Search

Cassava (Manihot esculenta Crantz) is a major staple food in many developing countries, including Brazil. However, it faces significant challenges due to diseases such as dry root rot (DRR) and black root rot (BRR) caused by soil-borne plant pathogenic fungi. This study explored the use of cover crops to suppress these diseases and to improve the agronomic traits of cassava. Over four cultivation cycles, various cover crops (sunn hemp, black oat, jack bean, maize, peanut and cowpea) were alternated with cassava varieties 'BRS Kiriris' (resistant) and 'BRS Formosa' (susceptible) in soil infested with DRR (Fusarium oxysporum, F. equiseti, F. verticillioides, F. solani, F. lateritium, F. chlamydosporum) and BRR (Lasiodiplodia theobramae, Neoscytalidium dimidiatum) pathogens. In the 2nd cycle, only germination showed significant differences, but by the 4th cycle, various agronomic parameters, including fresh weight (FW.AP), dry weight (DW.AP) of the aerial part, fresh weight (FW.Root), dry weight (DW.Root) of the roots, and plant vigor. Cowpea was identified as the most effective cover crop for reducing the disease index (DI %) by promoting healthier and taller cassava plants. Jack beans and peanuts also had positive effects on vigor, FW.AP, DW.AP, FW.root, and DW.root. In contrast, maize, black oats, Crotalaria ochroleuca, cassava, and fallow soils had minimal impacts. Throughout these cycles, the selected cover crops consistently contributed to disease reduction and improved the agronomic performance of the cassava. This study highlights the potential of holistic disease management strategies. [ABSTRACT FROM AUTHOR]

Understanding the microbial communities in asymptomatic oil palm seedlings is crucial for developing disease-suppressive microbiota against basal stem rot (BSR) in oil palm. In this study, we compared the microbial communities in bulk soil, rhizosphere, and endosphere of control, asymptomatic, and symptomatic seedlings following inoculation with Ganoderma boninense. Our findings revealed significant shifts in microbial structure and interactions, particularly in asymptomatic seedlings. Both Actinobacteriota and Ascomycota were notably enriched in these samples, with Actinobacteriota identified as keystone taxa. Long-read shotgun metagenomics demonstrated that 67.4% of enriched Actinobacteriota taxa were unique to asymptomatic seedlings. Similarly, Ascomycota members showed significant enrichment, suggesting their potential role in BSR suppression. The consistent identification of these phyla across various analyses underscores their importance in disease resistance. This is the first report detailing the shifts in prokaryotic and fungal communities in asymptomatic and symptomatic seedlings, offering insights into potential disease-suppressive taxa across three compartments: bulk soil, rhizosphere, and endosphere of oil palm seedlings. [ABSTRACT FROM AUTHOR]

The present investigation was designed to assess how administering biocontrol agents (BCAs) made from the nematophagous endophytic fungus MR20 (Purpureocillium lilacinum) or a mixture of endophytic plant growth-promoting bacteria MR12 (Pseudomonas fluorescens), and MR25 (Serratia marcescens), could enhance tomato growth and resistance to Meloidogyne incognita under in vivo conditions. The three strains' cell-free culture filtrates showed a strong nematocidal impact (P < 0.05) on M. incognita infective second-stage juveniles (J2s). The highest mortality rates by the three BCAs were at concentrations of 80%, followed by 60%, 40%, and 20%. The in vitro hatching of free eggs was found to be considerably (P < 0.05) reduced as the concentrations of the endophytic bacteria MR12, and MR25 were increased in the order 1 × 105, 1 × 106, 1 × 107, 0.5 × 108, to 1 × 108 colony forming units (CFU)/mL, and the maximum nematicidal activity in killing M. incognita free eggs occurred at 1 × 108 CFU/mL. A statistically significant (P < 0.05) reduction in the percentage of M. incognita-free eggs retrieved was seen in vitro when various concentrations of the endophytic fungus MR20 were applied compared to the negative control (distilled water). The endophytic fungus MR20 had the highest nematicidal activity against M. incognita free eggs at a concentration of 3 × 106 CFU/mL. The application of P. lilacinum or a combination of P. fluorescens and S. marcescens to tomato plants in the presence of M. incognita under greenhouse conditions resulted in a significant increase (P < 0.05) in root and shoot fresh weight, number of leaves, weight of leaves, and stem diameter when compared to the positive control treatment that contained only M. incognita. Treatment with P. lilacinum was more effective (P < 0.05) than P. fluorescens and S. marcescens in reducing egg masses per root, J2s per 100 g of soil, egg masses per 100 g of soil, J2s + eggs of M. incognita per 100 g of soil, reproduction factor, and reduction percentage after 60 days under greenhouse conditions. Nevertheless, the reduction of M. incognita gall size categorization (> 4 mm, 2–4 mm, and < 2 mm) was more effectively achieved by treatment with P. fluorescens and S. marcescens than by treatment with P. lilacinum. Under in vivo conditions, the tested P. lilacinum or a mixture of P. fluorescens and S. marcescens effectively controlled nematode population densities below the economic threshold. [ABSTRACT FROM AUTHOR]

BACKGROUND: Soft rot (Pectobacterium aroidearum and Dickeya) is a devastating soil‐borne bacterial disease that threatens konjac production. Intercropping with false acacia has been shown to significantly reduce soft rot incidence in konjac by shifting the microbial community. However, how intercropping shapes the root bacterial community and affects soft rot incidence remains unclear. To address this, we investigated three konjac intercropping systems (false acacia, paulownia, and maize) to explore the relationships among intercropping, soft rot incidence, root bacterial community, soil enzyme activity, and soil properties. RESULTS: Konjac intercropped with false acacia exhibited the lowest soft rot incidence and the lowest abundance of pathogenic taxa. Soft rot incidence was negatively correlated with total soil nitrogen and potassium but positively correlated with total and available soil phosphorus. The bacterial community structure and function in konjac roots differed among intercropping types, mainly driven by available soil phosphorus. Beneficial microorganisms such as Bradyrhizobium and Variovorax were enriched under a false acacia intercropping system and were negatively correlated with soil‐available phosphorus. Additionally, the stable bacterial community in healthy konjac roots under false acacia may make konjac less susceptible to pathogen invasion. CONCLUSION: The study showed that intercropping reduced the soft rot incidence by regulating the structure and stability of the konjac root bacterial community, and soil‐available phosphorus was the main factor affecting the difference in the konjac root bacterial community, which provided a basis for the management of soil fertilization in konjac cultivation. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Cucumber wilt, caused by Fusarium oxysporum f. sp. cucumerinum (FOC), is a soilborne disease that poses a significant threat to cucumber production, resulting in substantial yield losses. This study aimed to evaluate the biocontrol and growth-promoting effects of Bacillus velezensis, a highly active bacterial strain. In vitro assays revealed that B. velezensis F9 exhibited broad-spectrum antifungal activity against eight plant pathogenic fungi, with inhibition ratio ranging from 62.66% to 88.18%. Additionally, the strain displayed the ability to produce IAA (5.97 ± 1.75 µg/mL), fix nitrogen, produce siderophores, and form biofilms. In vitro growth promotion assays demonstrated that different concentrations of B. velezensis F9 significantly promoted cucumber seedling growth. Furthermore, two pot experiments revealed that the strain exhibited biocontrol efficacy against cucumber wilt, with disease control rates ranging from 42.86% to 67.78%. Notably, the strain significantly increased the plant height, fresh weight, and dry weight, with increases ranging from 20.67% to 60.04%, 40.27% to 75.51%, and 22.07% to 52.54%, respectively. Two field trials confirmed the efficacy of B. velezensis F9 in controlling cucumber wilt, with disease control rates of 44.95% and 33.99%, respectively. The strain effectively alleviated the dwarfing and wilting symptoms caused by the pathogen. Compared with the FOC treatment, the F9 + FOC treatment significantly increased the plant height, fresh weight, and dry weight, with increases of 43.85% and 56.28%, 49.49% and 23.70%, and 36.25% and 73.63%, respectively. Enzyme activity assays indicated that inoculation significantly increased SOD activity in cucumber leaves and neutral phosphatase, sucrase, and urease activity in rhizosphere soil. Correlation analysis revealed a negative correlation between the disease index and plant height, fresh weight, dry weight, and peroxidase activity, with correlation coefficients of −0.53, −0.60, −0.38, and −0.45, respectively. These findings suggest that plant height, fresh weight, and dry weight are significantly negatively correlated with the cucumber disease index, highlighting their importance as indicators for evaluating the biocontrol efficacy of B. velezensis F9. In conclusion, B. velezensis F9 is a highly effective plant growth-promoting rhizobacterium with excellent biocontrol potential, showcasing promising applications in agricultural production. [ABSTRACT FROM AUTHOR]

