Reduced Pathogen Growth Research Articles

Extracellular plant subtilases dampen cold-shock peptide elicitor levels.

Recognizing pathogen-associated molecular patterns on the cell surface is crucial for plant immunity. The proteinaceous nature of many of these patterns suggests that secreted proteases play important roles in their formation and stability. Here we demonstrate that the apoplastic subtilase SBT5.2a inactivates the immunogenicity of cold-shock proteins (CSPs) of the bacterial plant pathogen Pseudomonas syringae by cleaving within the immunogenic csp22 epitope. Consequently, mutant plants lacking SBT5.2a activity retain higher levels of csp22, leading to enhanced immune responses and reduced pathogen growth. SBT5.2 sensitivity is influenced by sequence variation surrounding the cleavage site and probably extends to CSPs from other bacterial species. These findings suggest that variations in csp22 stability among bacterial pathogens are a crucial factor in plant-bacteria interactions and that pathogens exploit plant proteases to avoid pattern recognition.

Assessing Biofungicides and Host Resistance against Rhizoctonia Large Patch in Zoysiagrass.

Rhizoctonia large patch (Rhizoctonia solani AG2-2 LP) significantly reduces turfgrass quality, aesthetics, and playability. Synthetic fungicides are commonly used for managing this disease, but they present high costs, potential for fungicide resistance, and environmental concerns. We conducted in vitro assays to test the effectiveness of three biofungicides, seven synthetic fungicides, and ten combinations against R. solani. We then assessed seven spray programs that included Bacillus subtilis QST713 and propiconazole, either alone or tank-mixed, on zoysiagrass 'El Toro' in a growth chamber and in field trials. Biofungicide B. subtilis QST713 reduced pathogen growth by up to 100% in vitro. B. subtilis QST713 alone or combined with synthetic fungicides and/or in rotation was as effective as the standalone synthetic fungicide, reducing disease severity and AUDPC by 81 and 77% (growth chamber) and by 71 and 52% (field), respectively, while maintaining acceptable turfgrass quality. Additionally, we screened zoysiagrass genotypes and advanced breeding lines against three R. solani isolates in growth chamber studies. Five genotypes and two breeding lines demonstrated resistance to Rhizoctonia large patch across isolates, highlighting their potential for developing disease-resistant cultivars. Our findings suggest that integrating biofungicides, resistant cultivars with chemical controls offer sustainable and effective strategies for managing Rhizoctonia large patch.

Transcriptome analysis of resistant and susceptible Medicago truncatula genotypes in response to spring black stem and leaf spot disease

Ascochyta blights cause yield losses in all major legume crops. Spring black stem (SBS) and leaf spot disease is a major foliar disease of Medicago truncatula and Medicago sativa (alfalfa) caused by the necrotrophic fungus Ascochyta medicaginicola. This present study sought to identify candidate genes for SBS disease resistance for future functional validation. We employed RNA-seq to profile the transcriptomes of a resistant (HM078) and susceptible (A17) genotype of M. truncatula at 24, 48, and 72 h post inoculation. Preliminary microscopic examination showed reduced pathogen growth on the resistant genotype. In total, 192 and 2,908 differentially expressed genes (DEGs) were observed in the resistant and susceptible genotype, respectively. Functional enrichment analysis revealed the susceptible genotype engaged in processes in the cell periphery and plasma membrane, as well as flavonoid biosynthesis whereas the resistant genotype utilized calcium ion binding, cell wall modifications, and external encapsulating structures. Candidate genes for disease resistance were selected based on the following criteria; among the top ten upregulated or downregulated genes in the resistant genotype, upregulated over time in the resistant genotype, hormone pathway genes, plant disease resistance genes, receptor-like kinases, contrasting expression profiles in QTL for disease resistance, and upregulated genes in enriched pathways. Overall, 22 candidate genes for SBS disease resistance were identified with support from the literature. These genes will be sources for future targeted mutagenesis and candidate gene validation potentially helping to improve disease resistance to this devastating foliar pathogen.

