Plant growth promotion and biocontrol properties of a synthetic community in the control of apple disease.

BACKGROUND: Apple Replant Disease (ARD) is common in major apple-growing regions worldwide, but the role of rhizosphere microbiota in conferring ARD resistance and promoting plant growth remains unclear. RESULTS: In this study, a synthetic microbial community (SynCom) was developed to enhance apple plant growth and combat apple pathogens. Eight unique bacteria selected via microbial culture were used to construct the antagonistic synthetic community, which was then inoculated into apple seedlings in greenhouse experiments. Changes in the rhizomicroflora and the growth of aboveground plants were monitored. The eight strains, belonging to the genera Bacillus and Streptomyces, have the ability to antagonize pathogens such as Fusarium oxysporum, Rhizoctonia solani, Botryosphaeria ribis, and Physalospora piricola. Additionally, these eight strains can stably colonize in apple rhizosphere and some of them can produce siderophores, ACC deaminase, and IAA. Greenhouse experiments with Malus hupehensis Rehd indicated that SynCom promotes plant growth (5.23%) and increases the nutrient content of the soil, including soil organic matter (9.25%) and available K (1.99%), P (7.89%), and N (0.19%), and increases bacterial richness and the relative abundance of potentially beneficial bacteria. SynCom also increased the stability of the rhizosphere microbial community, the assembly of which was dominated by deterministic processes (|ß NTI| > 2). CONCLUSIONS: Our results provide insights into the contribution of the microbiome to pathogen inhibition and host growth. The formulation and manipulation of similar SynComs may be a beneficial strategy for promoting plant growth and controlling soil-borne disease.

Biocontrol Efficacy of Pseudomonas Consortia Against Botrytis Blight in Petunias.

Botrytis cinerea, a fungal pathogen causing Botrytis blight, significantly impacts greenhouse crop management due to its broad host range and infection capabilities at various growth stages. Traditional control methods, primarily reliant on fungicides, are challenged by environmental concerns and the rise of fungicide-resistant strains. This study investigates the use of beneficial Pseudomonas bacteria as a sustainable alternative. We hypothesized that specific Pseudomonas consortia could provide more effective biocontrol of B. cinerea than individual strains. Our research investigated five Pseudomonas strains (14B11, AP54, 15H3, 94G2, and 89F1) known to reduce Botrytis blight in Petunia × hybrida. Compatibility for bacterial consortia was assessed through biofilm formation and direct bacterial inhibition assays. The biocontrol effects of the bacteria against B. cinerea were investigated in vitro using shared-air space dual culture assays and in planta by inoculating detached petunia flowers. We found strain 14B11 exhibited the highest biofilm formation, with consortia of 14B11 and 89F1 showing significant enhancement compared to individual cultures, while a slight, non-significant increase was observed in 14B11 and AP54 consortia. However, strain 14B11 efficacy was inhibited by strain 15H3. Genomic analyses identified antifungal compound-related gene clusters in 14B11 and AP54, contributing to their biocontrol potential. Trials with detached flowers of Petunia × hybrida 'Carpet Red Bright' confirmed significant disease severity reduction with 14B11, AP54, and their consortia. This research highlights strategic Pseudomonas consortia as promising, eco-friendly alternatives to chemical fungicides, promoting sustainable agriculture by enhancing our understanding of how microbial interactions can be used to manage Botrytis blight.

Effects of wildfire disturbance on forest soil microbes and colonization of ericoid mycorrhizal fungi in northern China.

Wildfires affect forest succession and restoration by changing the community structure of soil microorganisms. Mycorrhizal formation is essential for plant growth and development. However, the driving mechanism of their natural succession after wildfire is still unclear. In this study, we examined the community structure of soil bacteria and fungi along a time series of natural recovery after wildfires in the Greater Khingan Range of China (2020 fires, 2017 fires, 2012 fires, 2004 fires, 1991 fires, and unburned). By exploring the effects of wildfire on plant traits, fruit nutrition, colonization of mycorrhizal fungi and its influencing mechanism. The results show that natural succession after wildfires significantly changed the community composition of bacteria and fungi, with ß diversity having a greater impact but less impact on the α diversity of microorganisms. Wildfires significantly changed plant traits and fruit nutrient content. The changes in colonization rate and customization intensity of mycorrhizal fungi were caused by increased MDA content and soluble sugar content and increased MADS-box gene and DREB1 gene expression in lingonberry (Vaccinium vitis-idaea L.). Our results showed that the soil bacterial and fungal communities in the boreal forest ecosystem changed significantly during wildfire recovery and changed the colonization rate of lingonberry mycorrhizal fungi. This study provides a theoretical basis for the restoration of forest ecosystems after wildfires.

