produce compounds capable of inhibiting the growth of fungi and, depending on the assay, the evaluated antagonist-yeasts have differential biocontrolling-effect against the postharvest pathogens tested.
ARTICLE | doi:10.20944/preprints201806.0249.v1
Subject: Biology And Life Sciences, Horticulture Keywords: endophytes; tomato; biocontrol; PGPR; seed; microbiome
Online: 15 June 2018 (09:54:47 CEST)
Tomato (Solanum lycopersicum L.) is widely consumed around the world is mostly affected by stresses and diseases that reduce yield and production. Research on sustainable technologies like the use of beneficial microorganismsis crucial to development sustainable management strategies. Endophytic bacteria might increase production as well as plant health.. In this work we studied the endobiome of tomato seeds of different cultivars since the plant genotype might affect the microbial community structure in terms of plant growth promoters as well as organisms for biocontrol. The conditions prevailing within seeds along the maturation period might have affected bacterial survival. This is such that seed endophytes share features, which are different from those of bacteria from other plant tissues. The community associated with different cultivars reflects the different resources available in the seed and its potential to prevent the attack of pathogens and to promote plant growth.
REVIEW | doi:10.20944/preprints202305.0062.v1
Subject: Biology And Life Sciences, Food Science And Technology Keywords: biocontrol; non-Saccharomyces yeasts; functional yeasts; probiotics
Online: 2 May 2023 (05:41:37 CEST)
Fermented food matrices, including beverages, can be defined as the result of the activity of complex microbial ecosystems where different microorganisms interact according to different biotic and abiotic factors. Certainly, in industrial production the technological processes aim to control the fermentation to place safe foods on the market. Therefore, if food safety is the essential prerogative, consumers are increasingly oriented towards a healthy and conscious diet driving the production and consequently the applied research towards natural processes. In this regard, the aim to guarantee safety, quality and diversify of products should be reached limiting or avoiding the addition of antimicrobials or synthetic additives using the biological approach. In this paper, following the recent re-evaluation of non-Saccharomyces yeasts (NSYs) has been re-viewed the bio-protectant and biocontrol activity with a particular focus on their antimicrobial power, probiotic features and promoting functional aspects. In this review, the authors would underline the contribution of NSYs in all food production chain and its role in the technological and fermentative features for their practical and useful use as biocontrol agent in food preparations.
ARTICLE | doi:10.20944/preprints202209.0171.v1
Subject: Biology And Life Sciences, Forestry Keywords: Bruhinae; seed beetles; biocontrol; legumes; parasitoids; Serbia
Online: 13 September 2022 (10:26:44 CEST)
In order to reduce negative effects of application of chemical agents, biological control is becoming increasingly important. This paper therefore focused on research of effects of certain types of seed beetles on control of invasive plant species in Serbia. Numerous sources suggest that for legumes and seed beetles Bruhinae: Chrysomelidae the rule of coexistence in pairs applies in all ecozones. The species rely on one another, primarily in terms of geographical origin or association, thus one plant species is frequently attacked by only one type of seed beetle. Being confirmed to be expressly monophagous, bruchins have proven to be excellent potential agents of control of invasive and harmful host plants (to date, false indigo-bush in Serbia), as is the case of the seed beetle of Persian silk tree, which has been registered as monophagous in Serbia for the first time, making it the number one potential agent in control of the host plant – Persian silk tree in Greece. Standard entomological methods were used, from sample collections, to experiments in photo-eclectors, during dissection counting and placing the seed for development inside by the method 1 flacon – 1 seed, to maintain precise records of the origin of the emerged insects and their numbers, within standard laboratory conditions. The conditions favoring the expansion of the plant have already developed due to climatic circumstances (changes in terms of heat extremes – global warming and precipitation), and it is now gradually becoming invasive. Parasitoid accumulation of roughly one-third (30%) of the total number of false indigo-bush pods makes the false indigo-tree seed beetle a viable candidate for the status of a bioagent. The species has the extreme potential for the application of biological measures which is now quickly gaining importance, all for the purposes of developing the integral control of the plants. Species Acanthoscelides pallidipennis and Bruchidius terrenus have been recorded in this research for the first time in Serbia, while calendars of development have been made for the researched bruchin species, which represents a significant scientific contribution.
