Xanthomonas Oryzae Pv Research Articles

A natural allele of proteasome maturation factor improves rice resistance to multiple pathogens.

Crops with broad-spectrum resistance loci are highly desirable in agricultural production because these loci often confer resistance to most races of a pathogen or multiple pathogen species. Here we discover a natural allele of proteasome maturation factor in rice, UMP1R2115, that confers broad-spectrum resistance to Magnaporthe oryzae, Rhizoctonia solani, Ustilaginoidea virens and Xanthomonas oryzae pv. oryzae. Mechanistically, this allele increases proteasome abundance and activity to promote the degradation of reactive oxygen species-scavenging enzymes including peroxidase and catalase upon pathogen infection, leading to elevation of H2O2 accumulation for defence. In contrast, inhibition of proteasome function or overexpression of peroxidase/catalase-encoding genes compromises UMP1R2115-mediated resistance. More importantly, introduction of UMP1R2115 into a disease-susceptible rice variety does not penalize grain yield while promoting disease resistance. Our work thus uncovers a broad-spectrum resistance pathway integrating de-repression of plant immunity and provides a valuable genetic resource for breeding high-yield rice with multi-disease resistance.

Jasmonic Acid-Induced β-Cyclocitral Confers Resistance to Bacterial Blight and Negatively Affects Abscisic Acid Biosynthesis in Rice.

Jasmonic acid (JA) regulates the production of several plant volatiles that are involved in plant defense mechanisms. In this study, we report that the JA-responsive volatile apocarotenoid, β-cyclocitral (β-cyc), negatively affects abscisic acid (ABA) biosynthesis and induces a defense response against Xanthomonas oryzae pv. oryzae (Xoo), which causes bacterial blight in rice (Oryza sativa L.). JA-induced accumulation of β-cyc was regulated by OsJAZ8, a repressor of JA signaling in rice. Treatment with β-cyc induced resistance against Xoo and upregulated the expression of defense-related genes in rice. Conversely, the expression of ABA-responsive genes, including ABA-biosynthesis genes, was downregulated by JA and β-cyc treatment, resulting in a decrease in ABA levels in rice. β-cyc did not inhibit the ABA-dependent interactions between OsPYL/RCAR5 and OsPP2C49 in yeast cells. Furthermore, we revealed that JA-responsive rice carotenoid cleavage dioxygenase 4b (OsCCD4b) was localized in the chloroplast and produced β-cyc both in vitro and in planta. These results suggest that β-cyc plays an important role in the JA-mediated resistance against Xoo in rice.

Immune Mechanism of Ethylicin-Induced Resistance to Xanthomonas oryzae pv. oryzae in Rice

Ethylicin (ET) was reported to be promising in the control of rice bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo). The detailed mechanism for this process remains unknown. Disclosed here is an in-depth study on the action mode of ET to Xoo. Through plant physiological and biochemical analysis, it was found that ET could inhibit the proliferation of Xoo by increasing the content of defense enzymes and chlorophyll in rice (Oryza sativa ssp. Japonica cv. Nipponbare). Label-free quantitative proteomic analysis showed that ET affected the rice abscisic acid (ABA) signal pathway and made the critical differential calcium-dependent protein kinase 24 (OsCPK24) more active. In addition, the biological function of OsCPK24 as a mediator for rice resistance to Xoo was determined through the anti-Xoo phenotypic test of OsCPK24 transgenic rice and the affinity analysis of the OsCPK24 recombinant protein in vitro and ET. This study revealed the molecular mechanism of ET-induced resistance to Xoo in rice via OsCPK24, which provided a basis for the development of new bactericides based on the OsCPK24 protein.