Fusarium root rot caused by the Fusarium species complex significantly affects the yield and quality of Angelica sinensis, a valuable medicinal herb. Traditional management primarily relies on chemical fungicides, which have led to pathogen resistance, environmental hazards, and concerns regarding public health and the active components in A. sinensis. This study explores the efficacy of a novel plant-derived biopesticide Shi Chuang Zhi Feng Ning (T1; SCZFN), alongside Bacillus subtilis wettable powder (T2) and a chemical fungicide (T3), in controlling root rot and understanding their impacts on the rhizosphere microbial community and root metabolome. Results of the field experiment demonstrated that treatments T1 and T3 achieved control efficiencies of 73.17% and 75.45%, respectively, significantly outperforming T2 (39.99%) and the control. High-throughput sequencing revealed that all treatments altered the diversity and structure of microbial communities, with T1 and T2 reducing the abundance of taxa linked to root rot, such as Muribaculaceae spp., Humicola spp., Fusarium spp., and Mycochlamys spp. Treatment T1 notably enhanced beneficial bacterial taxa, including Acidobacteria spp., Nitrospira spp., and Pedosphaeraceae spp., involved in carbon cycling and plant growth promotion. Metabolomic analysis identified 39, 105, and 45 differentially expressed metabolites (DEMs) across the treatments, demonstrating T1's potential to modulate the root metabolome effectively. Further, a correlation analysis demonstrated a stronger correlation between distinct microorganisms with significant influence and DEMs of T1 treatment compared to other treatments. These findings underscore biopesticide SCZFN's role in enhancing plant health and disease suppression in A. sinensis, providing insights into its biocontrol mechanisms and supporting the development of sustainable disease management strategies in its cultivation. [ABSTRACT FROM AUTHOR]

Soil microbiomes play a pivotal role in shaping plant health and their ability to suppress the pathogens. However, the specific microbial features that confer disease suppression in agricultural soils have remained unknown. In this study, we aim to elucidate the mechanistic roles of soil key bacteria contributing to disease suppression in banana Panama disease by using a comprehensive soil survey focusing on suppressive, and conducive soils. Through an initial field survey across twelve paired locations, we identified five fields with significantly lower pathogen abundances compared to their co-located counterparts. Subsequent greenhouse experiments validated the disease-suppressive nature of soils collected from Jianfeng (JF) and Lingao (LG), both exhibiting low pathogen densities. Furthermore, four OTUs classified as Massilia (OTU44), Flavisolibacter (OTU396), Brevundimonas (OTU632) and Pseudomonas (OTU731), respectively, were identified as key players in suppressing pathogen invasion as they were significantly enriched in suppresive groups and pathogen inoculated treatments. The present results might suggest a vital link between these soil bacteria and pathogen inhibition in banana rhizosphere via a greenhouse experiment. The abundance of nonribosomal peptide synthetase (NRPS) genes, which was responsible for antibiotic synthesis and significantly enriched in the banana rhizosphere after beneficial microorganism inoculation, displayed a significant and negative correlation with pathogen abundance while a positive correlation with relative abundance of Pseudomonas. This result suggests that the up-regulation of NRPS genes may play a key role in bolstering banana plant immunity. These findings not only provide promising biocontrol strategies but also offer valuable insights into the dynamic relationship between soil microbiomes and plant physiology, paving the way for sustainable agriculture and disease management. [ABSTRACT FROM AUTHOR]

ABSTRACT Black shank disease in tobacco, caused by Phytophthora nicotianae, can lead to yield losses of 30%–50% upon outbreak. Recently, biochar derived from agricultural waste has shown significant potential in controlling soil-borne diseases, though its mechanisms remain unclear. Over a 3-year observation period, we found that the incidence of black shank was significantly lower in plots amended with biochar compared with normal cultivation plots. To investigate the underlying mechanisms, we studied both the direct and indirect effects of biochar on black shank. Direct antifungal assays indicated that biochar reduced the total number of sporangia by 53.91%. Further pot experiments revealed a 62.34% reduction in the P. nicotianae population in the soil following biochar application. Additionally, biochar application led to notable changes in soil physicochemical properties and microbial community composition. Microbial species analysis showed that biochar promoted the aggregation of beneficial microbes such as Sphingomonas, Flavisolibacter, and Mucoromycota. Functional predictions using the PICRUSt 2 software revealed that biochar enhances bacterial functions related to antimicrobial substance synthesis (Tetracycline biosynthesis), detoxification metabolism (D-arginine and D-ornithine metabolism, arginine and proline metabolism), and lipid and fatty acid metabolism (Lipopolysaccharide biosynthesis, fatty acid biosynthesis), while fungal functions showed no significant changes. This suggests that rhizosphere bacteria play a more prominent role in the suppression of black shank by biochar, a finding supported by partial least squares path modeling analysis. Therefore, we hypothesize that biochar not only directly inhibits P. nicotianae growth but also regulates the composition of the rhizosphere microbial community, inducing the production of antimicrobial substances by rhizosphere bacteria, effectively preventing P. nicotianae invasion.IMPORTANCEBlack shank, a global soil-borne fungal disease in tobacco, currently lacks effective control methods. Notably, biochar derived from agricultural waste has shown significant potential in controlling soil-borne diseases. Over a 3-year observation period, we found that plots amended with biochar had a significantly lower incidence of black shank compared with normal cultivation plots. However, the mechanisms of disease suppression remained unclear. Through in vitro antifungal assays and pot experiments, we discovered that tobacco-derived biochar can directly inhibit the growth of the pathogen. Additionally, biochar regulates the composition of the rhizosphere microbial community, inducing rhizosphere bacteria to produce antimicrobial substances, effectively preventing pathogen invasion. This discovery reveals both the direct and indirect mechanisms by which biochar suppresses black shank in tobacco. It provides a scientific basis for developing green control technologies for black shank and offers theoretical support for the application of biochar in managing soil-borne diseases in tobacco cultivation areas.

