Biological Control Of Diseases Research Articles

Patlıcanda Kurşuni Küf Hastalığı (Botrytis cinerea) Üzerine Bazı Bakteriyel İzolatların in vitro ve in vivo Koşullarda Biyolojik Mücadele Etkinliklerinin Araştırılması

Gray mold agent Botrytis cinerea (teleomorph: Botryotinia fuckliana (de Barry) Whetzel) causes significant yield losses in many economically important vegetables. Chemicals are used in the control to reduce yield loss. As a result of the intensive use of chemicals in the control of plant diseases, human health and the environment are adversely affected. Therefore, interest in environmentally friendly control practices has increased recently. One such application is the use of benefical bacteria in the biological control of diseases. In this study; biocontrol potentials of 12 bioagent bacteria strains (1 Bacillus cereus, 2 Bacillus megaterium, 2 Bacillus pumilus, 2 Bacillus subtilis, 1 Bacillus thuringiensis subsp. kurstaki, 1 Paenibacillus polymyxa, 2 Pantoea agglomerans and 1 Pseudomonas fluorescens) have been determined against gray mold disease agent B. cinerea on eggplant in vitro and in vivo. Pseudomonas chlororaphis supsp. aurofaciens and Bacillus amyloliquefaciens, which were the most efficient strains found in vitro conditions, were also effective against B. cinerea in vivo. In conclusion, it was determined that two most effective bacterial strains could be used as a biocontrol agent in the biological control of B. cinerea in eggplant growing.

A Little Helper: Beneficial Bacteria with Growth-Promoting Mechanisms Can Reduce Asian Soybean Rust Severity in a Cell-Free Formulation

Growth-promoting bacteria are already used in sustainable agricultural systems in Brazil. The market is dominated by inoculants and biological pesticides, which do not reach the full potential of this tool in the agricultural sector. This study aimed to evaluate four bacterial strains for the presence of growth promotion mechanisms, as well as the reduction of Asian rust severity in soybean plants and its effects on three antioxidant enzymes during pathogenesis. The plants were treated using the bacterial cells and/or their biosurfactants before inoculation of the pathogen (IOP). Severity was measured based on a diagrammatic scale at 14, 18 and 21 days after IOP, and the activities of the enzymes SOD, CAT, and APX were evaluated 21 days after IOP. Treatments containing only bacterial cells were not efficient in reducing the severity, with losses of leaf area reaching 15%, while the addition of biosurfactants led to a result that is similar to the biofungicide, based on Bacillus subtilis (Serenade®). The presence of direct growth promotion mechanisms can be observed in all isolates, as well as the role of bacterial metabolites, especially lipopeptides, in the biological control of diseases and the modulation of the plant’s immune response.

Approaches for the establishment of optimized co-culture system of multiple Trichoderma strains for culture metabolites highly effective in cucumber growth promotion.

In most cases, co-culture of Trichoderma and other microorganism principally takes advantage of biological control of plant diseases, which is superior to axenic culture. However, the approach to establish the optimal co-culture system of multiple Trichoderma strains was less studied, particularly for high production of microbial metabolites synergistically to promote plant growth and antagonistic activity against pathogens. The inoculation technique, fermentation kinetic modeling and response surface methodology were used to obtain the optimal inoculum sequence, fermentation time and co-culture nutrient formula. It was demonstrated that co-culture metabolites of Trichoderma strains obtained by simultaneous inoculation were more effective than those by sequence inoculation in promoting cucumber seedling growth. Furthermore, the optimal fermentation time was determined at 96–120 h by evaluating fermentation kinetic model, the activities of inhibitory potential of pathogenic Fusarium and cucumber seedling hypocotyl growth. Interestingly, the optimized nutrient formula was set to make co-culture metabolites of Trichoderma strains more effective in the plant growth promotion, which was determined through the assessment of cucumber test-tube plantlet. The components and each concentration in the optimized medium were confirmed at corn flour 16.22 g⋅L–1, potassium hydrogen phosphate 1.13 g⋅L–1, tryptophan 0.154 g⋅L–1, seaweed residue 30 g⋅L–1, ferrous sulfate heptahydrate 1 g⋅L–1 and ammonium sulfate 1.5 g⋅L–1. The hypocotyl length increased in the treatment with co-culture metabolites from the optimal medium by 2.3-fold compared with control. Thus, the results provide an optimal co-culture system of Trichoderma multiple strains aiming to produce high activity of metabolites in plant growth promotion.