ARTICLE | doi:10.20944/preprints202310.0813.v1
Subject: Biology And Life Sciences, Food Science And Technology Keywords: Lactic acid bacteria; probiotic; biocontrol; niches; Tunisian; tomato
Online: 12 October 2023 (10:54:06 CEST)
The continued exploration of the diversity of lactic acid bacteria in little-studied ecological niches represents a fundamental activity to understand the diffusion and biotechnological significance of this heterogeneous class of prokaryotes. In this study, Lactiplantibacillus plantarum (Lpb. plantarum) strains have been isolated from Tunisian vegetable sources, including fermented olive, fermented pepper and from dead locust intestines, subsequently evaluated for their antimicrobial activity against foodborne pathogenic bacteria, including Escherichia coli O157:H7 CECT 4267 and Listeria monocytogenes CECT 4031, as well as against some fungi, including Penicillium expansum, Aspergilus niger and Botrytis cinerea. In addition, their resistance to the oro-gastro-intestinal transit, aggregation capabilities, biofilm production capacity, adhesion to human enterocyte-like cells and cytotoxicity to colorectal adenocarcinoma cell line were determined. Further, the adhesion to tomatoes and the biocontrol potential on this model food matrix were analyzed. It has been found that all the strains were able to inhibit the indicator growth, mostly through organic acids production. Besides, these strains showed promising probiotic traits, including in vitro tolerance to oro-gastrointestinal conditions, adhesion to abiotic surface and to Caco-2 cells. Moreover, all tested Lpb. plantarum strains were able to adhere to tomatoes with similar rate (4.0-6.0 LogCFU/g tomato). The co-culture of LAB strains with pathogens on tomatoes showed that Lpb. plantarum could be a good candidate to control pathogen growth. Nonetheless, further studies are needed to guarantee their use as probiotic strains for biocontrol on food matrices.
ARTICLE | doi:10.20944/preprints202307.1885.v1
Subject: Biology And Life Sciences, Food Science And Technology Keywords: food safety; fresh produce; biocontrol; foodborne; phage application
Online: 27 July 2023 (08:28:53 CEST)
A commercial phage biocontrol for reducing Listeria monocytogenes has been described as an effective tool for improving fresh produce safety. Critical challenges in the phage application must be overcome for the industrial application. The validation studies were performed in two processing lines of two industry collaborators in Spain and Denmark, selecting shredded iceberg lettuce as the ready-to-eat (RTE) product of higher process volume. The biocontrol treatment optimized in lab-scale trials for the application of PhageGuard ListexTM was confirmed in industrial settings by four tests, two in Spain and two in Denmark. Results showed that the method of application that included the device and the processing operation step were appropriate for the correct application. The proper dose of Phage Guard ListexTM was reached in shredded iceberg lettuce and the surface was adequately covered for the successful application of phages. There was no impact on the headspace gas composition (CO2 and O2 levels), nor on the color when untreated and treated samples were compared. The post-process treatment PhageGuard ListexTM did not cause any detrimental impact on the sensory quality, including flavor, texture, browning, spoilage and visual appearance of over the shelf-life as the phage solution was applied as a fine, mist solution.
ARTICLE | doi:10.20944/preprints202306.1407.v1
Subject: Biology And Life Sciences, Food Science And Technology Keywords: wine yeasts; Torulaspora delbrueckii; low sulfites wines; biocontrol
Online: 20 June 2023 (08:30:06 CEST)
Torulaspora delbrueckii showed renewed interest in recent years in the fermentation of wine, for its biotechnological potential linked to the ability to enhance flavor and aroma and it probably is the non-Saccharomyces yeast currently widely used in winemaking. On the base of this, sequential fermentations with a selected native strain of T. delbrueckii (DiSVA 130) and low sulfite native strain of Saccharomyces cerevisiae (DiSVA 709) were carried out to establish their contribution in biocontrol and aroma profile. A first set trials, carried out in winery, were set up to establish the effect of the sulfur dioxide addition on pure and T. debrueckii/S. cerevisiae sequential fermentations. A second set of sequential fermentations without SO2 addition were conducted in the same conditions, to evaluate the biocontrol and aromatic effectiveness of the T. delbrueckii native strain and a commercial one. The effective biocontrol action of native T. delbrueckii inoculated in sequential fermentation was shown, indeed without SO2 addition the presence of native T. delbrueckii revealed an effective fungistatic action in the first two days of fermentation. Moreover, the native T. delbrueckii strain seems to have fermentative performances comparable to those of T. delbrueckii commercial strain showing a more evident biocontrol action (wild yeasts reduced by c.a. 1 Log at 2nd day) and its presence did not negatively affect S. cerevisiae fermentation activity. Finally, the combination of both native and commercial T. delbrueckii/S. cerevisiae trials led distinctive aromatic profile of wines with a significant enhancement of isoamyl acetate, phenyl ethyl acetate, supported by positive appreciations, from the tasters, for ripe and tropical fruits, citrus and balance. The whole results indicate that the proposed strain could be a potential biocontrol tool toward wild yeasts in the first phase of fermentation also contributing to improve and differentiate the final aroma wine.