Abstract Background Plant microbiota contributes to plant growth and health, including enhancing plant resistance to various diseases. Despite remarkable progress in understanding diseases resistance in plants, the precise role of rhizosphere microbiota in enhancing watermelon resistance against soil-borne diseases remains unclear. Here, we constructed a synthetic community (SynCom) of 16 core bacterial strains obtained from the rhizosphere of grafted watermelon plants. We further simplified SynCom and investigated the role of bacteria with synergistic interactions in promoting plant growth through a simple synthetic community. Results Our results demonstrated that the SynCom significantly enhanced the growth and disease resistance of ungrafted watermelon grown in non-sterile soil. Furthermore, analysis of the amplicon and metagenome data revealed the pivotal role of Pseudomonas in enhancing plant health, as evidenced by a significant increase in the relative abundance and biofilm-forming pathways of Pseudomonas post-SynCom inoculation. Based on in vitro co-culture experiments and bacterial metabolomic analysis, we selected Pseudomonas along with seven other members of the SynCom that exhibited synergistic effects with Pseudomonas. It enabled us to further refine the initially constructed SynCom into a simplified SynCom comprising the eight selected bacterial species. Notably, the plant-promoting effects of simplified SynCom were similar to those of the initial SynCom. Furthermore, the simplified SynCom protected plants through synergistic effects of bacteria. Conclusions Our findings suggest that the SynCom proliferate in the rhizosphere and mitigate soil-borne diseases through microbial synergistic interactions, highlighting the potential of synergistic effects between microorganisms in enhancing plant health. This study provides a novel insight into using the functional SynCom as a promising solution for sustainable agriculture. Video Abstract

Background: Plant microbiota contributes to plant growth and health, including enhancing plant resistance to various diseases. Despite remarkable progress in understanding diseases resistance in plants, the precise role of rhizosphere microbiota in enhancing watermelon resistance against soil-borne diseases remains unclear. Here, we constructed a synthetic community (SynCom) of 16 core bacterial strains obtained from the rhizosphere of grafted watermelon plants. We further simplified SynCom and investigated the role of bacteria with synergistic interactions in promoting plant growth through a simple synthetic community. Results: Our results demonstrated that the SynCom significantly enhanced the growth and disease resistance of ungrafted watermelon grown in non-sterile soil. Furthermore, analysis of the amplicon and metagenome data revealed the pivotal role of Pseudomonas in enhancing plant health, as evidenced by a significant increase in the relative abundance and biofilm-forming pathways of Pseudomonas post-SynCom inoculation. Based on in vitro co-culture experiments and bacterial metabolomic analysis, we selected Pseudomonas along with seven other members of the SynCom that exhibited synergistic effects with Pseudomonas. It enabled us to further refine the initially constructed SynCom into a simplified SynCom comprising the eight selected bacterial species. Notably, the plant-promoting effects of simplified SynCom were similar to those of the initial SynCom. Furthermore, the simplified SynCom protected plants through synergistic effects of bacteria. Conclusions: Our findings suggest that the SynCom proliferate in the rhizosphere and mitigate soil-borne diseases through microbial synergistic interactions, highlighting the potential of synergistic effects between microorganisms in enhancing plant health. This study provides a novel insight into using the functional SynCom as a promising solution for sustainable agriculture. 6UoEKpA3MAKccxe2Gy9v1z Video Abstract [ABSTRACT FROM AUTHOR]

Fruits and vegetables are an integral part of our diet attributed to their appealing taste, flavor, and health-promoting characteristics. However, due to their high-water activity, they are susceptible to microbial spoilage and diseases at any step in the food supply chain, from pre-harvest treatment to post-harvest storage and transportation. As a result, food researchers and engineers are developing innovative technologies that can be used to reduce the loss of fruits and vegetables on-farm and during postharvest processing. The purpose of this study was to gather and discuss the scientific data on the disease-suppressive activity of nanoparticles against plant pathogens. The progress and limitations of innovative approaches for improving nanoparticles' efficiency and dependability have been studied to develop effective substitutes for synthetic chemical fungicides and pesticides, in managing disease in fruits and vegetables. The findings of this study strongly suggests that nanotechnology has the required ability for disease suppression in fruits and vegetables. Applications of specific nanoparticles under specified conditions can enhance nutrition delivery to plants, provide better antibacterial and disease suppression activity. Nanoparticles can also lessen the quantity of agrichemicals/metals released into the environment as compared to standard formulations, which is one of the most impressive advances. [ABSTRACT FROM AUTHOR]

Background: Plasmodiophora brassicae is an ever-increasing threat to cruciferous crop production worldwide. Aims and methods: This study investigated the impact of pre-soil fumigation with ammonium bicarbonate (N) and lime (NB) to manage clubroot disease in Chinese cabbage through 16S rRNA gene amplification sequencing. Results: We found that soil fumigation with N and NB suppressed disease incidence by reducing the soil acidity and population of P. brassicae in the rhizosphere. Minimum disease incidence and maximum relative control effect of about 74.68 and 66.28% were achieved in greenhouse and field experiments, respectively, under the combined application of ammonium bicarbonate and lime (LNB) as compared with N, NB, and control (GZ). Microbial diversity analysis through Miseq sequencing proved that pre-soil fumigation with N, NB, and LNB clearly manipulated rhizosphere microbial community composition and changed the diversity and structure of rhizosphere microbes compared with GZ. Bacterial phyla such as Proteobacteria, Bacteriodetes, and Acidobacteria and fungal phyla including Olpidiomycota and Ascomycota were most dominant in the rhizosphere of Chinese cabbage plants. Soil fumigation with N and NB significantly reduced the abundance of clubroot pathogen at genus (Plasmodiophora) level compared with GZ, while decreased further under combined application LNB. Microbial co-occurrence network analysis showed a highly connected and complex network and less competition for resources among microbes under combined application LNB. Conclusion: We conclude that for environmentally friendly and sustainable agriculture, soil fumigation with combined ammonium bicarbonate and lime plays a crucial role in mitigating Chinese cabbage clubroot disease by alleviating soil pH, reducing pathogen population, and manipulating the rhizosphere microbiome. [ABSTRACT FROM AUTHOR]

Promoting soil suppressiveness against soil borne pathogens could be a promising strategy to manage crop diseases. One way to increase the suppression potential in agricultural soils is via the addition of organic amendments. This microbe-mediated phenomenon, although not fully understood, prompted our study to explore the microbial taxa and functional properties associated with Rhizoctonia solani disease suppression in sugar beet seedlings after amending soil with a keratin-rich waste stream. Soil samples were analyzed using shotgun metagenomics sequencing. Results showed that both amended soils were enriched in bacterial families found in disease suppressive soils before, indicating that the amendment of keratin-rich material can support the transformation into a suppressive soil. On a functional level, genes encoding keratinolytic enzymes were found to be abundant in the keratin-amended samples. Proteins enriched in amended soils were those potentially involved in the production of secondary metabolites/antibiotics, motility, keratin-degradation, and contractile secretion system proteins. We hypothesize these taxa contribute to the amendment-induced suppression effect due to their genomic potential to produce antibiotics, secrete effectors via the contractile secretion system, and degrade oxalate—a potential virulence factor of R. solani —while simultaneously possessing the ability to metabolize keratin. [ABSTRACT FROM AUTHOR]

