Soil-borne Diseases Research Articles

Dynamic transcription analysis reveals the underlying key mechanism of L-arabinose-enhanced tomato resistance to bacterial wilt

Tomato bacterial wilt caused by Ralstonia solanacearum is a serious economic soil-borne disease worldwide. L-arabinose (L-Ara) increases tomato resistance to bacterial wilt, but the resistance mechanism remains unclear. In this study, we conducted an RNA sequencing (RNA-seq) analysis of tomato root and stem that exhibited differential expression in response to R. solanacearum infection at 2 dpi and 5 dpi under L-Ara application. As a result, 797 and 5605 differentially expressed genes (DEGs) were identified in response to R. solanacearum infection at 2 dpi and 5 dpi, respectively. In particular, 4504 DEGs with 2501 up-regulated and 2001 down-regulated were presented in the stem at 5 dpi, specifying that most defense responses were expressed at the wilting stage. In the function analysis (GO and KEGG), the DEGs were primarily enriched in response to stress, cell wall, glutathione and phenylpropanoid biosynthesis and plant hormone signaling transduction. Among the DEGs, potential candidate genes related to plant hormone biosynthesis and signaling, phenylpropanoid biosynthesis, and cell wall metabolism were perceived. Furthermore, the transcription factors had high expression in ERF, bHLH, C2H2, MYB, NAC, WRKY, HD-ZIP, bZIP, MYB-related, and GRAS families. This research could provide theoretical support and valuable resources for further study of the prevention and control of bacterial wilt disease under L-Ara treatment .

Untargeted metabolomic analysis reveals a potential role of saponins in the partial resistance of pea (Pisum sativum) against a root rot pathogen, Aphanomyces euteiches.

In soil-borne diseases, the plant-pathogen interaction begins as soon as the seed germinates and develops into a seedling. Aphanomyces euteiches, an oomycete, stays dormant in soil and gets activated by sensing the host through chemical signals present in the root exudates. The composition of plant exudates may, thus, play an important role during the early phase of infection. To better understand the role of root exudates in plant resistance, we investigated the interaction between partially resistant lines (PI660736 and PI557500) and susceptible pea cultivars (CDC Meadow and AAC Chrome) against Aphanomyces euteiches during the pre-invasion phase. The root exudates of two sets of cultivars clearly distinguished from each other in inducing oospore germination. PI557500 root exudate not only had diminished induction but also inhibited the oospore germination. The contrast between the root exudates of resistance and susceptible cultivars was reflected in their metabolic profiles. Data from fractionation and oospore germination inhibitory experiments identified a group of saponins that accumulated differentially in susceptible and resistant cultivars. We detected 56 saponins and quantified 44 of them in pea root and 30 from root exudate; the majority of them, especially Soyasaponin I and dehydrosoyasaponin I with potent in vitro inhibitory activities, were present in significantly higher amounts in both roots and root exudates of PI660736 and PI557500 as compared to Meadow and Chrome. Our results provide evidence for saponins as deterrents against Aphanomyces euteiches, which might have contributed to the resistance against root rot in the studied pea cultivars.

Effects of application methods of microbial mixture on early blight disease (Alternaria solani) and growth of potato

Early blight (Alternaria solani) is one of important diseases in potato in Indonesia. In previous study, a microbial consortium (Trichoderma harzianum, Bacillus subtilis and Pseudomonas sp.) suppressed the bacterial wilt disease in potato. For application, the microbial consortium was mixed with compost (10%). As the microbial consortium is originally intended for controlling soil-borne diseases, this study examined the ability of the microbial consortium to suppress early blight disease and the effects of application methods on its efficacy. The application methods examined were the methods that targeted for soil-borne as well as airborne diseases. The experiment was conducted in a greenhouse at the Department of Plants and Diseases, Faculty of Agriculture, Universitas Padjadjaran, Sumedang, West Java, Indonesia. The experiment used Randomized Complete Block Design with 10 treatments and three replications. The treatments included application of microbes mixed with compost in planting hole solely or in combination with soaking the potato tubers in suspension of the microbes, drenching water extract of the mixture at 2, 4, 6 weeks after planting (WAP) with or without foliar application of the water extract. The result showed that application method influenced the abilities of the microbial mixture in suppressing early blight disease and supporting the potato growth. Even though the application of microbe-compost in planting medium inhibited the development of early blight disease by 37.8-39.5%, the regular foliar spray of the water extract of the mixture enhanced the disease suppression. Combination between application of the microbe-compost in the planting hole, drenching its water extract at 2, 4, 6 WAP and weekly foliar spray of the water extract suppressed early blight disease by 80.8%. This combination of application methods also supported better plant height, numbers of potato leaflets, roots fresh weight and production of potato tuber.