Structure, Functionality, Compatibility with Pesticides and Beneficial Microbes, and Potential Applications of a New Delivery System Based on Ink-Jet Technology.

Accurate application of agrochemicals is an important way to achieve efficient use of chemicals and to combine limited pollution with effective control of weeds, pests, and diseases. In this context, we investigate the potential application of a new delivery system based on ink-jet technology. First, we describe the structure and functionality of ink-jet technology for agrochemical delivery. We then evaluate the compatibility of ink-jet technology with a range of pesticides (four herbicides, eight fungicides, and eight insecticides) and beneficial microbes, including fungi and bacteria. Finally, we investigated the feasibility of using ink-jet technology in a microgreens production system. The ink-jet technology was compatible with herbicides, fungicides, insecticides, and beneficial microbes that remained functional after passing through the system. In addition, ink-jet technology demonstrated higher area performance compared to standard nozzles under laboratory conditions. Finally, the application of ink-jet technology to microgreens, which are characterized by small plants, was successful and opened the possibility of full automation of the pesticide application system. The ink-jet system proved to be compatible with the main classes of agrochemicals and showed significant potential for application in protected cropping systems.

Tissue-Specific Hormone Signalling and Defence Gene Induction in an In Vitro Assembly of the Rapeseed Verticillium Pathosystem.

Priming plants with beneficial microbes can establish rapid and robust resistance against numerous pathogens. Here, compelling evidence is provided that the treatment of rapeseed plants with Trichoderma harzianum OMG16 and Bacillus velezensis FZB42 induces defence activation against Verticillium longisporum infection. The relative expressions of the JA biosynthesis genes LOX2 and OPR3, the ET biosynthesis genes ACS2 and ACO4 and the SA biosynthesis and signalling genes ICS1 and PR1 were analysed separately in leaf, stem and root tissues using qRT-PCR. To successfully colonize rapeseed roots, the V. longisporum strain 43 pathogen suppressed the biosynthesis of JA, ET and SA hormones in non-primed plants. Priming led to fast and strong systemic responses of JA, ET and SA biosynthesis and signalling gene expression in each leaf, stem and root tissue. Moreover, the quantification of plant hormones via UHPLC-MS analysis revealed a 1.7- and 2.6-fold increase in endogenous JA and SA in shoots of primed plants, respectively. In roots, endogenous JA and SA levels increased up to 3.9- and 2.3-fold in Vl43-infected primed plants compared to non-primed plants, respectively. Taken together, these data indicate that microbial priming stimulates rapeseed defence responses against Verticillium infection and presumably transduces defence signals from the root to the upper parts of the plant via phytohormone signalling.

Camalexin accumulation as a component of plant immunity during interactions with pathogens and beneficial microbes.

MAIN CONCLUSION: This review provides an overview on the role of camalexin in plant immunity taking into account various plant-pathogen and beneficial microbe interactions, regulation mechanisms and the contribution in basal and induced plant resistance. In a hostile environment, plants evolve complex and sophisticated defense mechanisms to counteract invading pathogens and herbivores. Several lines of evidence support the assumption that secondary metabolites like phytoalexins which are synthesized de novo, play an important role in plant defenses and contribute to pathogens' resistance in a wide variety of plant species. Phytoalexins are synthesized and accumulated in plants upon pathogen challenge, root colonization by beneficial microbes, following treatment with chemical elicitors or in response to abiotic stresses. Their protective properties against pathogens have been reported in various plant species as well as their contribution to human health. Phytoalexins are synthesized through activation of particular sets of genes encoding specific pathways. Camalexin (3'-thiazol-2'-yl-indole) is the primary phytoalexin produced by Arabidopsis thaliana after microbial infection or abiotic elicitation and an iconic representative of the indole phytoalexin family. The synthesis of camalexin is an integral part of cruciferous plant defense mechanisms. Although the pathway leading to camalexin has been largely elucidated, the regulatory networks that control the induction of its biosynthetic steps by pathogens with different lifestyles or by beneficial microbes remain mostly unknown. This review thus presents current knowledge regarding camalexin biosynthesis induction during plant-pathogen and beneficial microbe interactions as well as in response to microbial compounds and provides an overview on its regulation and interplay with signaling pathways. The contribution of camalexin to basal and induced plant resistance and its detoxification by some pathogens to overcome host resistance are also discussed.