Expression and role of defense components in Bacillus subtilis treated rice plants against Xanthomonas oryzae pv. oryzae

Expression and role of defense components in Bacillus subtilis treated rice plants against Xanthomonas oryzae pv. oryzae

Seed treatments and seedling root soaking in biological agents improved plant growth and reduced bacterial leaf blight disease incidence in rice

Bacterial leaf blight (BLB) is caused by Xanthomonas oryzae pv. oryzae (Xoo), a seed-soil-air-borne pathogen that can reduce 60% of rice yield. The primary study intended to investigate the effect of seed treatments and root soaking with biological agents (a mixture of Pseudomonas diminuta and Bacillus subtilis) on plant growth and the severity of BLB in a greenhouse. A split-plot experimental design was used with seed treatments as the main plot: negative control, positive control (Xoo inoculated), bactericide (streptomycin sulfate 20%) 0.2%, biopriming with biological agents 108 CFU ml−1, matriconditioning plus bactericide 0.2%, biomatriconditioning with biological agents 108 CFU ml−1. The subplots were root soaking: untreated, bactericide 0.1%, 0.2%, 0.4%, 0.6%; biological agents 106 CFU ml−1, 108 CFU ml−1, and 1010 CFU ml−1. Biomatriconditioning reduced the BLB incidence three weeks after sowing from 10.6% to 1.7% and increased plant height four weeks after transplanting (WAT). Biomatriconditioning followed by root soaking in the biological agents or 0.4 % bactericide increased plant dry weight 3 WAT. Biomatriconditioning or root soaking in the biological agents (106 CFU ml−1) provided the most significant number of tillers 4 WAT.

Identification of bacterial leaf blight (Xanthomonas oryzae pv. Oryzae) resistant genes in rice plants and its validation through molecular markers

Identification of bacterial leaf blight (Xanthomonas oryzae pv. Oryzae) resistant genes in rice plants and its validation through molecular markers

Characterization of the chemical fungicides-responsive and bacterial pathogen-preventing Bacillus licheniformis in rice spikelet

Abstract Seed-borne bacterial pathogens cause severe yield loss and biotoxin contamination in rice, leading to increasing concern on the global food supply and environmental safety. Plant native microbes play an important role in defending against diseases, but their actions are often influenced by the chemical fungicides applied in the field. Here, Bacillus licheniformis mmj was isolated from rice spikelet, which uniquely showed not only fungicide-responsiveness but also broad-spectrum antimicrobial activity against major rice bacterial pathogens including Xanthomonas oryzae pv. oryzae, Burkholderia plantarii and Burkholderia glumae. To understand the hallmark underlying the environmental adaptation and antimicrobial activity of B. licheniformis mmj, the genome sequence was determined by SMRT and subjected to bioinformatics analysis. Genome sequence analysis enabled the identification of a set of antimicrobial-resistance and antibacterial activity genes together with an array of harsh environment-adaptive genes. Moreover, B. licheniformis mmj metabolites were analyzed with gas chromatography coupled to triple quadrupole mass spectrometry, and the volatile components that were linked with the antimicrobial activity were preliminarily profiled. Collectively, the present findings reveal the genomic and metabolic landscapes underlying fungicide-responsive B. licheniformis, which offers a new opportunity to design harsh environment-adaptive biopesticides to cope with prevalent bacterial phytopathogens.

Management of bacterial leaf blight disease of rice in farmer's field condition at Bhaktapur district of Nepal

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae is considered as one of the major threats to rice production in Nepal. To identify the effective control measures, an experiment was done in a randomized complete block design with three replications in a farmer's rice field at Bhaktapur, during the summer seasons of 2018 and 2019. Three plants extracts; 1% Neem extract, 2% Asuro leaf extract, and 2% Titepati leaf extract along with two fungicides viz. 0.1% Agricin and 0.2% Blitox 50, and one bio-control agent 1%Kisan Pseudomonas were used as treatments. The first spray was given as a prophylactic spray at the jointing stage, and they were applied 3 times at 50, 60 and 70 days interval. All the treatments significantly reduced disease and improved test weight higher than control. Among the tested treatments, 0.1% Agricin performed as the best with 65.70% disease control and increase in yield over control by 28.13%. Among the tested botanicals, 2% stock solution of Titepati performed as the best with 50.59% disease control and increase in yield by 13.51%. Therefore, three times application of 0.1% Agricinat 10 day interval starting from jointing stage can be used to control BLB disease for higher rice production.