ARTICLE | doi:10.20944/preprints202304.1176.v1
Subject: Biology And Life Sciences, Agricultural Science And Agronomy Keywords: Watermelon; damping-off; Pythium aphanidermatum; Streptomyces murinus; biocontrol
Online: 28 April 2023 (11:11:41 CEST)
Damping-off caused by Pythium aphanidermatum (Pa) is one of the most destructive diseases for watemelon seedlings. Application of biological control agents against Pa has attracted attention of many researchers for a long time. In this study, an actinomycete isolate JKTJ-3 with strong and broad-spectrum antifungal effect was screened from 23 bacterial isolates. Based on the morphological, cultural, physiological, and biochemical characteristics as well as the feature of 16S rDNA sequence, isolate JKTJ-3 was identified as Streptomyces murinus. We compared the biocontrol efficacy of isolate JKTJ-3 and its metabolites. The results revealed that seed and substrate treatments with the JKTJ-3 cultures showed a significant inhibitory effect on watermelon damping-off disease. Seed treatment with the JKTJ-3 cultural filtrates (CF) had higher control efficacy that of the fermentation cultures (FC). Treatment of the seeding substrate with the wheat grain cultures (WGC) of JKTJ-3 exhibited better control efficacy than that of the seeding substrate with the JKTJ-3 CF. Moreover, the JKTJ-3 WGC showed the preventive effect on suppression of the disease, and the efficacy increased with increase in the inoculation interval between the WGC and Pa. Production of the antifungal metabolite actinomycin D by isolate JKTJ-3 and cell wall-degrading enzymmes such as β-1,3-glucanase and chitosanase was probably the mechanisms for effective control of watermelon damping-off. It was showed for the first time that S. murinus can produce anti-oomycete substances including chitinase and actinomycin D. This is the first report about S. murinus used as biocontrol agent against watermelon Pa-induced damping-off.
ARTICLE | doi:10.20944/preprints202304.0468.v1
Subject: Biology And Life Sciences, Agricultural Science And Agronomy Keywords: Bacillus; biocontrol; volatile organic compound; GC-MS; sporulation
Online: 18 April 2023 (03:28:47 CEST)
Magnaporthe oryzae Triticum (MoT) pathotype is the causal agent of wheat blast, which has caused significant economic losses and threatens wheat production in South America, Asia and Africa. Three bacterial strains from rice and wheat seeds (B. subtilis BTS-3, B. velezensis BTS-4, and B. velezensis BTLK6A) were used to explore the antifungal effects of volatile organic compounds (VOCs) of Bacillus spp. as a potential biocontrol mechanism against MoT. All bacterial treatments significantly inhibited both mycelial growth and sporulation of MoT in vitro. We found that this inhibition was caused by Bacillus VOCs in a dose-dependent manner. In addition, biocontrol assays using detached wheat leaves infected with MoT showed reduced leaf lesions and sporulation compared to the untreated control. VOCs from B. velezensis BTS-4 alone or a consortium (mixture of B. subtilis BTS-3, B. velezensis BTS-4, and B. velezensis BTLK6A) treatments consistently suppressed MoT in vitro and in vivo. Compared to the untreated control, VOCs from BTS-4 and Bacillus consortium reduced MoT lesions in vivo by 85% and 81.25%, respectively. A total of thirty-nine VOCs (from 9 different VOC groups) from 4 Bacillus treatments were identified by gas chromatography-mass spectrometry (GC-MS), of which 11 were produced in all Bacillus treatments. Alcohols, fatty acids, ketones, aldehydes, and S-containing compounds were detected in all four bacterial treatments. In vitro assays using pure VOCs revealed that hexanoic acid, 2-methylbutanoic acid, and phenylethyl alcohol are potential VOCs emitted by Bacillus spp. that are suppressive for MoT. The minimum inhibitory concentrations for MoT sporulation were 250 mM for phenylethyl alcohol and 500 mM for 2-methylbutanoic acid and hexanoic acid. Therefore, our results indicate that VOCs from Bacillus spp. are effective compounds to suppress the growth and sporulation of MoT. Understanding the MoT sporulation reduction mechanisms by Bacillus VOCs may provide novel options to manage the further spread of wheat blast by spores.
REVIEW | doi:10.20944/preprints202112.0069.v1
Subject: Biology And Life Sciences, Agricultural Science And Agronomy Keywords: microbiome; golf turf; turfgrasses; biocontrol; microbial communities; endophytes
Online: 6 December 2021 (12:19:16 CET)
Golf courses have a significant environmental impact. High water demands and the intensive use of agricultural chemicals have been a concern for decades and are therefore in the focus of efforts to make golf courses more environmentally sustainable. Products based on modifying or using plant-associated microbiota are one of the fastest growing sectors in agriculture, but their application on turfgrasses on golf courses is so far negligible. In this review, we summarize the limited knowledge on microbiomes of golf turf ecosystems and show that the lack of holistic studies addressing structure and function of golf turf microbiomes, including their responses to intense turf management procedures, is currently the main bottleneck for development and improvement of reliable, well-functioning microbial products. We further highlight the endosphere of turfgrasses, which is easily accessible for microbial cultivation through constant mowing, as the most stable and protected micro-environment. Many grass species do possess endophytic bacteria and fungi that have shown to improve the plants’ resistance towards microbial pathogens and insect pests, and several products using endophyte-enhanced grass varieties are commercially successful. We anticipated that this trend would tee-off on golf courses, too, once a more comprehensive understanding of golf turf microbiomes is available.