Mitigating abiotic stress: microbiome engineering for improving agricultural production and environmental sustainability.

MAIN CONCLUSION: The responses of plants to different abiotic stresses and mechanisms involved in their mitigation are discussed. Production of osmoprotectants, antioxidants, enzymes and other metabolites by beneficial microorganisms and their bioengineering ameliorates environmental stresses to improve food production. Progressive intensification of global agriculture, injudicious use of agrochemicals and change in climate conditions have deteriorated soil health, diminished the microbial biodiversity and resulted in environment pollution along with increase in biotic and abiotic stresses. Extreme weather conditions and erratic rains have further imposed additional stress for the growth and development of plants. Dominant abiotic stresses comprise drought, temperature, increased salinity, acidity, metal toxicity and nutrient starvation in soil, which severely limit crop production. For promoting sustainable crop production in environmentally challenging environments, use of beneficial microbes has emerged as a safer and sustainable means for mitigation of abiotic stresses resulting in improved crop productivity. These stress-tolerant microorganisms play an effective role against abiotic stresses by enhancing the antioxidant potential, improving nutrient acquisition, regulating the production of plant hormones, ACC deaminase, siderophore and exopolysaccharides and accumulating osmoprotectants and, thus, stimulating plant biomass and crop yield. In addition, bioengineering of beneficial microorganisms provides an innovative approach to enhance stress tolerance in plants. The use of genetically engineered stress-tolerant microbes as inoculants of crop plants may facilitate their use for enhanced nutrient cycling along with amelioration of abiotic stresses to improve food production for the ever-increasing population. In this chapter, an overview is provided about the current understanding of plant-bacterial interactions that help in alleviating abiotic stress in different crop systems in the face of climate change. This review largely focuses on the importance and need of sustainable and environmentally friendly approaches using beneficial microbes for ameliorating the environmental stresses in our agricultural systems.

A balanced gut microbiota is essential to maintain health in captive sika deer.

Certain animals harbor a high proportion of pathogens, particular the zoonotic pathogens, in their gut microbiome but are usually asymptomic; however, their carried pathogens may seriously threaten the public health. By understanding how the microbiome overcomes the negative effects of pathogens to maintain host health, we can develop novel solutions to control animal-mediated pathogen transmission including identification and application of beneficial microbes. Here, we analyzed the gut microbiota of 10 asymptomic captive sika deer individuals by full-length 16S rDNA sequencing. Twenty-nine known pathogens capable of infecting humans were identified, and the accumulated proportions of the identified pathogens were highly variable among individuals (2.33 to 39.94%). The relative abundances of several beneficial bacteria, including Lactobacillus and Bifidobacterium, were found to be positively correlated with the relative abundances of accumulated pathogens. Whole-genome metagenomic analysis revealed that the beneficial- and pathogenic-associated functions, such as genes involved in the synthesis of short chain fatty acids and virulence factors, were also positively correlated in the microbiome, indicating that the beneficial and pathogenic functions were maintained at a relatively balanced ratio. Furthermore, the bacteriophages that target the identified pathogens were found to be positively correlated with the pathogenic content in the microbiome. Several high-quality genomes of beneficial bacteria affiliated with Lactobacillus and Bifidobacterium and bacteriophages were recovered from the metagenomic data. Overall, this study provides novel insights into the interplay between beneficial and pathogenic content to ensure maintenance of a healthy gut microbiome, and also contributes to discovery of novel beneficial microbes and functions that control pathogens. KEY POINTS: • Certain asymptomic captive sika deer individuals harbor relatively high amounts of zoonotic pathogens. • The beneficial microbes and the beneficial functions are balanced with the pathogenic contents in the gut microbiome. • Several high-quality genomes of beneficial bacteria and bacteriophages are recovered by metagenomics.

Plant growth-promoting microbes improve stormwater retention of a newly-built vertical greenery system.