Pyramiding of Four Broad Spectrum Bacterial Blight Resistance Genes in Cross Breeds of Basmati Rice.

Pyramiding of major resistance (R) genes through marker-assisted selection (MAS) is a useful way to attain durable and broad-spectrum resistance against Xanthomonas oryzae pv. oryzae pathogen, the causal agent of bacterial blight (BB) disease in rice (Oryza sativa L.). The present study was designed to pyramid four broad spectrum BB-R genes (Xa4, xa5, xa13 and Xa21) in the background of Basmati-385, an indica rice cultivar with much sought-after qualitative and quantitative grain traits. The cultivar, however, is susceptible to BB and was therefore, crossed with IRBB59 which possesses R genes xa5, xa13 and Xa21, to attain broad and durable resistance. A total of 19 F1 plants were obtained, some of which were backcrossed with Basmati-385 and large number of BC1F1 plants were obtained. In BC1F2 generation, 31 phenotypically superior genotypes having morphological features of Basmati-385, were selected and advanced up to BC1F6 population. Sequence-tagged site (STS)-based MAS was carried out and phenotypic selection was made in each successive generation. In BC1F6 population, potentially homozygous recombinant inbred lines (RILs) from each line were selected and evaluated on the bases of STS evaluation and resistance to local Xanthomonas oryzae pv. oryzae (Xoo) isolates. Line 23 was found pyramided with all four BB-R genes i.e., Xa4, xa5, xa13 and Xa21. Five genotypes including line 8, line 16, line 21, line 27 and line 28 were identified as pyramided with three R genes, Xa4, xa5 and xa13. Pathological study showed that rice lines pyramided with quadruplet or triplet R genes showed the highest level of resistance compared to doublet or singlet R genes. Thus, line 23 with quadruplet, and lines 8, 16, 21, 27, and 28 with triplet R genes, are recommended for replicated yield and resistance trials before release as new rice varieties. Further, traditional breeding coupled with MAS, is a solid way to attain highly effective BB-resistant rice lines with no yield cost.

Diversity of Antimicrobial Peptide Genes in Bacillus from the Andaman and Nicobar Islands: Untapped Island Microbial Diversity for Disease Management in Crop Plants.

Taxonomic and functional characterization of a total of 90 bacterial isolates representing bulk and rhizosphere soils of diverse niches of Andaman and Nicobar Islands, India were carried out. Twelve bacterial isolates were found promising for the biological suppression of agriculturally important fungal and bacterial plant pathogens such as Ralstonia solanacearum, Xanthomonas oryzae pv. oryzae, and Colletotrichum gloeosporioides. The 16S rRNA gene sequence analysis revealed their identity as belonging to Bacillus subtilis, Bacillus amyloliquefaciens, and Lysinibacillus sphaericus. The isolates were positive for plant growth promotion (PGP) traits including siderophore production, and nutrient solubilization especially phosphorous, zinc, and potassium. Interestingly, the PCR test confirmed the presence of 62 antimicrobial peptides (AMP) biosynthesis genes specific to the genus Bacillus. Whilst all tested species of Bacillus harboured the bacD biosynthesis gene, the B. subtilis (Ba_Abi), and B. amyloliquefaciens (Ba_Abi) harboured the maximum AMP biosynthesis genes analysed in the study. Upon in planta evaluation, the biocontrol potential of the bacterial isolates against leaf spot disease of chilli was observed. The study culminated in the isolation and identification of diverse Bacillus species for exploitation as bioinoculants for plant health management programmes.