ARTICLE | doi:10.20944/preprints202305.2095.v1
Subject: Biology And Life Sciences, Agricultural Science And Agronomy Keywords: biocontrol; natural products; phytopathogens; microbial metabolites; entomopathogens; endophytic fungi.
Online: 30 May 2023 (09:02:51 CEST)
The genus Beauveria include important entomopathogenic and endophytic fungi, among them, Beauveria bassiana is the most studied species. However, there are few knowledge regarding their antimicrobial activity. The current research has been conducted to evaluate in vitro antagonistic activity of B. bassiana and the antimicrobial efficacy of its Exo and Endo metabolites against Bacillus cereus, B. megaterium, Clavibacter michiganensis (gram positive bacteria, G+ve), Xanthomonas campestris, Pseudomonas aeruginosa and P. fluorescence (gram negative bacteria, G-ve). In addition, Solid-phase microextraction (SPME) was coupled to Gas Chromatography-Mass Spectrometry (GC/MS) to qualitatively measure the volatile organic compounds (VOCs) metabolic profile of the most efficient studied isolate of B. bassiana. The obtained results showed that, the isolate UniB2439-3 has promising antibacterial effect against most of studied target bacteria. SPME-GC/MS analysis of VOCs revealed the presence of ethanol; butanal,2-methyl; 2,4-dimethyl-1-heptene; octane, 4-methyl and β-elemene as the main dominant bioactive compounds. The outgoing results explicated that the efficient isolate of B. bassiana can be potentially used as a biocontrol agent against several bacteria especially G+ve ones.
ARTICLE | doi:10.20944/preprints202304.0134.v1
Subject: Biology And Life Sciences, Agricultural Science And Agronomy Keywords: biocontrol; natural products; phytopathogens; microbial metabolites; entomopathogens; endophytic fungi
Online: 10 April 2023 (03:06:01 CEST)
The genus Beauveria include important entomopathogenic and endophytic fungi, among them, B. bassiana is the most studied species. However, there are few knowledge regarding their antimicrobial activity. The current research has been conducted to evaluate in vitro antibacterial efficacy of five isolates of B. bassiana against Bacillus cereus, B. megaterium, B. mojavensis, Clavibacter michiganensis (gram positive bacteria, G+ve), Xanthomonas campestris, X. vesicatoria, Escherichia coli, Pseudomonas aeruginosa and P. fluorescence (gram negative bacteria, G-ve). In addition, chemical composition of the principal diffusible metabolites and volatile organic compounds (VOCs) of the most efficient studied isolate of B. bassiana has been carried out using GC-MS analysis. The obtained results showed that, the isolate UniB2439-3 has promising antibacterial effect against most of studied target bacteria. GC-MS analysis of diffusible metabolites detected the presence of hexanedioic acid, bis(2-ethylhexyl) ester as the main compound in the cell-free culture filtrate. Furthermore, GC-MS analysis of VOCs revealed the presence of ethanol; butanal,2-methyl; 2,4-dimethyl-1-heptene; octane, 4-methyl and β-elemene as the main dominant bioactive compounds. The outgoing results explicated that, the isolates of B. bassiana have promising antibacterial activity which could be correlated to their diffusible and VOCs metabolites. Therefore, the selected isolate can be potentially used as a biocontrol agent against several bacteria especially G+ve ones. Taking in consideration that the antibiotics are forbidden in agriculture in many countries worldwide, search for possible natural alternatives as efficient antimicrobial agents are highly interesting.
REVIEW | doi:10.20944/preprints202112.0503.v1
Subject: Biology And Life Sciences, Plant Sciences Keywords: Plant Pathogen; Biocontrol; Microbes; AMF; Bacteriophages; Microbiome; Sustainable strategies
Online: 31 December 2021 (10:45:32 CET)
Food security has become a major concern worldwide in recent years due to ever increasing population. Providing food for the growing billions without disturbing environmental balance is incessantly required in the current scenario. In view of this, sustainable modes of agricultural practices offer better promise and hence are gaining prominence recently. Moreover, these methods have taken precedence currently over chemical-based methods of pest restriction and pathogen control. Adoption of Biological Control is one such crucial technique that is currently in the forefront. Over a period of time, various biocontrol strategies have been experimented with and some have exhibited great success and promise. This review highlights the different methods of plant-pathogen control, types of plant pathogens, their modus operandi and various biocontrol approaches employing a range of microorganisms and their byproducts. The study lays emphasis on the use of upcoming methodologies like microbiome management and engineering, phage cocktails, genetically modified biocontrol agents and microbial volatilome as available strategies to sustainable agricultural practices. More importantly, a critical analysis of the various methods enumerated in the paper indicates the need to amalgamate these techniques in order to improve the degree of biocontrol offered by them.