On-site decentralized urban stormwater management has gained significant momentum in urban planning. Recently, vegetated roofs have been recommended as a viable decentralized stormwater management system and nature-based solution to meet the challenge of urban floods. However, as another type of unconventional green infrastructure, vertical greenery systems (VGS), also known as vegetated facades, have received much less research attention. Even though some researchers suggest that stormwater management by VGS is comparable to that of vegetated roofs, empirical evidence to substantiate this claim is limited. In this study, we conducted rain simulations on newly-built vegetation containers with water storage compartments. These vegetation containers were designed to be incorporated into a VGS specifically for stormwater management. We tested variables that could influence water retention efficiency and evapotranspiration of the containers under field conditions, i.e., inoculation of plant growth-promoting microbes (PGPMs) (Rhizophagus irregularis and Bacillus amyloliquefaciens), different substrate types (sandy loam and reed-based substrate), simulated rain quantity, natural precipitation, substrate moisture, and air temperature. The inoculation of PGPMs significantly reduced runoff quantity from the vegetation containers. Meanwhile, the well-ventilated sandy-loam substrate significantly reduced the remaining water in the water storage compartments over 1-week periods between rain simulation events, achieving high water-use efficiency. The selected microbes were established successfully in the containers and promoted the growth of 2 out of 5 plant species. R. irregularis colonization responded to substrate type and host plant species, while B. amyloliquefaciens population density in the substrate did not respond to these factors. Environmental conditions, such as antecedent substrate moisture, air temperature, and natural precipitation also influenced the efficiency of stormwater retention and/or evapotranspiration. In conclusion, this study provides instructive and practical insights to reduce urban flood risk by using VGS.

The future of functional food: Emerging technologies application on prebiotics, probiotics and postbiotics.

This review was the first to gather literature about the effect of emerging technologies on probiotic, prebiotic, and postbiotic products. Applying emerging technologies to probiotic products can increase probiotic survival and improve probiotic properties (cholesterol attachment, adhesion to Caco-2 cells, increase angiotensin-converting enzyme (ACE) inhibitory, antioxidant, and antimicrobial activities, and decrease systolic blood pressure). Furthermore, it can optimize the fermentation process, produce or maintain compounds of interest (bacteriocin, oligosaccharides, peptides, phenolic compounds, flavonoids), improve bioactivity (vitamin, aglycones, calcium), and sensory characteristics. Applying emerging technologies to prebiotic products did not result in prebiotic degradation. Still, it contributed to higher concentrations of bioactive compounds (citric and ascorbic acids, anthocyanin, polyphenols, flavonoids) and health properties (antioxidant activity and inhibition of ACE, α-amylase, and α-glucosidase). Emerging technologies may also be applied to obtain postbiotics with increased health effects. In this way, current studies suggest that emerging food processing technologies enhance the efficiency of probiotics and prebiotics in food. The information provided may help food industries to choose a more suitable technology to process their products and provide a basis for the most used process parameters. Furthermore, the current gaps are discussed. Emerging technologies may be used to process food products resulting in increased probiotic functionality, prebiotic stability, and higher concentrations of bioactive compounds. In addition, they can be used to obtain postbiotic products with improved health effects compared to the conventional heat treatment.

Sinorhizobium meliloti succinylated high-molecular-weight succinoglycan and the Medicago truncatula LysM receptor-like kinase MtLYK10 participate independently in symbiotic infection.

The formation of nitrogen-fixing nodules on legume hosts is a finely tuned process involving many components of both symbiotic partners. Production of the exopolysaccharide succinoglycan by the nitrogen-fixing bacterium Sinorhizobium meliloti 1021 is needed for an effective symbiosis with Medicago spp., and the succinyl modification to this polysaccharide is critical. However, it is not known when succinoglycan intervenes in the symbiotic process, and it is not known whether the plant lysin-motif receptor-like kinase MtLYK10 intervenes in recognition of succinoglycan, as might be inferred from work on the Lotus japonicus MtLYK10 ortholog, LjEPR3. We studied the symbiotic infection phenotypes of S. meliloti mutants deficient in succinoglycan production or producing modified succinoglycan, in wild-type Medicago truncatula plants and in Mtlyk10 mutant plants. On wild-type plants, S. meliloti strains producing no succinoglycan or only unsuccinylated succinoglycan still induced nodule primordia and epidermal infections, but further progression of the symbiotic process was blocked. These S. meliloti mutants induced a more severe infection phenotype on Mtlyk10 mutant plants. Nodulation by succinoglycan-defective strains was achieved by in trans rescue with a Nod factor-deficient S. meliloti mutant. While the Nod factor-deficient strain was always more abundant inside nodules, the succinoglycan-deficient strain was more efficient than the strain producing only unsuccinylated succinoglycan. Together, these data show that succinylated succinoglycan is essential for infection thread formation in M. truncatula, and that MtLYK10 plays an important, but different role in this symbiotic process. These data also suggest that succinoglycan is more important than Nod factors for bacterial survival inside nodules.