Transcriptome Analysis in Response to Infection of Xanthomonas oryzae pv. oryzicola Strains with Different Pathogenicity

Bacterial leaf streak (BLS) caused by Xanthomonas oryzae pv. oryzicola (Xoc) is one of the most important quarantine diseases in the world. Breeding disease-resistant varieties can solve the problem of prevention and treatment of BLS from the source. The discovery of the molecular mechanism of resistance is an important driving force for breeding resistant varieties. In this study, a BLS-resistant near isogenic line NIL-bls2 was used as the material. Guangxi Xoc strain gx01 (abbreviated as WT) and its mutant strain (abbreviated as MT) with a knockout type III effectors (T3Es) gene were used to infect rice material NIL-bls2. The molecular interaction mechanism of rice resist near isogenic lines in response to infection by different pathogenic strains was analyzed by transcriptome sequencing. The results showed that there were 415, 134 and 150 differentially expressed genes (DEGs) between the WT group and the MT group at 12, 24 and 48 h of post inoculation (hpi). Through GO and KEGG enrichment analysis, it was found that, compared with non-pathogenic strains, the T3Es secreted by pathogenic strains inhibited the signal transduction pathway mediated by ethylene (ET), jasmonic acid (JA) and salicylic acid (SA), and the MAPKK (MAPK kinase) and MAPKKK (MAPK kinase kinase) in the MAPK (mitogen-activated protein kinase) cascade reaction, which prevented plants from sensing extracellular stimuli in time and starting the intracellular immune defense mechanism; and inhibited the synthesis of lignin and diterpenoid phytochemicals to prevent plants from establishing their own physical barriers to resist the invasion of pathogenic bacteria. The inhibitory effect was the strongest at 12 h, and gradually weakened at 24 h and 48 h. To cope with the invasion of pathogenic bacteria, rice NIL-bls2 material can promote wound healing by promoting the synthesis of traumatic acid at 12 h; at 24 h, hydrogen peroxide was degraded by dioxygenase, which reduced and eliminated the attack of reactive oxygen species on plant membrane lipids; and at 48 h, rice NIL-bls2 material can resist the invasion of pathogenic bacteria by promoting the synthesis of lignin, disease-resistant proteins, monoterpene antibacterial substances, indole alkaloids and other substances. Through transcriptome sequencing analysis, the molecular interaction mechanism of rice resistance near isogenic lines in response to infection by different pathogenic strains was expounded, and 5 genes, Os01g0719300, Os02g0513100, Os03g0122300, Os04g0301500, and Os10g0575100 closely related to BLS, were screened. Our work provides new data resources and a theoretical basis for exploring the infection mechanism of Xoc strain gx01 and the resistance mechanism of resistance gene bls2.

Assessment of copper (Cu) nanoparticle for their biocontrol activity against Xanthomonas oryzae pv. oryzae, growth promotion, and physiology of rice (Oryza sativa L.) plants.

Among the various biotic factors that disrupt crop yield, Xanthomonas oryzae pv oryzae (Xoo) is the most ruinous microbe of rice and causes bacterial leaf blight (BLB) disease. The present study focused on the utilization of copper nanoparticles (Cu-NPs) to control BLB. The copper nanosuspension (259.7 nm) prepared using Na-CMC, CuSO4·7H2O, and NaOH showed effectively inhibited Xoo (65.0μg/ml). The performance of Cu-NPs in vivo showed enhanced plant attributes (127.9% root length and 53.9% shoot length) compared to the control and CuSO4 treated seedling. Furthermore, Cu-NPs treated seedlings showed 23.01% disease incidence (DI) compared to CuSO4 (85.71%) treated and control plants (91.83%). In addition to enhancing the growth parameters and reducing DI, seed priming with Cu-NPs improved the total chlorophyll content to 36.0% compared to the control. The assessment of antioxidant enzymes such as superoxide dismutase (1.9 U), polyphenol oxidase, peroxidase, and phenylalanine ammonia-lyase (two- to three-fold) in roots and shoots of rice plants revealed significant enhancement in Cu-NPs treated seedlings (P<0.05). The present study suggests that Cu-NPs can be used to control Xoo and enhance rice growth.

