Rice Blast Research Articles

Silencing Osa-miR827 via CRISPR/Cas9 protects rice against the blast fungus Magnaporthe oryzae

MicroRNAs (miRNAs) are short, non-coding RNAs that regulate gene expression at the post-transcriptional level. In plants, miRNAs participate in diverse developmental processes and adaptive responses to biotic and abiotic stress. MiR827 has long been recognized to be involved in plant responses to phosphate starvation. In rice, the miR827 regulates the expression of OsSPX-MFS1 and OsSPX-MFS2, these genes encoding vacuolar phosphate transporters. In this study, we demonstrated that miR827 plays a role in resistance to infection by the fungus Magnaporthe oryzae in rice. We show that MIR827 overexpression enhances susceptibility to infection by M. oryzae which is associated to a weaker induction of defense gene expression during pathogen infection. Conversely, CRISPR/Cas9-induced mutations in the MIR827 gene completely abolish miR827 production and confer resistance to M. oryzae infection. This resistance is accompanied by a reduction of leaf Pi content compared to wild-type plants, whereas Pi levels increase in leaves of the blast-susceptible miR827 overexpressor plants. In wild-type plants, miR827 accumulation in leaves decreases during the biotrophic phase of the infection process. Taken together, our data indicates that silencing MIR827 confers resistance to M. oryzae infection in rice while further supporting interconnections between Pi signaling and immune signaling in plants. Unravelling the role of miR827 during M. oryzae infection provides knowledge to improve blast resistance in rice by CRISPR/Cas9-editing of MIR827.

Impact of Quorum Sensing on the Virulence and Survival Traits of Burkholderia plantarii.

Quorum sensing (QS) is a mechanism by which bacteria detect and respond to cell density, regulating collective behaviors. Burkholderia plantarii, the causal agent of rice seedling blight, employs the LuxIR-type QS system, common among Gram-negative bacteria, where LuxI-type synthase produces QS signals recognized by LuxR-type regulators to control gene expression. This study aimed to elucidate the QS mechanism in B. plantarii KACC18965. Through whole-genome analysis and autoinducer assays, the plaI gene, responsible for QS signal production, was identified. Motility assays confirmed that C8-homoserine lactone (C8-HSL) serves as the QS signal. Physiological experiments revealed that the QS-defective mutant exhibited reduced virulence, impaired swarming motility, and delayed biofilm formation compared to the wild type. Additionally, the QS mutant demonstrated weakened antibacterial activity against Escherichia coli and decreased phosphate solubilization. These findings indicate that QS in B. plantarii significantly influences various pathogenicity and survival traits, including motility, biofilm formation, antibacterial activity, and nutrient acquisition, highlighting the critical role of QS in pathogen virulence and adaptability.

Pyricularia oryzae enhances Streptomyces griseus growth via non-volatile alkaline metabolites.

Chemical compounds that affect microbial interactions have attracted wide interest. In this study, Streptomyces griseus showed enhanced growth when cocultured with the rice blast fungus Pyricularia oryzae on potato dextrose agar (PDA) medium. An improvement in S. griseus growth was observed before contact with P. oryzae, and no growth-promoting effect was observed when the growth medium between the two microorganisms was separated. These results suggested that the chemicals produced by P. oryzae diffused through the medium and were not volatile. A PDA plate supplemented with phenol red showed that the pH of the area surrounding P. oryzae increased. The area with increased pH promoted S. griseus growth, suggesting that the alkaline compounds produced by P. oryzae were involved in this growth stimulation. In contrast, coculture with the soilborne plant pathogen Fusarium oxysporum and entomopathogenic fungus Cordyceps tenuipes did not promote S. griseus growth. Furthermore, DL-α-Difluoromethylornithine, a polyamine biosynthesis inhibitor, prevented the increase in pH and growth promotion of S. griseus by P. oryzae. These results indicated that P. oryzae increased pH by producing a polyamine.

