ARTICLE | doi:10.20944/preprints202211.0473.v1
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/preprints202204.0309.v1
Subject: Life Sciences, 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, Agricultural Sciences & 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
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.
ARTICLE | doi:10.20944/preprints202209.0171.v1
Subject: Biology, 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.
REVIEW | doi:10.20944/preprints202112.0069.v1
Subject: Biology, Agricultural Sciences & 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.
REVIEW | doi:10.20944/preprints202112.0503.v1
Subject: Life Sciences, Other 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: Life Sciences, 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/preprints202301.0383.v1
Subject: Biology, Agricultural Sciences & 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, 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.
REVIEW | doi:10.20944/preprints202001.0276.v1
Subject: Biology, Entomology 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/preprints202102.0241.v1
Subject: Biology, Anatomy & Morphology 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.