Cyclic Depsipeptides and Linear Peptides With Cytotoxic and Antiphytopathogenic Activities From Symbiotic Bacteria ofXenorhabdus(Enterobacteriales: Morganellaceae) Genus

AbstractOn the basis of biological activities of the ethyl acetate extracts of four Xenorhabdus sp., including Xenorhabdus nematophila FUM 220, Xenorhabdus nematophila FUM 221, Xenorhabdus bovienii FUM 222, and Xenorhabdus bovienii FUM 223, X. nematophila FUM 220 was preferentially selected to track the isolation of responsible compounds. Chemical study on the ethyl acetate extract of X. nematophila isolate FUM220 which is derived from the native nematode Steinernema carpocapsae (Rhabditida: Steinernematidae), was evaluated, and eleven compounds, including xenocoumacin II (1), xenortide-396 (2), xenortide A (3), xenortide-410 (4), xenortide-449 (5), xenematide A 663 (6), rhabdopeptide-574 (7), rhabdopeptide-588 (8), rhabdopeptide-687 (9), rhabdopeptide-701 (10), and nematophin-273 (11) were characterized. In this experimental study, we surveyed the antitumoral potential of bacterial extract and bacterial metabolites to treat human breast cancer (MCF-7), human lung cancer (A549), and murine Tumor (B16) cell lines. We observed that all samples were cytotoxic, but bacterial extracts of X. nematophila FUM 220 and X. bovienii FUM 223 showed higher toxicity on mentioned cell lines. Potent cytotoxic activity was found for compounds 6 and 11 with IC50 of 6.2 μg/ml against human lung cancer A549 cell lines, too. These compounds showed moderated antibacterial activity against Xanthomonas oryzae pv. oryzae strain Xoo-IR42 (Xanthomonadales: Xanthomonadaceae) (MIC of 62.5 μg/ml) and Staphylococcus aureus strain 1112 (Bacillales: Staphylococcaceae) (MIC of 100 μg/ml). The bacterial extracts from X. bovienii FUM 222 showed strong inhibition of the growth of S. aureus strain 1112, by a minimal inhibitory concentration assay (MIC of 53.5 μg/ml). Xenorhabdus genera produce metabolites with potent cytotoxic and antibacterial activity. Single compounds can be isolated, identified, and commercialized, but various species or strains may change their anticancer or antimicrobial potential. The present study brings new clues regarding the qualified of Xenorhabdus as future peptide sources for supplying natural bioactive compounds and challenge multidrug-resistant bacteria, treat cancer, and plant diseases.

Marker-assisted Breeding and F3 Progenies Characterization for Improving Local Rice Variety “Tinggong”

Background: Tinggong is an indigenous rice variety in Aceh Province known for its excellent cooking quality and tolerance to adverse climatic conditions such as drought. However, this local rice has a long lifespan ranging from 150-160 days and is susceptible to Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial leaf blight (BLB). Methods: To improve the performance of Tinggong, the variety was cross-breed with the isogenic line IRBB27 which confers Xa-27 and sd-1 genes. The inheritance of both of these genes and the changes in their agronomic character and the resistance to Xoo were analyzed in the F3 progenies to identify the presence of both Xa-27 and sd-1 genes in the F3 progenies and the implication of their phenotypic characters. Result: The results showed that 58.33% of progenies inherited both Xa-27 and sd-1 genes. Of these, 4 progenies consisting #T5, T6, T29 and T30 are the potential to develop as they show both genotypic and phenotypic improvement. The 4 progenies produce earlier (116-120 days after sowing) with plant height 109-128 cm and more resistance to Xoo (lesion length 2.08-2.42 cm), the weight of grains per hill reached 26.24-34.12 g or yield potential (10.40-43.55%) higher compared to their parent Tinggong.