MoHG1 Regulates Fungal Development and Virulence in Magnaporthe oryzae

Magnaporthe oryzae causes rice blast disease, which threatens global rice production. The interaction between M. oryzae and rice is regarded as a classic model for studying the relationship between the pathogen and the host. In this study, we found a gene, MoHG1, regulating fungal development and virulence in M. oryzae. The ∆Mohg1 mutants showed more sensitivity to cell wall integrity stressors and their cell wall is more easily degraded by enzymes. Moreover, a decreased content of chitin but higher contents of arabinose, sorbitol, lactose, rhamnose, and xylitol were found in the ∆Mohg1 mutant. Combined with transcriptomic results, many genes in MAPK and sugar metabolism pathways are significantly regulated in the ∆Mohg1 mutant. A hexokinase gene, MGG_00623 was downregulated in ∆Mohg1, according to transcriptome results. We overexpressed MGG_00623 in a ∆Mohg1 mutant. The results showed that fungal growth and chitin contents in MGG_00623-overexpressing strains were restored significantly compared to the ∆Mohg1 mutant. Furthermore, MoHG1 could interact with MGG_00623 directly through the yeast two-hybrid and BiFC. Overall, these results suggest that MoHG1 coordinating with hexokinase regulates fungal development and virulence by affecting chitin contents and cell wall integrity in M. oryzae, which provides a reference for studying the functions of MoHG1-like genes.

Bacterial co-fermentation mediated synthesis of chitosan from Procambarus clarkii enhances disease resistance in rice

The increasing dietary demand for red swamp crayfish (Procambarus clarkii) in China has resulted in a significant rise in the quantity of its by-products, which are currently underutilized or discarded. Chitosan, a widely used plant immune inducer, is one of the major components found in red swamp crayfish shells (RSCS). However, the utilization of chitosan derived from RSCS in agriculture is hindered by the lack of an efficient microbial fermentation-based production system. To address this issue, this study aims to establish a chitosan fermentation procedure by using RSCS as substrate. The efficiency by using Bacillus followed with Acetobacter for a continuous co-fermentation tested. Bacillus NJ-B2 or NJ-B3 with Acetobacter NJ-A1 demonstrated the highest co-fermentation efficacy, achieving 95 % deproteinization and 90 % demineralization of RSCS, respectively. The extracted chitosan was characterized by fourier transform infrared and scanning electron microscopy. Notably, the application of this RSCS-derived chitosan significantly improves rice resistance against Xanthomonas oryzae pv. oryzae, Magnaporthe oryzae, and Ustilaginoidea virens. These findings collectively indicate that this established method can effectively produce chitosan from RSCS via microbial fermentation, providing an environmentally friendly way for plant protection.

Rice Varieties Intercropping Induced Soil Metabolic and Microbial Recruiting to Enhance the Rice Blast (Magnaporthe Oryzae) Resistance.

[Background] Intercropping is considered an effective approach to defending rice disease. [Objectives/Methods] This study aimed to explore the resistance mechanism of rice intraspecific intercropping by investigating soil metabolites and their regulation on the rhizosphere soil microbial community using metabolomic and microbiome analyses. [Results] The results showed that the panicle blast disease occurrence of the resistant variety Shanyou63 (SY63) and the susceptible variety Huangkenuo (HKN) were both decreased in the intercropping compared to monoculture. Notably, HKN in the intercropping system exhibited significantly decreased disease incidence and increased disease resistance-related enzyme protease activity. KEGG annotation from soil metabolomics analysis revealed that phenylalanine metabolic pathway, phenylalanine, tyrosine, and tryptophan biosynthesis pathway, and fructose and mannose metabolic pathway were the key pathways related to rice disease resistance. Soil microbiome analysis indicated that the bacterial genera Nocardioides, Marmoricola, Luedemannella, and Desulfomonile were significantly enriched in HKN after intercropping, while SY63 experienced a substantial accumulation of Ruminiclostridium and Cellulomonas. Omics-based correlation analysis highlighted that the community assembly of Cellulomonas and Desulfomonile significantly affected the content of the metabolites D-sorbitol, D-mannitol, quinic acid, which further proved that quinic acid had a significantly inhibitory effect on the mycelium growth of Magnaporthe oryzae, and these three metabolites had a significant blast control effect. The optimal rice blast-control efficiency on HKN was 51.72%, and Lijiangxintuanheigu (LTH) was 64.57%. [Conclusions] These findings provide a theoretical basis for rice varieties intercropping and sustainable rice production, emphasizing the novelty of the study in elucidating the underlying mechanisms of intercropping-mediated disease resistance.