Antimicrobial nature of specific compounds of Ampelomyces quisqualis identified from gas chromatography-mass spectrometry (GCMS) analysis and their mycoparasite nature against powdery mildew of grapes

Grapevine powdery mildew is the world's most important plant disease, and Ampelomyces frequently fight them. While it does not usually cause plant death, its major infections can result in significant production losses and severely impact wine quality. Fungicides are frequently used to control the disease, which can have long-term adverse effects on the ecosystem. As a result, alternative and environmentally friendly disease management approaches must be developed. The study aimed to reduce costly and toxic fungicide use by using Ampelomyces, a natural biofungicide, against various powdery mildew fungi. GC-MS analysis was also used to determine the antagonistic potential and efficacy of volatile organic chemicals produced by several Ampelomyces spp. against Erysiphe necator, which causes powdery mildew of grapes. The molecular characterization of A. quisqualis isolates based on using rDNA ITS region was also carried out and sequenced. GC-MS analysis identified various antimicrobial compounds, such as squalene (4.643%), octadecanoic acid (3.862%), tetradecanoic acid (3.600%), and 9,12-octadecadienoic acid (Z,Z) (1.451%). The least abundant compounds were 2-Hexadecanol, 1-Tricosanol, and 2-propenyl ester, with percentages of 0.485, 0.519, and 0.560, respectively. These bioactive compounds revealed by GC-MS analysis in crude extracts of A. quisqualis had a stronger antifungal and antibacterial activity against E. necator. As a result, using A. quisqualis to control the powdery mildew of grapes significantly reduced pathogen growth and disease incidence.

Efficacy of several species of fungi bioagents and fungicides against <i>Magnaporthe oryzae in vitro</i>

On rice (Oryza sativa L.), more than 70 diseases caused by fungi, bacteria, viruses, and nematodes have been listed. Among them, the blast disease caused by Magnaporthe oryzae B. Couch (syn. Pyricularia oryzae Cavara) seriously threatens global rice production worldwide. Effective management strategies such as the use of resistant cultivars and the application of fungicides individually cannot sustainably contain rice blast disease, because of the emergence of resistance genes and environmental threats. Therefore, applying bioagents to reduce M. oryzae infections, complete other strategies, and reduce pesticide dependence. The present work was carried out to evaluate the potential of not only plant rhizosphere-associated fungi in controlling Magnaporthe oryzae but also the effectiveness of five fungicides in coculture in vitro. Twenty-three biocontrol fungi mainly Trichoderma and Penicillium evaluated on six M. oryzae isolates were found to reduce pathogen growth in dual culture assay. The results obtained highlighted the good ability of bioagents to inhibit the growth of M. oryzae by 82.7 to 97% at 7 days after incubation. In addition, the fungicides tested namely Amistar, Horizon, Opu, Spartaktak, and Signum successfully inhibited the mycelial growth of M. oryzae. The major outcome of our study was evidence that all M. oryzae isolates were susceptible to the fungicides tested through their concentration (ppm) of 50% (EC50). No pathogen isolate was hypersensitive or resistant to fungicides with the EC50 average values of 0.24, 0.25, 0.28, 0.33, and 0.38 mg/l respectively for Spartak, Signum, Horizon, Amistar, and Opus. These good bioagents must be tested on plants in the greenhouse and the best of them could be used in IPM strategy with the combination of resistant cultivars and a reasoned use of fungicides for blast disease control.

