Control Of Plant Pathogens Research Articles

Phyllosphere symbiont promotes plant growth through ACC deaminase production

Plant growth promoting bacteria can confer resistance to various types of stress and increase agricultural yields. The mechanisms they employ are diverse. One of the most important genes associated with the increase in plant biomass and stress resistance is acdS, which encodes a 1-aminocyclopropane-1-carboxylate- or ACC-deaminase. The non-proteinogenic amino acid ACC is the precursor and means of long-distance transport of ethylene, a plant hormone associated with growth arrest. Expression of acdS reduces stress induced ethylene levels and the enzyme is abundant in rhizosphere colonizers. Whether ACC hydrolysis plays a role in the phyllosphere, both as assembly cue and in growth promotion, remains unclear. Here we show that Paraburkholderia dioscoreae Msb3, a yam phyllosphere symbiont, colonizes the tomato phyllosphere and promotes plant growth by action of its ACC deaminase. We found that acdS is required for improved plant growth but not for efficient leaf colonization. Strain Msb3 readily proliferates on the leaf surface of tomato, only occasionally spreading to the leaf endosphere through stomata. The strain can also colonize the soil or medium around the roots but only spreads into the root if the plant is wounded. Our results indicate that the degradation of ACC is not just an important trait of plant growth promoting rhizobacteria but also one of leaf dwelling phyllosphere bacteria. Manipulation of the leaf microbiota by means of spray inoculation may be more easily achieved than that of the soil. Therefore, the application of ACC deaminase containing bacteria to the phyllosphere may be a promising strategy to increasing plant stress resistance, pathogen control, and harvest yields.

Bacterial Bioprotectants: Biocontrol Traits and Induced Resistance to Phytopathogens

Plant growth and nutrition are adversely affected by various factors such as water stress, high temperature, and plant pathogens. Plant-associated microbes play a vital role in the growth and development of their hosts under biotic and abiotic stresses. The use of a rhizosphere microbiome for plant growth stimulation and the biological control of fungal disease can lead to improved crop productivity. Mechanisms used by plant-growth-promoting rhizobacteria (PGPR) to protect plants from soilborne pathogens include antibiosis, the production of lytic enzymes, indole-3 acetic acid production, decreasing ethylene levels by secreting 1-aminocyclopropane-1-carboxylate deaminase, competition for nutrients and niches, parasitism and induced systemic resistance. In this review, we emphasize the biological control of plant pathogens by root-associated microbes and discuss traits involved in pathogen reduction. Future research should focus on the effect of root exudation on plant–pathogen interactions under various abiotic factors. Moreover, the development of microbial fungicides with longer shelf lives will help farmers to opt for organic agriculture, reducing the use of chemical fertilizers. This trend is expected to drive the adoption of biological control methods in agriculture. The future prospects for the biological control of plant diseases are bright and are expected to play an increasingly important role in sustainable agriculture.

Biological Agent Trichoderma asperellum and Its in Vitro Inhibitory Activity Against Mango Fruit Rot Pathogens

Diseases are one of the major challenges in crop production which can lead to significant economic losses. Ironically, while having multiple negative impacts, synthetic chemical pesticides are considered the main strategy in tackling plant diseases. Trichoderma asperellum is one of the potential fungal species that can inhibit numerous plant diseases. This study reconfirmed the morphological characteristics of Trichoderma isolates obtained and identified it by molecular techniques. In addition, the inhibitory activity of the isolates was tested in vitro against the mango pathogens Colletotrichum asianum and Diaporthe pseudophoenicicola. The results showed that isolate T4 was identified as Trichoderma asperellum. Isolate T4 was able to inhibit C. asianum and D. pseudophoenicicola by 28.19% and 15.64%, respectively. Therefore, this isolate can be used as a biological agent to control plant pathogens in an environmentally friendly, sustainable manner, and as an alternative to synthetic chemical pesticides.