Effect of Streptomyces costaricanus Strain A-m1 as a Bioinoculant on Tea Garden Soil and Tea Quality

Chemical fertilization is usually associated with some unreasonable problems that affect the sustainable production of tea gardens. The micro-organism fertilizer created from plant growth-promoting microbes (PGPM) integrates the beneficial properties of functional micro-organisms and bioinoculants. Application of PGPM can activate soil nutrients, prevent soil-borne diseases, and promote crop growth, thus improving crop quality and yield. In this study, the effects of bioinoculants composed of Streptomyces costaricanus strain A-m1 on the properties, enzyme activity, and micro-organisms of soil in a tea garden and on the chemical composition and production of tea were investigated. The present results showed that the application of A-m1 bioinoculant could increase the activities of urease, protease and catalase, the content of alkali-hydrolyzable nitrogen, and the number of bacteria, fungi, and actinomycetes in tea garden soil. After application, the free amino acid content, 100-bud weight, and bud density of spring tea were also elevated. In the year of fertilization, the treatment composed of 70% bioinoculant + 30% chemical fertilizer showed the best effects on soil physical and chemical properties, enzyme activity, culturable microbial counts, and tea quality. A high ratio of organic to chemical fertilizer coapplication can significantly improve the growing conditions for tea plants, reduce the use of chemical fertilizers, improve the efficiency of nutrient utilization, and enhance both the yield and quality of tea. One year after fertilization, the 50% bioinoculant + 50% chemical fertilizer was more conducive to enhancing the quality of tea, while the 30% bioinoculant + 70% chemical fertilizer was more beneficial for improving the production of tea. A high ratio of chemical to bioinoculant coapplication is more favorable for maintaining high yield and quality in tea production, achieving healthy and sustainable tea garden management. The application of A-m1 bioinoculant will reduce the use of chemical fertilizers, improve the utilization efficiency of soil nutrients, and increase the production and quality of tea, contributing to the sustainable production of tea gardens.

Comparative Analysis of Transcriptomes Reveals Pathways and Verifies Candidate Genes for Clubroot Resistance in Brassica oleracea.

Clubroot, a soil-borne disease caused by Plasmodiophora brassicae, is one of the most destructive diseases of Brassica oleracea all over the world. However, the mechanism of clubroot resistance remains unclear. In this research, transcriptome sequencing was conducted on root samples from both resistant (R) and susceptible (S) B. oleracea plants infected by P. brassicae. Then the comparative analysis was carried out between the R and S samples at different time points during the infection stages to reveal clubroot resistance related pathways and candidate genes. Compared with 0 days after inoculation, a total of 4991 differential expressed genes were detected from the S pool, while only 2133 were found from the R pool. Gene function enrichment analysis found that the effector-triggered immunity played a major role in the R pool, while the pathogen-associated molecular pattern triggered immune response was stronger in the S pool. Simultaneously, candidate genes were identified through weighted gene co-expression network analysis, with Bol010786 (CNGC13) and Bol017921 (SD2-5) showing potential for conferring resistance to clubroot. The findings of this research provide valuable insights into the molecular mechanisms underlying clubroot resistance and present new avenues for further research aimed at enhancing the clubroot resistance of B. oleracea through breeding.

Evaluation of Chemical and Biological Products for Control of Crown Gall on Rose.

