Search Results (112)

Rice blast and bacterial blight are two major diseases that seriously threaten rice production. Developing rice germplasm with enhanced resistance to multiple diseases while maintaining favorable agronomic traits is essential for sustainable breeding. In this study, two rice landraces from Motuo County, Xizang Autonomous Region, China, Benglinba and Gare, were used to simultaneously edit OsERF922 and Xa41 using a structurally optimized dual-target CRISPR/Cas9 vector, pRGEB32-2T. A total of 32 and 28 T₀ transgenic plants were generated in the Benglinba and Gare backgrounds, respectively. Targeted mutagenesis generated eight homozygous oserf922 mutants and three homozygous xa41 mutants in Benglinba, and four and five homozygous mutants in Gare. Twelve double homozygous mutant lines (nine Benglinba and three Gare) were selected for further analysis. Disease resistance assays showed that these double mutants exhibited significantly enhanced resistance to the rice blast fungus strain GDYJ7 and the bacterial blight pathogen strain GDXO-1, with markedly reduced lesion size or lesion length compared with wild-type plants (p < 0.001, Student’s t-test). Importantly, three independent T-DNA-free double mutant lines from each genetic background displayed no significant differences from their corresponding wild types in major agronomic traits, including plant height, effective panicle number, panicle length, seed-setting rate, or thousand-grain weight (p > 0.05). Grain quality parameters, such as brown rice rate, milled rice rate, amylose content, and gel consistency, were also unaffected. Overall, this study generated rice materials with enhanced resistance to rice blast and bacterial blight while maintaining elite agronomic and quality traits, providing valuable germplasm resources and a feasible strategy for the precise improvement of disease resistance in rice landraces from Xizang Autonomous Region. Full article

Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is one of the most devastating diseases affecting global rice production. Plant essential oils (EOs) have been considered as a promising green alternative to synthetic fungicides. In this study, the antifungal activities of five plant EOs—Acorus calamus, Citrus reticulata, Syzygium aromaticum, Paeonia suffruticosa, and Melaleuca viridiflora—against M. oryzae were evaluated using the mycelial growth rate method. Among them, A. calamus EO (ACEO) exhibited the most pronounced inhibitory effect, with an EC₅₀ value of 0.37 μL/mL. It significantly delayed or inhibited conidial germination and appressorium formation. At higher concentrations (≥1 μL/mL), it also caused morphological abnormalities in appressoria. Observations by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the EO treatment caused hyphal surface wrinkling, cell wall thinning, organelle dissolution, and vacuolation. Pathogenicity tests further confirmed that ACEO reduced the virulence of the fungus remarkably, with nearly complete loss of pathogenicity at a concentration of 1 μL/mL. Finally, ACEO was analyzed using gas chromatography-mass spectrometry (GC-MS). The most abundant constituents identified were β-asarone (19.83%) and isoshyobunone (14.92%). Together, these findings demonstrate that ACEO impairs fungal pathogenicity by disrupting hyphal morphology and cellular integrity, highlighting its potential as an effective and eco-friendly fungicide for controlling rice blast. Full article

Rice blast, caused by the fungus Magnaporthe oryzae, is a devastating disease that threatens global food security, causing annual yield losses of 10–30%. Consequently, novel control strategies beyond conventional fungicides are urgently needed. Tetramycin, a polyene macrolide antibiotic, is known for its broad-spectrum antifungal activity. However, the specific mechanisms underlying its efficacy against rice blast remain to be fully elucidated. In this study, we demonstrate that tetramycin confers resistance through a dual mode of action. First, in vitro assays revealed that tetramycin directly inhibits M. oryzae mycelial growth. Second, and more critically, it functions as a potent immune elicitor in Oryza sativa. Transcriptome analysis coupled with physiological assays showed that tetramycin treatment triggers a rapid oxidative burst, characterized by significantly elevated activities of key defense enzymes, including superoxide dismutase, peroxidase, phenylalanine ammonia lyase, and polyphenol oxidase (PPO). This oxidative response is further orchestrated through the simultaneous activation of the jasmonic acid (JA) and salicylic acid (SA) signaling pathways, as evidenced by the distinct upregulation of their respective biosynthetic genes and hormone levels. Collectively, these findings indicate that tetramycin not only acts as a direct fungicide but also primes the rice innate immune system via a synergistic reactive oxygen species-JA-SA signaling network, offering a sustainable strategy for rice blast management. Full article