Optimization of amylase production by the biological control agent Bacillus halotolerans RFP74 using response surface methodology

BackgroundOver the years, excessive use of chemical pesticides to control plant pathogens has caused environmental problems. Therefore, biological solutions such as the use of microorganisms with antimicrobial capacity become indispensable. To inhibit the growth of plant pathogens, biological control agents use different mechanisms, including the production of hydrolytic enzymes. In this study, the production of amylase, an enzyme important for the prevention and control of plant diseases, by a biological control agent Bacillus halotolerans RFP74 was optimized using response surface methodology. ResultsBacillus halotolerans RFP74 inhibited the growth of various phytopathogens including Alternaria and Bipolaris with an inhibition rate of more than 60%. In addition, it also demonstrated an essential production of amylase. Based on previous studies of amylase production in Bacillus, three parameters were considered significant: initial pH of the medium, incubation time, and temperature. Using the central composite design with Design Expert software, the optimized amylase production for B.halotolerans RFP74 is at a temperature of 37 °C, incubation time 51 h and pH 6. ConclusionThe biological control agent B.halotolerans RFP74 inhibited the growth of Alternaria and Bipolaris, demonstrating its broad spectrum of activity. Knowledge of the optimal condition required for the production of hydrolytic enzymes such as amylase provides information on the most effective application of this biological control agent.

Pitsubcosides A-L, highly esterified eudesmane sesquiterpenoid glycosides with antibacterial activity from Pittosporum subulisepalum and their mechanism.

Plants from the genus Pittosporum are traditionally used as antibacterial, antifungal and antiviral agents. A bioassay evaluation of the extract of Pittosporum subulisepalum revealed antibacterial activity. This study focused on the discovery of the antibacterial metabolism in P. subulisepalum, as well as the modes of action of its active components. A chemical investigation of an ethyl acetate (EtOAc) extract of the aerial parts of P. subulisepalum led to the isolation of 12 previously undescribed eudesmane sesquiterpenoid glycoside esters (ESGEs), pitsubcosides A-L (1-12). Their structures were elucidated by extensive spectroscopic analysis, including one- and two-dimensional NMR, high-resolution electrospray ionization mass spectrometry, electronic circular dichroism spectra and single-crystal X-ray crystallography analysis or by comparing with authentic samples. The new ESGEs were characterized by their highly esterified glycoside moieties. Among them, compounds 1-3, 5 and 8 showed a moderate inhibitory effect against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Bacillus cereus, Bacillus subtilis, Pseudomonas syringae pv. actinidiae (Psa) and Erwinia carotovora with minimum inhibitory concentrations (MICs) ranging from 3.13 to 100 μm. Among them, compounds 3 and 5 showed remarkable antibacterial activity against S. aureus and Psa with MIC values of 6.25 and 3.13 μm, respectively. Live bacterial mass and the biofilms of S. aureus and Psa were quantified using methyl tetrazolium and crystal violet assays. Fluorescence microscopy and scanning electron microscopy experiments revealed an antibacterial mechanism of cell membrane architectural disruption. The results suggest that ESGEs possess great potential for the development of antibacterial agents to control plant pathogens. © 2023 Society of Chemical Industry.

Differences and biocontrol potential of haustorial endophytic fungi from Taxillus Chinensis on different host plants

BackgroundTo explore the community composition and diversity of the endophytic fungi in Taxillus chinensis, samples of the parasites growing on seven different hosts, Morus alba, Prunus salicina, Phellodendron chinense, Bauhinia purpurea, Dalbergia odorifera, Diospyros kaki and Dimocarpus longan, were isolated. The strains were identified by their morphological characteristics and their internal transcribed spacer (ITS) sequences.Results150 different endophytic fungi were isolated from the haustorial roots of the seven hosts with a total isolation rate of 61.24%. These endophytic fungi were found to belong to 1 phylum, 2 classes, 7 orders, 9 families, 11 genera and 8 species. Among of them, Pestalotiopsis, Neopestalotiopsis and Diaporthe were the dominant genera, accounting for 26.67, 17.33 and 31.33% of the total number of strains, respectively. Diversity and similarity analyses showed that the endophytic fungi isolated from D. longan (H’=1.60) had the highest diversity index. The highest richness indexes were found in M. alba and D. odorifera (both 2.23). The evenness index of D. longan was the highest (0.82). The similarity coefficient of D. odorifera was the most similar to D. longan and M. alba (33.33%), while the similarity coefficient of P. chinense was the lowest (7.69%) with M. alba and D. odorifera. Nine strains showed antimicrobial activities. Among them, Pestalotiopsis sp., N. parvum and H. investiens showed significant antifungal activity against three fungal phytopathogens of medicinal plants. At the same time, the crude extracts from the metabolites of the three endophytic fungi had strong inhibitory effects on the three pathogens. Pestalotiopsis sp., N. parvum and H. investiens had the strongest inhibitory effects of S. cucurbitacearum, with inhibitory rates of 100%, 100% and 81.51%, respectively. In addition, N. parvum had a strong inhibitory effect on D. glomerata and C. cassicola, with inhibitory rates of 82.35% and 72.80%, respectively.ConclusionsThese results indicate that the species composition and diversity of endophytic fungi in the branches of T. chinensis were varied in the different hosts and showed good antimicrobial potential in the control of plant pathogens.