Biological and biorational management of blast diseases in cereals caused by Magnaporthe oryzae.

Blast diseases, caused by the fungal pathogen Magnaporthe oryzae, are among the most destructive diseases that occur on at least 50 species of grasses, including cultivated cereals wheat, and rice. Although fungicidal control of blast diseases has widely been researched, development of resistance of the pathogen against commercially available products makes this approach unreliable. Novel approaches such as the application of biopesticides against the blast fungus are needed for sustainable management of this economically important disease. Antagonistic microorganisms, such as fungi and probiotic bacteria from diverse taxonomic genera were found to suppress blast fungi both in vitro and in vivo. Various classes of secondary metabolites, such as alkaloids, phenolics, and terpenoids of plant and microbial origin significantly inhibit fungal growth and may also be effective in managing blast diseases. Common modes of action of microbial biocontrol agents include: antibiosis, production of lytic enzymes, induction of systemic resistance in host plant, and competition for nutrients or space. However, the precise mechanism of biocontrol of the blast fungus by antagonistic microorganisms and/or their bioactive secondary metabolites is not well understood. Commercial formulations of biocontrol agents and bioactive natural products could be cost-effective and sustainable but their availability at this time is extremely limited. This review updates our knowledge on the infection pathway of the wheat blast fungus, catalogs naturally occurring biocontrol agents that may be effective against blast diseases, and discusses their role in sustainable management of the disease.

The endosphere microbial communities, a great promise in agriculture.

Agricultural food production and sustainability need intensification to address the current global food supply to meet human demand. The continuous human population increase and other anthropogenic activities threaten food security. Agrochemical inputs have long been used in conventional agricultural systems to boost crop productivity, but they are disadvantageous to a safe environment. Towards developing environmentally friendly agriculture, efforts are being directed in exploring biological resources from soil and plant microbes. The survival of the rhizosphere and endosphere microbiota is influenced by biotic and abiotic factors. Plant microbiota live interdependently with the host plants. Endophytes are regarded as colonizer microbes inhabiting and establishing microbial communities within the plant tissue. Their activities are varied and include fixing atmospheric nitrogen, solubilizing phosphate, synthesis of siderophores, secretion of metabolite-like compounds containing active biocontrol agents in the control of phytopathogens, and induced systemic resistance that stimulates plant response to withstand stress. Exploring beneficial endophyte resources in the formulation of bio-inoculants, such as biofertilizers, as an alternative to agrochemicals (fertilizers and pesticides) in developing environmentally friendly agriculture and for incorporation into crop breeding and disease control program is promising. Therefore, in this review, endosphere microbial ecology, associating environmental factors, and their roles that contribute to their effectiveness in promoting plant growth for maximum agricultural crop productivity were highlighted.

Insights into the Role of the Fungal Community in Variations of the Antibiotic Resistome in the Soil Collembolan Gut Microbiome.

Fertilization is known to affect antibiotic-resistance gene (ARG) patterns in the soil, even in the gut of soil fauna. Here, we conducted a microcosm experiment to investigate differences of effects of different fertilizers on collembolan gut ARG profiles and to further explore the microecological mechanisms that cause the differences. Although fertilization increased the abundance of ARGs, compared with the conventional manure, the application of antibiotic-reduced manure and vermicompost all curbed the enrichment of ARGs in the gut of collembolans. The results of the structural equation model revealed that changes in the microbial community caused by fertilizations have an important contribution to variations in the ARGs. We further found that the fungal community, like bacterial community, is also an important driver of ARG patterns in the collembolan gut. The fungi belonging to Dokmaia and Talaromyces were significantly correlated with the ARGs in the gut of collembolans. In addition, the application of vermicompost significantly increased the abundance of agricultural beneficial microbes in the soil environment. Together, our results provide an insight into the role of the fungal community on ARG patterns in the soil collembolan gut microbiome and highlight environmental friendliness of vermicomposting.

