Search Results (91)

Pepper (Capsicum annuum) production faces significant challenges from soil-borne pathogens, particularly Phytophthora capsici, which induces root rot and damping-off diseases. Management of this pathogen remains challenging owing to the scarcity of resistant cultivars and the ineffectiveness of chemical control methods. A single strain has been used to prevent pathogenic disease, and this approach limits the exploration of consortia comprising different genera. In this study, we isolated five bacterial strains (Bacillus sp. T3, Flavobacterium anhuiense T4, Cytobacillus firmus T8, Streptomyces roseicoloratus T14, and Pseudomonas frederiksbergensis A6) from the rhizosphere of healthy pepper plants. We then applied this 5-isolate synthetic microbial community (SynCom) to Capsicum annuum to evaluate its efficacy in improving pepper resilience against P. capsici. The SynCom members exhibited phosphate solubilization, indole-3-acetic acid production, catalase activity, siderophore synthesis, and strong antagonism against P. capsici. The SynCom reduced disease severity and enhanced the growth of pepper plants. Furthermore, the beneficial genera such as Bacillus, Fusicolla, and Trichoderma, significantly increased in the rhizosphere of pepper after the application of the SynCom. Microbial functional prediction analysis revealed that these microbial shifts were associated with nitrogen cycling and pathogen suppression. Our SynCom approach demonstrates the effectiveness of microbial consortia in promoting the growth of pathogen-infected plants by reprogramming the microbial community in the rhizosphere. Full article

Phytophthora capsici is a phytopathogen that affects postharvest bell peppers, as it causes rotting and decreases their commercial value. This study evaluates the efficacy of chitosan as a biocontrol agent against P. capsici on bell peppers using in vitro and in vivo assays. The antifungal activity of chitosan was evaluated at four concentrations (0.5, 1.0, 1.5, and 2.0 g L⁻¹). Its effect on mycelial growth inhibition, sporangial germination, disease incidence and severity, and fruit weight loss was determined. The results show that concentrations of 1.0 g L⁻¹ or higher completely inhibited P. capsici growth and sporangial germination in vitro and reduced disease incidence and severity to 0% in treated fruit. Furthermore, chitosan treatments preserved the fresh and dry weight of the fruit, which prevented postharvest deterioration. This study demonstrates that chitosan is an effective and environmentally friendly alternative for the management of postharvest diseases in bell peppers. This could reduce consumer dependence on synthetic fungicides and preserve fruit quality. Full article

Peppers are widely cultivated around the world, yet they suffer from infections caused by Phytophthora capsici fungi throughout the year, which severely impacts their yield. The β-1,3-glucanase gene has been shown in previous studies to significantly enhance plants’ ability to cope with both biotic and abiotic stresses, including fungal infections. However, its function in peppers has not been reported. In this study, 80 CaBG genes were initially identified, before being filtered down to 54 CaBGs in peppers, and analyses conducted on the physicochemical properties, chromosomal localization, phylogenetic tree relationships, synteny, promoters, and gene expression levels of the BG gene family. The results indicated that these 54 CaBG genes are located on 12 chromosomes. Phylogenetic tree analysis classified the CaBGs into three subfamilies, α, β, and γ, each with its own specific functions, with the γ subfamily being associated with disease resistance in peppers. Synteny analysis showed that CaBG genes are relatively conserved and have not undergone extensive whole-genome duplication events. Promoter analysis indicated that CaBGs are induced by plant hormones and various external stressors. Transcriptomic and RT-qPCR analyses revealed that the CaBG7 and CaBG12 genes were significantly activated following infection by P. capsici, with the expression levels of these two genes being markedly higher in resistant plants compared to susceptible ones. Based on the phylogenetic tree and gene expression analysis, we propose that CaBG7 and CaBG12 may be key genes for disease resistance in chili peppers. This study provides a theoretical basis for breeding P. capsici-resistant chili peppers by molecular breeding methods. Full article