The plant-associated microbiota confers beneficial traits to the plant host by promoting growth and preventing disease. However, it is not fully understood how the host and its associated microbiota interact with pathogens. In this work, we studied how the host plant modulates its associated microbiome to suppress disease. For this, we used two Arabidopsis thaliana lines with different host responses to Fusarium oxysporum f. sp. mathioli (FOM). We isolated bacterial consortia (BCs) from FOM-infected or healthy host plants of the two lines of Arabidopsis and studied their effect on the root-associated microbiota and FOM progression in the following generations of Arabidopsis plants. Root bacterial and fungal communities were profiled using 16S ribosomal RNA and internal transcribed spacer amplicon sequencing, respectively, while quantitative PCR was used for assessment of FOM quantities in shoots of Arabidopsis. Host- or pathogen-adapted BCs significantly reduced FOM quantities in shoots of both the resistant Col-0 and the susceptible Ler-0 Arabidopsis lines. Several bacterial taxa, including Chthoniobacter, Bacillus, Chryseobacterium and Actinoplanes negatively correlated with FOM, suggestive of an antagonistic effect. Furthermore, both host- and pathogen-adapted BCs significantly affected community composition with distinct differentially abundant taxa and co-occurrence network structures. Taken together, our findings suggest that using a subcommunity selection approach is a potential route for exploiting plant-associated rhizosphere microbiomes for engineering disease resilient microbiomes. [Graphic: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Developing innovative, eco-friendly fungicide alternatives is crucial to mitigate the substantial threat fungal pathogens pose to crop yields. In this study, we assessed the in vitro effectiveness of SiO2, CuO, and γFe2O3 nanoparticles against Rhizoctonia solani. Furthermore, greenhouse experiments were conducted in artificially infested soil to evaluate the in vivo impact of nanoparticles under study. Two application methods were employed: soil drenching with 10 mL per pot at concentrations of 50, 100, and 200 mg L−1, and seedling dipping in nanoparticle suspensions at each concentration combined with soil drench. The combined treatment of 200 mg L−1 γFe2O3 or CuO nanoparticles showed the highest in vitro antifungal activity. Conversely, SiO2 nanoparticles demonstrated the lowest in vitro activity. Notably, the application of 200 mg/L SiO2 via the dipping and soil drenching methods decreased counts of silicate-solubilizing bacteria and Azospirillum spp. Whereas, application of 100 mg L−1 γFe2O3 nanoparticles via soil drenching increased soil bacterial counts, and CuO nanoparticles at 50 mg L−1 through dipping and soil drenching had the highest dehydrogenase value. γFe2O3 nanoparticles improved plant photosynthetic pigments, reduced malondialdehyde levels, and minimized membrane leakage in lettuce plants. A root anatomical study showed that 200 mg L−1 CuO nanoparticles induced toxicity, whereas 200 mg L−1 γFe2O3 or SiO2 nanoparticles positively affected root diameter, tissue structure, and various anatomical measurements in lettuce roots. γFe2O3 nanoparticles hold promise as a sustainable alternative for managing crop diseases.

Developing innovative, eco-friendly fungicide alternatives is crucial to mitigate the substantial threat fungal pathogens pose to crop yields. In this study, we assessed the in vitro effectiveness of SiO2, CuO, and γFe2O3 nanoparticles against Rhizoctonia solani. Furthermore, greenhouse experiments were conducted in artificially infested soil to evaluate the in vivo impact of nanoparticles under study. Two application methods were employed: soil drenching with 10 mL per pot at concentrations of 50, 100, and 200 mg L−1, and seedling dipping in nanoparticle suspensions at each concentration combined with soil drench. The combined treatment of 200 mg L−1 γFe2O3 or CuO nanoparticles showed the highest in vitro antifungal activity. Conversely, SiO2 nanoparticles demonstrated the lowest in vitro activity. Notably, the application of 200 mg/L SiO2 via the dipping and soil drenching methods decreased counts of silicate-solubilizing bacteria and Azospirillum spp. Whereas, application of 100 mg L−1 γFe2O3 nanoparticles via soil drenching increased soil bacterial counts, and CuO nanoparticles at 50 mg L−1 through dipping and soil drenching had the highest dehydrogenase value. γFe2O3 nanoparticles improved plant photosynthetic pigments, reduced malondialdehyde levels, and minimized membrane leakage in lettuce plants. A root anatomical study showed that 200 mg L−1 CuO nanoparticles induced toxicity, whereas 200 mg L−1 γFe2O3 or SiO2 nanoparticles positively affected root diameter, tissue structure, and various anatomical measurements in lettuce roots. γFe2O3 nanoparticles hold promise as a sustainable alternative for managing crop diseases. [ABSTRACT FROM AUTHOR]

Background: The aim is to study the disease suppression efficiency, yield loss rate, and yield benefits of intercropped faba bean against chocolate spot under nitrogen (N) input, to clarify the effectiveness of intercropping faba beans in controlling chocolate spot and its contribution to yield increase. Results: Four N input levels and disease suppression treatments were discovered when faba bean–wheat intercropped was used. Adding N enhanced the chocolate spot's area under disease progression curve (AUDPC) by 27.1–69.9%. In contrast to monoculture, intercropping reduced the AUDPC of the chocolate spot by 32.4–51.0% (P < 0.05). Interestingly, the relative control efficacy (RCE) of intercropping at the EShan site was better. With disease suppression or non‐suppression, N input increased grain yield loss and its components in faba bean. The total yield advantage effect (TE) and disease‐suppression effect (DSE) of faba bean intercropped at the two experimental sites were significantly increased under N input (N1 and N2 level). The proportion of recovery yield due to intercropping suppressed disease (DSE/TE ratio) in EShan (52.1%) was higher than that in Xundian (40.9%), and the DSE of intercropping played an indispensable role in the two sites. Regression analysis of AUDPC and grain yield loss amount showed that one unit increase in chocolate spot AUDPC could cause a grain yield loss of 0.38–0.86 kg ha−1. The partial land equivalent ratio (pLER) of intercropping faba beans at the EShan site was > 0.33. Conclusion: In conclusion, intercropped faba bean with N treatment (45–90 kg ha−1) was the best choice for maximizing the intercropping disease control effect. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The potential application of biological copper (Cu) nanoparticles (BCuNPs) as fungicides, insecticides, and fertilizers has piqued the interest of agricultural scientists. In the current study, BCuNPs were biosynthesized by an isolate of Bacillus, which was determined to be Bacillus subtilis subsp. subtilis. This strain can tolerate copper concentrations up to 12 mM and reduce copper by synthesizing BCuNPs. Ultraviolet-visible spectroscopy, dynamic light scattering (DLS), Zeta potential, Fourier transform infrared (FTIR), and transmission electron microscopy (TEM) equipment were used to characterize BCuNPs. As assessed by TEM and DLS, they ranged in size from 15 to 45 nm, with an average particle size of 23 nm. It was necessary to conduct both in vitro and in vivo studies to confirm the nematicidal activity of the fabricated BCuNPs on the infective second-stage juveniles (J2s) and eggs of Meloidogyne incognita the causal agent of root knot disease of cucumber. The in vitro application of different concentrations (100, 125, 150, 175, 200, 225, and 250 ppm) of BCuNPs significantly (P<0.05) increased the number of dead (J2s) of M. incognita, and significantly (P<0.05) decreased the percentage of egg hatching of M. incognita after 12, 24, 48, 72, and 96 h of application compared to the negative control (distilled water) with 250 ppm being the most effective dose of application after 96 h of application. Furthermore, the in vitro application of these different concentrations of BCuNPs combined with nematicide Tervigo® (abamectin, at the recommended application rate (RAR) of 0.1), significantly (P<0.05) increased the number of dead (J2s), and significantly (P<0.05) decreased the percentage of egg hatching of M. incognita compared to the negative control (distilled water), the positive control (Tervigo® alone), and compared to the BCuNPs alone, with 250 ppm being the most effective dose of application after 96 h of application. The number of galls, number of egg masses, root gall index, egg mass index of M. incognita on infected cucumber, the population density of M. incognita J2s 100 g soil-1, as well as the population of Tylenchorhynchus spp., Pratylenchus spp., and Helicotylenchus spp. in soil, were all significantly (P<0.05) reduced by 100, 150, 200, and 250 ppm of BCuNPs when applied under greenhouse conditions, with 250 ppm being the most toxic compared to the untreated of M. incognita treatment. When the nematicide abamectin (used at 0.1 RAR) and BCuNPs (used at 250 ppm) were used together in vivo, they had a synergistic effect on M. incognita. This treatment was found to be significantly (P<0.05) better than the nematicide abamectin alone in reducing the number of galls, the number of egg masses, the root gall index, the egg mass index of M. incognita on infected cucumber, and the population density of J2s 100 g soil-1. These findings indicate that the use of BCuNPs at 250 ppm either individually or combined with nematicide abamectin in integrated pest management systems for controlling nematodes infesting cucumber is recommended. [ABSTRACT FROM AUTHOR]

