Methionine biosynthetic genes and methionine sulfoxide reductase A are required for Rhizoctonia solani AG1-IA to cause sheath blight disease in rice.

Rhizoctonia solani is a polyphagous necrotrophic fungal pathogen that causes sheath blight disease in rice. It deploys effector molecules as well as carbohydrate-active enzymes and enhances the production of reactive oxygen species for killing host tissues. Understanding R. solani ability to sustain growth under an oxidative-stress-enriched environment is important for developing disease control strategies. Here, we demonstrate that R. solani upregulates methionine biosynthetic genes, including Rs_MET13 during infection in rice, and double-stranded RNA-mediated silencing of these genes impairs the pathogen's ability to cause disease. Exogenous treatment with methionine restores the disease-causing ability of Rs_MET13-silenced R. solani and facilitates its growth on 10 mM H2O2-containing minimal-media. Notably, the Rs_MsrA gene that encodes methionine sulfoxide reductase A, an antioxidant enzyme involved in the repair of oxidative damage of methionine, is upregulated upon H2O2 treatment and also during infection in rice. Rs_MsrA-silenced R. solani is unable to cause disease, suggesting that it is important for the repair of oxidative damage in methionine during host colonization. We propose that spray-induced gene silencing of Rs_MsrA and designing of antagonistic molecules that block MsrA activity can be exploited as a drug target for effective control of sheath blight disease in rice.

Oschib1 gene encoding a GH18 chitinase confers resistance against sheath blight disease of rice caused by Rhizoctonia solani AG1-IA.

Sheath blight disease of rice caused by Rhizoctonia solani AG1-IA, is a major fungal disease responsible for huge loss to grain yield and quality. The major limitation of achieving persistent and reliable resistance against R. solani is the governance of disease resistance trait by many genes. Therefore, functional characterization of new genes involved in sheath blight resistance is necessary to understand the mechanism of resistance as well as evolving effective strategies to manage the disease through host-plant resistance. In this study, we performed RNA sequencing of six diverse rice genotypes (TN1, BPT5204, Vandana, N22, Tetep, and Pankaj) from sheath and leaf tissue of control and fungal infected samples. The approach for identification of candidate resistant genes led to identification of 352 differentially expressed genes commonly present in all the six genotypes. 23 genes were analyzed for RT-qPCR expression which helped identification of Oschib1 showing differences in expression level in a time-course manner between susceptible and resistant genotypes. The Oschib1 encoding classIII chitinase was cloned from resistant variety Tetep and over-expressed in susceptible variety Taipei 309. The over-expression lines showed resistance against R. solani, as analyzed by detached leaf and whole plant assays. Interestingly, the resistance response was correlated with the level of transgene expression suggesting that the enzyme functions in a dose dependent manner. We report here the classIIIb chitinase from chromosome10 of rice showing anti-R. solani activity to combat the dreaded sheath blight disease.

Rhizoctonia solani disease suppression: addition of keratin-rich soil amendment leads to functional shifts in soil microbial communities.

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.

Biocontrol and Growth Promotion Potential of Bacillus subtilis CTXW 7-6-2 against Rhizoctonia solani that Causes Tobacco Target Spot Disease.

Fungal diseases form perforated disease spots in tobacco plants, resulting in a decline in tobacco yield and quality. The present study investigated the antagonistic effect of Bacillus subtilis CTXW 7-6-2 against Rhizoctonia solani, its ability to promote the growth of tobacco seedlings, and the expression of disease resistance-related genes for efficient and eco-friendly plant disease control. Our results showed that CTXW 7-6-2 had the most vigorous growth after being cultured for 96 h, and its rate of inhibition of R. solani growth in vitro was 94.02%. The volatile compounds produced by CTXW 7-6-2 inhibited the growth of R. solani significantly (by 96.62%). The fungal growthinhibition rate of the B. subtilis CTXW 7-6-2 broth obtained after high-temperature and no-high-temperature sterile fermentation was low, at 50.88% and 54.63%, respectively. The lipopeptides extracted from the B. subtilis CTXW 7-6-2 fermentation broth showed a 74.88% fungal growth inhibition rate at a concentration of 100 mg/l. Scanning and transmission electron microscopy showed some organelle structural abnormalities, collapse, shrinkage, blurring, and dissolution in the R. solani mycelia. In addition, CTXW 7-6-2 increased tobacco seedling growth and improved leaf and root weight compared to the control. After CTXW 7-6-2 inoculation, tobacco leaves showed the upregulation of the PDF1.2, PPO, and PAL genes, which are closely related to target spot disease resistance. In conclusion, B. subtilis CTXW 7-6-2 may be an efficient biological control agent in tobacco agriculture and enhance plant growth potential.