One novel C₁₀ polyacetylene rhamnoside, 4,6,8-decatriyne-1-O-α-L-rhamnopyranoside, named xylariside A (1), together with two novel C₁₀ polyacetylene quinovopyranosides, 4,6,8-decatriyne-1-O-α-D-quinovopyranoside, xylariside B (2), and 8E-decaene-4,6-diyne-1-O-α-D-quinovopyranoside, xylariside C (3), were obtained from the solid fermentation of Xylaria sp. VDL4, an endophytic fungus isolated from Vaccinium dunalianum wight (Ericaceae). Their chemical structures were elucidated through a combination of spectroscopic techniques. The antifungal activities of these compounds were evaluated in vitro against four phytopathogenic fungi (Fusarium oxysporum, Botrytis cinerea, Phytophthora capsici, and Fusarium solani). Compound 2 demonstrated significant antifungal activities, with minimum inhibitory concentration (MIC) values ranging from 3.91 to 7.81 μg/mL. Compound 2’s effectiveness levels were similar to those of the reference drugs thiabendazole and carbendazim (each MIC = 0.98−15.62 μg/mL). Xylariside B (2) was further evaluated against B. cinerea in vivo. It exhibited remarkable efficacy in both the prevention and treatment of tomato and strawberry gray mold. Molecular docking studies confirmed the antifungal mechanism of compound 2 by revealing its binding interactions with key enzyme targets in B. cinerea, thereby supporting the observed in vitro and in vivo results. Additionally, compound 2 showed effective inhibition of α-glucosidase, with IC₅₀ values of 5.27 ± 0.0125 μg/mL. Full article

The production of ornamental plants in Mexico represents a job-generating activity that has grown in recent years; however, it is adversely affected by phytosanitary issues, notably those induced by Phytophthora. Studies of Phytophthora in ornamental nurseries are scarce in Mexico. The aim in this study was to identify Phytophthora species from selected ornamental plant nurseries in Mexico as potential new hosts. Samples of 13 genera diseased plant tissue and soil were collected from eight nurseries in Mexico during 2009–2010. Based on morphology and sequences of ITS rDNA, the 19 isolates obtained were identified as P. cactorum, P. capsici, P. cinnamomi, P. drechsleri, P. kelmanii, P. nicotianae, and P. tropicalis. Additional loci were sequenced to support species determinations within the P. capsici species complex; some of these isolates could not be confirmed as belonging to any described species, and one appeared to be an interspecific hybrid. This is the first report of P. kelmanii in Mexico; this is noteworthy due to being a broad host range, similar to most of the other species encountered. Evidence of nursery-grown plants serving as a Phytophthora vector to a home garden has been reported for the first time in Mexico. Cestrum nocturnum and Solanum ovigerum are new hosts for Phytophthora worldwide. Full article

Chili wilt is a significant challenge in producing jalapeño peppers, which has led to the implementation of strategies to help counteract or combat the microorganisms responsible for it. One of these strategies is the use of biological control microorganisms, such as Trichoderma, a fungus recognized as a natural enemy of the microorganisms that cause chili wilt. Therefore, this study aimed to isolate and identify Trichoderma species from the soils and roots of different plants, and evaluate their antagonism against Rhizoctonia solani, Phytophthora capsici, and Fusarium sp. Due to the complexity in identifying Trichoderma at the species level, performing a multilocus phylogenetic analysis was necessary, using the ITS, RPB2, and TEF1 regions. The species isolated were T. afroharzianum, T. lentiforme, T. rifaii, T. brevicompactum, T. arundinaceum, and T. longibrachiatum. Subsequently, they were used in three antagonism tests (dual culture, non-volatile organic compounds, and volatile organic compounds) against the phytopathogenic microorganisms. The tests demonstrated that the Trichoderma isolates could inhibit the mycelial growth of all three tested pathogens, obtaining the best results with the strains T. brevicompactum (19RCS), T. lentiforme (63DPS), T. longibrachiatum (71JES), T. rifaii (77JCR), and T. afroharzianum (24RQS, 87CCS, 88CCS and 17RCS). The strain with the best results in all three tests was 17RCS. Full article