Crown gall is a soil-borne bacterial disease caused by Agrobacterium tumefaciens, leading to significant economic losses in many plant species. For the assessment of the biological and chemical products on crown gall, each plant's crown region and roots were wounded, and then were dipped into their respective treatments. After the treatments, the plants were inoculated with a suspension of pathogenic A. tumefaciens isolate FBG1034 and maintained in a greenhouse for six months to assess them for gall formation. A quantitative real-time PCR assay was performed to quantify the A. tumefaciens using the chvE gene. Biological products such as the Agrobacterium radiobacter strain K1026, and strains 1 and 2, resulted in the lowest average root gall diameter and significantly reduced the crown gall diameter to stem diameter ratio, and the chemical product copper octanoate reduced the number of crown and root galls as well as the crown and root gall diameter compared to the inoculated, non-treated control. Moreover, both the A. radiobacter strain K1026 and strain 1 treatments resulted in an approximately 85% and 65% reduction in crown and root gall incidence, respectively, in both of the trials compared to the inoculated, non-treated plants. The findings of this study indicate that the use of biological and chemical products could help to suppress crown and root gall disease in rose plants.

Effects of Streptomyces melanosporofaciens X216 on microbial diversity in oilseed rape soil.

Clubroot disease is a devastating soil borne disease caused by infection with Plasmodiophora brassicae, which primarily affects cruciferous plants. The microbial diversity of the soil is an essential indicator of its quality. This study measured the physicochemical properties of the soil to study the effect of its microbial diversity on the infection of oilseed rape with P. brassicae. High-throughput sequences of the soil bacteria and fungi in the inter-root soils of P. brassicae were analyzed under different treatment conditions. In the study, it was found that the efficiency of strain X216 in preventing and controlling the root disease of rapeseed was positively correlated with the amount of solution used to irrigate the root system. The results of the greenhouse and field trials showed that the efficiency of strain X216 against the root disease of rapeseed was 43.16% in the field and 62.14% in the greenhouse. Proteobacteria, Chloroflexi, Rozellomycota, and Basidiomycota are critical phylum in the development of clubroot disease. The application of biocontrol increased the relative abundance of Actinobacteria, Bacillus, Mesorhizobium, Mycobacterium, Streptomyces and Filobasidium, which affected the structure and abundance of microbial communities. A principal coordinate analysis showed that the microbial structure in the soil varied substantially in the bacterial community, and there was no significant difference in soil structure in the fungal community. The occurrence of clubroot disease affected the structure of inter-root microbial community composition in the soil, which resulted in a decrease in its community diversity. The application of the biocontrol bacterium X216 increased the soil microbial diversity. It effectively reduced the occurrence of P. brassicae, and this study provides a basis to study the microbial diversity in cruciferous crops.

Associations Among Cultivar Cropping Sequence, 2,4-Diacetlyphloroglucinol-Producing Pseudomonad Populations, and Take-All Disease of Winter Wheat in Oregon.

Take-all of wheat (Triticum aestivum L.), caused by Gaeumannomyces tritici (syn. G. graminis var. tritici), is perhaps the most important soil-borne disease of wheat globally and can cause substantial yield losses under several cropping scenarios in Oregon. Though resistance to take-all has not been identified in hexaploid wheat, continuous cropping of wheat for several years can reduce take-all severity through the development of suppressive soils, a process called "take-all decline" (TAD). Extensive work has shown that TAD is driven primarily by members of the Pseudomonas fluorescens complex that produce 2,4-diacetlyphloroglucinol (DAPG), an antibiotic that is associated with antagonism and induced host resistance against multiple pathogens. Field experiments were conducted to determine the influence of agronomically relevant first year wheat cultivars on take-all levels and ability to accumulate DAPG-producing pseudomonads within their rhizospheres in second-year field trials and in greenhouse trials. One first year wheat cultivar consistently resulted in less take-all in second-year wheat and accumulated significantly more DAPG-producing pseudomonads than other cultivars, suggesting a potential mechanism for take-all reduction associated with that cultivar. An intermediate level of take-all suppression in other other cultivars was not clearly associated with population size of DAPG-producing pseudomonads, however. The first year cultivar effect on take-all dominated in subsequent plantings, and its impact was not specific to the first year cultivar. Our results confirm that wheat cultivars may be used to suppress take-all when deployed appropriately over cropping seasons, an approach that is cost effective, sustainable, and currently being utilized by some wheat growers in Oregon to reduce take-all.