Unveiling the intricacies of the rice-Rhizoctonia pathosystem: a comprehensive review of host-pathogen interactions, molecular mechanisms, and strategies for sustainable management

Sheath blight disease in rice, induced by the necrotrophic basidiomycetes Rhizoctonia solani, has emerged as a significant menace to global rice cultivation, especially with the widespread adoption of high-yielding varieties. The pathogen’s capacity to endure unfavorable conditions and its wide host range contribute to the increased challenge for management. The occurrence of sheath blight in rice is intensified when high-yielding semi-dwarf cultivars are employed, coupled with dense planting and the application of substantial amounts of nitrogenous fertilizers. Managing this pathogen is a formidable challenge due to its broad host range, substantial genetic variability, and the absence of satisfactory levels of natural resistance in the existing rice germplasm. Due to the absence of complete resistance sources, the predominant approach for managing sheath blight has been through chemical control methods. It is imperative to explore solutions to combat this pathogen, in order to reduce rice yield losses and safeguard global food security. Developing genetic resistance provides an alternative to the use of potentially harmful chemical fungicides. This review crucially delivers efforts to enhance the understanding of the host–pathogen relationship, which involves identification of gene loci/markers associated with resistance responses, modification of host genome through transgenic approaches, examining the wide host range, epidemiology and its managemental approaches. Recent advancements and current research on the R. solani–rice pathosystem, along with a gap analysis, are presented.

Whole genome regulatory effect of MoISW2 and consequences for the evolution of the rice plant pathogenic fungus Magnaporthe oryzae.

Isw2 proteins, ubiquitous across eukaryotes, exhibit a propensity for DNA binding and exert dynamic influences on local chromosome condensation in an ATP-dependent fashion, thereby modulating the accessibility of neighboring genes to transcriptional machinery. Here, we report the deletion of a putative MoISW2 gene, yielding substantial ramifications on plant pathogenicity. Subsequent gene complementation and chromatin immunoprecipitation sequencing (ChIP-seq) analyses were conducted to delineate binding sites. RNA sequencing (RNA-seq) assays revealed discernible impacts on global gene regulation along chromosomes in both mutant and wild-type strains, with comparative analyses against 55 external RNA-seq data sets corroborating these findings. Notably, MoIsw2-mediated binding and activities delineate genomic loci characterized by pronounced gene expression variability proximal to MoIsw2 binding sites, juxtaposed with comparatively stable expression in surrounding regions. The contingent genes influenced by MoIsw2 activity predominantly encompass niche-determinant genes, including those encoding secreted proteins, secondary metabolites, and stress-responsive elements, alongside avirulence genes. Furthermore, our investigations unveil a spatial correlation between MoIsw2 binding motifs and known transposable elements (TEs), suggesting a potential interplay wherein TE transposition at these loci could modulate the transcriptional landscape of Magnaporthe oryzae in a strain-specific manner. Collectively, these findings position MoIsw2 as a plausible master regulator orchestrating the delicate equilibrium between genes vital for biomass proliferation, akin to housekeeping genes, and niche-specific determinants crucial for ecological adaptability. Stress-induced TE transposition, in conjunction with MoIsw2 activity, emerges as a putative mechanism fostering enhanced mutagenesis and accelerated evolution of niche-determinant genes relative to housekeeping counterparts.IMPORTANCEIsw2 proteins are conserved in plants, fungi, animals, and other eukaryotes. We show that a fungal Isw2 protein in the rice pathogen Magnaporthe oryzae binds to retrotransposon (RT) DNA motifs and affects the epigenetic gene expression landscape of the fungal genome. Mainly ecological niche determinant genes close to the binding motifs are affected. RT elements occur frequently in DNA between genes in most organisms. They move place and multiply in the genome, especially under physiological stress. We further discuss the Isw2 and RT combined activities as a possible sought-after mechanism that can cause biased mutation rates and faster evolution of genes necessary for reacting to abiotic and biotic challenges. The most important biotic challenges for plant pathogens are the ones from the host plants' innate immunity. The overall result of these combined activities will be an adaptation-directed evolution of niche-determinant genes.