Antifungal activity of metabolites from Trichoderma spp. against Fusarium oxysporum

The Trichoderma genus is well known as one of the most valuable biological control agents against several phytopathogens used in different plant species. Managing phytopathogenic fungi using the Trichoderma genus through various associated antifungal mechanisms is a sustainable and eco-friendly strategy that reduces the harmful presence of pathogens in soil, roots and aerial parts of plants. However, using biocontrol agents combined with chemical pesticides has evidenced further potential to reduce pathogen growth and benefit plant development. A better characterization of active metabolites secreted by Trichoderma and their mechanisms of action is necessary to improve its use as a biocontrol agent. This review summarizes current evidence on Trichoderma spp., used as a biocontrol against Fusarium oxysporum, the active secondary metabolites secreted by the former fungi, and the effect of three widely used agrochemicals to control the latter, namely Mancozeb, Chlorothalonil, and Propiconazole. A total of 155 studies were selected and used to extract information that was analyzed, resulting in more than 590 identified secondary metabolites. Fifty-four percent of these have at least one biological function. Results highlight the potential of T. harzianum and T. reesei as biological control agents to control Fusarium oxysporum. The antifungal activity of T. Espirale is associated with enzymatic reactions. Additional findings show that management of diseases caused by F. oxysporum can be combined by using Trichoderma as biological control and agrochemicals to reach: (1) higher access to the different plant tissues; (2) higher degradation of the cell wall; and (3) and activation of oxidative metabolism of Trichoderma. Keywords: Trichoderma, secondary metabolites, fungicide, mycoparasitism, biocontrol, Fusarium oxysporum

Sensitivity of Clarireedia spp. to benzimidazoles and dimethyl inhibitors fungicides and efficacy of biofungicides on dollar spot of warm season turfgrass.

Dollar spot caused by Clarireedia spp. (formerly Sclerotinia homoeocarpa) is an economically destructive fungal disease of turfgrass that can significantly compromise turf quality, playability, and aesthetic value. Fungicides are frequently used to manage the disease but are costly and potentially unfavorable to the environment. Repeated use of some active ingredients has resulted in reduced efficacy on C. jacksonii causing dollar spot in cool-season turfgrasses in the US. Experiments were conducted to study fungicide sensitivity of Clarireedia spp. as well as to develop alternatives to fungicides against dollar spot on warm-season turfgrass in Georgia. First, 79 isolates of Clarireedia spp. collected across the state were tested on fungicide-amended agar plates for their sensitivity to thiophanate-methyl (benzimidazole) and propiconazole (dimethyl inhibitor). Seventy-seven isolates (97.5%) were sensitive (0.001 to 0.654 μg/mL) and two isolates (2.5%) were found resistant (>1000 μg/mL) to thiophanate-methyl. However, in the case of propiconazole, 27 isolates (34.2%) were sensitive (0.005 to 0.098 μg/mL) while 52 isolates (65.8%) were resistant (0.101 to 3.820 μg/mL). Next, the efficacy of three bio- and six synthetic fungicides and ten different combinations were tested in vitro against C. monteithiana. Seven bio- and synthetic fungicide spray programs comprising Bacillus subtilis QST713 and propiconazole were further tested, either alone or in a tank mix in a reduced rate, on dollar spot infected bermudagrass 'TifTuf' in growth chamber and field environments. These fungicides were selected as they were found to significantly reduce pathogen growth up to 100% on in vitro assays. The most effective spray program in growth chamber assays was 100% B. subtilis QST713 in rotation with 75% B. subtilis QST713 + 25% propiconazole tank mix applied every 14 days. However, the stand-alone application of the biofungicide B. subtilis QST713 every seven days was an effective alternative and equally efficacious as propiconazole, suppressing dollar spot severity and AUDPC up to 75%, while resulting in acceptable turf quality (>7.0) in field experiments. Our study suggests that increased resistance of Clarireedia spp. to benzimidazoles and dimethyl inhibitors warrants continuous surveillance and that biofungicides hold promise to complement synthetic fungicides in an efficacious and environmentally friendly disease management program.