(Z)-3-hexenol primes callose deposition against whitefly-mediated begomovirus infection in tomato.

Rapid callose accumulation has been shown to mediate defense in certain plant-virus interactions. Exposure to the green leaf volatile (Z)-3-hexenol (Z-3-HOL) can prime tomato (Solanum lycopersicum) for an enhanced defense against subsequent infection by whitefly-transmitted Tomato yellow leaf curl virus (TYLCV). However, the molecular mechanisms affecting Z-3-HOL-induced resistance are poorly understood. Here, we explored the mechanisms underlying Z-3-HOL-induced resistance against whitefly-transmitted TYLCV infection and the role of callose accumulation during this process. Tomato plants pre-treated with Z-3-HOL displayed callose priming upon whitefly infestation. The callose inhibitor 2-deoxy-d-glucose abolished Z-3-HOL-induced resistance, confirming the importance of callose in this induced resistance. We also found that Z-3-HOL pre-treatment enhanced salicylic acid levels and activated sugar signaling in tomato upon whitefly infestation, which increased the expression of the cell wall invertase gene Lin6 to trigger augmented callose deposition against TYLCV infection resulting from whitefly transmission. Using virus-induced gene silencing, we demonstrated the Lin6 expression is relevant for sugar accumulation mediated callose priming in restricting whitefly-transmitted TYLCV infection in plants that have been pre-treated with Z-3-HOL. Moreover, Lin6 induced the expression of the callose synthase gene Cals12, which is also required for Z-3-HOL-induced resistance of tomato against whitefly-transmitted TYLCV infection. These findings highlight the importance of sugar signaling in the priming of callose as a defense mechanism in Z-3-HOL-induced resistance of tomato against whitefly-transmitted TYLCV infection. The results will also increase our understanding of defense priming can be useful for the biological control of viral diseases.

Inhibition of the Growth and Development of Potato Early Blight Pathogen (Alternaria solani) by Combining Penicillium chrysogenum VKM F-4876D with Some Strobilurin-, Triazole-, and Phenylpyrrole-Based Fungicides

The biological control of fungal crop diseases based on the use of micro-organisms or their metabolites is a promising environmentally friendly alternative to common fungicide-based technologies. Penicillium fungi which synthesize various biologically active compounds with a wide range of antimicrobial activity are of special interest as potential producers of antifungal biopreparations. The purpose of this study was the evaluation of the antifungal activity of a dry biomass of the Penicillium chrysogenum VKPM F-4876D strain (DMP), both individually and combined with commercial azoxystrobin-, fludioxonil-, difenoconazole-, and tebuconazole-based fungicides commonly used to control early blight, towards Alternaria solani, an infectious agent of this potato disease. The study was performed under in vitro (cultivation on solid and liquid media) and in vivo (detached potato leaves) conditions. The cultivation of A. solani on agarized medium supplemented with 5 g/L of DMP caused significant morphological changes in pathogen colonies, whereas 7.5 g/L of DMP resulted in complete suppression of pathogen development. DMP addition to the liquid culture of A. solani significantly increased electrolyte release, i.e., impaired the cell membrane integrity in the pathogen. Combining DMP (1–2 g/L) with fungicides at a dose range of 0.01–10 mg/L resulted in significant in vitro growth inhibition of A. solani. The best result was obtained for the combination of DMP (1 g/L) with fludioxonil (1–5 mg/L) or tebuconazole (10 mg/L): a significant and prolonged antifungal effect (96–97% growth inhibition) was observed during the whole 14-day period of observation. The treatment of detached potato leaves with 1 g/L of DMP prior to artificial infection with A. solani resulted in a four-fold increase in the number of uninfected leaves and a two-fold reduction in the number of severely infected leaves compared to the control. These results demonstrate the possibility to develop an efficient environmentally friendly approach to manage potato early blight and provide prerequisites for the reduction in pesticide load on agrobiocoenoses, thus contributing to the restoration of ecological balance and the prevention of the emergence and spread of resistant pathogen strains.