Chitosan Modulates Volatile Organic Compound Emission from the Biocontrol Fungus Pochonia chlamydosporia.

Fungal volatile organic compounds (VOCs) are responsible for fungal odor and play a key role in biological processes and ecological interactions. VOCs represent a promising area of research to find natural metabolites for human exploitation. Pochonia chlamydosporia is a chitosan-resistant nematophagous fungus used in agriculture to control plant pathogens and widely studied in combination with chitosan. The effect of chitosan on the production of VOCs from P. chlamydosporia was analyzed using gas chromatography-mass spectrometry (GC-MS). Several growth stages in rice culture medium and different times of exposure to chitosan in modified Czapek-Dox broth cultures were analyzed. GC-MS analysis resulted in the tentative identification of 25 VOCs in the rice experiment and 19 VOCs in the Czapek-Dox broth cultures. The presence of chitosan in at least one of the experimental conditions resulted in the de novo production of 3-methylbutanoic acid and methyl 2,4-dimethylhexanoate, and oct-1-en-3-ol and tetradec-1-ene in the rice and Czapek-Dox experiments, respectively. Other VOCs changed their abundance because of the effect of chitosan and fungal age. Our findings suggest that chitosan can be used as a modulator of the production of VOCs in P. chlamydosporia and that there is also an effect of fungal age and exposure time.

Management of Fusarium Wilt Disease of Maize (Zea mays L.) with Selected Antimycotic Plant Extracts and Inhibitory Bacillus Strains.

Maize (Zea mays L. var. Everta) is an economically significant crop cultivated worldwide. Unfortunately, microbial diseases, especially, mycopathogens such as Fusarium species, militate against the production of maize. Protective microbial species and bioactive plant extracts have been studied in the control of plant pathogens. However, there is a dearth of information on their comparative efficacy and effect on wilt disease of maize caused by Fusarium solani, as investigated in this study. Using the ITS and 16s rDNA primers for fungal pathogen and bacterial strains, respectively, the mycopathogen was confirmed as Fusarium solani FCI20, while biocontrol Bacillus strains were identified as Bacillus velezensis EBs02 and Bacillus thuringiensis EBs04. Fusarium solani FCI20 successfully infected maize seedlings through rhizosphere inoculation, and caused severe leaf chlorosis, necrosis and wilt in maize seedlings. Bacillus thuringiensis EBs04 expressed the highest in vitro mycelial inhibition (85.20%), followed by Gmelina arborea (78.58%), while Milicia excelsa appeared to express the lowest mycelial inhibition potential (49.95%). Bacillus velezensis EBs02 expressed the highest in vivo disease severity reduction in maize seedlings (with percentage disease control of 84.16), while B. thuringiensis-treated plants had the lowest incidence of wilt disease (4.32%). However, contrary to their in vitro mycelial inhibition potential, B. velezensis EBs02, Gmelina arborea, Milicia excelsa and Cola nitida expressed radically different levels of in vivo wilt disease control in maize seedlings. Consequent upon the biocontrol patterns observed in this study, in vivo assay should be considered in the preliminary selection of promising biocontrol agents against phytopathogens, such as Fusarium species.

The Role of the Residue at Position 2 in the Catalytic Activity of AA9 Lytic Polysaccharide Monooxygenases.