Evaluation of Endospore-Forming Bacteria for Suppression of Postharvest Decay of Apple Fruit

The use of microbial biocontrol agents for control of postharvest disease has been the subject of intensive research over the past three decades resulting in commercialization of several biocontrol products. The objective of this research was to test endospore-forming bacteria collected from apple leaves for suppression of bitter rot and blue mold on apple. Bacteria were collected from abandoned, low-input, organic, and conventionally managed orchards in Pennsylvania and were screened for their ability to produce endospores, hydrolyze chitin, reduce pathogen growth in vitro, and suppress postharvest disease in vivo. Several isolates reduced bitter rot lesion size on 'Rome Beauty' from 40-89% compared to untreated controls. Bacillus megaterium isolates, A3-6 and Ae-1, resulted in the greatest suppression of bitter rot lesion size. One isolate, A3-2, suppressed blue mold lesion size. Scanning electron microscopy of inoculated apple wounds suggests parasitism as a mode of action explains the suppression of bitter rot lesion size by isolate A3-6. Of the top seventeen isolates exhibiting biocontrol potential, 70% were collected from abandoned or unmanaged locations. This research demonstrates abandoned apple orchards can be a source of new biocontrol agents for control of postharvest diseases of apple.

Sensitivity of infrared sensor faucet on different skin colours and how it can potentially effect equity in public health

Hand hygiene is essential to human health and day-to-day activities. Maintaining proper hand hygiene can help reduce pathogen growth and transmission of diseases. The automated sensor used for bathroom faucets and soap dispensers can be dated back to the 1950s. These types of fixtures are usually equipped with sensors using a near-infrared beam to detect hands. Its introduction has improved hand hygiene and facilitated good handwashing behaviour. At the same time, disadvantages that come along with advanced technologies should not be neglected, and these disadvantages may lead to inequity in the society.

Essential Oils in Broiler Chicken Production, Immunity and Meat Quality: Review of Thymus vulgaris, Origanum vulgare, and Rosmarinus officinalis

The use of essential oils in animal nutrition has attracted attention as a potential substitute for antibiotic growth promoters in the past twenty-five years. This paper will review the current scientific evidence on the usage of essential oils from Lamiaceae family members such as Thymus vulgaris (thyme), Origanum vulgare (oregano), and Rosmarinus officinalis (rosemary) in broiler nutrition in terms of production results, immunity, and meat quality properties. Essential oils are effective in broiler nutrition when incorporated into the diet on a variety of levels, such as dietary composition, level of feed inclusion, and bird genetics. Moreover, the efficacy of essential oils is influenced by many factors, such as the composition of the oil. Due to big differences in the composition and sources of essential oils, comparing different studies using them can be challenging. Therefore, biological effects may differ significantly. Despite this, a great deal of research supports essential oils’ potential use as natural, antibiotic-free growth promoters for broilers. Growth promotion mechanisms are still not clearly understood as there is limited information on essential oils’ effect on nutrient digestibility, gut function, and the immune system. There is no question that essential oil consumption can reduce pathogen growth in the gut, but their effects on the intricate gut ecosystem as yet remain unclear. This review concludes with further recommendations regarding the application of dietary essential oils in broiler nutrition.

Microbiota from Specific Pathogen-Free Mice Reduces Campylobacter jejuni Chicken Colonization.

Campylobacter jejuni, a prevalent foodborne bacterial pathogen, is mainly transmitted from poultry with few effective prevention approaches. In this study, we aimed to investigate the role of microbiota on C. jejuni chicken colonization. Microbiota from specific pathogen-free (SPF) mouse stools were collected as SPF-Aerobe and SPF-Anaerobe. Birds were colonized with SPF-Aerobe or SPF-Anaerobe at day 0 and infected with C. jejuni AR101 at day 12. Notably, C. jejuni AR101 colonized at 5.3 and 5.6 log10 C. jejuni CFU/g chicken cecal digesta at days 21 and 28, respectively, while both SPF-Aerobe and SPF-Anaerobe microbiota reduced pathogen colonization. Notably, SPF-Aerobe and SPF-Anaerobe increased cecal phylum Bacteroidetes and reduced phylum Firmicutes compared to those in the nontransplanted birds. Interestingly, microbiota from noninfected chickens, SPF-Aerobe, or SPF-Anaerobe inhibited AR101 in vitro growth, whereas microbiota from infected birds alone failed to reduce pathogen growth. The bacterium Enterobacter102 isolated from infected birds transplanted with SPF-Aerobe inhibited AR101 in vitro growth and reduced pathogen gut colonization in chickens. Together, SPF mouse microbiota was able to colonize chicken gut and reduce C. jejuni chicken colonization. The findings may help the development of effective strategies to reduce C. jejuni chicken contamination and campylobacteriosis.