The long road to a sustainable banana trade

Societal Impact StatementBananas are the world's most popular dessert fruit and a staple starch crop for millions in low‐ and middle‐income countries. The banana export trade that supplies North America, Europe, and other wealthy nations has a history fraught with exploitation and conflict. The price of cheap bananas has been environmental degradation, violence, and poverty. Only recently have efforts to address the power imbalances in this trade been made. Voluntary certification schemes aim to address multiple sustainability issues, while research into biological control, accelerated plant breeding, and efficient irrigation will help prepare the industry for emerging threats from pests, diseases, and climate change.SummaryBananas are the world's favorite dessert fruit, a staple starch crop for millions, and an important source of income for producers across the tropics and subtropics. Bananas evolved and diversified as giant perennial herbs of open habitats within the humid forests of Southeast Asia and West Oceania and were domesticated around 7000 years BP through a series of hybridization events. This review considers the journey from rainforest riversides to intensively managed monoculture plantations, focussing on the Cavendish banana that comprises nearly the entire global export trade. Climate change increasingly threatens economic sustainability in several major producer regions, requiring responses such as efficient irrigation systems to maintain productivity and water security. Pests and diseases are spreading globally and have severe direct impacts on production as well as indirect impacts via harm to ecological and human health caused by pesticides. New pest and disease management methods employing biological controls and enhancing soil health and new plant breeding techniques must be developed and implemented. The banana production and trade system has been characterized by power imbalances between international firms that own plantations and supply the market and the local agricultural workers who cultivate and harvest the fruit. Voluntary certification schemes have been developed to address the numerous environmental, social, and economic sustainability issues faced by the industry. There are indications, from research on biological disease control to new deals on wages and benefits for banana workers, that change is slowly coming to the global banana trade.

Beauty and the pathogens: A leaf-less control presents a better image of Cymbidium orchids defense strategy.

Biological control is a safe way of combating plant diseases using the living organisms. For the precise use of microbial biological control agents, the genetic information on the hypersensitive response (HR), and defense-related gene induction pathways of plants are necessary. Orchids are the most prominent stakeholders of floriculture industry, and owing to their long-awaited flowering pattern, disease control is imperative to allow healthy vegetative growth that spans more than 2 years in most of the orchids. We observed leaf-less flowering in three orchid species (Cymbidium ensifolium, C. goeringii and C. sinense). Using these materials as reference, we performed transcriptome profiling for healthy leaves from non-infected plants to identify genes specifically involved in plant-pathogen interaction pathway. For this pathway, a total of 253 differentially expressed genes (DEGs) were identified in C. ensifolium, 189 DEGs were identified in C. goeringii and 119 DEGs were found in C. sinense. These DEGs were mainly related to bacterial secretion systems, FLS2, CNGCs and EFR, regulating HR, stomatal closure and defense-related gene induction. FLS2 (LRR receptor-like serine/threonine kinase) contained the highest number of DEGs among three orchid species, followed by calmodulin. Highly upregulated gene sets were found in C. sinense as compared to other species. The great deal of DEGs, mainly the FLS2 and EFR families, related to defense and immunity responses can effectively direct the future of biological control of diseases for orchids.

Biological control of fig root rot disease

The study aimed to isolate and diagnose pathogens of fig root rot disease in addition to evaluation effect of the biological control agents Trichoderma harzianum and Penicillium cyclpium in control of the pathogens of fig root rot. It was found fungi accompanying the roots of fig plantlets. Fusarium solani was the most frequent pathogenic fungus, followed by Rhizoctonia solani. The results showed a high effectiveness of biological agents in inhibiting the growth of pathogenic fungi, as the percentage of inhibition of the fungus T. harzianum against the fungus F. solani reached 100%. The percentage of inhibition against the pathogenic fungus R.solani was 89.99%. As for the bioagent P. cyclopium, the results displayed its high antagonistic ability against the two pathogenic fungi. As well as, the test results revealed the antagonistic ability of the microorganism EM-1 formula against the pathogenic fungi F.solani and R.solani that cause the root rot disease of fig plantlets.