Fusarium wilt of watermelon caused by Fusarium oxysporum f. sp. niveum (Fon) results in a substantial economic losses in agriculture. Biological control agents (BCAs) help in controlling the infection of Fon. However, it remains unclear whether the application of BCAs can invoke soil suppression by inducing specific microbial groups concerned with disease suppression to synergistically resist fungal pathogens. The objective of this project was to determine the microbial mechanisms involved in disease suppression by BCAs. Here, we conducted pot experiments to explore Fusarium wilt in watermelon and soil microbial communities in response to different treatments. We found that the application of Bacillus velezensis WB enhanced disease suppression in nonsterilized soil. We further found that disease suppression in the WF treatment was connected to influence on the resident soil microbial communities, explicitly by causing an increase in Hyphomicrobiaceae and Chitinophagaceae. Pathogen suppression by the above two families was further studied in laboratory and pot experiments. The results showed that a synthetic community consisting of specific bacterial taxa effectively decreased the incidence of Fusarium wilt. B. velezensis WB introduction impacts the resident soil microbiome and invokes soil suppression by inducing resident microbes. Our results should help in designing synthetic microbial communities to improve soil function.

Cucumber wilt, caused by Fusarium oxysporum f. sp. cucumerinum (FOC), is a soilborne disease that poses a significant threat to cucumber production, resulting in substantial yield losses. This study aimed to evaluate the biocontrol and growth-promoting effects of Bacillus velezensis, a highly active bacterial strain. In vitro assays revealed that B. velezensis F9 exhibited broad-spectrum antifungal activity against eight plant pathogenic fungi, with inhibition ratio ranging from 62.66% to 88.18%. Additionally, the strain displayed the ability to produce IAA (5.97 ± 1.75 µg/mL), fix nitrogen, produce siderophores, and form biofilms. In vitro growth promotion assays demonstrated that different concentrations of B. velezensis F9 significantly promoted cucumber seedling growth. Furthermore, two pot experiments revealed that the strain exhibited biocontrol efficacy against cucumber wilt, with disease control rates ranging from 42.86% to 67.78%. Notably, the strain significantly increased the plant height, fresh weight, and dry weight, with increases ranging from 20.67% to 60.04%, 40.27% to 75.51%, and 22.07% to 52.54%, respectively. Two field trials confirmed the efficacy of B. velezensis F9 in controlling cucumber wilt, with disease control rates of 44.95% and 33.99%, respectively. The strain effectively alleviated the dwarfing and wilting symptoms caused by the pathogen. Compared with the FOC treatment, the F9 + FOC treatment significantly increased the plant height, fresh weight, and dry weight, with increases of 43.85% and 56.28%, 49.49% and 23.70%, and 36.25% and 73.63%, respectively. Enzyme activity assays indicated that inoculation significantly increased SOD activity in cucumber leaves and neutral phosphatase, sucrase, and urease activity in rhizosphere soil. Correlation analysis revealed a negative correlation between the disease index and plant height, fresh weight, dry weight, and peroxidase activity, with correlation coefficients of −0.53, −0.60, −0.38, and −0.45, respectively. These findings suggest that plant height, fresh weight, and dry weight are significantly negatively correlated with the cucumber disease index, highlighting their importance as indicators for evaluating the biocontrol efficacy of B. velezensis F9. In conclusion, B. velezensis F9 is a highly effective plant growth-promoting rhizobacterium with excellent biocontrol potential, showcasing promising applications in agricultural production.

Fusarium root rot caused by the Fusarium species complex significantly affects the yield and quality of Angelica sinensis, a valuable medicinal herb. Traditional management primarily relies on chemical fungicides, which have led to pathogen resistance, environmental hazards, and concerns regarding public health and the active components in A. sinensis. This study explores the efficacy of a novel plant-derived biopesticide Shi Chuang Zhi Feng Ning (T1; SCZFN), alongside Bacillus subtilis wettable powder (T2) and a chemical fungicide (T3), in controlling root rot and understanding their impacts on the rhizosphere microbial community and root metabolome. Results of the field experiment demonstrated that treatments T1 and T3 achieved control efficiencies of 73.17% and 75.45%, respectively, significantly outperforming T2 (39.99%) and the control. High-throughput sequencing revealed that all treatments altered the diversity and structure of microbial communities, with T1 and T2 reducing the abundance of taxa linked to root rot, such as Muribaculaceae spp., Humicola spp., Fusarium spp., and Mycochlamys spp. Treatment T1 notably enhanced beneficial bacterial taxa, including Acidobacteria spp., Nitrospira spp., and Pedosphaeraceae spp., involved in carbon cycling and plant growth promotion. Metabolomic analysis identified 39, 105, and 45 differentially expressed metabolites (DEMs) across the treatments, demonstrating T1’s potential to modulate the root metabolome effectively. Further, a correlation analysis demonstrated a stronger correlation between distinct microorganisms with significant influence and DEMs of T1 treatment compared to other treatments. These findings underscore biopesticide SCZFN’s role in enhancing plant health and disease suppression in A. sinensis, providing insights into its biocontrol mechanisms and supporting the development of sustainable disease management strategies in its cultivation.