Editing of the rice importin gene IMPα1b results in sequestration of TAL effectors from plant cell nuclei

Transcription activator-like effectors (TALEs) produced by plant pathogenic bacteria mainly belonging to the genus Xanthomonas cause plant diseases through activation of host susceptibility genes in plant cell nuclei. How TALEs enter plant cell nuclei was not clear until recent studies about PthXo1 and TALI, two TALEs produced by Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc), the rice (Oryza sativa) pathogens that cause bacterial blight and bacterial leaf streak, respectively. Here, we report that rice importin IMPα1b serves as a nuclear transport receptor in rice plants to facilitate the nuclear import of PthXo1 and TALI from Xoo and Xoc, respectively. While wild-type (WT) rice plants support the nuclear import of PthXo1 and TALI, nuclear trafficking is defective in OsIMPα1b loss-of-function mutants generated by clustered regularly interspaced short palindromic repeats (CRISPR)–CRISPR-associated 9 (Cas9)-based gene editing. In the edited plants infected by Xoo, OsIMPα1b sequesters PthXo1 from the nucleus, the PthXo1-targeted rice susceptibility gene is no longer activated, and bacterial virulence and blight disease are alleviated as a result. In the edited plants infected by Xoc, OsIMPα1b sequesters TALI from the nucleus, the role of TALI in suppressing rice defense responses is nullified, and rice defense responses are in turn activated to inhibit bacterial virulence and alleviate bacterial leaf streak severity.

A new NLR disease resistance gene Xa47 confers durable and broad-spectrum resistance to bacterial blight in rice.

Bacterial blight (BB) induced by Xanthomonas oryzae pv. oryzae (Xoo) is a devastating bacterial disease in rice. The use of disease resistance (R) genes is the most efficient method to control BB. Members of the nucleotide-binding domain and leucine-rich repeat containing protein (NLR) family have significant roles in plant defense. In this study, Xa47, a new bacterial blight R gene encoding a typical NLR, was isolated from G252 rice material, and XA47 was localized in the nucleus and cytoplasm. Among 180 rice materials tested, Xa47 was discovered in certain BB-resistant materials. Compared with the wild-type G252, the knockout mutants of Xa47 was more susceptible to Xoo. By contrast, overexpression of Xa47 in the susceptible rice material JG30 increased BB resistance. The findings indicate that Xa47 positively regulates the Xoo stress response. Consequently, Xa47 may have application potential in the genetic improvement of plant disease resistance. The molecular mechanism of Xa47 regulation merits additional examination.

Two new sesquiterpene derivatives, dendocarbin B and bisaborosaol C with antifungal activity from the endophytic fungus Nigrospora chinensis GGY-3

Two novel sesquiterpene derivatives, dendocarbin B (1), bisaborosaol C (2), and nine known compounds (3-11), were isolated from Nigrospora chinensis GGY-3 derived from Ilex cornuta. The structures of new compounds were elucidated using HR-ESI-MS, 1 D and 2 D NMR spectra, X-ray diffraction analysis as well as ECD calculation and comparison. Compound 1 showed moderate antifungal activities against Rhizoctonia solani and Botrytis cinerea. Compounds 5 and 6 exhibited significant inhibitory activity against Phytophthora capsici, Magnaporthe oryzae and R. solani with EC50 values ranging from 13.91 to 29.49 μg/mL. Compounds 10 and 11 displayed moderate antibacterial effects on Bacillus subtilis and Xanthomonas oryzae pv. oryzae (Xoo), with MIC values of 16-64 μg/mL. Particularly, 11 presented strong antibacterial activity against Staphylococcus aureus with an MIC value of 4 μg/mL (2 μg/mL for streptomycin sulfate). In addition, compound 11 also possessed DPPH radical scavenging capability with an IC50 value of 14.80 μg/mL.

The Gain-of-Function Mutation, OsSpl26, Positively Regulates Plant Immunity in Rice.