Biological Control of Oomycete Soilborne Diseases Caused by Phytophthora capsici, Phytophthora infestans, and Phytophthora nicotianae in Solanaceous Crops

Oomycete pathogens that belong to the genus Phytophthora cause devastating diseases in solanaceous crops such as pepper, potato, and tobacco, resulting in crop production losses worldwide. Although the application of fungicides efficiently controls these diseases, it has been shown to trigger negative side effects such as environmental pollution, phytotoxicity, and fungicide resistance in plant pathogens. Therefore, biological control of Phytophthora-induced diseases was proposed as an environmentally sound alternative to conventional chemical control. In this review, progress on biological control of the soilborne oomycete plant pathogens, Phytophthora capsici, Phytophthora infestans, and Phytophthora nicotianae, infecting pepper, potato, and tobacco is described. Bacterial (e.g., Acinetobacter, Bacillus, Chryseobacterium, Paenibacillus, Pseudomonas, and Streptomyces) and fungal (e.g., Trichoderma and arbuscular mycorrhizal fungi) agents, and yeasts (e.g., Aureobasidium, Curvibasidium, and Metschnikowia) have been reported as successful biocontrol agents of Phytophthora pathogens. These microorganisms antagonize Phytophthora spp. via antimicrobial compounds with inhibitory activities against mycelial growth, sporulation, and zoospore germination. They also trigger plant immunity-inducing systemic resistance via several pathways, resulting in enhanced defense responses in their hosts. Along with plant protection, some of the microorganisms promote plant growth, thereby enhancing their beneficial relations with host plants. Although the beneficial effects of the biocontrol microorganisms are acceptable, single applications of antagonistic microorganisms tend to lack consistent efficacy compared with chemical analogues. Therefore, strategies to improve the biocontrol performance of these prominent antagonists are also discussed in this review.

Acremonium variecolor strain 130360 VS Trichoderma harzianum STRAIN MGQ2 IN BIOCONTROL: AN OVERVIEW OF FUNGAL ANTAGONIST APPLIED AGAINST FUNGAL PATHOGEN Fusarium oxysporum, A CAUSE OF MOLER’S DISEASE IN SHALLOT

One of the common diseases of shallot is moler disease, caused by Fusarium oxysporum. This disease causes some damage to the plant. The attack mechanism of Fusarium oxysporum is by penetrating, colonizing, and multiplying in the root area, then parasitizing and inhibiting the process of carrying water to whole parts of the plant. Biological control of moler diseases using fungal antagonist has developed considerably in recent years. Fungal antagonists play a significant role in controlling plant pathogens and moler diseases caused by Fusarium oxysporum, such as Trichoderma harzianum and Acremonium variecolor. A series of experiments in field conducted to assess the comparison of ability between Trichoderma harzianum strain MGQ2 and Acremonium variecolor strain 130360 in effectively controling moler in shallot.

Differential response of chili pepper genotypes to single and combined association with the mycorrhizal fungus Rhizophagus irregularis and the root pathogen Phytophthora capsici

Chili pepper (Capsicum annuum L.) is an important horticultural crop in Mexico in terms of both diet and culture. However, chili pepper production is associated with excessive use of agrochemicals both pesticides and mineral fertilizers causing adverse environmental and human health problems. Hence, alternative biological disease control measures and crop nutrition strategies are needed. Arbuscular mycorrhizal fungi (AMF) that naturally associate with roots of most crop plants including chili pepper are known to promote plant nutrition and root health, represent a biological alternative to reduce the use of agrochemicals in chili pepper production.In three greenhouse pot experiments, we examined the response of five chili pepper genotypes to single and combined inoculation with the AMF Rhizophagus irregularis and the root pathogen P. capsici in terms of plant growth response and root disease development. Main results showed that inoculation with R. irregularis caused differential plant growth promotion in the five chili pepper genotypes examined, but had no effect on the disease development caused by P. capsici. Single inoculation with P. capsici resulted in differential root disease development in the chili pepper genotypes. Most interesting, a Chilaca landrace genotype not only showed resistance against P. capsici, but on the contrary also resulted in plant growth promotion. In conclusion, our work show that the examined chili pepper genotypes responded differentially to single inoculation with R. irregularis and P. capsici, but dual inoculation had no effect on the level of root disease caused by P. capsici. The observed resistance to P. capsici in the Chilaca landrace could be a source of resistance to the pathogen in plant breeding programs and used directly by chili pepper growers that could also benefit from pre-inoculating chili pepper transplants with AMF before planting in terms of plant growth promotion.