Bacillus velezensis YC89-mediated recruitment of rhizosphere bacteria improves resistance against sugarcane red rot

BackgroundSugarcane red rot is a soil-borne disease caused by Colletotrichum falcatum. It can reduce the yield of sugarcane and the purity of sugarcane juice, which seriously restricts the development of sucrose industry. Biocontrol bacteria can control diseases by regulating rhizosphere microecology. In this study, the effects of biocontrol bacteria on sugarcane rhizosphere microecology were studied by metagenomics and metabolomics, and the control effects of biocontrol bacteria and rhizosphere dominant bacteria on sugarcane red rot were further explored by pot experiment.ResultsThe results of metagenomic sequencing showed that inoculation with B. velezensis YC89 and pathogens could significantly change the microbial diversity of the sugarcane rhizosphere. The relative abundance of beneficial strains such as Streptomyces, Burkholderia, Sphingomonas, and Rhizobium increased significantly in the rhizosphere of sugarcane in the YC treatment group. Pseudomonas was significantly enriched in the rhizosphere of sugarcane in the C treatment group. The results of metabolome sequencing showed that the content of amino acids in sugarcane root exudates increased after inoculation with B. velezensis YC89, and the contents of phenolic acids and flavonoids decreased. Spearman correlation analysis showed that there was a significant correlation between differential metabolites and rhizosphere microorganisms. The results of pot experiment showed that YC89 strain and three rhizosphere microorganisms could significantly reduce the disease index of red rot and promote the growth of sugarcane plants. In addition, these strains can also significantly increase the JA and SA content of sugarcane leaves and induce plant system resistance-related enzyme activities. Among them, the synthetic community treatment group had the best biocontrol effect on red rot, and its relative control effect was 67.50%.ConclusionsTherefore, we conclude that B. velezensis YC89 could recruit beneficial rhizosphere microorganisms to enrich the rhizosphere and change the content of some phenolic acids and flavonoids in the root exudates. In addition, the isolated rhizosphere dominant bacteria and YC89 strain can resist red rot by inducing plant systemic resistance and promote the growth of sugarcane plants. This study provides a theoretical basis for the use of biocontrol bacteria to regulate rhizosphere bacteria to jointly control plant soil-borne diseases.Graphical

Sustainable management of peanut damping-off and root rot diseases caused by Rhizoctonia solani using environmentally friendly bio-formulations prepared from batch fermentation broth of chitinase-producing Streptomyces cellulosae.

Soil-borne plant diseases represent a severe problem that negatively impacts the production of food crops. Actinobacteria play a vital role in biocontrolling soil-borne fungi. The target of the present study is to test the antagonistic activity of chitinase-producing Streptomyces cellulosae Actino 48 (accession number, MT573878) against Rhizoctonia solani. Subsequently, maximization of Actino 48 production using different fermentation processes in a stirred tank bioreactor. Finally, preparation of bio-friendly formulations prepared from the culture broth of Actino 48 using talc powder (TP) and bentonite in a natural as well as nano forms as carriers. Meanwhile, investigating their activities in reducing the damping-off and root rot diseases of peanut plants, infected by R. solani under greenhouse conditions. Actino 48 was found to be the most significant antagonistic isolate strain at p ≤ 0.05 and showed the highest inhibition percentage of fungal mycelium growth, which reached 97%. The results of scanning electron microscope (SEM) images analysis showed a large reduction in R. solani mycelia mass. Additionally, many aberrations changes and fungal hypha damages were found. Batch fermentation No. 2, which was performed using agitation speed of 200rpm, achieved high chitinase activity of 0.1163 U mL- 1 min- 1 with a yield coefficient of 0.004 U mL- 1 min- 1 chitinase activity/g chitin. Nano-talc formulation of Actino 48 had more a significant effect compared to the other formulations in reducing percentages of damping-off and root rot diseases that equal to 19.05% and 4.76% with reduction percentages of 60% and 80%, respectively. The healthy survival percentage of peanut plants recorded 76.19%. Furthermore, the nano-talc formulation of Actino 48 was sufficient in increasing the dry weight of the peanut plants shoot, root systems, and the total number of peanut pods with increasing percentages of 47.62%, 55.62%, and 38.07%, respectively. The bio-friendly formulations of actinobacteria resulting from this investigation may play an active role in managing soil-borne diseases.