REVIEW | doi:10.20944/preprints201911.0350.v3
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: aflatoxins; incidence; toxicity; risk assessment; biocontrol; atoxigenic A. flavus
Online: 5 January 2020 (16:44:52 CET)
This review aimed to update the main aspects of aflatoxin production, occurrence and incidence in selected countries, and associated aflatoxicosis outbreaks. Means to reduce aflatoxin incidence in crops were also presented with an emphasis on the environment-friendly technology using atoxigenic strains of Aspergillus flavus. Aflatoxins are unavoidable widespread natural contaminants of foods and feeds with serious impact on health, agricultural and livestock productivity, and food safety. They are secondary metabolites produced by Aspergillus species distributed on three main sections of the genus (section Flavi, section Ochraceorosei, and section Nidulantes). Poor economic status of a country exacerbates the risk and the extent of crop contamination due to faulty storage conditions that are usually suitable for mold growth and mycotoxin production: temperature of 22 to 29°C and water activity of 0.90 to 0.99. This situation paralleled the prevalence of high liver cancer and the occasional acute aflatoxicosis episodes that have been associated with these regions. Risk assessment studies revealed that Southeast Asian and Sub-Saharan African countries remain at high risk and that, apart from the regulatory standards revision to be more restrictive, other actions to prevent or decontaminate crops are to be taken for adequate public health protection. Indeed, a review of publications on the incidence of aflatoxins in selected foods and feeds from countries whose crops are classically known for their highest contamination with aflatoxins, reveals that despite the intensive efforts made to reduce such an incidence, there has been no clear tendency, with the possible exception of South Africa, towards sustained improvements. Nonetheless, a global risk assessment of the new situation regarding crop contamination with aflatoxins by international organizations with the required expertise is suggested to appraise where we stand presently.
ARTICLE | doi:10.20944/preprints202308.1062.v1
Subject: Biology And Life Sciences, Agricultural Science And Agronomy Keywords: Antagonistic capacity; Biocontrol agents; ITS1-5.8s-ITS2 region; Dual Cultures
Online: 15 August 2023 (08:59:30 CEST)
Stevia rebaudiana (Bert.) is a natural sweetener with diterpenic glycosides, offering 300 times more sweetness than sucrose, and boasting low-calorie content, along with medicinal and therapeutic properties. To address a limited genetic diversity, a germplasm bank comprising 115 segregated lines of stevia was established in Colombia. Notwithstanding, the fungus Athelia rolfsii adversely impacted key stevia lines, leading to wilting and plant mortality. For this reason our study aimed to explore the biocontrol potential of native strains of Trichoderma spp., isolated from productive lots in Colombia's Cordoba department, as a solution to manage A. rolfsii. Soil samples underwent serial dilution technique (103 conidia.mL-1) to obtain Trichoderma spp. isolates, which were thoroughly morphologically and molecularly characterized. A total five native strains were identified through sequencing the PCR products using universal ITS primers, and comparisons with the GENBANK database confirmed their identity (OK310695.1, ON237703.1, ON238106.1, ON237737.1, and ON237923.1). Their biocontrol efficacy against A. rolfsii was evaluated using the dual culture technique. Remarkably, all strains exhibited significant biocontrol capacity against the A. rolfsii isolate INVEPAR-05 (OK271308.1), except for Trichoderma viride INVEPAR-T10 (ON237923.1). These findings suggest that Trichoderma spp. could be a potential option to manage the fungus in stevia.