Target prediction of potential candidate miRNAs from Oryza sativa to silence the Pyricularia oryzae genome in rice blast

Rice (Oryza sativa) is a staple food for billions of people across the globe, that feeds nearly three-quarters of the human population on Earth, particularly in Asian countries. Rice yield has been drastically reduced and severely affected by various biotic and abiotic stresses, especially pathogens. Controlling the attack of such pathogens is a matter of immediate concern as yield losses in rice crops could deprive millions of lives of nourishment worldwide. Pyricularia oryzae is one such pathogen that has been considered the major disease of rice because of its worldwide geographic distribution. P. oryzae belongs to the kingdom fungi, that causes rice blast ultimately adversely affecting the yield of the rice crop. Keeping in view this alarming scenario, the present study was designed so that the identifications of genome-encoded miRNAs of Oryza sativa were employed to target and silence the genome of P. oryzae. This study accomplished the computational analysis of algorithms related to miRNA target prediction. Four computational target prediction algorithms i.e., psRNATarget, RNA22, miRanda, and RNAhybrid were utilized in this investigation. The consensus among target prediction algorithms was created to discover six miRNAs from the O. sativa genome with the conservation of the target site fully evaluated on the genome of P. oryzae. The discovery of these novel six miRNAs in Oryza sativa paved a strong way toward the control of this disease in rice. It will open doors for further research in the field of gene silencing in rice. These miRNAs can be designed and employed in the future as experimentation to create constructs regarding the silencing of P. oryzae in rice crops. In the future, this research would be surely helpful for the development of P. oryzae resistant rice varieties.

Evolutionary Systems Biology Identifies Genetic Trade-offs In Rice Defense Against Above- and Belowground Attackers.

Like other plants, wild and domesticated rice species (Oryza nivara, O. rufipogon, and O. sativa) evolve in environments with various biotic and abiotic stresses that fluctuate in intensity through space and time. Microbial pathogens and invertebrate herbivores such as plant-parasitic nematodes and caterpillars show geographical and temporal variation in activity patterns and may respond differently to certain plant defensive mechanisms. As such, plant interactions with multiple community members may result in conflicting selection pressures on genetic polymorphisms. Here, through assays with different above- and belowground herbivores, the fall armyworm (Spodoptera frugiperda) and the southern root-knot nematode (Meloidogyne incognita), respectively, and comparison with rice responses to microbial pathogens, we identify potential genetic trade-offs at the KSL8 and MG1 loci on chromosome 11. KSL8 encodes the first committed step towards biosynthesis of either stemarane- or stemodane-type diterpenoids through the japonica (KSL8-jap) or indica (KSL8-ind) allele. Knocking out KSL8-jap and CPS4, encoding an enzyme that acts upstream in diterpenoid synthesis, in japonica rice cultivars increased resistance to S. frugiperda and decreased resistance to M. incognita. Furthermore, MG1 resides in a haplotype that provided resistance to M. incognita, while alternative haplotypes are involved in mediating resistance to the rice blast fungus Magnaporthe oryzae and other pests and pathogens. Finally, KSL8 and MG1 alleles are located within trans-species haplotypes and may be evolving under long-term balancing selection. Our data are consistent with a hypothesis that polymorphisms at KSL8 and MG1 may be maintained through complex and diffuse community interactions.