The F-box protein ZmFBL41 negatively regulates disease resistance to Rhizoctonia solani by degrading the abscisic acid synthase ZmNCED6 in maize.

KEY MESSAGE: The maize F-box protein ZmFBL41 targets abscisic acid synthase 9-cis-epoxycarotenoid dioxygenase 6 for degradation, and this regulatory module is exploited by Rhizoctonia solani to promote infection. F-box proteins are crucial regulators of plant growth, development, and responses to abiotic and biotic stresses. Previous research identified the F-box gene ZmFBL41 as a negative regulator of maize (Zea mays) defenses against Rhizoctonia solani. However, the precise mechanisms by which F-box proteins mediate resistance to R. solani remain poorly understood. In this study, we show that ZmFBL41 interacts with an abscisic acid (ABA) synthase, 9-cis-epoxycarotenoid dioxygenase 6 (ZmNCED6), promoting its degradation via the ubiquitination pathway. We discovered that the ectopic overexpression of ZmNCED6 in rice (Oryza sativa) inhibited R. solani infection by activating stomatal closure, callose deposition, and jasmonic acid (JA) biosynthesis, indicating that ZmNCED6 enhances plant immunity against R. solani. Natural variation at ZmFBL41 across different maize haplotypes did not affect the ZmFBL41-ZmNCED6 interaction. These findings suggest that ZmFBL41 targets ZmNCED6 for degradation, leading to a decrease in ABA levels in maize, in turn, inhibiting ABA-mediated disease resistance pathways, such as stomatal closure, callose deposition, and JA biosynthesis, ultimately facilitating R. solani infection.

Efficacy of ergosterol peroxide obtained from the endophytic fungus Acrophialophora jodhpurensis against Rhizoctonia solani.

AIM: To investigate antifungal activity of the extract and major metabolite of the endophytic fungus Acrophialophora jodhpurensis (belonging to Chaetomiaceae) against crown and root rot caused by Rhizoctonia solani (teleomorph: Thanatephorus cucumeris), as an important pathogen of tomato. METHODS AND RESULTS: The endophytic fungus A. jodhpurensis, has high inhibitory effect against R. solani AG4-HG II in vitro and in vivo. The media conditions were optimized for production of the endophyte's metabolites. The highest amounts of secondary metabolites were produced at pH 7, 30°C temperature, and in the presence of 0.5% glucose, 0.033% sodium nitrate, and 1 gl-1 asparagine as the best carbon, nitrogen, and amino acid sources, respectively. The mycelia were extracted by methanol and the obtained extract was submitted to various chromatography techniques. Phytochemical analysis via thin-layer chromatography (TLC) and nuclear magnetic resonance (NMR) spectroscopy showed that ergosterol peroxide was the major component in the extract of this endophyte. Antifungal activities of the methanolic extract and ergosterol peroxide in the culture media were studied against R. solani. Minimum inhibitory concentrations of the extract and ergosterol peroxide against the pathogen were 600 and 150 µg ml-1, respectively. Ergosterol peroxide revealed destructive effects on the pathogen structures in microscopic analyses and induced sclerotia production. Histochemical analyses revealed that it induced apoptosis in the mycelia of R. solani via superoxide production and cell death. Application of ergosterol peroxide in the leaf disc assay reduced the disease severity in tomato leaves. CONCLUSIONS: Antifungal metabolites produced by A. jodhpurensis, such as ergosterol peroxide, are capable of controlling destructive Rhizoctonia diseases on tomato.