AA9 lytic polysaccharide monooxygenases (LPMOs) are copper-dependent metalloenzymes that play a major role in cellulose degradation and plant infection. Understanding the AA9 LPMO mechanism would facilitate the improvement of plant pathogen control and the industrial application of LPMOs. Herein, via point mutation, we investigated the role of glycine 2 residue in cellulose degradation by Thermoascus aurantiacus AA9 LPMOs (TaAA9). A computational simulation showed that increasing the steric properties of this residue by replacing glycine with threonine or tyrosine altered the H-bonding network of the copper center and copper coordination geometry, decreased the surface charge of the catalytic center, weakened the TaAA9-substrate interaction, and enhanced TaAA9-product binding. Compared with wild-type TaAA9, G2T-TaAA9 and G2Y-TaAA9 variants showed attenuated copper affinity, reduced oxidative product diversity and decreased substrate Avicel binding, as determined using ITC, MALDI-TOF/TOF MS and cellulose binding analyses, respectively. Consistently, the enzymatic activity and synergy with cellulase of the G2T-TaAA9 and G2Y-TaAA9 variants were lower than those of TaAA9. Hence, the investigated residue crucially affects the catalytic activity of AA9 LPMOs, and we propose that the electropositivity of copper may correlate with AA9 LPMO activity. Thus, the relationship among the amino acid at position 2, surface charge and catalytic activity may facilitate an understanding of the proteins in AA9 LPMOs.

The Effect Of Bacillus subtilis Formulation On The Intensity Of Attack Of Bipolaris maydis In Maize (Zea mays L.)

The use of antagonistic microorganisms in controlling plant pathogens is considered an important component in integrated pest control management. The effectiveness of Bacillus subtilis in controlling plant disease-causing pathogens has been widely proven. To simplify application and increase storage time, these bacteria can be formulated in liquid and powder form. This study aims to test the effectiveness of several B. subtilis isolates formulated in powder form to control maize leaf blight. The study was conducted at the Maros Cereal Research Institute. The study was arranged in a completely randomized design consisting of 8 treatments of B. subtilis isolates namely BS-TLB1, BS-BJ6, BS-TM3, BS-TM4, BS -BNt4, BS-BNt5, BS-BNt6, BS-BNt8 and three controls (K1 with the use of synthetic pesticides, K2 with Bipolaris maydis suspension (no formulation) and K3 with no treatment). Parameters observed include the intensity of leaf blight disease which was observed when the plants were 4 MST, 5 MST and 6 MST. The results showed that spraying maize leaves with the B. subtilis formulation had a positive effect on the attack intensity of B. maydis, treatment with BS-BNt4 had the lowest attack intensity, namely 68.00%.

Bio-fabrication of zinc oxide nanoparticles from Picea smithiana and their potential antimicrobial activities against Xanthomonas campestris pv. Vesicatoria and Ralstonia solanacearum causing bacterial leaf spot and bacterial wilt in tomato.

Due to an inevitable disadvantage of chemical or physical synthesis routes, biosynthesis approach to nanoparticles, especially metallic oxide is attractive nowadays. Metallic oxides nanoparticles present a new approach to the control of plant pathogens. ZnO nanoparticles (ZNPs) have very important role in phytopathology. In current study, biosynthesized ZNPs were tested against two devastating bacterial pathogens including Xanthomonas campestris pv. vesicatoria and Ralstonia solanacearum causing bacterial leaf spot and bacterial wilt in tomato. ZNPs were produced using a new extract from the plant Picea smithiana using an environmentally friendly, cost-effective and simple procedure. Zinc acetate was added to P. smithiana extract, stirred and heated to 200°C. The white precipitation at the bottom were clear indication of synthesis of nanoparticles, which were further dried by subjecting them at 450°C. X-ray diffraction pattern determined that the ZNPs had a crystallite size of about 26nm, Fourier transform infrared spectroscopy indicated a peak between 450 and 550cm-1 and the particle size estimated by dynamic light scattering was about 25nm on average. Scanning electron microscopic analysis indicated that the particles were hexagonal in shape 31nm in diameter. Antibacterial tests showed ZNPs synthesized by P. smithiana resulted in clear inhibition zones of 20.1 ± 1.5 and 18.9 ± 1.5mm and 44.74 and 45.63% reduction in disease severity and 78.40 and 80.91% reduction in disease incidence in X. compestris pv. vesicatoria and R. solanacearum respectively at concentration of 100µg/ml. Our findings reveal that the concentration of ZNPs was important for their efficient antibacterial activity. Overall, the biosynthesized ZNPs have been found to have effective antimicrobial activities against bacterial wilt and bacterial leaf spot in tomato.

Bacillus paralicheniformis RP01 Enhances the Expression of Growth-Related Genes in Cotton and Promotes Plant Growth by Altering Microbiota inside and outside the Root.