Effectiveness of some novel fungicides against the sheath blight pathogen Rhizoctonia solani in rice under in vitro and in vivo conditions

Sheath blight of rice, caused by Rhizoctonia solani, is one of the most aggressive and damaging diseases in rice cultivation, leading to significant crop losses. Consequently, chemical fungicides are the most effective method to inhibit R. solani infection and control this disease. In the present study, R. solani isolate was obtained from infected rice plants, and its pathogenicity was confirmed using Koch’s postulates on 20-day-old rice seedlings at three different inoculum levels. The lowest percent disease index and disease incidence were recorded with the 1 ml pathogen inoculum suspension, while the 2 ml and 3 ml suspensions resulted in 100% disease incidence, significantly affecting plant parameters. Furthermore, five different fungicides, Duphetar Plus, Evito, Nativo, Ridomil Gold, and Shincar, were evaluated at three concentrations (10, 100, and 1000 ppm) against R. solani using poisoned food method. The results revealed that two fungicides, Shincar and Nativo, resulted in maximum mycelial growth inhibition of R. solani, whereas the other fungicides failed to inhibit the mycelial growth of the pathogen at all concentrations. Shincar and Nativo were further tested in a greenhouse setting to control pathogen infection in rice plants. These fungicides showed excellent results, reducing R. solani infection and minimizing disease incidence in treated rice plants compared to the control. The highest root length, shoot length, and plant weight were observed with Shincar, followed by Nativo. It is suggested that the use of these fungicides may reduce sheath blight disease incidence, effectively control pathogen infection, and improve plant growth parameters in field conditions.

PARylation of 14-3-3 proteins controls the virulence of Magnaporthe oryzae

Magnaporthe oryzae is a devastating fungal pathogen that causes the rice blast disease worldwide. The post-translational modification of ADP-ribosylation holds significant importance in various fundamental biological processes. However, the specific function of this modification in M. oryzae remains unknown. This study revealed that Poly(ADP-ribosyl)ation (PARylation) executes a critical function in M. oryzae. M. oryzae Poly(ADP-ribose) polymerase 1 (PARP1) exhibits robust PARylation activity. Disruption of PARylation by PARP1 knock-out or chemical inhibition reveals its involvement in M. oryzae virulence, particularly in appressorium formation. Furthermore, we identified two M. oryzae 14-3-3 proteins, GRF1 and GRF2, as substrates of PARP1. Deletion of GRF1 or GRF2 results in delayed and dysfunctional appressorium, diminished plant penetration, and reduced virulence of the fungus. Biochemical and genetic evidence suggest that PARylation of 14-3-3s is essential for its function in M. oryzae virulence. Moreover, PARylation regulates 14-3-3 dimerization and is required for the activation of the mitogen-activated protein kinases (MAPKs), Pmk1 and Mps1. GRF1 interacts with both Mst7 and Pmk1, and bridges their interaction in a PARylation-dependent manner. This study unveils a distinctive mechanism that PARylation of 14-3-3 proteins controls appressorium formation through MAPK activation, and could facilitate the development of new strategies of rice blast disease control.

OsWRKY70 Plays Opposite Roles in Blast Resistance and Cold Stress Tolerance in Rice

The transcription factor WRKYs play pivotal roles in the adapting to adverse environments in plants. Prior research has demonstrated the involvement of OsWRKY70 in resistance against herbivores and its response to abiotic stress. Here, we reported the functional analysis of OsWRKY70 in immunity against fungal diseases and cold tolerance. The results revealed that OsWRKY70 was induced by various Magnaporthe oryzae strains. Knock out mutants of OsWRKY70, which were generated by the CRISPR/Cas9 system, exhibited enhanced resistance to M. oryzae. This was consistent with fortifying the reactive oxygen species (ROS) burst after inoculation in the mutants, elevated transcript levels of defense-responsive genes (OsPR1b, OsPBZ1, OsPOX8.1 and OsPOX22.3) and the observation of the sluggish growth of invasive hyphae under fluorescence microscope. RNA sequencing (RNA-seq) and quantitative real-time PCR (qRT-PCR) validations demonstrated that differentially expressed genes were related to plant-pathogen interactions, hormone transduction and MAPK cascades. Notably, OsbHLH6, a key component of the JA signaling pathway, was down-regulated in the mutants compared to wild type plants. Further investigation confirmed that OsWRKY70 bound to the promoter of OsbHLH6 by semi-in vivo chromatin immunoprecipitation (ChIP). Additionally, the loss-function of OsWRKY70 impaired cold tolerance in rice. The enhanced susceptibility in the mutants characterized by excessive ROS production, elevated ion leakage rate and increased malondialdehyde content, as well as decreased activity of catalase (CAT) and peroxidase (POD) under low temperature stress was, which might be attributed to down-regulation of cold-responsive genes (OsLti6b and OsICE1). In conclusion, our findings indicate that OsWRKY70 negatively contributes to blast resistance but positively regulates cold tolerance in rice, providing a strategy for crop breeding with tolerance to stress.