ARTICLE | doi:10.20944/preprints202306.1904.v1
Subject: Biology And Life Sciences, Food Science And Technology Keywords: Bacteriophages; Shiga-toxigenic E. coli; biocontrol; biofilms; food-contact surfaces
Online: 27 June 2023 (12:36:36 CEST)
(1) Background: Formation of biofilms on food-contact surfaces by Shiga-toxigenic Escherichia coli (STEC) can pose a significant challenge to the food industry, making conventional control-methods insufficient. Targeted use of bacteriophages to disrupt these biofilms could reduce this problem. Previously isolated and characterized bacteriophages (n=52) were evaluated against STEC biofilms in-vitro and on food-contact surfaces. (2) Methods: Phage-treatments (9 logs PFU/ml), in phosphate-buffered-saline, were used individually or as cocktails. Biofilms of STEC (O157, O26, O45, O103, O111, O121, and O145) were formed in 96-well micro-titer plates (7 logs CFU/ml; 24 h) or on stainless-steel (SS) and high-density-polyethylene (HDPE) coupons (9 logs CFU/cm2; 7 h), followed by phage-treatment. Biofilm-disruption was measured in-vitro at 0, 3, and 6 h as a change in optical-density (A595). Coupons were treated with STEC-serotype-specific phage-cocktails or a 21-phage cocktail (3 phages/serotype) for 0, 3, 6 and 16 h and surviving STEC populations enumerated. (3) Results: Of the 52 pages, 77% showed STEC-biofilm disruption in-vitro. Serotype-specific phage-treatments reduced pathogen population within the biofilms by 1.9-4.1 and 2.3-5.6 logs CFU/cm2, while the 21-pahge cocktail reduced it by 4.0 and 4.8 logs CFU/cm2 on SS and HDPE, respectively. (4) Conclusions: Bacteriophages can be used to reduce STEC and their biofilms.
ARTICLE | doi:10.20944/preprints202301.0383.v1
Subject: Biology And Life Sciences, Agricultural Science And Agronomy Keywords: Bipolaris sorokiniana; Bacillus halotolerans; common root rot; biocontrol agent; wheat
Online: 23 January 2023 (01:40:03 CET)
Common root rot caused by Bipolaris sorokiniana infestation of wheat is one of the main reasons of yield reduction in wheat crops worldwide. In current study, strain JK-25 was isolated from soil of wheat rhizosphere and identified as Bacillus halotolerans based on morphological, physiological, biochemical characteristics and molecular identification. The strain showed significant antagonism to B.sorokiniana and broad-spectrum resistance to Fusarium oxysporum, Fusarium graminearum and Rhizoctonia zeae. Inhibition of Bipolaris sorokiniana mycelial dry weight and spore germination rate by JK-25 fermentation supernatant reached 60% and 88% respectively. The crude extract of JK-25 was found by MALDI-TOF-MS to contain the surfactin that exerted an inhibitory effect on B.sorokiniana. The disruption of mycelial cell membranes was observed under microscopy (LSCM) after treatment of B.sorokiniana mycelium with the crude extract. The antioxidant enzyme activity of B.sorokiniana was significantly reduced and the oxidation product MDA content increased after treatment with the crude extract. The incidence of root rot was significantly reduced in pot experiments with the addition of JK-25 culture ferment, which had a significant biological control effect of 72.06%. Its ability to produce siderophores may help to promote wheat growth, and the production of proteases and pectinases may also be part of the strain's role in suppressing pathogens. These results demonstrate the excellent antagonistic effect of JK-25 against B.sorokiniana and suggest that this strain has great potential as a resource for biological control of wheat root rot strains.
ARTICLE | doi:10.20944/preprints202109.0309.v1
Subject: Biology And Life Sciences, Plant Sciences Keywords: Trichoderma atroviride; volatile organic compounds; tomato; biostimulation; biocontrol; Fusarium wilt disease
Online: 17 September 2021 (12:03:42 CEST)
The promotion of plant growth and suppression of plant disease using beneficial microorganisms is considered an alternative to the application of chemical fertilizers or pesticides in the field. In this study, a coconut-scented antagonistic Trichoderma strain LZ42, previously isolated from Genoderma lucidum-cultivated soil, was investigated for biostimulatory and biocontrol functions in tomato seedlings. Morphological and phylogenetic analyses suggested that strain LZ42 is closely related to T. atroviride. Tomato plants showed increased aerial and root dry weights in greenhouse trials after treatment with T. atroviride LZ42 formulated in talc, indicating the biostimulatory function of this fungus. T. atroviride LZ42 effectively suppressed Fusarium wilt disease in tomato seedlings, with an 82.69% control efficiency, which is similar to that of fungicide treatment. The volatile organic compounds (VOCs) emitted by T. atroviride LZ42 were found to affect the primary root growth direction and promote the root growth of tomato seedlings in root Y-tube olfactometer assays. The fungal VOCs from T. atroviride LZ42 were observed to significantly inhibit F. oxysporum in a sandwiched Petri dish assay. SPME-GC-MS analysis revealed several VOCs emitted by T. atroviride LZ42; the dominant compound was tentatively identified as 6-pentyl-2H-pyran-2-one (6-PP). 6-PP exhibited a stronger ability to influence the direction of the primary roots of tomato seedlings but not the length of the primary roots. The inhibitory effect of 6-PP on F. oxysporum was the highest among the tested pure VOCs, showing a 50% effective concentration (EC50) of 5.76 μL mL-1 headspace. In conclusion, T. atroviride LZ42, which emits VOCs with multiple functions, is a promising agent for the biostimulation of vegetable plants and integrated management of Fusarium wilt disease.