Assessing Aerated Vermicompost Tea Combined with Microbial Biological Control Agents for Suppression of Fusarium and Rhizoctonia.

Biological control of plant diseases is important in organic greenhouse vegetable production, where fungicide use is limited. Organic producers use microbially diverse substrates, including composts, as media for plant growth. Previous research into the impact of vermicompost on the efficacy of applied biocontrol agents is limited. An invitro assay was developed to test the efficacy of two biological control agents in a competitive microbial background. Suppression of the pathogen Fusarium oxysporum f. sp. radicis-cucumerinum by Clonostachys rosea f. catenulata (Gliocladium catenulatum strain J1446 [Prestop]) and Bacillus subtilis strain QST 713 (Rhapsody), was assessed on agar media amended with aerated vermicompost tea (ACT). Pathogen growth was reduced more by C. rosea than ACT alone, and C. rosea was equally effective when combined with ACT. In contrast, B. subtilis reduced pathogen growth less than ACT and, when combined, reduced pathogen growth no more than ACT alone. Both biocontrol agents were similarly tested with ACT against F. oxysporum f. sp. radicis-cucumerinum and Rhizoctonia solani on cucumber and radish. Additive, neutral, and antagonistic responses, depending on host, pathogen, and biocontrol agent, were observed. ACT alone provided more consistent disease suppression on cucumber compared with B. subtilis or C. rosea. In combination, disease suppression was most often better than each biocontrol alone but not better than ACT alone. ACT had antagonistic or additive interactions with C. rosea in the radish/R. solani pathosystem, depending on the experiment. The specific and general suppression of plant diseases by biological control agents in microbially rich environments is variable and warrants further study.

Cytotoxicity, apoptosis, and IL-8 gene expression induced by some foodborne pathogens in presence of Bacillus coagulans in HT-29 cells

Food poisoning caused by bacteria is one of the most important concerns in food hygiene. The use of probiotics in prevention, control, and treatment of these infections has been considerably increased in recent years. This study evaluated the effect of B. coagulans cell free supernatant (CFS) on growth of Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, non-pathogenic Escherichia coli, and Escherichia coli 0157:H7 by the broth dilution method. The cytotoxicity, and apoptosis induced by pathogens alone and in co-culture with B. coagulans or its CFS were measured by trypan blue, and fluorescence staining methods. The expression level of interleukin-8 (IL-8) cytokine-encoding genes was also investigated by a qRT-PCR assay in all pathogens and co-cultured groups in HT-29 cells. Our results showed that 4% B. coagulans CFS reduced pathogen growth. The highest rate of growth inhibition was observed in L. monocytogenes. We also found that B. coagulans, and its 4% CFS reduced the cytotoxic effects of pathogens, with the exception of S. aureus. Non-pathogenic E. coli also had no significant cytotoxic effect on the cells. Examination of the treated cells with acridine orange/ethidium bromide staining showed reductions in the rate of cell damage (including early apoptosis, late apoptosis, and necrosis) in pathogen-probiotic co-cultures. Furthermore, we showed that co-culture of pathogens with B. coagulans significantly down-regulated IL-8 gene expression (P < 0.05). The greatest down-regulation compared with pathogen alone was observed in S. aureus. Hence, B. coagulans can be considered as an appropriate probiotic to diminish cytotoxicity, and inflammatory response of enteropathogenic bacteria.