Relative efficiency of some chemical fungicides used for the control of rice blast (Magnaporthe oryzae B. Cauch) in Jigawa State, Nigeria

Relative efficiency of some chemical fungicides used for the control of rice blast (Magnaporthe oryzae B. Cauch) in Jigawa State, Nigeria

Identification of hub genes and potential networks by centrality network analysis of PCR amplified Fusarium oxysporum f. sp. lycopersici EF1α gene

BackgroundFusarium wilt is a devastating soil-borne fungal disease of tomato across the world. Conventional method of disease prevention including usage of common pesticides and methods like soil solarisation are usually ineffective in the treatment of this disease. Therefore, there is an urgent need to identify virulence related genes in the pathogen which can be targeted for fungicide development.ResultsPathogenicity testing and phylogenetic classification of the pathogen used in this study confirmed it as Fusarium oxysporum f. sp. lycopersici (Fol) strain. A recent discovery indicates that EF1α, a protein with conserved structural similarity across several fungal genera, has a role in the pathogenicity of Magnaporthe oryzae, the rice blast fungus. Therefore, in this study we have done structural and functional classification of EF1α to understand its role in pathogenicity of Fol. The protein model of Fol EF1α was created using the template crystal structure of the yeast elongation factor complex EEF1A:EEF1BA which showed maximum similarity with the target protein. Using the STRING online database, the interactive information among the hub genes of EF1α was identified and the protein–protein interaction network was recognized using the Cytoscape software. On combining the results of functional analysis, MCODE, CytoNCA and CytoHubba 4 hub genes including Fol EF1α were selected for further investigation. The three interactors of Fol EF1α showed maximum similarity with homologous proteins found in Neurospora crassa complexed with the known fungicide, cycloheximide. Through the sequence similarity and PDB database analysis, homologs of Fol EF1α were found: EEF1A:EEF1BA in complex with GDPNP in yeast and EF1α in complex with GDP in Sulfolobus solfataricus. The STITCH database analysis suggested that EF1α and its other interacting partners interact with guanosine diphosphate (GDPNP) and guanosine triphosphate (GTP).ConclusionsOur study offers a framework for recognition of several hub genes network in Fusarium wilt that can be used as novel targets for fungicide development. The involvement of EF1α in nucleocytoplasmic transport pathway suggests that it plays role in GTP binding and thus apart from its use as a biomarker, it may be further exploited as an effective target for fungicide development. Since, the three other proteins that were found to be tightly associated Fol EF1α have shown maximum similarity with homologous proteins of Neurospora crassa that form complex with fungicide- Cycloheximide. Therefore, we suggest that cycloheximide can also be used against Fusarium wilt disease in tomato. The active site cavity of Fol EF1α can also be determined for computational screening of fungicides using the homologous proteins observed in yeast and Sulfolobus solfataricus. On this basis, we also suggest that the other closely associated genes that have been identified through STITCH analysis, they can also be targeted for fungicide development.

Genomic Characterization of Phage ZP3 and Its Endolysin LysZP with Antimicrobial Potential against Xanthomonas oryzae pv. oryzae.