Microbial community-based disease management approaches have the potential to substitute or combine with currently employed strategies. Suppressive soils are great examples of microbial communities that suppress soilborne plant disease after severe outbreaks and are maintained over multiple years or crop cycles. Although there are many suppressive soil examples, to our knowledge, there are no descriptions of disease-suppressive phyllosphere communities. Therefore, we investigated whether a phyllosphere microbial community could be developed through a selective passaging method to suppress disease using the model pathosystem of Pseudomonas syringae pv. tomato (Pto) and tomato. Field tomato phyllosphere microbial communities were recovered and spray transferred to greenhouse tomato plants, after which they were inoculated with Pto. Disease severity was visually estimated and the microbial communities were recovered to be independently applied to the next passage. Overall, greenhouse passaging resulted in an increase in disease severity for all passage lines from the initial passage, which peaked at passage 4 to 5, followed by a sharp decline until passage 9. The disease severity at passage 9 was also significantly lower than a non-passaged Pto-only comparison. Heat treatment of passage 9 communities resulted in elevated disease severity over several subsequent passages in the growth chamber, whereas the untreated community maintained low disease. Community-only passage lines (without Pto inclusion during passaging) did not show disease suppression after subsequent pathogen introduction. This work presents an experimental approach to develop phyllosphere microbial communities in the presence of a phytopathogen to enrich for a low disease phenotype and results in maintained disease suppression. [Graphic: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Soil-dwelling phages have enormous biocontrol potentials and very little has been documented on the use of phages to enhance soil fertilization with the aim of achieving sustainable plant protection and crop yield. To the best of our knowledge, previous reports on phage therapy and phage biocontrol of plant-related diseases do not focus on assessing the potential of phages in manipulating microbial communities in soils through the application of organic fertilizer. Key methods that have been used to control plant pathogens comprise the foliar application of phages and soil drenching. However, these approaches provide limited biocontrol results. Phage introduction into the soil via soil drench is limited by phage adsorption to clay particles and foliar application potency is impaired by UV radiation inactivation of the phages. This review provides a critical perspective on the sustainability of manipulating physical, chemical, and biological properties of the soil through phage-directed fertilization with the aim of increasing phage abundance, infectivity, and survival within different soil environments.

ABSTRACT The replant problem is a widespread challenge in agricultural production and results in significant financial losses. The survival and development of American ginseng (Panax quinquefolius L.), a well-known perennial medicinal plant, also typically suffer from replant problems. At present, efficient strategies for this issue and the underlying mechanisms are still lacking. Here, a series of in situ field experiments over a 4-year period were conducted to investigate the effectiveness and possible mechanisms of soil fumigation and fungicide in improving American ginseng survival under continuous cropping. During the 4-year ginseng cultivation, the seedling emergence rates in the dazomet fumigation-treated group (DF) decreased from 90.67% to 52.92%, from 78.67% to 0% in the lime sulfur fungicide-treated group (LS), and from 66.67% to 0% in the control. The fresh root weight in DF increased from 0.36 to 28.72 g, from 0.32 to 13.74 g in LS, and from 0.42 to 9.06 g in the control for the first 2 years. However, no ginseng survived during the following 2 years. Moreover, DF significantly decreased root rot disease incidence by 55.55% compared to LS-treated soil and 69.39% compared to non-treated soil. The correlation analysis results showed that both diversity and structure indices of bacteria and fungi were significantly correlated with root biomass and disease incidence in the second year. In summary, DF has presented a significant beneficial effect on American ginseng development. Additionally, the second year is the critical period to shape the soil microbial community, which could have a long-lasting effect on the development of American ginseng. IMPORTANCE Numerous reports of soil fumigants and fungicides on annual crops exist; however, it is unclear whether the single application to perennial plants persistently improves plant growth and controls disease or whether it has a long-lasting impact on soil microbes. We found that soil fumigation enhances ginseng growth and suppresses root rot disease by reshaping the soil microbial community. Our findings benefit the agricultural development of ginseng and provide a theoretical basis for the prevention of ginseng diseases.

Fusarium wilt of watermelon caused by Fusarium oxysporum f. sp. niveum (Fon) results in a substantial economic losses in agriculture. Biological control agents (BCAs) help in controlling the infection of Fon. However, it remains unclear whether the application of BCAs can invoke soil suppression by inducing specific microbial groups concerned with disease suppression to synergistically resist fungal pathogens. The objective of this project was to determine the microbial mechanisms involved in disease suppression by BCAs. Here, we conducted pot experiments to explore Fusarium wilt in watermelon and soil microbial communities in response to different treatments. We found that the application of Bacillus velezensis WB enhanced disease suppression in nonsterilized soil. We further found that disease suppression in the WF treatment was connected to influence on the resident soil microbial communities, explicitly by causing an increase in Hyphomicrobiaceae and Chitinophagaceae. Pathogen suppression by the above two families was further studied in laboratory and pot experiments. The results showed that a synthetic community consisting of specific bacterial taxa effectively decreased the incidence of Fusarium wilt. B. velezensis WB introduction impacts the resident soil microbiome and invokes soil suppression by inducing resident microbes. Our results should help in designing synthetic microbial communities to improve soil function. [ABSTRACT FROM AUTHOR]

Plant growth-promoting rhizobacteria are helpful soil microorganisms that are used extensively in the agricultural industry. In the current investigation, a total of 120 extremophilic bacterial isolates were successfully obtained from a variety of drastic soils. These bacterial isolates were tested to determine their effectiveness as plant growth promoters and biocontrol agents against the two most frequent soil-borne plant pathogenic fungi, Pythium ultimum, and Rhizocotnia solani. Results indicated that numerous isolates demonstrated antifungal activity against P. ultimum and R. solani, through the production of diffusible antifungal metabolites, cell-wall degrading enzymes (chitinase, cellulase), and siderophores. In addition, many of these extremophilic bacteria fixed atmospheric nitrogen, solubilized insoluble phosphate and zinc, and produced indole-3-acetic acid (IAA) and salicylic acid. The 16 S rRNA analysis revealed that the most potent isolates with multiple modes of action were identified as Bacillus halotolerans, Massilia alkalitolerans, and Bacillus aryabhattai. Under greenhouse conditions, these three isolates, either individually or in combination were used as microbial inoculants, and their effects on the development of tomato and maize were evaluated both with and without the presence of the two pathogens. Application of the three isolates as individual or combined treatments significantly (P < 0.05) reduced the growth of P. ultimum and R. solani in vivo, and significantly (P < 0.05) increased the percentage of survived seedlings as evidenced by the significant (P < 0.05) increase in plant resistance as measured by the in planta contents of total phenols, polyphenol oxidase, and peroxidase. Additionally, the treatment of any one of the three isolates, either individually or in combination, significantly (P < 0.05) improved the development of tomato and maize, as evidenced by a considerable increase in the amount of total nitrogen and dry weight yield. The utilization of these bacterial isolates presents a potentially fruitful alternative to the excessive use of potentially harmful agrochemicals. [ABSTRACT FROM AUTHOR]

Abiotic and biotic stresses have been a serious threat to crop growth and productivity in the agricultural system. In this study, four strains (HS1, H30-3, KJ40, and BC42), which have biological activities related to disease suppression or alleviation of salinity and drought stresses, were tested for broad-spectrum biocontrol activity against anthracnose caused by Colletotrichum orbiculare, a bacterial fruit blotch caused by Acidovorax citrulli, and Fusarium wilt caused by Fusarium oxysporum in cucumber plants. As a result of test, when the four strains were drenched into the soil, anthracnose in cucumber leaves significantly decrease; strain KJ40 suppressed disease incidence by A. citrulli; strain BC42 significantly reduced bacterial fruit blotch and Fusarium wilt compared to control. Therefore, strain KJ40 could be a biocontrol candidate for controlling anthracnose through induced systemic resistance and the disease caused by A. citrulli as well as alleviating drought stress; strain BC42 has broad-spectrum biocontrol activity against anthracnose, Fusarium wilt, and bacterial fruit blotch.