Taguchi Grey Relational Analysis for Multi-Response Optimization of Bacillus Bacteria Flocculation Recovery from Fermented Broth by Chitosan to Enhance Biocontrol Efficiency.

Degradation of environment is a challenge to crop production around the world. Biological control of various plant diseases using antagonistic bacteria is an encouraging alternative to traditionally used chemical control strategies. Chitosan as a well-known natural flocculation agent also exhibits antimicrobial activity. The goal of this study was to investigate a dual nature of chitosan in flocculation of Bacillus sp. BioSol021 cultivation broth intended for biocontrol applications. Experiments were performed based on L18 standard Taguchi orthogonal array design with five input parameters (chitosan type and dosage, pH value, rapid and slow mixing rates). In this study, the grey relational analysis was used to perform multi-objective optimization of the chosen responses, i.e., flocculation efficiency and four inhibition zone diameters against the selected phytopathogens. The results have indicated a great potential of a highly efficient method for removal of the Bacillus bacteria from the cultivation broth using chitosan. The good flocculation efficiency and high precipitate antimicrobial activity against the selected phytopathogens were achieved. It has been shown that multiple flocculation performance parameters were improved, resulting in slightly improved response values.

Potential for Biological Control of Pythium schmitthenneri Root Rot Disease of Olive Trees (Olea europaea L.) by Antagonistic Bacteria.

Several diseases affect the productivity of olive trees, including root rot disease caused by Pythium genera. Chemical fungicides, which are often used to manage this disease, have harmful side effects on humans as well as environmental components. Biological management is a promising control approach that has shown its great potential as an efficient eco-friendly alternative to treating root rot diseases. In the present study, the antagonistic activity of ten bacterial isolates was tested both in vitro and in planta against Pythium schmitthenneri, the causal agent of olive root rot disease. These bacterial isolates belonging to the genera Alcaligenes, Pantoea, Bacillus, Sphingobacterium, and Stenotrophomonas were chosen for their potential antimicrobial effects against many pathogens. Results of the in vitro confrontation bioassay revealed a high reduction of mycelial growth exceeding 80%. The antifungal effect of the volatile organic compounds (VOCs) was observed for all the isolates, with mycelial inhibition rates ranging from 28.37 to 70.32%. Likewise, the bacterial cell-free filtrates showed important inhibition of the mycelial growth of the pathogen. Overall, their efficacy was substantially affected by the nature of the bacterial strains and their modes of action. A greenhouse test was then carried out to validate the in vitro results. Interestingly, two bacterial isolates, Alcaligenes faecalis ACBC1 and Bacillus amyloliquefaciens SF14, were the most successful in managing the disease. Our findings suggested that these two antagonistic bacterial isolates have promising potential as biocontrol agents of olive root rot disease.

Uptake and transport of antibiotic kasugamycin in castor bean (Ricinus communis L.) seedlings.