Selenium nanoparticles (SeNPs) are currently receiving attention for controlling plant pathogenic microorganisms, are expected to be especially effective against the genus Phytophthora, and show high anti-oomycete activity. SeNPs synthesized with plant extracts have shown low toxicity, high bioavailability, and mechanisms of action that alter cellular integrity and damage key components of phytopathogen metabolism, causing denaturation and cell death. The aim of this study was to evaluate the inhibitory activity of SeNPs on mycelial growth and the development of reproductive structures in Phytophthora capsici in vitro. Different concentrations of SeNPs (0 to 400 µg/mL) in culture media were used to analyze mycelial growth, sporangium formation, zoospores, and germination of the germ tube. To explain the changes in morphology and development of P. capsici, increased relative conductance and activation of glycerol synthesis were related to osmotic stress and damage to membrane permeability. In addition, SeNPs inhibited the production of exopolysaccharides (EPSs), which are compounds associated with pathogen virulence. A lower accumulation of its biomass evidences alterations in the oomycete growth. The percentage of inhibition of mycelial growth increased with higher SeNP concentrations and incubation time, reaching 100% growth inhibition at 300 and 400 µg/mL. A concentration-dependent reduction in the number of spores, sporangia, and zoospore germination was observed. Concentrations of 50 and 100 µg/mL of SeNPs reduced biomass production by 30%. The increase in glycerol levels indicated an osmoregulatory response to SeNP-induced stress. Also, the increase in electrical conductivity suggested plasma membrane damage, which supports the potential of SeNPs as antifungal agents by inducing cell disruption and structural damage in P. capsici. These results provide new knowledge on the in vitro mechanism of action of SeNPs against P. capsici and offer a new biological alternative for the control of diseases caused by oomycetes. Full article

Botanical extracts are being considered for integration into disease management programs to control plant pathogenic fungi and oomycetes. A promising extract with potential is the essential oil of Lippia graveolens. However, its extraction process has not been optimized. Since optimizing process conditions can impact fungicidal and/or oomyceticidal effects, this research implemented time, temperature, and solid/liquid ratio conditions to maximize the fungicidal and oomyceticidal effects. The effectiveness was evaluated through parameters of mycelial growth inhibition, spore germination inhibition, minimum inhibitory and fungicidal/oomyceticidal concentration for the fungi Gilbertella persicaria, Agroathelia rolfsii, and Colletotrichum gloeosporioides, as well as the oomycete Phytophthora capsici. Optimal conditions were as follows: time: 46.27 min; temperature: 329.34 °C; and solid/liquid ratio: 80.35 g/L. In general, the optimized treatment was more effective in A. rolfsii ≥ P. capsica > G. persicaria ≥ C. gloeosporioides in all assays. These results demonstrate the fungicidal and oomiceticidal effects of L. graveolens essential oil, with potential for commercial product formulation. Full article

Pepper Phytophthora blight caused by Phytophthora capsici results in substantial losses in global pepper cultivation. The use of biocontrol agents with the dual functions of disease suppression and crop growth promotion is a green and sustainable way of managing this pathogen. In this study, six biocontrol strains of Trichoderma with high antagonistic activity against P. capsici were isolated and screened from the rhizosphere soil of healthy peppers undergoing long-term continuous cultivation. Morphological identification and molecular biological identification revealed that strains 2213 and 2221 were T. harzianum, strains 5111, 6311, and 6321 were T. brevicompactum, and strain 7111 was T. virens. The results showed that T. brevicompactum 6311 had the greatest inhibitory effect against P. capsici. The inhibition rate of 6311 on the mycelial growth of P. capsici was 82.22% in a double-culture test, whereas it reached 100% in a fermentation liquid culture test. Meanwhile, the pepper fruit tests showed that 6311 was 29% effective against P. capsici on pepper, and a potting test demonstrated that the preventive and controlling effect of 6311 on pepper epidemics triggered by P. capsici was 55.56%. The growth-promoting effect, germination potential, germination rate, radicle-embryonic axis length, germination index, and fresh weight of peppers cultured in the 6311 fermentation broth were significantly increased compared with the results for the control group. Scanning electron microscopy revealed that 6311 achieved the parasitism of P. capsici, producing siderophores and the growth hormone indoleacetic acid (IAA) to achieve disease-suppressive and growth-promoting functions. Transcriptomic results indicated that genes encoding proteins involved in plant disease resistance, namely flavanone 3-hydroxylase (F3H) and growth transcription factor (AUX22), were generally upregulated after the application of 6311. This study demonstrated that 6311 exhibits significant bioprotective and growth-promoting functions. Full article