Maize-Soybean Rotation and Intercropping Increase Maize Yield by Influencing the Structure and Function of Rhizosphere Soil Fungal Communities.

Soil-borne diseases are exacerbated by continuous cropping and negatively impact maize health and yields. We conducted a long-term (11-year) field experiment in the black soil region of Northeast China to analyze the effects of different cropping systems on maize yield and rhizosphere soil fungal community structure and function. The experiment included three cropping systems: continuous maize cropping (CMC), maize-soybean rotation (MSR), and maize-soybean intercropping (MSI). MSI and MSR resulted in a 3.30-16.26% lower ear height coefficient and a 7.43-12.37% higher maize yield compared to CMC. The richness and diversity of rhizosphere soil fungi were 7.75-20.26% lower in MSI and MSR than in CMC. The relative abundances of Tausonia and Mortierella were associated with increased maize yield, whereas the relative abundance of Solicoccozyma was associated with decreased maize yield. MSI and MSR had higher proportions of wood saprotrophs and lower proportions of plant pathogens than CMC. Furthermore, our findings indicate that crop rotation is more effective than intercropping for enhancing maize yield and mitigating soil-borne diseases in the black soil zone of Northeast China. This study offers valuable insights for the development of sustainable agroecosystems.

Melatonin and copper oxide nanoparticles synergistically mitigate clubroot disease and enhance growth dynamics in Brassica rapa

Clubroot, a devastating soil borne disease affecting 30%∼50% of Brassicaceae crops worldwide, lacks effective control measures. In the present study, we explored the potential of melatonin (MT) and copper oxide nanoparticle (CuO-NPs) in mitigating clubroot severity in the Brassica rapa ssp. pekinensis. Following 18 h priming with MT, CuO-NPs, or both seeds were grown in controlled environment using synthetic potting mix. Inoculated with Plasmodiophora brassicae spores on 5th day, followed by a soil drench phyto-nano treatment with a week interval. Plants were assessed for various health and growth indices including disease, biometrics, photosynthesis, reactive oxygen species (ROS), antioxidant enzyme activity, hormones and genes expression at onset of secondary clubroot infection using established protocols. Statistical analysis employed ANOVA with Fisher's LSD for significance assessment (P < 0.05). Our results revealed that seed priming with both MT (50 μMol/L) and CuO-NPs (200 mg/L), followed by soil drenching significantly reduced clubroot incidence (38%) and disease index (57%), compared to control treatments. This synergistic effect was associated with enhanced plant growth (shoots: 48% and roots: 59%). Plants treated with both MT and CuO-NPs showed robust antioxidant defenses, significantly increased superoxide dismutase (SOD (25/29%)), catalase (CAT (83/55%)), and ascorbate peroxidase (APX (83/46%)) activity in both shoots/roots, respectively, compared to infected control. Notably, salicylic acid and jasmonic acid levels doubled in treated plants, while stress hormone abscisic acid (ABA) decreased by 80% in roots and 21% in shoots. Gene expression analysis corroborated these findings, showing that the combined treatment activated antioxidant defense genes (SOD, APX and CAT) by 1.9–7.2-fold and upregulated hormone signaling genes JAZ1 (7.8-fold), MYC2 (3.9-fold) and SABP2 (36-fold). Conversely, ABA biosynthesis genes (ABA1 and NCED1) were downregulated up to 7.2-fold, while plant resistance genes NPR1, PRB1 and PDF1.2 were dramatically increased by up to 6.3-fold compared to infected plants. Overall, our combined treatment approach significantly reduces clubroot severity in B. rapa via enhanced antioxidant defenses, improved ROS scavenging, coordinated hormonal regulation and increased pathogen response genes. This study offers promising strategy for developing effective control measures against clubroot in susceptible cruciferous crops.