Kasugamycin (KSM), an aminoglycoside antibiotic, has been widely used for the management of plant diseases, especially for the control of rice blast in Asia. However, its uptake mechanism and transport in plants are still obscure. The castor bean (Ricinus communis L.) seeding, a model plant for phloem transport, was used to study the mechanism of uptake and transport of KSM. Results showed that cotyledon-applied KSM could transport into the phloem and distributed in root and shoot of plant. The temperature, concentration, and pH had significant effects on the uptake of KSM, indicating that the uptake of KSM was mediated by an active carrier system. Compared with the control, competitive inhibitors of sugar transporters D-glucose, D-chiro-inositol, and phloridzin inhibited 71.03%, 67.95%, and 61.73% uptake of KSM, respectively. Energy inhibitor dinitrophenol (DNP) and carbonyl cyanide chlorophenylhydrazone (CCCP) also affected the uptake of KSM, and the inhibition rates were 34.23% and 48.06%. All the results showed that the uptake of KSM was mediated by a sugar transporter, and it could transport from shoot to root in plants via the phloem. The study preliminary elucidated the plant–microbe interactions in the context of the transport of microbial secondary metabolites in plants. It has certain significance for scientific application of antibiotics and biological control of plant diseases and provides theoretical basis for the development of bidirectional transport pesticides.

The hunt for beneficial fungi for tomato crop improvement – Advantages and perspectives

Beneficial fungi with antagonistic and entomopathogenic properties have shown promising effect in the biological control of diseases and pests in a variety of commercially significant crops, including tomato, in recent years. Despite the fact that such treatments are environmentally safe, their risk on non-target species in tomato fields remains unknown. Beneficial fungi that have been commercialised for field use have had little effects on the population of arthropod pests and the incidence of diseases in tomato fields due to various reasons. The use of fungal antagonists and entomopathogenic fungi-based products for the management of diseases and pests of tomato crop has been done all over the world. The investigated reports, however, are scattered throughout the research papers, so they need to be compiled and discussed. Therefore, efficiency of antagonistic and entomopathogenic fungi against important pests and pathogens of tomato crop, as well as their practical use as biofungicides and bioinsecticides to reduce the use of synthetic pesticides, are discussed in this review paper. Besides, plant growth promotion activity of beneficial fungi, their appropriateness as an alternative of synthetic pesticides, and future prospects are also discussed.

Biocontrol potential of Burkholderia sp. BV6 against the rice blast fungus Magnaporthe oryzae.

To investigate the broad-spectrum antifungal activity of Burkholderia sp. BV6, that is isolated from rice roots and its biocontrol potential against rice blast caused by Magnaporthe oryzae. We evaluated the ability to isolate BV6 in the biological control of rice blast disease and investigated its antifungal mechanisms. BV6 strongly inhibited the hyphal growth of M. oryzae Guy11 and other plant pathogenic fungi, and pot experiments showed that BV6 significantly decreases the disease index of rice blast from 47.5 to 24.6. The secreted small-molecule secondary metabolites were regarded as weapons during the antifungal process by inhibiting the germination of M. oryzae conidia and mycelial growth, and thereby prevent the following infection. Liquid chromatography-mass spectrometry analysis of the metabolites from the supernatant of isolate BV6 showed that the antifungal weapons of isolate BV6 are novel, small, molecular hydrophilic compounds that are different from reported antifungal compounds. The isolate BV6 inhibits the M. oryzae infection by the production of small-molecule antifungal compounds. The current study discovers the role of the Burkholderia sp. BV6 in the biocontrol of plant pathogenic fungi. Therefore, isolate BV6 is a potential candidate for developing a microbial formulation for the biocontrol of the most common disease of rice blast.

Evaluation of the agronomical performance of five new tomato varieties (Solanum lycopersicum L.) against two pest and disease control treatments in the province of Loja

Tomato is one of the most consumed vegetables, with abundant pests and diseases problems limiting its production. This research had two objectives: in the first one, the morphological characteristics of five different tomato populations, were described; in the second, the yield response of candidate-to-be varieties genotypes was evaluated when submitted to chemical or biological control of pest and diseases that commonly attack the crop. The populations showed distinctive morphological characteristics, fruit firmness, size, and shape. The experimental test results indicated significant differences among varieties and in the interaction of variety x method of control. The control variety showed the lowest yield (28,630 kg·ha-1) when compared to the candidate varieties, especially Variety 2 (66,090 kg·ha-1). Variety 2 (cherry-size-fruit) and Variety 3 (large-size-fruit) should be taken into consideration for large-scale cultivation due to their high yield. Varieties 2 and 3 reacted adequately to both kind of pesticides, with an advantage in yield under chemical control. Nonetheless, the use of chemical products was minimal (3-4 applications were enough), as compared to the high number of applications that are currently used under the traditional tomato cultivation in Ecuador.