Genome and transcriptome sequencing of Trichoderma harzianum T4, an important biocontrol fungus of Rhizoctonia solani, reveals genes related to mycoparasitism.

Trichoderma harzianum is a well-known biological control strain and a mycoparasite of Rhizoctonia solani. To explore the mechanisms of mycoparasitism, the genome and transcriptome of T. harzianum T4 were both assembled and analyzed in this study. The genome of T. harzianum T4 was assembled into 106 scaffolds, sized 41.25 Mb, and annotated with a total of 8118 predicted genes. We analyzed the transcriptome of T. harzianum T4 against R. solani in a dual culture in three culture periods: before contact (BC), during contact (C), and after contact (AC). Transcriptome sequencing identified 1092, 1222, and 2046 differentially expressed genes (DEGs), respectively. These DEGs, which are involved in pathogen recognition and signal transduction, hydrolase, transporters, antibiosis, and defense-related functional genes, are significantly upregulated in the mycoparasitism process. The results of genome and transcriptome analysis indicated that the mycoparasitism process of T. harzianum T4 was very complex. T. harzianum successfully recognizes and invades host cells and kills plant pathogens by regulating various DEGs at different culture periods. The relative expression levels of the 26 upregulated DEGs were confirmed by RT-qPCR to validate the reliability of the transcriptome data. The results provide insight into the molecular mechanisms underlying T. harzianum T4's mycoparasitic processes, and they provide a potential molecular target for the biological control mechanism of T. harzianum T4.

Hydrogel capsules as new delivery system for Trichoderma koningiopsis Th003 to control Rhizoctonia solani in rice (Oryza sativa).

The incorporation of biological control agents (BCAs) such as Trichoderma spp. in agricultural systems favors the transition towards sustainable practices of plant nutrition and diseases control. Novel bioproducts for crop management are called to guarantee sustainable antagonism activity of BCAs and increase the acceptance of the farmers. The encapsulation in polymeric matrices play a prominent role for providing an effective carrier/protector and long-lasting bioproduct. This research aimed to study the influence of biopolymer in hydrogel capsules on survival and shelf-life of T. koningiopsis. Thus, two hydrogel capsules prototypes based on alginate (P1) and amidated pectin (P2), containing conidia of T. koningiopsis Th003 were formulated. Capsules were prepared by the ionic gelation method and calcium gluconate as crosslinker. Conidia releasing under different pH values of the medium, survival of conidia in drying capsules, storage stability, and biocontrol activity against rice sheath blight (Rhizoctonia solani) were studied. P2 prototype provided up to 98% survival to Th003 in fluid bed drying, faster conidia releasing at pH 5.8, storage stability greater than 6 months at 18 °C, and up to 67% of disease reduction. However, both biopolymers facilitate the antagonistic activity against R. solani, and therefore can be incorporated in novel hydrogel capsules-based biopreparations. This work incites to develop novel biopesticides-based formulations with potential to improve the delivery process in the target site and the protection of the active ingredient from the environmental factors.

Genome analysis and hyphal movement characterization of the hitchhiker endohyphal Enterobacter sp. from Rhizoctonia solani.

Bacterial-fungal interactions are pervasive in the rhizosphere. While an increasing number of endohyphal bacteria have been identified, little is known about their ecology and impact on the associated fungal hosts and the surrounding environment. In this study, we characterized the genome of an Enterobacter sp. Crenshaw (En-Cren), which was isolated from the generalist fungal pathogen Rhizoctonia solani, and examined the genetic potential of the bacterium with regard to the phenotypic traits associated with the fungus. Overall, the En-Cren genome size was typical for members of the genus and was capable of free-living growth. The genome was 4.6 MB in size, and no plasmids were detected. Several prophage regions and genomic islands were identified that harbor unique genes in comparison with phylogenetically closely related Enterobacter spp. Type VI secretion system and cyanate assimilation genes were identified from the bacterium, while some common heavy metal resistance genes were absent. En-Cren contains the key genes for indole-3-acetic acid (IAA) and phenylacetic acid (PAA) biosynthesis, and produces IAA and PAA in vitro, which may impact the ecology or pathogenicity of the fungal pathogen in vivo. En-Cren was observed to move along hyphae of R. solani and on other basidiomycetes and ascomycetes in culture. The bacterial flagellum is essential for hyphal movement, while other pathways and genes may also be involved.IMPORTANCEThe genome characterization and comparative genomics analysis of Enterobacter sp. Crenshaw provided the foundation and resources for a better understanding of the ecology and evolution of this endohyphal bacteria in the rhizosphere. The ability to produce indole-3-acetic acid and phenylacetic acid may provide new angles to study the impact of phytohormones during the plant-pathogen interactions. The hitchhiking behavior of the bacterium on a diverse group of fungi, while inhibiting the growth of some others, revealed new areas of bacterial-fungal signaling and interaction, which have yet to be explored.