Plant growth-promoting bacteria (PGPB) can promote plant growth in various ways, allowing PGPB to replace chemical fertilizers to avoid environmental pollution. PGPB is also used for bioremediation and in plant pathogen control. The isolation and evaluation of PGPB are essential not only for practical applications, but also for basic research. Currently, the known PGPB strains are limited, and their functions are not fully understood. Therefore, the growth-promoting mechanism needs to be further explored and improved. The Bacillus paralicheniformis RP01 strain with beneficial growth-promoting activity was screened from the root surface of Brassica chinensis using a phosphate-solubilizing medium. RP01 inoculation significantly increased plant root length and brassinosteroid content and upregulated the expression of growth-related genes. Simultaneously, it increased the number of beneficial bacteria that promoted plant growth and reduced the number of detrimental bacteria. The genome annotation findings also revealed that RP01 possesses a variety of growth-promoting mechanisms and a tremendous growth-promoting potential. This study isolated a highly potential PGPB and elucidated its possible direct and indirect growth-promoting mechanisms. Our study results will help enrich the PGPB library and provide a reference for plant-microbe interactions.

Topical application of coat protein specific dsRNA molecules confers resistance against cognate Potato virus Y (PVY) infecting potato of North-East India

Sustainable agriculture relies on techniques and technology that combine efficiency with the smallest possible ecological and environmental impact. RNA interference (RNAi), a post-transcriptional eukaryotic pathway in eukaryotes can be co-opted for the control of plant pathogens in the topical application system. RNAi is the biological mechanism of mRNA degradation triggered by endogenous or exogenous double-stranded small interfering RNAs (dsRNA/siRNA) and regulates the target gene expression. Topically applied double-stranded RNA (dsRNA) molecules on plants imitate the viral RNA intermediate which is involved in plant virus replication and thereby triggers post-transcriptional gene silencing via., RNAi pathway and reducing viral replication. In this study, a non-transgenic-based RNAi approach was adopted to induce resistance against PVY in potato crop. dsRNA was successfully produced through in vitro transcription and hybridization. To test the effect of dsRNA molecules, in vitro synthesized dsRNA were applied on potato leaves along with PVY. dsRNA-treated plants showed higher resistance to viral disease and exhibited normal growth compared with PVY-treated plants. Therefore, the topical application of dsRNA molecules from the PVY CP gene could serve as a promising method for suppressing PVY infection and ultimately enhancing potato yield.

Research progress of volatile organic compounds produced by plant endophytic bacteria in control of postharvest diseases of fruits and vegetables

Pathogen infestation results in significant losses of fruits and vegetables during handling, transportation, and storage. The use of synthetic fungicides has been a common measure for controlling plant pathogens. However, their excessive use of chemicals has led to increased environmental pollution, leaving large amounts of chemicals in agricultural products, posing a threat to human and animal health. There is now an increasing amount of research activities to explore safer and more innovative ways to control plant pathogens. In this regard, endophytic bacteria contribute significantly. Endophytic bacteria are ubiquitous in the internal tissues of plants without causing damage or disease to the host. Due to their high volatility and difficulties in residue in fruits and vegetables, volatile organic chemicals (VOCs) produced by endophytic bacteria have received a lot of attention in recent years. VOCs are a potential biofumigant for the effective control of postharvest fruits and vegetables diseases. This review focuses mainly on the recent progress in using endophytic bacteria VOCs to control post-harvest fruits and vegetables disease. This review provides a brief overview of the concept, characteristics, and summarises the types, application effect, and control mechanisms of endophytic bacterial VOCs. The research area that is being developed has great application value in agriculture and living practice.