Xanthomonas oryzae pv. oryzae (Xoo) is a significant bacterial pathogen responsible for outbreaks of bacterial leaf blight in rice, posing a major threat to rice cultivation worldwide. Effective management of this pathogen is crucial for ensuring rice yield and food security. In this study, we identified and characterized a novel Xoo phage, ZP3, isolated from diseased rice leaves in Zhejiang, China, which may offer new insights into biocontrol strategies against Xoo and contribute to the development of innovative approaches to combat bacterial leaf blight. Transmission electron microscopy indicated that ZP3 had a short, non-contractile tail. Genome sequencing and bioinformatic analysis showed that ZP3 had a double-stranded DNA genome with a length of 44,713 bp, a G + C content of 52.2%, and 59 predicted genes, which was similar to other OP1-type Xoo phages belonging to the genus Xipdecavirus. ZP3's endolysin LysZP was further studied for its bacteriolytic action, and the N-terminal transmembrane domain of LysZP is suggested to be a signal-arrest-release sequence that mediates the translocation of LysZP to the periplasm. Our study contributes to the understanding of phage-Xoo interactions and suggests that phage ZP3 and its endolysin LysZP could be developed into biocontrol agents against this phytopathogen.

First Report of Burkholderia glumae Causing Bacterial Panicle Blight in Rice in Bangladesh.

Bacterial panicle blight (BPB) is one of the emerging diseases occurring in different Agro-Ecological Zones (AEZ) of Bangladesh and can cause up to 75% yield loss. In Bangladesh, the typical symptoms of BPB include sheath rot, panicle blight, grain spotting, and grain rot in both inbred and hybrid rice varieties, which resemble those reported by Zhou (2019). To confirm, 300 field samples of 20 panicles each with typical BPB symptoms from 20 districts (3 locations each district and 5 fields per location) were collected during mid-November 2022 for the causal pathogen(s) isolation. Nearly 70% of the panicles showed a dark brown chaffy appearance in the fields. For identification of the causal pathogen(s), 1 g of rice grains with typical BPB symptoms was surface sterilized by immersing for 15 seconds in 70% ethanol, 1 min in 3% sodium hypochlorite solution followed by rinsing the grains three times, and soaked in 1 mL sterile distilled water for 10 min (Mirghasempour et al. 2018). During grinding using mortar and pestle, 5 mL water was added (Islam et al. 2023) after which the suspension (20 μL) was then streaked onto the selective medium (S-PG) (Tsushima et al. 1986). Purple color colonies on the S-PG medium were selected and purified as candidate pathogens. For further confirmation, the genomic DNA of the bacterial isolates was extracted and amplified by PCR using 16SF (5'-AGAGTTTGATCCTGGCTCAG-3') and 16SR (5'-GGCTACCTTGTTACGACTT-3') (Nandakumar et al. 2009), and glu-FW (5'-GAAGTGTCGCCGATGGAG-3') and glu-RV (5'-CCTTCACCGACAGCACGCAT-3') primers (Maeda et al. 2006). The PCR products were visualized on 1% agarose gel resulting amplicons of 1494bp for 16S-rDNA and 529bp for gyrB. The PCR results revealed 529bp amplification for gyrB gene in one sample that was collected from a field in Natore (24°21'0.00" N 89°04'59.88" E) district cultivating Swarna (a local rice variety), primarily indicating the causal pathogen is Burkholderia glumae. The PCR products were sequenced using both primers and sequence data was analyzed by the BLAST nucleotide program. The obtained partial sequences of 16S rDNA and gyrB were deposited in Genbank (OR573691 and PP332812 respectively). The homology of 16S rDNA resulted over 98% with B. glumae (OK559611 and ON870618.1) and 100% with B. glumae (PP332812 and KX213523) for gyrB gene. To confirm B. glumae by pathogenicity test, 10 mL (108 UFC/ml) suspension of the representative strains, 0.5 mL was then injected into the panicles and sheaths of Horidhan (a susceptible local variety) in greenhouse condition and a control was inoculated with distilled water (Nandakumar et al. 2009). Typical BPB like symptoms were observed after 3 weeks post inoculation. The pathogen was again confirmed by reisolating from the infected spots as B. glumae to fulfill Koch's postulates. This report confirms the presence of B. glumae causing BPB of rice in Bangladesh. Future research for the investigation of BPB and the evolutionary origins of its causal bacteria is necessary to reduce the emergence of the disease and its management in Bangladesh.