Integrated Management of Collar Rot of Chickpea (Cicer arietinum) Caused by Sclerotium rolfsii under Greenhouse Conditions

Collar rot, one of the major soil borne diseases of chickpea incited by Sclerotium rolfsii causes significant economic losses in chickpea crop. The present study was undertaken to identify the eco-friendly management of this soil borne disease in chickpea. In this study, the efficacy of chemical, biocontrol and biofumigation to manage the chickpea collar rot disease was tested under Greenhouse conditions. Our results revealed that the treatments involving the sole application of chemical fungicide Tebuconazole 60 FS (as seed treatment or soil application) or in combination with other treatments resulted in 100% germination of chickpea seeds. Two treatments namely T5 (SA of Tebuconazole 60 FS) and T12 (ST with Tebuconazole and SA of mustard seed cake) recorded 0.00% total mortality and hence found to be highly effective in protecting chickpea seeds from both pre emergence seed rot and post emergence seedling mortality.The results on the percent disease incidence revealed that, T10 (ST with Trichoderma spp and SA of mustard seed cake) provided maximum disease reduction of 81.93 per cent (PDI 12.04%) and 75.93 (PDI 24.07% ) per cent over the control at 30 and 45 DAS respectively. This was followed by Treatment T7 which exhibited 72.22 % (PDI 18.52%) and 69.45 % (PDI 30.55%) disease reduction over the control at 30 and 45 DAS respectively. Overall, the results of our study (considering both germination and percent disease incidence percentages), revealed that T7 (ST and SA of Trichoderma spp.) was the most effective treatment in managing the collar rot disease of chickpeas.

Joint metabolomic and transcriptomic analysis identify unique phenolic acid and flavonoid compounds associated with resistance to fusarium wilt in cucumber (Cucumis sativus L.).

Fusarium wilt (FW) caused by Fusarium oxysporum f. sp. cucumerinum (Foc) is a destructive soil-borne disease in cucumber (Cucumis sativus. L). However, there remains limited knowledge on the molecular mechanisms underlying FW resistance-mediated defense responses in cucumber. In this study, metabolome and transcriptome profiling were carried out for two FW resistant (NR) and susceptible (NS), near isogenic lines (NILs) before and after Foc inoculation. NILs have shown consistent and stable resistance in multiple resistance tests conducted in the greenhouse and in the laboratory. A widely targeted metabolomic analysis identified differentially accumulated metabolites (DAMs) with significantly greater NR accumulation in response to Foc infection, including many phenolic acid and flavonoid compounds from the flavonoid biosynthesis pathway. Transcriptome analysis identified differentially expressed genes (DEGs) between the NILs upon Foc inoculation including genes for secondary metabolite biosynthesis and transcription factor genes regulating the flavonoid biosynthesis pathway. Joint analysis of the metabolomic and transcriptomic data identified DAMs and DEGs closely associated with the biosynthesis of phenolic acid and flavonoid DAMs. The association of these compounds with NR-conferred FW resistance was exemplified by in vivo assays. These assays found two phenolic acid compounds, bis (2-ethylhexyl) phthalate and diisooctyl phthalate, as well as the flavonoid compound gallocatechin 3-O-gallate to have significant inhibitory effects on Foc growth. The antifungal effects of these three compounds represent a novel finding. Therefore, phenolic acids and flavonoids play important roles in NR mediated FW resistance breeding in cucumber.

Phytotoxic Isocassadiene-Type Diterpenoids from Tomato Fusarium Crown and Root Rot Pathogen Fusarium oxysporum f. sp. radicis-lycopersici.

Fusarium crown and root rot (FCRR) has emerged as a highly destructive soil-borne disease, posing a significant threat to the safe cultivation of tomatoes in recent years. The pathogen of tomato FCRR is Fusarium oxysporum f. sp. radicis-lycopersici (Forl). To explore potential phytotoxins from Forl, eight undescribed diterpenoids namely fusariumic acids A-H (1-8) were isolated. Their structures were elucidated by using spectroscopic data analyses, quantum chemical calculations, and X-ray crystallography. Fusariumic acids A (1) and C-H (3-8) were typical isocassadiene-type diterpenoids, while fusariumic acid B (2) contained a cage-like structure with an unusual 7,8-seco-isocassadiene skeleton. A biosynthetic pathway of 2 was proposed. Fusariumic acids A (1) and C-H (3-8) were further assessed for their phytotoxic effects on tomato seedlings at 200 μg/mL. Among them, fusariumic acid F (6) exhibited the strongest inhibition against the hypocotyl and root elongation of tomato seedlings, with inhibitory rates of 61.3 and 45.3%, respectively.