Comparative Analysis of Foliar Diseases of Some Native and Non-Native Tree Species in Belarus and Siberia

Urban green spaces are known to be subjected to additional anthropogenic stress. Using native plants in monoculture, i.e., planting trees of the same species, may favour disease outbreaks and plant death. Non-native plants to be used in large cities for creating sustainable plantations are being searched for worldwide. Meanwhile, it is necessary to control plant pathogens in the variable conditions of the region and natural habitat. In Siberian cities, non-native European trees are used, and non-native Siberian plants are introduced in Belarus. This article reports long-term observations of foliar fungal pathogens attacking 21 woody plants (19 European, 2 Siberian) in Siberian and Belarusian cities. In both regions, 48 leaf fungal pathogens were detected, with powdery mildew fungi predominating in Belarus and leaf spotting fungi prevailing in Siberia. In both research regions, the greatest number of fungal species was found on Syringa vulgaris L. In Siberia, many pathogens were found on the non-native European plant Berberis vulgaris (9 species) and native plant Caragana arborescens Lam. (8 species). We have not detected the pathogens on European plants: Acer campestre L., Acer platanoides L., Euonymus europaeus L., Lonicera caprifolium L. in urban green areas in Siberia, while we have identified one to four foliar fungal pathogens on these plants in Belarus. To sum up: more pathogens were found on native plants in Siberia and Belarus; some leaf pathogen species (Sawadaea tulasnei (Fuckel) Homma, Erysiphe alphitoides (Griffon & Maubl.) U. Braun & S. Takam., Cladosporium syringae (Oudem.) Montem., Erysiphe syringae Schwein., Erysiphe palczewskii (Jacz.) U. Braun & S. Takam.) followed their host plants (Acer tataricum L., Syringa vulgaris L., Caragana arborescens Lam.) when introduced into new areas; and some local pathogens were also observed to spread to the non-native plants of closely related species.

Genome exploration and ecological competence are key to developing effective Pseudomonas-based biocontrol inoculants

Numerous plant-beneficial Pseudomonas strains have been isolated and characterized for their ability to control plant pathogens and the diseases they cause under controlled conditions. Only a few have, however, demonstrated consistent field efficacy. Better exploitation of genomic information and consideration of the ecological competence of strains of interest could help overcome this major inconsistency. In this minireview, we will discuss these two important aspects that we consider crucial in the development of effective Pseudomonas biocontrol inoculants. We will first explore how the increasing availability of genomic data can empower researchers who study Pseudomonas-mediated biocontrol to better understand the mechanisms at play. We will then discuss the key roles played by ecological competence in the successful development of Pseudomonas-based biocontrol inoculants and how researchers can better select ecologically competent strains. A better understanding of these factors could help accelerate the development of effective Pseudomonas inoculants and prevent wasting precious time and resources performing field experiments with strains that have little chance to succeed.

Biocontrol of Diseases Caused by Phytophthora capsici and P. parasitica in Pepper Plants

The main objective of this study was to evaluate the ability of Trichoderma aggressivum f. europaeum, T. longibrachiatum, Paecilomyces variotii, and T. saturnisporum as biological control agents (BCAs) against diseases caused by P. capsici and P. parasitica in pepper. For this purpose, their antagonistic activities were evaluated both in vitro and in vivo. We analysed the expression patterns of five defence related genes, CaBGLU, CaRGA1, CaBPR1, CaPTI1, and CaSAR8.2, in leaves. All BCAs showed a high in vitro antagonistic activity, significantly reducing the mycelial growth of P. capsici and P. parasitica. The treatments with T. aggressivum f. europaeum, T. longibrachiatum, and P. variotii substantially reduced the severity of the disease caused by P. capsici by 54, 76, and 70%, respectively, and of the disease caused by P. parasitica by 66, 55, and 64%, respectively. T. saturnisporum had the lowest values of disease reduction. Reinoculation with the four BCAs increased the control of both plant pathogens. Markedly different expression patterns were observed in the genes CaBGLU, CaRGA1, and CaSAR8.2. Based on the results, all four BCAs under study could be used as a biological alternative to chemicals for the control of P. capsici and P. parasitica in pepper with a high success rate.

Semi-VOCs of Wood Vinegar Display Strong Antifungal Activities against Oomycete Species Globisporangium ultimum and Pythium aphanidermatum