Composition and Distribution of Bacteria, Pathogens, and Antibiotic Resistance Genes at Shanghai Port, China

As one of the biggest ports, the aquatic ecology of Shanghai Port has a significant impact on the health of surrounding residents and aquatic animals. Therefore, this study explored the composition and distribution of bacteria, pathogens, and ARGs at Shanghai Ports by high-throughput sequencing. The results showed that the bacterial community was dominated by the Proteobacteria at the phylum level. With the refinement of classification level, the main composition of bacteria in different samples shows significant differences. In contrast, there was no significant difference in the composition and distribution of pathogens among the samples. It indicates that pathogens and ARGs have steady community composition at Shanghai Port. Pseudomonas aeruginosa and Salmonella enterica could be regarded as candidate indicator pathogens. macB, tetA (58), and evgS were the main ARGs, and they showed a close relationship with Mycobacterium tuberculosis, Magnaporthe oryzae, Streptococcus pneumonia, Xanthomonas oryzae, and Vibrio cholerae in different sites and layers. This may lead to the transfer of ARGs between different pathogens, resulting in more threatening pathogens. The results showed that the pathogens and ARGs present posed a risk of transmission and were potentially harmful to residents in the environment. They can spread to any other ports in the world through the transmission of ballast water, posing a threat to humans and local ecology. In order to keep human health, it is necessary to pay more attention to the water environment of ports and increase the monitoring. Furthermore, it is essential to strengthen the supervision of external source pollution input due to the special features of the port.

Advances in breeding, biotechnology, and nanotechnological approaches to combat sheath blight disease in rice.

Sheath blight, caused by the fungus Rhizoctonia solani, is a major problem that significantly impacts rice production and can lead to substantial yield losses. The disease has become increasingly problematic in recent years due to the widespread use of high-yielding semi-dwarf rice cultivars, dense planting, and heavy application of nitrogenous fertilizers. The disease has become more challenging to manage due to its diverse host range and the lack of resistant cultivars. Despite utilizing traditional methods, the problem persists without a satisfactory solution. Therefore, modern approaches, including advanced breeding, transgenic methods, genome editing using CRISPR/Cas9 technology, and nanotechnological interventions, are being explored to develop rice plants resistant to sheath blight disease. This review primarily focuses on these recent advancements in combating the sheath blight disease.

Multi-Population Analysis for Leaf and Neck Blast Reveals Novel Source of Neck Blast Resistance in Rice.

Rice blast is one of the most devastating biotic stresses that limits rice productivity. The North Eastern Hill (NEH) region of India is considered to be one of the primary centres of diversity for both rice and pathotypes of Magnaporthe grisea. Therefore, the present study was carried out to elucidate the genetic basis of leaf and neck blast resistance under Meghalaya conditions. A set of 80 diverse genotypes (natural population) and 2 F2 populations involving resistant parent, a wildtype landrace, LR 5 (Lal Jangali) and susceptible genotypes Sambha Mahsuri SUB 1 (SMS) and LR 26 (Chakhao Poireiton) were used for association analysis of reported major gene-linked markers with leaf and neck blast resistance to identify major effective genes under local conditions. Genotyping using twenty-five gene-specific markers across diverse genotypes and F2 progenies revealed genes Pi5 and Pi54 to be associated with leaf blast resistance in all three populations. Genes Pib and qPbm showed an association with neck blast resistance in both natural and LR 5 × SMS populations. Additionally, a set of 184 genome-wide polymorphic markers (SSRs and SNPs), when applied to F2-resistant and F2-susceptible DNA bulks derived from LR 5 × LR 26, suggested that Pi20(t) on chromosome 12 is one of the major genes imparting disease resistance. Markers snpOS318, RM1337 and RM7102 and RM247 and snpOS316 were associated with leaf blast and neck blast resistance, respectively. The genotypes, markers and genes will help in marker-assisted selection and development of varieties with durable resistance.