ARTICLE | doi:10.20944/preprints202307.0784.v1
Subject: Chemistry And Materials Science, Analytical Chemistry Keywords: 7-hydroxytropolone; iron-complex; Pseudomonas; Dickeya; Pectobacteriaceae; Biocontrol; Blackleg; Soft Rot; Potato
Online: 12 July 2023 (07:49:33 CEST)
Soft Rot Pectobacteriaceae (SRP) bacteria as Pectobacterium and Dickeya are phytopathogenic agents responsible of blackleg disease on several crop as potato, affecting the yield and depressing the seed production quality. However, neither conventional nor biocontrol product are available on the market to control this disease. In this study Pseudomonas PA14H7, a bacteria isolated from potato rhizosphere, was selected as a potential antagonist agent against Dickeya. In order to understand the mechanism involved in this antagonism we managed to identify the main active(s) molecule(s) produced by PA14H7. In that way, cell-free supernatant (CFS) of PA14H7 cultures were extracted and analyzed by LC-MS, GC-MS and NMR. We have correlated biological activity in extracted CFS-PA14H7 to the presence of 7-hydroxytropolone (7-HT) complexed with iron. Even if this molecule is produced by other Pseudomonas and mostly known for its antibacterial and antifungal activities, it is the first description of its involvement as an effective molecule against pectinolytic bacteria. We have synthesized 7-HT in order to determine the real amount produced by PA14H7 and to compare its activity at the same concentration with that of CFS-PA14H7. This study aims to understand the origin of the antagonist activity of PA14H7 as a potential biocontrol agent against potato blackleg.
ARTICLE | doi:10.20944/preprints202305.2247.v1
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: lung microbiome; bronchoalveolar lavage fluid (BALF); antagonistic bacteria; biocontrol; Pseudomonas aeruginosa; aspergillosis
Online: 31 May 2023 (12:52:50 CEST)
Fungi of the genus Aspergillus are widespread in the environment where they produce large quantities of airborne conidia. Inhalation of Aspergillus spp. conidia in immunocompromised individuals can cause a wide spectrum of diseases, ranging from hypersensitivity responses to lethal invasive infections. Upon deposition in the lung epithelial surface, conidia encounter and interact with complex microbial communities that constitute the lung microbiota. The lung microbiota has been suggested to influence the establishment and growth of Aspergillus spp. in the human airways. However, the mechanisms underlying this interaction have not yet been sufficiently investigated. In this study, we aimed to evaluate the presence of commensal bacteria antagonistic to Aspergillus in the lung. To this end, we enriched and isolated bacterial strains able to inhibit the germination of conidia from bronchoalveolar lavage fluid (BALF) samples of lung transplant recipients. We used a novel enrichment method based on a soft agar overlay plate assay in which bacteria are directly in contact with conidia and for which inhibition can be readily observed during enrichment. We isolated a total of five bacterial strains, identified as Pseudomonas aeruginosa, and able to inhibit the germination and growth of Aspergillus fumigatus in a soft agar confrontation assay, as well as in a high-throughput multiplate assay. Moreover, we also showed a strong inhibition of A. fumigatus growth on Calu-3 cell culture monolayers. However, the isolated P. aeruginosa strains were shown to cause significant damage to the cell monolayers. Overall, we validated this novel one-step enrichment approach for the isolation of bacterial strains antagonistic to A. fumigatus from BALF samples. This opens up a new venue for targeted enrichment of antagonistic bacterial strains against specific fungal pathogens.
REVIEW | doi:10.20944/preprints202001.0276.v1
Subject: Biology And Life Sciences, Insect Science Keywords: genetic improvement; genetic variation; heritability; systematic review; biocontrol agent; life history traits
Online: 24 January 2020 (10:39:55 CET)
The concept of genetic improvement in relation to biological control involves the exploitation of natural genetic variation for the benefit of existing biological control agents (BCAs). Despite recent calls for this process to be adopted in biological control research, there is no clear overview of the current state of research into genetic variation within a biological control context, including quantifiable estimates such as narrow-sense heritability (h2). In this systematic review, we aim to determine the current state of research on the genetic variation of biological control traits in natural enemies. After the searching process, screening for papers that can deliver on our research question reduced the initial 2,927 search hits to only a mere 69 papers for data extraction. Of these, the majority (73.6%) did not report quantitative values for genetic variation. Extracting the traits measured in these papers, we categorized them according to two approaches; the first related to fitness components, and the second related to biological control importance. This systematic review highlights the need for more rigorous reporting of the quantitative values of genetic variation to enable the successful genetic improvement of biological control agents.