Plant disease outbreaks are increasingly exacerbated by climate change and the conditions of stress combinations. They are negatively affecting crop yield and driving threats to food security in many areas of the world. Although synthetic pesticides offer relative success in the control of pests and plant diseases, they are often overused, and this method faces numerous drawbacks, including environmental toxicity, soil degradation, and adverse effects on human health. Therefore, alternatives are being developed and examined, including the biocontrol of pests and pathogens and biomass pyrolysis leading to wood vinegar that has shown great promise in agriculture and organic farming. However, while wood vinegar use is expanding and allows the control of numerous pests and bacterial and fungal diseases, its application to control oomycete diseases is limited. This study aimed to test wood vinegar for the control of oomycete plant pathogens from which six wood vinegars of pistachio, pomegranate, almond, pine, cypress, and walnut were produced. The inhibitory effects of volatile metabolites (semi-VOCs) of different wood vinegars concentrations (100%, 50%, 25%, 12.5%, and 6.25%) were examined against the hyphal growth of Globisporangium ultimum and Pythium aphanidermatum isolates. An in vitro analysis unambiguously demonstrated that for Globisporangium ultimum, the wood vinegar semi-VOCs of almond, pistachio (C 100% and 50%), and walnut (C 100%) totally inhibited mycelial growth. On the other hand, Pythium aphanidermatum, pistachio (C 100%, 50%, and 25%), and cypress (C 100%) expressed their abilities to completely inhibit the mycelial growth. Other treatments, including relevant concentrations of pine and pomegranate significantly inhibited the growth of mycelia of both species compared to the control (p ≤ 0.05). Therefore, wood vinegar could be considered a natural and organic product to use in agriculture to cope not only against pests, bacterial and fungal pests but also against emerging oomycete plant diseases.

A Novel Based Synthesis of Silver/Silver Chloride Nanoparticles from Stachys emodi Efficiently Controls Erwinia carotovora, the Causal Agent of Blackleg and Soft Rot of Potato.

In recent years, the biological synthesis of silver nanoparticles has captured researchers' attention due to their unique chemical, physical and biological properties. In this study, we report an efficient, nonhazardous, and eco-friendly method for the production of antibacterial silver/silver chloride nanoparticles utilizing the leaf extract of Stachys emodi. The synthesis of se-Ag/AgClNPs was confirmed using UV-visible spectroscopy, DPPH free radical scavenging activity, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). An intense peak absorbance was observed at 437 nm from the UV-visible analysis. The Stachys emodi extract showed the highest DPPH scavenging activity (89.4%). FTIR analysis detected various bands that indicated the presence of important functional groups. The SEM morphological study revealed spherical-shaped nanoparticles having a size ranging from 20 to 70 nm. The XRD pattern showed the formation of a spherical crystal of NPs. The antibacterial activity performed against Erwinia carotovora showed the maximum inhibition by centrifuged silver nanoparticles alone (se-Ag/AgClNPs) and in combination with leaf extract (se-Ag/AgClNPs + LE) and leaf extract (LE) of 98%, 93%, and 62% respectively. These findings suggested that biosynthesized NPs can be used to control plant pathogens effectively.

Detection of azole-resistant Aspergillus fumigatus in the environment from air, plant debris, compost, and soil.

Aspergillus fumigatus is a ubiquitous fungus, a saprophyte of plants, and an opportunistic pathogen of humans. Azole fungicides are used in agriculture to control plant pathogens, and azoles are also used as a first line of treatment for aspergillosis. The continued exposure of A. fumigatus to azoles in the environment has likely led to azole resistance in the clinic where infections result in high levels of mortality. Pan-azole resistance in environmental isolates is most often associated with tandem-repeat (TR) mutations containing 34 or 46 nucleotides in the cyp51A gene. Because the rapid detection of resistance is important for public health, PCR-based techniques have been developed to detect TR mutations in clinical samples. We are interested in identifying agricultural environments conducive to resistance development, but environmental surveillance of resistance has focused on labor-intensive isolation of the fungus followed by screening for resistance. Our goal was to develop assays for the rapid detection of pan-azole-resistant A. fumigatus directly from air, plants, compost, and soil samples. To accomplish this, we optimized DNA extractions for air filters, soil, compost, and plant debris and standardized two nested-PCR assays targeting the TR mutations. Sensitivity and specificity of the assays were tested using A. fumigatus DNA from wild type and TR-based resistant isolates and with soil and air filters spiked with conidia of the same isolates. The nested-PCR assays were sensitive to 5 fg and specific to A. fumigatus without cross-reaction with DNA from other soil microorganisms. Environmental samples from agricultural settings in Georgia, USA were sampled and tested. The TR46 allele was recovered from 30% of samples, including air, soil and plant debris samples from compost, hibiscus and hemp. These assays allow rapid surveillance of resistant isolates directly from environmental samples improving our identification of hotspots of azole-resistant A. fumigatus.