Impact of a new pesticide on rhizosphere microbes and plant health: case study of Y17991 against sharp eyespot in wheat

Sharp eyespot (Rhizoctonia cerealis) is a widespread soil-borne fungal disease that poses a severe threat to wheat health, and it is one of the main obstacles to achieving stable and high-quality wheat yields in China. Our collaborative team has developed a novel, efficient, and low-toxicity fungicide named Y17991 (N-(2-(2,4-bis-(trifluoromethyl)phenoxy)phenyl)-3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carboxamide). Preliminary laboratory tests confirmed the significant inhibitory effect of this agent on R. cerealis. Large-area field trials also demonstrated its efficacy, with a disease prevention index of 83.52%, which is 1.97% greater than that of the widely used thifluzamide, and it significantly increased the wheat yield. Moreover, this study explored the impacts of Y17991 on the structure and function of the microbial community in wheat rhizosphere soil. Bacterial communities were more strongly affected than fungal communities. Y17991 significantly modulated key amino acid metabolic pathways and certain biosynthetic processes in diseased wheat rhizospheres, and it also enhanced certain biosynthetic pathways and metabolic activities in healthy wheat rhizospheres. Additionally, the application of Y17991 regulated rhizosphere metabolites, thus exerting significant control over the microbial community. We identified 15 microbial strains potentially involved in the prevention and treatment of R. cerealis, and Y17991 treatment promoted the growth of Pedobacter and Bacillus strains. These strains not only aid in plant growth but they also have the potential for disease prevention. In summary, Y17991 application at a reasonable dose does not cause significant disruption to nontarget rhizosphere microbial communities. In future studies, we will continue to investigate the impacts of Y17991 on nonmicrobial components in soil ecosystems, such as protozoa and nematodes. Our research provides a theoretical basis for the scientific application and promotion of new fungicides and offers a significant reference for establishing a comprehensive system for assessing the ecological impact of pesticides on the environment.

Streptomyces-Secreted Fluvirucin B6 as a Potential Bio-Fungicide for Managing Banana Fusarium Wilt and Mycotoxins and Modulating the Soil Microbial Community Structure.

Banana Fusarium wilt caused by Fusarium oxysporum f. sp. cubense (Foc TR4) is the most destructive soil-borne fungal disease. Until now, there has been a lack of effective measures to control the disease. It is urgent to explore biocontrol agents to control Foc TR4 and the secretion of mycotoxin. In this study, fluvirucin B6 was screened from Streptomyces solisilvae using an activity-guided method. Fluvirucin B6 exhibited strong antifungal activity against Foc TR4 (0.084 mM of EC50 value) and significantly inhibited mycelial growth and spore germination. Further studies demonstrated that fluvirucin B6 could cause the functional loss of mitochondria, the disorder of metabolism of Foc TR4 cells, and the decrease of enzyme activities in the tricarboxylic acid cycle and electron transport chain, ultimately inhibiting mycotoxin metabolism. In a pot experiment, the application of fluvirucin B6 significantly decreased the incidence of banana Fusarium wilt and the amount of Foc TR4 and controlled fungal toxins in the soil. Additionally, fluvirucin B6 could positively regulate the changes in the structure of the banana rhizosphere microbial community, significantly enriching beneficial microbes associated with disease resistance. In summary, this study identifies fluvirucin B6, which plays versatile roles in managing fungal diseases and mycotoxins.

Pathotype Identification and Host Resistance Evaluation of Clubroot in Zhejiang Province, China.