Wheat (Triticum aestivum L.), as one of the most important cultivated crops in the world and Iran, is constantly threatened by many diseases, including Fusarium contamination. Due to the unique characteristics of nanoparticles, copper oxide nanoparticles show high antibacterial and antifungal properties. The purpose of this research was to comparatively investigate the antifungal effects of copper oxide nanoparticles and its bulk form on the suppression of Fusarium calmorum in wheat. For this purpose, a pot experiment was done with four levels (10, 250, 500, and 1000 mg L-1) of nanoparticles and bulk form of copper oxide treatments in wheat (Roshan cultivar). The results showed that the maximum inhibition of root pathogenicity was observed in a high concentration of nanoparticles as compared to bulk form. The 250 and 500 mg L-1 concentrations of copper oxide nanoparticles caused the highest stem and root length and the highest dry weight of the aerial part and root, respectively. Treatment with 10 and 250 mg L-1 nanoparticles also increased the content of chlorophyll a, total chlorophyll, carotenoid, chlorophyll stability index, membrane stability coefficient, and relative leaf water content. While the content of chlorophyll b, malondialdehyde, hydrogen peroxide, and proline increased with the increasing concentration of both nanoparticle and bulk forms. The results of this research showed that the low and medium concentrations of nanoparticles were more successful in inhibiting the aforementioned fungus than the bulk form.

The plant microbiome can enhance disease suppression by providing life-supporting functions to their host, including stress resilience, health, and growth. However, our understanding of the core mechanisms of microbiome assembly and activity is still emerging. This article explores the role of plant-associated microbes in enhancing host resistance against pathogen infection through disease suppression. We discuss the factors that influence the community assembly and functioning of the plant microbiome, along with an overview of the mechanisms of disease suppression by the plant microbiota. Additionally, we highlight plant characteristics and mechanisms that recruit and stimulate microbial allies for disease suppression. By uncovering the power of plant-microbe interactions, we can create sustainable disease management strategies in agriculture and beyond.

Plant roots host numerous microorganisms around and inside their roots, forming a community known as the root microbiome. An increasing bulk of research is underlining the influences root-associated microbial communities can have on plant health and development. However, knowledge on how plant roots and their associated microbes interact to bring about crop growth and yield is limited. Here, we presented (i) the communication strategies between plant roots and root-associated microbes and (ii) the applications of plant root-associated microbes in enhancing plant growth and yield. This review has been divided into three main sections: communications between root microbiome and plant root; the mechanism employed by root-associated microbes; and the chemical communication mechanisms between plants and microbes and their application in plant growth and yield. Understanding how plant root and root-associated microbes communicate is vital in designing ecofriendly strategies for targeted disease suppression and improved plant growth that will help in sustainable agriculture. Ensuring that plants become healthy and productive entails keeping plants under surveillance around the roots to recognize disease-causing microbes and similarly exploit the services of beneficial microorganisms in nutrient acquisition, stress mitigation, and growth promotion. [ABSTRACT FROM AUTHOR]

Anthracnose disease is a serious threat to red pepper crops in Korea and many other countries, resulting in considerable yield losses. There are now no effective control techniques available except for fungicide sprays, which may directly impact consumers. This study aims to investigate the biological activity of Trichoderma isolates in controlling red pepper anthracnose caused by Colletotrichum acutatum in vitro and in the field. Out of 11 Trichoderma isolates screened for biocontrol agents against three fungal pathogens, including C. acutatum; two effective Trichoderma isolates, T. atroviride ATR697 (ATR697) and T. longibrachiatum LON701 (LON701) were selected for further investigation. Using the overlapping plates experiment, it was discovered that the volatile organic compounds (VOCs) produced by ATR697 strongly inhibited C. acutatum mycelial growth to a larger extent than the isolate LON701. A cellophane membrane experiment has shown that mycelial growth of C. acutatum was inhibited by 36% and 27% when treated with ATR697 and LON701, respectively. Culture filtrates (CFs) of two Trichoderma isolates inhibited the mycelial growth of C. acutatum in vitro. When red peppers were treated with spore suspensions of LON701 and ATR697, the disease severity (%) was 44.1% and 55.8%, respectively, in a curative method; while the disease severity (%) was 5% and 11.6%, in LON701- and ATR697-treated red peppers, respectively, in a preventive method. These results showed the suppression of disease severity (%) was relatively higher in the preventive method than in the curative method. Furthermore, Trichoderma isolates ATR697 and LON701 were resistant to commercial chemical fungicides in vitro, indicating these strains may also be used synergistically with a chemical fungicide (pyraclostrobin) against the growth of C. acutatum. There was no difference in the inhibition rate (%) of the pathogen between the treatment with LON701 alone and LON701 +pyraclostrobin. Based on in vitro findings, ATR697 and LON701 played a role in effectively controlling red pepper anthracnose in field conditions, with LON701 treatment resulting in a disease rate of 14% when compared to ATR697, chemical, and non-treated controls. Overall, our study showed the ability of Trichoderma isolates to control red pepper anthracnose and their potential to develop as novel biocontrol agents to replace chemical fungicides for ecofriendly, sustainable agriculture [ABSTRACT FROM AUTHOR]

Bacterial wilt is a soil-borne disease that causes severe damage in ginger-growing regions of Japan (eight prefectures in the Shikoku, Kyushu, and Honshu regions). Because the pathogen Ralstonia pseudosolanacearum usually lives in deeper soil and infects host plants via the roots, it is not easy to eliminate even with chemical pesticides (such as soil fumigants). In our previous study, we found that anaerobic soil disinfestation with diluted ethanol (Et-ASD) effectively eliminated this pathogen. We conducted field experiments to confirm the effectiveness of Et-ASD in a ginger monoculture system. Eight trials were conducted in seven different ginger fields from spring to autumn. Excluding one trial in early spring, seven trials in summer successfully eliminated the pathogen from the field soil (below the detection limit by the developed sensitive bio-PCR method), and no disease recurrence was observed after ASD treatment. In addition, other useful methods for controlling the disease were explored, including proper field management after the disease outbreak and the disinfection of seed rhizomes. Based on these results, a comprehensive control system for bacterial wilt disease in ginger was developed. [ABSTRACT FROM AUTHOR]

In this study, biopolymers (sodium alginate, carboxymethylcellulose, gum arabic, xanthan gum) were used to bioprime the biocontrol agent (BCA) Pseudomonas fluorescens to pak choy (Brassica rapa) and chilli (Capsicum annum) seeds. The compatibility of the biopolymers with seeds and BCA was assessed by evaluating the survival of BCA, the percentage of BCA entrapped, and the influence of bacterial concentration on seed germination. The optimal condition was then selected for seed biopriming and disease tolerance studies. Results revealed that all biopolymers were compatible with P. fluorescens with the most effective biopolymer identified as 0.2% w:v xanthan gum (XG0.2). XG0.2 coated 70.48% and 69.91% of viable bioagent on pak choy and chilli seeds, respectively, and retained viability of P. fluorescens (4.33 – 4.64 Log CFU/seed) 24 h post biopriming. The most effective bacterial concentration for biopriming pak choy and chilli seeds were recorded as 107 and 102 bacterial cells/mL, respectively. The pot trial revealed that the bioprimed chilli seeds performed better against Pythium ultimum as lower disease severity (DS, 4.00 ± 2.19%) and better physiological attributes were recorded. On the contrary, P. fluorescens was less effective in suppressing disease in pak choy compared to chillies. The disease suppresion of Fusarium solani by P. fluorescens was not observed in potted trial. To conclude, our study showed the importance of xanthan gum as an effective coating matrix to coat P. fluorescens on seeds and their potential in promoting seedling growth and suppressing disease infection.