Wheat-durum pasta added of inactivated Bifidobacterium animalis decreases glucose and total cholesterol levels and modulates gut microbiota in healthy rats.

This study investigated the effects of consumption of wheat-durum pasta added of Bifidobacterium animalis inactivated by gamma-irradiation (paraprobiotic) on health and gut microbiota of rats. Twenty-one male rats were divided into three groups as follow: control (Control) receiving standard diet; pasta control (PC) receiving diet containing pasta, and paraprobiotic pasta Bifidobacterium-irradiated (PPBI), receiving paraprobiotic pasta. The serum levels of glucose and total cholesterol were reduced (p < 0.05) in PPBI when compared to the Control (p < 0.05). PPBI showed high abundance (p ˂ 0.05) of Firmicutes and Actinobacteria and a lower abundance of Bacteriodes compared to Control and PC. Besides, the PPBI showed high abundance (p ˂ 0.05) of Clostridiales, Lactobacillales; Bifidobacteriales, Bacillales, and Coriobacteriales in comparison to Control. Specific genera such as Bifibacterium, Lactobacillus, Ruminococcus, Allobaculum, and Blautia were more related to PPBI. Findings reveal wheat-durum pasta as a potential vehicle for delivering paraprobiotics B. animalis.

Effects of Abiotic Stress on Soil Microbiome.

Rhizospheric organisms have a unique manner of existence since many factors can influence the shape of the microbiome. As we all know, harnessing the interaction between soil microbes and plants is critical for sustainable agriculture and ecosystems. We can achieve sustainable agricultural practice by incorporating plant-microbiome interaction as a positive technology. The contribution of this interaction has piqued the interest of experts, who plan to do more research using beneficial microorganism in order to accomplish this vision. Plants engage in a wide range of interrelationship with soil microorganism, spanning the entire spectrum of ecological potential which can be mutualistic, commensal, neutral, exploitative, or competitive. Mutualistic microorganism found in plant-associated microbial communities assist their host in a number of ways. Many studies have demonstrated that the soil microbiome may provide significant advantages to the host plant. However, various soil conditions (pH, temperature, oxygen, physics-chemistry and moisture), soil environments (drought, submergence, metal toxicity and salinity), plant types/genotype, and agricultural practices may result in distinct microbial composition and characteristics, as well as its mechanism to promote plant development and defence against all these stressors. In this paper, we provide an in-depth overview of how the above factors are able to affect the soil microbial structure and communities and change above and below ground interactions. Future prospects will also be discussed.

Beneficial soil-borne bacteria and fungi: a promising way to improve plant nitrogen acquisition.

Nitrogen (N) is an essential element for plant productivity, thus, it is abundantly applied to the soil in the form of organic or chemical fertilizers that have negative impacts on the environment. Exploiting the potential of beneficial microbes and identifying crop genotypes that can capitalize on symbiotic associations may be possible ways to significantly reduce the use of N fertilizers. The best-known example of symbiotic association that can reduce the use of N fertilizers is the N2-fixing rhizobial bacteria and legumes. Bacterial taxa other than rhizobial species can develop associative symbiotic interactions with plants and also fix N. These include bacteria of the genera Azospirillum, Azotobacter, and Bacillus, some of which are commercialized as bio-inoculants. Arbuscular mycorrhizal fungi are other microorganisms that can develop symbiotic associations with most terrestrial plants, favoring access to nutrients in a larger soil volume through their extraradical mycelium. Using combinations of different beneficial microbial species is a promising strategy to boost plant N acquisition and foster a synergistic beneficial effect between symbiotic microorganisms. Complex biological mechanisms including molecular, metabolic, and physiological processes dictate the establishment and efficiency of such multipartite symbiotic associations. In this review, we present an overview of the current knowledge and future prospects regarding plant N nutrition improvement through the use of beneficial bacteria and fungi associated with plants, individually or in combination.

Feeding Honeybee Colonies with Honeybee-Specific Lactic Acid Bacteria (Hbs-LAB) Does Not Affect Colony-Level Hbs-LAB Composition or Paenibacillus larvae Spore Levels, Although American Foulbrood Affected Colonies Harbor a More Diverse Hbs-LAB Community.