Establishment and application of quantitative detection of Bacillus velezensis HMB26553, a biocontrol agent against cotton damping-off caused by Rhizoctonia.

A highly sensitive quantitative PCR (qPCR) method was developed for detection and quantification of Bacillus velezensis HMB26553 in cotton rhizosphere. The study aimed to develop a quantitative detection method for the strain HMB26553, and explore the relationship between its colonization of the cotton rhizosphere and its control effect. The whole genome sequence of strain HMB26553 was obtained by genome sequencing and a unique specific sequence pB-gene0026 on plasmid plaBV2 was identified by using high-throughput alignment against NCBI. Plasmid plaBV2 could be stably genetically inherited. Based on this sequence, specific primers for amplifying 106 bp and a minor groove binder (MGB) TaqMan probe for enhancing sensitivity were designed. The copy number of plaBV2 in strain HMB26553, which was 2, was confirmed by internal reference primers and the MGB TaqMan probe based on housekeeping gene gyrB. The established detection technique based on these primers and probes had high specificity and sensitivity compared to traditional plate counting method, with a detection limit of 1.5 copy genome. Using this method, the study discovered a likely correlation between the quantity of colonization in cotton rhizosphere and efficacy against cotton damping-off caused by Rhizoctonia after seed soaking and irrigation with strain HMB26553. Thus, this method provides scientific support for the rational application of strain HMB26553 in the future.

Discovery of Arylfluorosulfates as Novel Fungicidal Agents against Plant Pathogens.

A series of arylfluorosulfates were synthesized as fungicide candidates through a highly efficient sulfur fluoride exchange (SuFEx) reaction. A total of 32 arylfluorosulfate derivatives with simple structures have been synthesized, and most of them exhibited fungal activities in vitro against five agricultural pathogens (Rhizoctonia solani, Botrytis cinerea, Fusarium oxysporum, Pyricularia oryzae, and Phytophthora infestans). Among the target compounds, compound 31 exhibited great antifungal activity against Rhizoctonia solani (EC50 = 1.51 µg/mL), which was comparable to commercial fungicides carbendazim and thiabendazole (EC50 = 0.53 and 0.70 µg/mL, respectively); compounds 17 and 30 exhibited antifungal activities against Pyricularia oryzae (EC50 = 1.64 and 1.73 µg/mL, respectively) comparable to carbendazim (EC50 = 1.02 µg/mL). The in vitro antifungal effect of compound 31 was also evaluated on rice plants against Rhizoctonia solani. Significant preventive and curative efficacies were observed (89.2% and 91.8%, respectively, at 200 µg/mL), exceeding that of thiabendazole. Primary study on the mechanism of action indicated that compound 31 could suppress the sclerotia formation of Rhizoctonia solani even at a very low concentration (1.00 µg/mL), destroy the cell membrane and mitochondria, trigger the release of cellular contents, produce excessive reactive oxygen species (ROS), and suppress the activity of several related enzymes. This work could bring new insights into the development of arylfluorosulfates as novel fungicides.

Characterization of a novel endornavirus isolated from the phytopathogenic fungus Rhizoctonia solani.