Actinomycetes are a group of bacteria that have been reported as potential controllers of several plant pathogens and plant growth-promoting agents. This study focused on the isolation of 60 actinobacterial strains from the Cuatro Cienegas Basin, Coahuila, Mexico, with an emphasis on evaluating their potential as biocontrol agents against plant pathogens. Among the strains tested, the isolate PR69 exhibited significant in vitro antagonistic activity against eight plant pathogens, with inhibition rates ranging from 44% to 73%, including Phytophthora capsici. The genome of PR69 was sequenced and assembled. It was identified as Streptomyces by phylogenetic analysis based on concatenated multiple sequence alignments of 81 core bacterial genes. Additionally, volatile compounds produced by PR69 enhanced the growth of Arabidopsis thaliana seedlings in vitro, increasing seedling weight, primary root length, and the number of secondary roots. Furthermore, the soil treated with Streptomyces sp. PR69 effectively controlled the infection caused by the pathogen P. capsici in bell pepper plants, reducing mortality by 47% compared to plants inoculated solely with the pathogen. PR69-treated plants also showed 30% increase in fresh weight compared to untreated controls. These findings suggest that Streptomyces sp. PR69 holds promise as a bioinoculant for promoting pepper plant growth and controlling P. capsici populations. Full article

The use of biological methods to control plant diseases has garnered attention due to their eco-friendly and economically viable nature. Trichoderma spp. are the most ubiquitous fungal saprophytes that can often grow as opportunistic symbionts, are eco-friendly, and are not reported to exert any environmental hazard. Soil-borne pathogens can significantly impact the yield of chilli and tomato crops. The study was conducted to explore the impact of various salts (NaCl, MgCl₂, CaCl₂, and KCl) and their concentrations (1%, 5%, 10%, and 15%) on the mycelial growth and sporulation of Trichoderma viride followed by its mass multiplication on diverse organic substrates like wheat seeds, wheat husks, mungbean seeds, maize seeds, rice seeds, pea seeds, sorghum seeds, banana peel, apple peel, pomegranate peel, citrus peel, tomato waste, chilli waste, spinach waste, cabbage waste, potato peel, onion peel, cucumber peel, carrot peel, used black tea leaves, used green tea leaves, poultry waste, and cow and goat dung. The study assessed the biocontrol potential of Trichoderma viride against important soil-borne pathogens in chilli (Pythium aphanidermatum, Phytophthora capsici, and Fusarium oxysporum) and tomato (Pythium aphanidermatum, Phytophthora infestans, and F. oxysporum) cropping in the pot and field experiments using saline and alkaline soils. Seed treatment with T. viride significantly enhanced the germination rates of both chilli and tomato crops, with sorghum being the most conducive substrate for mass-multiplying T. viride. The results revealed that lower salt concentrations minimally affected T. viride growth, while higher concentrations hampered both growth and sporulation. Optimal disease control and plant height were observed at a 20 mg concentration of T. viride, consequently applied in vivo using various application methods, i.e., seed treatment, root dip, irrigation, and mixed treatments (all the methods like seed treatment, root dip method, and irrigation method applied together) to manage soil-borne pathogens. Particularly, T. viride application through irrigation and mixed treatments demonstrated strong efficacy. These findings underscore the potential of T. viride application in saline and alkaline soils to manage soil-borne pathogens like Pythium, Phytophthora spp., and Fusarium spp. This study lays the foundation for the practical application of biocontrol agents, like T. viride, in Pakistani agricultural conditions. Moreover, there is a need for further exploration into the genetic mechanisms involved in disease inhibition and plant growth promotion, along with understanding the impact of T. viride on the metabolic pathways of host plants. Full article

Phytophthora capsici is a devastating pathogen in horticultural crops, particularly affecting Capsicum annuum (pepper). The overuse of chemical fungicides has led to resistance development, necessitating alternative strategies. This study investigates the antagonistic effects of four rhizobacterial isolates (Bacillus sp., Pseudomonas putida, Bacillus subtilis, Bacillus amyloliquefaciens) against P. capsici, focusing on the production of volatile organic compounds (VOCs). Using in vitro dual culture assays, we observed a significant inhibition of mycelial growth and sporangia production, especially by B. subtilis and B. amyloliquefaciens. The GC-MS/SPME-HS analysis identified key VOCs responsible for these antagonistic effects. Our findings demonstrate that specific rhizobacteria and their VOCs offer a promising biocontrol strategy, potentially reducing the reliance on chemical fungicides and contributing to sustainable agriculture. Full article