Introduction: A broad spectrum of rhizosphere bacteria and fungi were shown to play a central role for health, fitness and productivity of their host plants. However, implications of host metabolism on microbiota assembly in the phyllosphere and potential consequences for holobiont functioning were sparsely addressed. Previous observations indicated that tea plants might reduce disease occurrence in various forests located in their proximity; the underlying mechanisms and potential implications of the phyllosphere microbiota remained elusive. Objectives: This study aimed at deciphering microbiome assembly in the tea plant phyllosphere throughout shoot development as well as elucidating potential implications of host metabolites in this process. The main focus was to explore hidden interconnections between the homeostasis of the phyllosphere microbiome and resistance to fungal pathogens. Methods: Profiling of host metabolites and microbiome analyses based on high-throughput sequencing were integrated to identify drivers of microbiome assembly throughout shoot development in the phyllosphere of tea plants. This was complemented by tracking of beneficial microorganisms in all compartments of the plant. Synthetic assemblages (SynAss), bioassays and field surveys were implemented to verify functioning of the phyllosphere microbiota. Results: Theophylline and epigallocatechin gallate, two prevalent metabolites at the early and late shoot development stage respectively, were identified as the main drivers of microbial community assembly. Flavobacterium and Myriangium were distinct microbial responders at the early stage, while Parabacteroides and Mortierella were more enriched at the late stage. Reconstructed, stage-specific SynAss suppressed various tree phytopathogens by 13.0%-69.3% in vitro and reduced disease incidence by 8.24%-41.3% in vivo. Conclusion: The findings indicate that a functional phyllosphere microbiota was assembled along with development-specific metabolites in tea plants, which continuously suppressed prevalent fungal pathogens. The insights gained into the temporally resolved metabolite response of the tea plant microbiota could provide novel solutions for disease management.

ABSTRACT The interactions between soil microbiomes at various trophic levels are essential for restoring soil functions. Legumes are considered as “pioneer crops” in degraded or contaminated soils because they can fix nitrogen through symbiotic relationships with rhizobacteria, which promotes soil fertility. However, little is known about the abilities of legumes to contribute to the health of soil contaminated with cadmium (Cd). In this research, we applied a soil amendment (commercial Mg–Ca–Si conditioner, CMC) at two rates (1,500 and 3,000 kg/ha) in a Cd-contaminated soybean field. Bulk and rhizosphere soil samples were collected to assess the amendment-induced effects on four microbial lineages (bacteria, fungi, arbuscular mycorrhizal fungi [AMF], and nematodes) and their functions including Cd stabilization, nutrient cycling, and pathogen control. Compared with the control, both CMC application rates increased the pH and reduced labile Cd fraction in the bulk and rhizosphere soils. Although the total Cd concentrations in the soil were similar, the Cd accumulation in the grains was significantly reduced in treatments of soil amendments. It was observed that the application of CMC can significantly reduce the AMF diversity but increased the diversity of the other three communities. Moreover, the biodiversity within keystone modules (identified by co-occurrence network analysis) played key roles in driving soil multifunctionality. Specifically, key beneficial groups in module 2 such as Aggregicoccus (bacteria), Sordariomycetes (fungi), Glomus (AMF), and Bursaphelenchus (nematode) were strongly associated with soil multifunctionality. By co-culturing bacterial suspensions with the soybean root rot pathogen Fusarium solani in the in vitro assays, we experimentally validated that the application of CMC promoted the suppression of soil bacterial community on pathogens by inhibiting the mycelium growth and spore germination. Also, the bacterial community was more resistant to Cd stress in soils receiving CMC amendment. Our findings provide valuable theoretical references for enhancing soil functions and health via applying a soil amendment (CMC) during Cd-contaminated soil remediation. IMPORTANCE Restoration of microbiome-driven soil functions and health is of great importance during Cd-contaminated soil remediation via soil amendment. Soybean and its symbiotic mutualism can provide abundant nitrogen and phosphorus to relieve the nutrient deficiency of Cd-contaminated soil. This study provides a novel perspective on the potential role of applying a soil amendment (CMC) in enhancing the functions and health of Cd-contaminated soils. Our results showed the distinct differences in soil microbial community responding to amendment-induced changes in edaphic properties. The biodiversity within keystone modules had major contributions to the maintenance of the soil’s multifunctionality and health. Additionally, a higher CMC application rate showed more beneficial effects. Collectively, our results enhance our understanding about the effects of applying CMC, together with soybean rotation, to enhance and maintain soil functions and health during the field Cd stabilization process.

The large outbreak of banana Fusarium wilt has become a bottleneck limiting the industry's development, and crop rotation is a cost-effective and essential measure to overcome the obstacles of banana crop monoculture. The present work was carried out to explore the mechanisms of how changes in soil chemical properties and the reestablishment of soil microorganisms in high-incidence soils are affected by crop rotation and plant residue. In this study, pineapple–banana crop rotation and pineapple residue amendment were carried out to alleviate banana Fusarium wilt, and their effects on bacterial and fungal communities were analyzed using the MiSeq Illumina sequencing platform. Both pineapple–banana rotation and residue addition significantly reduced disease incidence. Moreover, pineapple rotation and residue amendment altered the bacterial and fungal community composition. The taxonomic and phylogenetic alpha diversity of bacteria and fungi significantly increased against disease suppression and nutrition competition. The relative abundances of the Burkholderia, Pseudomonas, Elaphocordyceps, Penicillium, and Talaromyces genera were higher, and the number of Fusarium was significantly lower in rotational soil than in banana monoculture soil. Finally, linear models (LM) showed that the Burkholderia and Talaromyces in crop rotation, and Aspergillus in residue amendment had a significantly negative relationship to disease incidence, which plays a key role in Fusarium reduction. To consider the economic benefits and protect the vitality of the soil, this study suggested that pineapple–banana rotation and pineapple residue amendment both could be considered for the sustainable management of banana wilt. [ABSTRACT FROM AUTHOR]

Plants activate defense mechanisms in response to biotic stress in the rhizosphere. The defensive action of date palm seedlings treated with green compost and/or phosphate sludge (PS) was investigated in a greenhouse experiment in soil infected with Fusarium oxysporum f. sp. albedinis (Foa). In addition, the effect of green compost alone or in combination with phosphate sludge (PS) on growth, physiological, biochemical and tolerance of date palm seedlings was assessed under greenhouse conditions. Our results showed that compost alone or in combination with PS improved plant growth, physiological, biochemical, and soil attributes compared to non-amended date palm seedlings. The root/shoot antioxidant enzyme activity was significantly higher in the compost and compost+PS treatments compared to the control. The hydrogen peroxide concentration was significantly reduced in the presence of compost and/or compost+PS treatments compared to the control. As a result, physicochemical characteristics in infested soil were changed by compost and compost+PS, which boosted the plant's ability to withstand damages caused by Foa and stimulated growth performances. [ABSTRACT FROM AUTHOR]