Rhizoctonia solani endornavirus 8 (RsEV8) was isolated from strain XY175 of Rhizoctonia solani AG-1 IA. The full-length genome of RsEV8 is 16,147 nucleotides (nt) in length and contains a single open reading frame that encodes a large polyprotein of 5227 amino acids. The polyprotein contains four conserved domains: viral methyltransferase, putative DEAH box helicase, viral helicase, and RNA-dependent RNA polymerase (RdRp). RsEV8 has a shorter 3'-UTR (58 nt) and a longer 5'-UTR (404 nt). A multiple sequence alignment indicated that the RdRp of RsEV8 possesses eight typical RdRp motifs. According to a BLASTp analysis, RsEV8 shares 39.31% sequence identity with Rhizoctonia cerealis endornavirus-1084-7. Phylogenetic analysis demonstrated that RsEV8 clusters with members of the genus Betaendornavirus.

Inhibitory role of copper and silver nanocomposite on important bacterial and fungal pathogens in rice (Oryza sativa).

Rice (Oryza sativa) being among the most important food crops in the world is also susceptible to various bacterial and fungal diseases that are the major stumbling blocks in the way of increased production and productivity. The bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae and the sheath blight disease caused by Rhizoctonia solani are among the most devastating diseases of the rice crop. In spite of the availability of array of chemical control, there are chances of development of resistance. Thus, there is a need for the nanotechnological intervention for management of disease in the form of copper and silver nano-composites. The copper (CuNPs) and silver nanoparticles (AgNPs) were synthesized using green route and characterized using different high throughput techniques, i.e., UV-Vis, FT-IR, DLS, XRD, FE-SEM, TEM. The particle size and zeta potential of synthesized CuNPs and AgNPs were found 273 nm and - 24.2 mV; 95.19 nm and - 25.5 mV respectively. The nanocomposite of CuNPs and AgNPs were prepared having particle size in the range of 375-306 nm with improved stability (zeta potential - 54.7 to - 39.4 mV). The copper and silver nanoparticle composites evaluated against Xanthomonas oryzae pv. oryzae and Rhizoctonia solani were found to have higher antibacterial (inhibition zone 13 mm) and antifungal activities (77%) compared to only the copper nanoparticle (8 mm; 62% respectively). Net house trials of nano-composite formulations against the bacterial blight of rice also corroborated the potential of nanocomposite formulation. In silico studies were carried out selecting two disease-causing proteins, peptide deformylase (Xanthomonas oryzae) and pectate lyase (Rhizoctonia solani) to perform the molecular docking. Interaction studies indicatedthat both of these proteins generated better complex with CuNPs than AgNPs. The study suggested that the copper and silver nano-composites could be used for developing formulations to control these devastating rice diseases.

Efficacy of endophytic bacteria as promising inducers for enhancing the immune responses in tomato plants and managing Rhizoctonia root-rot disease.

Around the world, a variety of crops, including tomatoes, suffer serious economic losses due to the Rhizoctonia root-rot disease. Herein, Bacillus velezensis, Bacillus megaterium, and Herpaspirillum huttiense isolated from strawberry (Fragaria chiloensis var. ananassa) plants were pragmatic as plant growth promotors for battling the Rhizoctonia root rot disease and bringing about defense mechanisms as well as growth promotional strategies in tomato plants. These endophytic bacteria demonstrated potent antifungal activity against R. solani in vitro along in vivo. Data explained that the isolated endophytic bacteria could produce Indole acetic acid, Gibberellic acid GA, and siderophore as well as solubilize phosphate in the soil. The consortium of (Bacillus velezensis, Bacillus megaterium, and Herpaspirillum huttiense) increased the protection % against Rhizoctonia infection by (79.4%), followed by B. velezensis by (73.52%), H. huttiense by (70.5%), and B. megaterium by (67.64%), respectively. There was an increase in soluble proteins and carbohydrates in infected plants treated with a consortium of endophytic bacteria by 30.7% and 100.2% over untreated infected plants, respectively. Applying endophytic bacteria either alone or in combination lowered the level of malondialdehyde MDA and hydrogen peroxide H2O2 and improved the activities of antioxidant enzymes in both infected and uninfected plants. Also, bacterial endophytes have distinctive reactions regarding the number and concentrations of isozymes in both infected and uninfected plants. It could be recommended the commercial usage of a mixture of targeted bacterial endophyte strains as therapeutic nutrients against Rhizoctonia root-rot disease as well as plant growth inducer.