Application of plant extracts and Trichoderma harzianum for the management of tomato seedling damping-off caused by Rhizoctonia solani

Seedling production under smallholder farming systems can be negatively affected by both abiotic and biotic factors. Seedling damping-off caused by Rhizoctonia solani is one of the major biotic factors which causes significant yield reduction. Management is mainly based on the application of synthetic fungicides and cultural practices. However, both methods have limitations which result in their inefficiency. Several studies have reported on the use of plant extracts and biological control to manage plant diseases. The aim of this study was to formulate an effective and practical approach to manage tomato seedling damping-off using extracts of Monsonia burkeana and Moringa oleifera and a biological control agent Trichoderma harzianum. The efficacy of both extracts was investigated under laboratory conditions to determine the most suppressive concentration to R. solani growth. Methanolic extracts from both plants significantly suppressed pathogen growth at different concentrations. M. burkeana significantly reduced R. solani growth at 8 g/mL (71%) relative to control whilst Moringa oleifera extract reduced pathogen growth by 60% at a concentration of 6 g/mL. The highest suppressive concentrations were further evaluated under greenhouse conditions to test their efficacy on seedling damping-off. In damping-off treatments, both plant extracts and T. harzianum also significantly reduced (p=0.5) pre- and post-emergence damping-off incidence. M. burkeana recorded the highest suppression at 78%, followed by M. oleifera at 64%. Trichoderma harzianum reduced incidence of damping-off by 60% and this was higher than both plant extract treatments.&#x0D; Significance:&#x0D; &#x0D; The use of M. burkeana and M. oleifera extracts and T. harzianum effectively suppressed pathogen growth and disease incidence and can be used to reduce the use of synthetic pesticides that are harmful to the environment and human health.&#x0D; Application of plant extracts and biological control agents as possible alternatives to synthetic fungicides is considered a sustainable and affordable practice for smallholder farmers.&#x0D;

Daily fluctuating temperatures decrease growth and reproduction rate of a lethal amphibian fungal pathogen in culture

BackgroundEmerging infectious diseases (EIDs) are contributing to species die-offs worldwide. We can better understand EIDs by using ecological approaches to study pathogen biology. For example, pathogens are exposed to variable temperatures across daily, seasonal, and annual scales. Exposure to temperature fluctuations may reduce pathogen growth and reproduction, which could affect pathogen virulence, transmission, and environmental persistence with implications for disease. We examined the effect of a variable thermal environment on reproductive life history traits of the fungal pathogen Batrachochytrium dendrobatidis (Bd). Bd causes chytridiomycosis, an emerging infectious disease of amphibians. As a pathogen of ectothermic hosts, Bd can be exposed to large temperature fluctuations in nature. To determine the effect of fluctuating temperatures on Bd growth and reproduction, we collected temperature data from breeding pools of the Yosemite toad (Anaxyrus canorus), a federally threatened species that is susceptible to chytridiomycosis. We cultured Bd under a daily fluctuating temperature regime that simulated Yosemite toad breeding pool temperatures and measured Bd growth, reproduction, fecundity, and viability.ResultsWe observed decreased Bd growth and reproduction in a diurnally fluctuating thermal environment as compared to cultures grown at constant temperatures within the optimal Bd thermal range. We also found that Bd exhibits temperature-induced trade-offs under constant low and constant high temperature conditions.ConclusionsOur results provide novel insights on variable responses of Bd to dynamic thermal conditions and highlight the importance of incorporating realistic temperature fluctuations into investigations of pathogen ecology and EIDs.

The Ectomycorrhizospheric Habitat of Norway Spruce and Tricholoma vaccinum: Promotion of Plant Growth and Fitness by a Rich Microorganismic Community.