ARTICLE | doi:10.20944/preprints202311.1896.v1
Subject: Biology And Life Sciences, Agricultural Science And Agronomy Keywords: Biocontrol; Diplodia seriata; Botryosphaeria dieback; Grapevine trunk diseases; GTDs; Botryosphaeriaceae; Pseudomonas; Rhodococcus; Demelanizing activity
Online: 29 November 2023 (13:48:37 CET)
Grapevine trunk diseases (GTDs) attack the vine's wood, devastating vineyards worldwide. Chile is the world's fourth largest wine exporter, and Cabernet Sauvignon leads the red wine varieties. Botryosphaeria dieback is an important GTDs and Diplodia seriata is one of the main pathogenic species. Biocontrol studies of these pathogens are commonly carried out at different incubation times but at a single temperature. This study aimed to evaluate the biocontrol effect of native Chilean bacteria against D. seriata isolates at different temperatures. We analyzed the biocontrol effects of Pseudomonas sp. GcR15a, Pseudomonas sp. AMCR2b and Rhodococcus sp. PU4, with three D. seriata isolates (PUCV 2120, PUCV 2142 and PUCV 2183) at 8, 22 and 35°C. Agar plug diffusion and double plate methods were used to evaluate the effect of diffusible and volatile organic compounds (DOC and VOC), and an in vivo test was performed with Cabernet Sauvignon cuttings. Pseudomonas strains showed the most significant inhibition in the DOC assay, and a demelanizing activity was observed. Rhodococcus sp. PU4 showed VOC biocontrol potential at high temperatures (35°C). In vivo, a biocontrol effect was observed against two D. seriata isolates, while the PUCV 2142 isolate proved to be more resistant to being controlled. The biocontrol ability at low temperatures is promising for effective control in the field, where infections occur primarily in winter.
ARTICLE | doi:10.20944/preprints202102.0241.v1
Subject: Biology And Life Sciences, Anatomy And Physiology Keywords: plant-growth-promoting bacteria; spore-forming bacteria; Bacillus vallismortis; Macrophomina phaseolina; phenotypic and genotypic characterization; Biocontrol agents
Online: 9 February 2021 (15:09:32 CET)
In the last decades, intensive crop management has involved excessive use of pesticides or fertilizers, compromising environmental integrity and public health. Accordingly, there has been worldwide pressure to find an eco-friendly and safe strategy to ensure agricultural productivity. Recently, Plant Growth-Promoting (PGP) rhizobacteria are receiving increasing attention as suitable biocontrol agents against agricultural pests. In the present study, 22 spore-forming bacteria were selected among a salt-pan rhizobacteria collection for their PGP traits and their antagonistic activity against the plant pathogen fungus Macrophomina phaseolina. Based on the higher antifungal activity, strain RHFS10, identified as Bacillus vallismortis, was furtherly examined and cell-free supernatants assays, column purification, and tandem mass spectrometry employed to purify and preliminarily identify the antifungal metabolites. Interestingly, the minimum inhibitory concentration assessed for the fractions active against M. phaseolina, resulted 10 times lower and more stable than the one estimated for the commercial fungicide pentachloronitrobenzene. These results suggest the use of B. vallismortis strain RHFS10 as a potential Plant Growth Promoting Rhizobacteria to efficiently control phytopathogenic fungus M. phaseolina, in alternative to chemical pesticides.
ARTICLE | doi:10.20944/preprints202310.0635.v2
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: Bacillus cereus; phylogenomics; DNA-DNA hybridization (ddH); biocontrol; plant growth promotion (PGP); biosynthesis gene cluster (BGC); kurstakin; thumolycin
Online: 11 October 2023 (12:22:18 CEST)
Seventeen bacterial strains able to suppress plant pathogens have been isolated from healthy Vietnamese crop plants, and taxonomically assigned as members of the Bacillus cereus group. In order to prove their potential as biocontrol agents, we performed a comprehensive analysis which included whole genome sequencing of selected strains, and mining for genes and gene clusters involved in the synthesis of endo- and exotoxins, and secondary metabolites, such as antimicrobial peptides (AMPs). Kurstakin, thumolycin, and other AMPs were detected and characterized by different mass spectrometric methods, such as MALDI-TOF-MS, and LIFT-MALDI-TOF/TOF fragment analysis. Based on their whole genome sequences, the plant-associated isolates were assigned to the following species and subspecies: B. cereus subsp. cereus (6), B. cereus subsp. bombysepticus (5), Bacillus tropicus (2), and Bacillus pacificus. Three isolates represented novel genomospecies. Genes encoding entomopathogenic crystal and vegetative proteins were detected in B. cereus subsp. bombysepticus TK1. In vitro assays revealed that many plant-associated isolates enhanced plant growth and suppressed plant pathogens. Our findings indicated that plant-associated representatives of the B. cereus group are a rich source of putative antimicrobial compounds with potential in sustainable agriculture. However, the presence of virulence genes might restrict their application as biologicals in agriculture.