Diversity of Endophytic Bacterial Populations in Citrus grandis cv. Tomentosa

It is necessary to understand the microbial interactions with this plant to study the effect of its medicinal quality. In the present study, high-throughput sequencing was used to analyze the diversity of endophytic bacteria on leaves, branches and fruits of C. grandis cv. Tomentosa. This study obtained a total of 607,952 high-quality sequence fragments of the V3-V4 region from nine samples that belonged to three groups, and 382 operational taxonomic units. The diversity of endophytic bacteria is high while occurrence was different in fruits, branches and leaves. There were 191 OTUs in the three groups. Candidatus Liberibacter was the most abundant class in branches and fruits, while the dominant population of leaves was Massilia. The 16S rRNA function prediction was taken to understand the function of C. grandis cv. Tomentosa. All results not only have reference signifi cance for the functional study of endophytic fungi and the utilization of endophytic fungi, but also have reference signifi cance for the biological control of plant diseases on C. grandis cv. Tomentosa.

Bacillus velezensis SYL-3 suppresses Alternaria alternata and tobacco mosaic virus infecting Nicotiana tabacum by regulating the phyllosphere microbial community.

The occurrence of plant diseases is closely associated with the imbalance of plant tissue microecological environment. The regulation of the phyllosphere microbial communities has become a new and alternative approach to the biological control of foliar diseases. In this study, Bacillus velezensis SYL-3 isolated from Luzhou exhibited an effective inhibitory effect against Alternaria alternata and tobacco mosaic virus (TMV). The analysis of phyllosphere microbiome by PacBio sequencing indicated that SYL-3 treatment significantly altered fungal and bacterial communities on the leaves of Nicotiana tabacum plants and reduced the disease index caused by A. alternata and TMV. Specifically, the abundance of P. seudomo, Sphingomonas, Massilia, and Cladosporium in the SYL-3 treatment group increased by 19.00, 9.49, 3.34, and 12.29%, respectively, while the abundances of Pantoea, Enterobacter, Sampaiozyma, and Rachicladosporium were reduced. Moreover, the abundance of beneficial bacteria, such as Pseudomonas and Sphingomonas, was negatively correlated with the disease indexes of A. alternata and TMV. The PICRUSt data also predicted the composition of functional genes, with significant differences being apparent between SYL-3 and the control treatment group. Further functional analysis of the microbiome also showed that SYL-3 may induce host disease resistance by motivating host defense-related pathways. These results collectively indicate that SYL-3 may suppress disease progression caused by A. alternata or TMV by improving the microbial community composition on tobacco leaves.

Potential Role of Biocontrol Agents for Sustainable Management of Fungal Pathogens Causing Canker and Fruit Rot of Pistachio in Italy.

Pistachio (Pistacia vera) is an important Mediterranean crop. In Italy, pistachio is cultivated in the southern regions, of which Sicily is the main production area. Recently, the phytopathological situation of this crop has started to be updated, and new diseases have been discovered, studied, and reported. Botryosphaeriaceae spp. and Leptosillia pistaciae are major canker/rot pathogens, and Cytospora pistaciae and Eutypa lata have been reported as minor canker pathogens. In this paper, we evaluated different biological control agents, belonging to Trichoderma asperellum, T. atroviride and T. harzianum, as well as some Bacillus amyloliquefaciens strains, against above-mentioned pathogens. Results of dual culture assays showed that all the biological products, both fungi and bacteria, were able to inhibit the mycelial growth of the pathogens in vitro. Experiments using detached twigs showed no effect of biocontrol agents in reducing infections, except for Neofusicoccum hellenicum treated with T. harzianum T22 and Leptosillia pistaciae treated with B. amyloliquefaciens D747. Results of detached fruit experiments showed an efficacy ranging from 32.5 to 66.9% of all the biological products in reducing the lesions caused by N. mediterraneum. This study provides basic information for future research on biological control of pistachio diseases and future prospects for search of more effective biological control agents for canker diseases than those studied here.