The contribution of the mycorrhizospheric microbes in a stand of ectomycorrhizal Norway spruce (Picea abies) featuring mycorrhiza with the basidiomycete Tricholoma vaccinum was addressed by microbiome analysis and in vitro reconstruction of microbial as well as plant-microbe interactions. The protective role of the mycorrhizal fungus with respect to pathogen attack could be validated against Botrytis cinerea and Heterobasidion annosum in co-cultures revealing reduced pathogen growth, higher survival rate of the spruce trees and reduced symptoms on needles upon symbiosis with T. vaccinum. The community structure was shown to yield a high diversity in ECM forming basidiomycetes of Thelephorales and Agaricales associated with a rich bacterial diversity dominated by Rhizobiales with the most abundant Nitrobacter winogradski (3.9%). Isolated bacteria were then used to address plant growth promoting abilities, which included production of the phytohormone indole-3-acetic acid (performed by 74% of the bacterial isolates), siderophores (22%), and phosphate mobilization (23%). Among the isolates, mycorrhiza helper bacteria (MHB) were identified, with Bacillus cereus MRZ-1 inducing hyperbranching in T. vaccinum, supporting tree germination, shoot elongation, and root formation as well as higher mycorrhization rates. Thus, a huge pool of potential MHB and fungal community with widely distributed auxin-production potential extended the ability of T. vaccinum to form ectomycorrhiza. The forest community profited from the mycorrhizal fungus T. vaccinum, with spruce survival enhanced by 33% in microcosms using soil from the native habitat. A higher fungal abundance and diversity in cases where the tree had died during the experiment, showing that decomposition of plant litter from a dead tree supported a different community. T. vaccinum thus actively structured the community of microorganisms in its habitat.

Rhizosphere pseudomonads as probiotics improving plant health.

Many root-colonizing microbes are multifaceted in traits that improve plant health. Although isolates designated as biological control agents directly reduce pathogen growth, many exert additional beneficial features that parallel changes induced in animal and other hosts by health-promoting microbes termed probiotics. Both animal and plant probiotics cause direct antagonism of pathogens and induce systemic immunity in the host to pathogens and other stresses. They also alter host development and improve host nutrition. The probiotic root-colonizing pseudomonads are generalists in terms of plant hosts, soil habitats and the array of stress responses that are ameliorated in the plant. This article illustrates how the probiotic pseudomonads, nurtured by the carbon (C) and nitrogen (N) sources released by the plant in root exudates, form protective biofilms on the root surface and produce the metabolites or enzymes to boost plant health. The findings reveal the multifunctional nature of many of the microbial metabolites in the plant-probiotic interplay. The beneficial effects of probiotics on plant function can contribute to sustainable yield and quality in agricultural production.

Evaluating crude extracts of Monsonia burkeana and Moringa oleifera against Fusarium wilt of tomato

ABSTRACTFusarium wilt is one of the major soil-borne diseases of tomato crop globally. The study aimed to evaluate the efficacy of medicinal plants in the control of Fusarium wilt in tomato. Methanolic extracts of Monsonia burkena and Moringa oleifera were assessed in vitro and under greenhouse conditions. The in vitro experiments evaluated the effect of both extracts on Fusarium oxysporum f. sp lycopersici growth and response to varying concentrations. In greenhouse experiment, tomato seedlings cv. HTX14 were inoculated with conidial suspension of F. oxysporum and transplanted into pasteurised growth media amended with plant extract. Seedlings were treated with aqueous extracts at varying concentrations with an interval of 7 days between applications. Control treatments were treated with sterile distilled water. Both plant extracts significantly reduced pathogen growth in vitro and reduced wilt severity under greenhouse conditions. The highest mycelial growth suppression was observed in Mon. burkeana treatments. Under greenhouse conditions, both plant extracts significantly (P ≤ 0.05) reduced Fusarium wilt severity and had a positive effect on plant growth parameters. A significant increase in soil-pH was also recorded in extract treated soil resulting in reduction in disease severity. The results further provide new scientific information on how their effect on soil pH can be beneficial in the control of Fusarium wilt.