Phenolylazoindole scaffold for facilely synthesized and bis-functional photoswitches combining controllable fluorescence and antifungal properties using theoretical methods.

Functionalization is a major challenge for the application of photoswitches. With the aim to develop novel bis-functional azo photoswitches with stationary photophysical properties, a series of phenolylazoindole derivatives were designed, synthesized, and characterized via NMR spectroscopy studies and high-resolution mass spectrometry (HRMS). Herein, UV/Vis and 1H NMR spectra revealed that the photostationary state (PSS) proportions for PSScis and PSStrans were 76-80% and 68-81%, respectively. Furthermore, the thermal half-lives (t1/2) of compounds A2-A4 and B2 ranged from 0.9 to 5.3 h, affected by the diverse substituents at the R1 and R2 positions. The results indicated that azo photoswitches based on the phenolylazoindole scaffold had stationary photophysical properties and wouldn't be excessively affected by modifying the functional groups. Compounds A4 and B2, which were modified with an aryl group, also exhibited fluorescence emission properties (the quantum yields of A4 and B2 were 2.32% and 13.34%) through the modification of the flexible conjugated structure (benzene) at the R2 position. Significantly, compound C1 was obtained via modification with a pharmacophore in order to acquire antifungal activities against three plant fungi, Rhizoctonia solani (R. solani), Botrytis cinerea (B. cinerea), and Fusarium graminearum (F. graminearum). Strikingly, the inhibitory activity of the cis-isomer of compound C1towards R. solani (53.3%) was significantly better than that of the trans-isomer (34.2%) at 50 µg mL-1. In order to further reveal the antifungal mechanism, molecular docking simulations demonstrated that compound C1 effectively integrates into the cavity of succinate dehydrogenase (SDH); the optically controlled cis-isomer showed a lower binding energy with SDH than that of the trans-isomer. This research confirmed that phenolylazoindole photoswitches can be appropriately applied as molecular regulatory devices and functional photoswitch molecules via bis-functionalization.

Effects of Voltage and Treatment Time of Pulsed Electric Field on Electroporation in Rhizoctonia solani.

The pulsed electric field (PEF) of µs duration can induce electroporation by causing permanent damage to the membrane, leading to cell death. The microbe was treated by a homemade PEF generator instrument. The sterilization effect of PEF on the Rhizoctonia solani was observed by scanning electron microscope (SEM) and transmission electron microscope (TEM), and the leakage of the intracellular contents was measured with a conductometer and an ultraviolet spectrophotometer. The increases in the electrical conductivity and the optical density (OD) value indicated that the cell membrane was damaged, and the intracellular contents overflowed. As a result, according to our experimental conditions, the optimum condition was the high-pulsed electric voltage of 26 kV, and the treatment time was 4 min. It could be concluded that the PEF could damage the cell membrane, and the ratio of electroporation reached 100%, which provides a new method of killing R. solani efficiently.

Characterization of heteropolysaccharides from Rhizoctonia solani AG1 IA cell wall and comparison of their effect on inducing plant defense.

Rhizoctonia solani (R. solani) is an important pathogenic fungus that causes symptoms of sheath blight, and the polysaccharide-rich cell wall plays a major role in plant-pathogen interactions. However, the composition and structure of its cell wall polysaccharides are insufficiently understood, and its specific function in plant-pathogen interactions is unknown, which makes effective control of sheath blight difficult at present. Herein, five cell wall polysaccharides (WF-1, WF-2, CAF-1, HAF-1 and HAF 2-1) were sequentially extracted by boiling water, cold and hot alkali from R. solani AG1 IA. They were heteropolysaccharides containing mainly glucose, mannose and galactose and less fucose, with molecular weights above 1100 kDa. These five polysaccharides mainly composed of →4)-Glcp-(1→, →6)-Glcp-(1→, →4,6)-Glcp-(1→, →3,4)-Glcp-(1→, and Manp-(1→. Several polysaccharides, except WF-1, showed different induced resistance degrees on rice plant, with HAF 2-1 having the most significant effect. Further analysis using NMR confirmed that the backbone of HAF 2-1 mainly consisted of →4)-α-D-Glcp-(1→ and →6)-α-D-Glcp-(1→ with branches of →4,6)-D-Glcp-(1→. HAF 2-1 enhance the resistance of rice against R. solani through salicylic acid (SA)-mediated immune signaling pathway. This work improves our knowledge of the cell wall polysaccharides in plant pathogens and facilitates the study of pathogenic mechanisms and effective disease control.