Phytopathogenic oomycetes, particularly Phytophthora capsici, the causal agent of Phytophthora blight disease in essential vegetables and fruit crops, remains a persistent challenge in the vegetable production industry. However, the core molecular regulators of the pathophysiology and broad-range host characteristics of P. capsici remain unknown. Here, we used transcriptomics and CRISPR-Cas9 technology to functionally characterize the contributions of a novel gene (PcTBCC1) coding for a hypothetical protein with a tubulin-binding cofactor C domain with a putative chloroplast-targeting peptide (cTP) to the pathophysiological development of P. capsici. We observed significant upregulation in the expression of PcTBCC1 during pathogen–host interactions. However, the vegetative growth of the ∆Pctbcc1 strains was not significantly different from the wild-type strains. PcTBCC1 gene replacement significantly compromised the sporulation, pathogenic differentiation, and virulence of P. capsici. At the same time, ∆Pctbcc1 strains were sensitive to cell wall stress-inducing osmolytes. These observations, coupled with the close evolutionary ties between PcTBCC1 and pathogenic oomycetes and algae, partly support the notion that PcTBCC1 is a conserved determinant of pathogenesis. This study provides insights into the significance of tubulin-binding cofactors in P. capsici and underscores the potential of PcTbcc1 as a durable target for developing anti-oomycides to control phytopathogenic oomycetes. Full article

Phytophthora capsici is a destructive oomycete pathogen that poses a significant threat to global agriculture by infecting a wide range of economically important crops in the Solanaceae and Cucurbitaceae families. In Canada, the pathogen has been responsible for substantial losses in greenhouse and field-grown crops. Despite extensive worldwide research on P. capsici, little is known about the effector content and pathogenicity of the Canadian isolates. In this study, we sequenced and analyzed the genomes of two Canadian P. capsici strains, namely 55330 and 55898, and conducted a comparative secretome analysis with globally referenced strains LT1534 and LT263. The Canadian strains displayed smaller genomes at 57.3 Mb and 60.2 Mb compared to LT263 at 76 Mb, yet retained diverse effector repertoires, including RxLR and CRN effectors, and exhibited robust pathogenic potential. Our analysis revealed that while the Canadian strains have fewer unique effector clusters compared to LT263, they possess comparable CAZyme profiles, emphasizing their capacity to degrade plant cell walls and promote infection. The differences in effector content likely reflect host adaptation, as P. capsici infects a variety of plant species. This study provides valuable insights into the genetic features of Canadian P. capsici isolates and offers a foundation for future efforts in developing targeted disease-management strategies. Full article

Pepper (Capsicum annuum L.) suffers severe quality and yield loss from oomycete diseases caused by Phytophthora capsici. CaSGT1 was previously determined to positively regulate the immune response of pepper plants against P. capsici, but by which mechanism remains elusive. In the present study, the potential interacting proteins of CaSGT1 were isolated from pepper using a yeast two-hybrid system, among which CaARP1 was determined to interact with CaSGT1 via bimolecular fluorescence complementation (BiFC) and microscale thermophoresis (MST) assays. CaARP1 belongs to the auxin-repressed protein family, which is well-known to function in modulating plant growth. The transcriptional and protein levels of CaARP1 were both significantly induced by infection with P. capsici. Silencing of CaARP1 promotes the vegetative growth of pepper plants and attenuates its disease resistance to P. capsici, as well as compromising the hypersensitive response-like cell death in pepper leaves induced by PcINF1, a well-characterized typical PAMP from P. capsici. Chitin-induced transient expression of CaARP1 in pepper leaves enhanced its disease resistance to P. capsici, which is amplified by CaSGT1 co-expression as a positive regulator. Taken together, our result revealed that CaARP1 plays a dual role in the pepper, negatively regulating the vegetative growth and positively regulating plant immunity against P. capsici in a manner associated with CaSGT1. Full article