Inhibition of virulent and hypovirulent Cryphonectria parasitica growth in dual culture by fungi commonly isolated from chestnut blight cankers

Chestnut blight cankers, caused by the fungus Cryphonectria parasitica, are prone to invasion by other microorganisms as the canker ages. This microbial community has the potential to alter canker expansion, which may influence the probability that the canker girdles the infected stem. Hypoviruses infect the pathogen mycelium directly and are known to decrease pathogen virulence (i.e. hypovirulent). These viral infections can slow pathogen growth, decreasing the rate of canker expansion and lowering the probability of girdling. Saprophytic fungi also invade the expanding canker and may antagonize C. parasitica leading to reduced pathogen growth. The combined effects of fungal antagonism and a hypovirulent pathogen could work in combination to reduce the probability of girdling the infected stem. We assessed the ability of different fungal taxa, isolated from low severity cankers, to inhibit the growth of virulent and hypovirulent forms of C. parasitica in dual culture tests on two cultural media. Percent growth inhibition of virulent C. parasitica by potentially antagonistic fungi ranged from 2 % to 34 %, while inhibition of hypovirulent C. parasitica ranged from 18 % to 54 %. Only one isolate, identified as Umbelopsis isabellina (UmbelopsisWS) inhibited the virulent form of the pathogen more than the hypovirulent form. All three Trichoderma isolates caused the greatest growth inhibition of virulent C. parasitica, but they, like all other fungal isolates tested, inhibited the hypovirulent form of the pathogen more than the virulent form. These results suggest that commonly occurring fungi in chestnut blight cankers, including Trichoderma, may inhibit the hypovirulent C. parasitica more than virulent C. parasitica. Thus, the presence of other fungi in cankers may not enhance the effect of hypovirulent C. parasitica to delay cankers from girdling a stem but instead intensify canker development.

Rhizoctonia Root Rot of Pepper (Capsicum annuum): Comparative Pathogenicity of Causal Agent and Biocontrol Attempt using Fungal and Bacterial Agents

Rhizoctoniaroot rot of pepper (Capsicum annuum L.) is becoming serious in Tunisia. Comparative pathogenicity tests performed for Rhizoctonia solani isolates recovered from pepper and potato showed that Rhiz.7 and Rhiz.4 were the most aggressive. They reduced by 53.5%-91.4% the aerial part fresh weight of inoculated cv. Baklouti plants relative to control. Rhiz.7 decreased by 81%-88% the root fresh weight on cvs. Beldi and Baklouti. Various fungal and bacterial agents were tested against R. solani. Dual culture trials showed that Trichoderma harzianum, T. viride and Glicladiumvirensgrew and sporulated profusely over R. solani colonies and altered its hyphae. Pseudomonas huttiensis 69, P. aureofaciens 31 and Burkholderiaglathei 35 reduced pathogen growth by 9.71-12.87%. These bio-agents were tested for their effects on rhizoctonia root rot disease and pepper growth. On cv. Beldi, pre-emergence damping-off, noted after 15 days, was suppressed by 55 (for G. virens), 45 (for T. viride) and 50% (for T. harzianum). This inhibition reached 57.14% using Bacillus pumilus 420 and P. putida 227. Tested on pepper cv. Altar, all tested fungi decreased by 40% post-emergence damping-off, and significantly increased the plant height of R. solani -inoculated and treated plants by 21.13 (for T. viride) to 36.34% (for T. harzianum) relative to control. P. aureofaciens 314 and P. putida 227 completely suppressed R. solani post-emergence expression. Treatments with P. aureofaciens 314, P. aureofaciens 31, Bacillus pumilus 420, P. fluorescens Pf and P. putida 227 induced a significant increase in their height compared to control. An improvement of the aerial part fresh weight by 54.54, 48.09 and 47.74%, as compared to control, was induced by P. aureofaciens 314, B. glathei 35 and P. huttiensis 69, respectively.