Rice spotted-leaf mutants are ideal materials to study the molecular mechanism underlying programmed cell death and disease resistance in plants. LOC_Os07g04820 has previously been identified as the candidate gene responsible for the spotted-leaf phenotype in rice Spotted-leaf 26 (Spl26) mutant. Here, we cloned and validated that LOC_Os07g04820 is the locus controlling the spotted-leaf phenotype of Spl26 by reverse functional complementation and CRISPR/Cas9-mediated knockout of the mutant allele. The recessive wild-type spl26 allele (Oryza sativa spotted-leaf 26, Osspl26) is highly conservative in grass species and encodes a putative G-type lectin S-receptor-like serine/threonine protein kinase with 444 amino acid residuals. OsSPL26 localizes to the plasma membrane and can be detected constitutively in roots, stems, leaves, sheaths and panicles. The single base substitution from T to A at position 293 leads to phenylalanine/tyrosine replacement at position 98 in the encoded protein in the mutant and induces excessive accumulation of H2O2, leading to oxidative damage to cells, and finally, formation of the spotted-leaf phenotype in Spl26. The formation of lesions not only affects the growth and development of the plants but also activates the defense response and enhances the resistance to the bacterial blight pathogen, Xanthomonas oryzae pv. oryzae. Our results indicate that the gain-of-function by the mutant allele OsSpl26 positively regulates cell death and immunity in rice.

Allicin-inspired disulfide derivatives containing quinazolin-4(3H)-one as a bacteriostat against Xanthomonas oryzae pv. oryzae.

Plant bacterial diseases have seriously affected the yield and quality of crops, among which rice bacterial leaf blight (BLB), caused by Xanthomonas oryzae pv. oryzae has seriously affected the yield of rice. As plant-pathogenic bacteria gradually become resistant to existing bactericides, it is necessary to find effective bactericides with novel structures. Herein, a series of compounds containing quinazolin-4(3H)-one and disulfide moieties were designed and synthesized using a facile synthetic method. The bioassay results revealed that most target compounds possessed noticeable antibacterial activity against Xanthomonas oryzae pv. oryzae. Particularly, compound 2-(butyldisulfanyl) quinazolin-4(3H)-one (1) exhibited remarkable antibacterial activity with the half effective concentration (EC50 ) of 0.52 μg mL-1 . Additionally, compound 1 was confirmed to inhibit the growth of the bacteria, change the bacterial morphology, and increase the level of reactive oxygen species. Proteomics, and RT-qPCR analysis results indicated that compound 1 could downregulate the expression of Pil-Chp histidine kinase chpA encoded by the pilL gene, and the potting experiments proved that compound 1 exhibits significant protective activity against BLB. Compound 1 may weaken the pathogenicity of Xanthomonas oryzae pv. oryzae by inhibiting the bacterial growth and blocking the pili-mediated twitching motility without inducing the bacterial apoptosis. This study indicates that such derivatives could be a promising scaffold to develop a bacteriostat to control BLB. © 2022 Society of Chemical Industry.

Bioformulation Development of Bacillus velezensis Strain N1 to Control Rice Bacterial Leaf Blight

Bacterial leaf blight is a serious disease of rice caused by Xanthomonas oryzae pv. oryzae (Xoo). The objective of this study was to develop a bioformulation of Bacillus velezensis strain N1 by using microencapsulation techniques through spray drying and to then evaluate its performance in controlling rice bacterial leaf blight under greenhouse conditions. Three formulations with a different main carrier were studied and the viability after spray drying, moisture content, characteristic of formulation powder under scanning electron microscope and storage stability were examined. The results showed that formulation 3 (10 % skimmed milk, 20 % maltodextrin, 0.06 % sodium alginate and 5 % tapioca starch) had the highest antagonistic bacterial viability after spray drying of 1.24×107 CFU/g. Formulation 2 had the highest antagonistic bacterial viability of 1.44×106 CFU/g and had the lowest viability reduction of 0.61 Log CFU/g after storage at room temperature for 3 months. Moisture content of each formulation was less than 4 %. Among the 3 formulations of strain N1 bacteria against Xoo, formula 2 was able to control rice bacterial blight disease with the highest disease reduction index (45.87 %). All the results indicated that Bacillus velezensis strain N1 can be an effective antagonist and could potentially be used to develop a more successful bioformulation against rice bacterial leaf blight.&#x0D; GRAPHICAL ABSTRACT