Clubroot, caused by Plasmodiophora brassicae, is a globally destructive soil-borne disease affecting cruciferous plants. Here, the predominant pathotypes of P. brassicae in six cities within Zhejiang Province were identified using the Williams and European Clubroot Differential (ECD) systems. A phylogenetic analysis of P. brassicae isolates infecting cruciferous crops worldwide was conducted using MEGA, and their ITS2 secondary structures were predicted through the ITS2 database. Accessions of B. rapa, B. oleracea, B. juncea, and Eruca sativa Mill. were employed to assess clubroot resistance. The results revealed that the prevalent pathotypes in Zhejiang Province were pathotype 1, ECD20/31/12 and ECD24/16/30; pathotype 3, ECD20/15/4; pathotype 8, ECD16/0/0 and ECD24/0/0; and pathotype 2, ECD16/15/15. Isolates from distinct genera of Brassicaceae formed separate branches in the evolutionary tree. Moreover, isolates of Brassica crops from Zhejiang Province exhibited homology with those from other global regions, a finding corroborated by their ITS2 secondary structure. Approximately 80% and 95% of B. rapa and B. juncea crops displayed susceptible phenotypes for pathotype 8, ECD16/0/0, whereas approximately 60% of B. oleracea crops exhibited resistance. Furthermore, three Brassica crop accessions showed significant variation in resistance to the pathogen, both among morphological and geographical origin groups. This study contributes to understanding the distribution of diverse P. brassicae pathotypes in different regions of Zhejiang Province and facilitates the identification of Brassica crops with potential disease resistance suitable for cultivation in the province.

In vitro efficacy of various fungicides against fungi associated with leaf, stem, and soilborne diseases of Proteaceae in Hawai‘i, USA

Species in the Proteaceae have been important ornamental plants cultivated for both cut flowers and foliage in Hawaiian agriculture since the 1960’s. Symptoms ranging from spots on leaves and flowers, to branch lesions and cankers, as well as dieback have been reported on various Proteaceae in Hawai‘i and attributed to various fungi. Nurseries can experience significant economic losses if symptoms are not controlled. Few studies are available regarding the effectiveness of chemical treatments to reduce disease incidence and severity. The efficacy of six ornamental fungicides from various Fungicide Resistance Action Committee (FRAC) groups were evaluated in vitro for their ability to inhibit the mycelial growth of nine fungal isolates of six known or suspected protea pathogen genera (Diaporthe, Alternaria, Neofusicoccum, Neopestalotiopsis, Phompsis, and Calonectria). Isolates were recovered from symptomatic stems and leaves, as well as soil surrounding diseased Proteaceae grown at the Maui Agricultural Research Center (MARC), Kula, HI and from 10 commercial farms on Maui. All fungicides evaluated in the study inhibited the in vitro growth of some, if not all, of the nine isolates to some capacity. Tebuconazole was the most effective fungicide, reducing mycelial growth of all isolates by &gt;85% or more compared to nonamended control plates. Rotation of these fungicides could potentially be used for disease management against a broad range of pathogens infecting Proteaceae in Hawaiʻi.

Light stress elicits soilborne disease suppression mediated by root-secreted flavonoids in Panax notoginseng.

Developing disease-suppressive soils is an effective approach for managing soilborne diseases, which can be achieved through crop metabolism and root secretion modification to recruit beneficial soil microbiota. Many factors, such as light, can elicit and modify plant metabolomic activities, resulting in disease suppression. To investigate the impact of light, Panax notoginseng was planted in a greenhouse and forest, conditioned with three levels of light intensities, including the optimal (15% light transmittance of full light), suboptimal low (5% light transmittance of full light) and suboptimal high (30% light transmittance of full light) intensities. We assessed the rhizosphere microbiota of P. notoginseng and root rot disease caused by soilborne pathogen Ilyonectria destructans, and elucidated the mechanism. Results showed that suboptimal light conditions alleviated root rot disease of P. notoginseng by enriching beneficial microbiota in the rhizosphere. Both low and high light stresses enhanced the secondary metabolism profile in favor of plant defense, particularly the flavonoid pathway. Notably, high light stress demonstrated a robust ability to promote flavonoid metabolism and secretion, resulting in the enrichment of more beneficial microorganisms that suppressed the soilborne pathogen I. destructans. These findings highlight the potential for adjusting canopy light intensities to improve soil health and promote sustainable agriculture.