Molecular characterization of a novel mycovirus from binucleate Rhizoctonia AG-A strain A46.

The complete genome sequence of a positive-sense single-stranded RNA (+ ssRNA) virus, Rhizoctonia beny-like virus 1 (RBLV1), isolated from binucleate Rhizoctonia AG-A strain A46, was determined. The RBLV1 genome is 10,280 nt in length and contains a short stretch of adenines at the 3' terminus. It contains a single open reading frame (ORF) encoding a 376.30-kDa protein with viral helicase and RNA-dependent RNA polymerase (RdRp) motifs. The encoded protein exhibited the highest sequence similarity to Rhizoctonia cerealis beny-like virus 0928-1 (RcBeLV 0928-1, 45.25%), with a sequence coverage of 63%. Phylogenetic analysis based on ORF protein sequences revealed that RBLV1 is a novel unclassified mycovirus.

Preparation and assessment of alginate-microencapsulated Trichoderma harzianum for controlling Sclerotinia sclerotiorum and Rhizoctonia solani on tomato.

This study aimed to develop microencapsulation technology using alginate to improve the viability and performance of Trichoderma harzianum. The method of ionic gelation was used to prepare the microparticles, and the efficiency of encapsulation was estimated to be 99%. The average size of the prepared microspheres was 2600 µm (wet) and 1000 µm (dry). Scanning electron microscopy revealed that the microspheres were approximately spherical. Fourier transform infrared spectrophotometer analysis indicated an interaction between T. harzianum and the microspheres. The results of temperature resistance and light stability against ultraviolet radiation emphasized the positive impact of microencapsulation in improving the viability and resistance of T. harzianum compared to the non-microencapsulated state. The disease percentage of Rhizoctonia solani and Sclerotinia sclerotiorum in plants treated with microencapsulated T. harzianum microcapsules was 8.88 % and 20 % respectively, but in the control group was 73.33 % (p ≤ 0.05).

RNA interference-based exogenous double-stranded RNAs confer resistance to Rhizoctonia solani AG-3 on Nicotiana tabacum.

BACKGROUND: Rhizoctonia solani Kühn is a pathogenic fungus causing tobacco target spot disease, and leads to great losses worldwide. At present, resistant varieties and effective control strategy on tobacco target spot disease are very limited. Host-induced gene silencing (HIGS) as well as the exogenous dsRNA can be used to suppress disease progression, and reveal the function of crucial genes involved in the growth and pathogenesis of the fungus. RESULTS: The silencing of endoPGs or RPMK1 in host plants by TRV-based HIGS resulted in a significant reduction in disease development in Nicotiana benthamiana. In vitro analysis validated that red fluorescence signals were consistently observed in the hyphae treated with Cy3-fluorescein-labeled dsRNA at 12, 24, 48 and 72 h postinoculation (hpi). Additionally, application of dsRNA-endoPGs, dsRNA-RPMK1 and dsRNA-PGMK (fusion of partial endoPGs and RPMK1 sequences) effectively inhibited the hyphal growth of R. solani YC-9 in vitro and suppressed disease progression in the leaves, and quantitative real-time PCR confirmed that the application of dsRNAs significantly reduced the expression levels of endoPGs and RPMK1. CONCLUSION: These results provide theoretical basis and new direction for RNAi approaches on the prevention and control of disease caused by R. solani. © 2024 Society of Chemical Industry.