The main current methods for controlling American Foulbrood (AFB) in honeybees, caused by the bacterial pathogen Paenibacillus larvae, are enforced incineration or prophylactic antibiotic treatment, neither of which is fully satisfactory. This has led to an increased interest in the natural relationships between the pathogenic and mutualistic microorganisms of the honeybee microbiome, in particular, the antagonistic effects of Honeybee-Specific Lactic Acid Bacteria (hbs-LAB) against P. larvae. We investigated whether supplemental administration of these bacteria affected P. larvae infection at colony level over an entire flowering season. Over the season, the supplements affected neither colony-level hbs-LAB composition nor naturally subclinical or clinical P. larvae spore levels. The composition of hbs-LAB in colonies was, however, more diverse in apiaries with a history of clinical AFB, although this was also unrelated to P. larvae spore levels. During the experiments, we also showed that qPCR could detect a wider range of hbs-LAB, with higher specificity and sensitivity than mass spectrometry. Honeybee colonies are complex super-organisms where social immune defenses, natural homeostatic mechanisms, and microbiome diversity and function play a major role in disease resistance. This means that observations made at the individual bee level cannot be simply extrapolated to infer similar effects at colony level. Although individual laboratory larval assays have clearly demonstrated the antagonistic effects of hbs-LAB on P. larvae infection, the results from the experiments presented here indicate that direct conversion of such practice to colony-level administration of live hbs-LAB is not effective.

Understanding the Plant-microbe Interactions in CRISPR/CAS9 Era: Indeed a Sprinting Start in Marathon.

Plant-microbe interactions can be either beneficial or harmful depending on the nature of the interaction. Multifaceted benefits of plant-associated microbes in crops are well documented. Specifically, the management of plant diseases using beneficial microbes is considered to be eco-friendly and the best alternative for sustainable agriculture. Diseases caused by various phytopathogens are responsible for a significant reduction in crop yield and cause substantial economic losses globally. In an ecosystem, there is always an equally daunting challenge for the establishment of disease and development of resistance by pathogens and plants, respectively. In particular, comprehending the complete view of the complex biological systems of plant-pathogen interactions, co-evolution and plant growth promotions (PGP) at both genetic and molecular levels requires novel approaches to decipher the function of genes involved in their interaction. The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 (CRISPR-associated protein 9) is a fast, emerging, precise, eco-friendly and efficient tool to address the challenges in agriculture and decipher plant-microbe interaction in crops. Nowadays, the CRISPR/CAS9 approach is receiving major attention in the field of functional genomics and crop improvement. Consequently, the present review updates the prevailing knowledge in the deployment of CRISPR/CAS9 techniques to understand plant-microbe interactions, genes edited for the development of fungal, bacterial and viral disease resistance, to elucidate the nodulation processes, plant growth promotion, and future implications in agriculture. Further, CRISPR/CAS9 would be a new tool for the management of plant diseases and increasing productivity for climate resilience farming.

Beneficial effects of Trichoderma secondary metabolites on crops.

Selected microbial strains used as active ingredients of biopesticides for agricultural management practices (e.g., IPM, Integrated Pest Management) are known for their ability to control phytopathogens, promote plant growth, and/or induce disease resistance. Microbes belonging to the Trichoderma genus are considered as an appropriate example of beneficial microbes and are model organisms to study plant-microbe interactions. Several Trichoderma strains are marketed as biocontrol agents and are known to increase plant growth, stress tolerance, and nutrient availability. These effects have sometimes been related to the production of effector metabolites that beneficial microbes produce during the interaction with plant and other microbes. Secondary metabolites (SMs) comprise different classes of natural compounds with low molecular weight and having numerous biological roles, especially in the interactions among organisms. Metabolomic analysis of the interactions between plants, phytopathogens, and beneficial fungi aided in the identification of several bioactive fungal SMs that positively affect plant metabolism. Some of these compounds showed direct activity against phytopathogens, but also increased disease resistance by triggering the plant defence system, and/or enhanced vegetative growth. A new generation of bioformulations based on microbial metabolites and living consortia responsible for the desired beneficial effects on crops may overcome the difficulties associated with the use of a single living microbial strain.