The crude ethyl acetate extract of the culture of a marine sponge-associated fungus, Aspergillus unguis KUFA 0098, was tested for its capacity to inhibit the growth of ten phytopathogenic fungi, viz. Alternaria brassicicola, Bipolaris oryzae, Colletotrichum capsici, Curvularia oryzae, Fusarium semitectum, Lasiodiplodia theobromae, Phytophthora palmivora, Pyricularia oryzae, Rhizoctonia oryzae, and Sclerotium roflsii. At a concentration of 1 g/L, the crude extract was most active against P. palmivora, causing the highest growth inhibition (55.32%) of this fungus but inactive against R. oryzae and S. roflsii. At a concentration of 10 g/L, the crude extract completely inhibited the growth of most of the fungi, except for L. theobromae, R. oryzae, and S. roflsii, with 94.50%, 74.12%, and 67.80% of inhibition, respectively. The crude extract of A. unguis KUFA 0098 exhibited growth-inhibitory effects against B. oryzae and P. oryzae, causative agents of brown leaf spot disease and leaf blast disease, respectively, on rice plant var. KDML105, under greenhouse conditions. Chromatographic fractionation and purification of the extract led to the isolation of four previously described depsidones, viz. unguinol (1), 2-chlorounguinol (2), 2,4-dichlorounguinol (3), and folipastatin (4), as well as one polyphenol, aspergillusphenol A (5). The major compounds, i.e., 1, 2, and 4, were tested against the ten phytopathogenic fungi. Compounds 1 and 4 were able to inhibit growth of most of the fungi, except L. theobromae, R. oryzae, and S. roflsii. Compound 1 showed the same minimum inhibitory concentration (MIC) values as that of carbendazim against A. brassicicola, C. capsici, C. oryzae, and P. oryzae, while compound 4 showed the same MIC values as that of carbendazim against only C. capsici and P. oryzae. Compound 2 was not active against all of the ten phytopathogenic fungi tested. Full article

Fungal effectors play an important role in plant immunity. The Magnaporthe oryzae effector PWL2 plays a significant role in rice blast disease caused by this fungus. However, the function of PWL2 in rice immunity is not fully understood. In this study, transgenic rice lines overexpressing PWL2 showed resistance to rice blast. Subcellular localization showed that PWL2-GFP fusion protein is localized on the plasma membrane and cytoplasm. Salicylic acid (SA) induces rice resistance to M. oryzae. Notably, the expression of the NPR1 gene exhibited a rhythmic pattern during the early stages of M. oryzae infection in the transgenic rice lines. However, during later stages of infection, transgenic plants showed reduced levels of the NPR1, WRKY45, PR1a and PR10a genes, along with decreased H₂O₂ accumulation, while SA levels remained unchanged. Transcriptome analysis revealed that SA treatment induced the expression of the ARGONAUTE11 (AGO11) gene in rice. Furthermore, during the later infection stage in the transgenic rice lines, the expression levels of both AGO11 and PWL2 genes increased. Intriguingly, PWL2-derived small interfering RNAs (siRNA) were detected in these transgenic rice lines. It suggests that both the SA signaling pathway and PWL2-derived siRNAs function in rice resistance to blast disease caused by M. oryzae. Full article

Most terrestrial plants establish symbiotic relationships with microorganisms to acquire nutrients and simultaneously restrict pathogen infection. In rice, the receptor-like kinase OsARK1 is essential for the colonization and development of arbuscular mycorrhizal (AM) fungi. However, whether OsARK1 participates in plant–pathogen interactions remain unknown. Here, we demonstrate that OsARK1 is involved in the transcriptional reprogramming of immune defense-related genes prior to and following AM colonization. Mutation of OsARK1 resulted in increased susceptibility to Magnaporthe oryzae (blast fungus) and Xanthomonas oryzae (bacterial blight). Transcriptomic profiling during blast infection demonstrated OsARK1 coordinates early immune responses; particularly, the upregulation of genes encoding lectin receptor-like kinases (LecRLKs), nucleotide-binding leucine-rich repeat (NLR) immune receptors and secondary metabolism-related genes was significantly impaired in Osark1 mutant. Collectively, OsARK1 acts as a positive regulator of rice immunity against pathogens while fine-tuning defense suppression during beneficial AM symbiosis. Full article

In the present study, a new Ganoderma sp. (ZHM1939) was collected from Lincang, Yunnan, China, and described on the basis of morphological characters and multigene phylogenetic analysis of rDNA-ITS, TEF1α and RPB2 sequences. This fungus is characterized by the exceptionally large basidiomata, oval shape, a pileus measuring 63.86 cm long, 52.35 cm wide, and 21.63 cm thick, and a fresh weight of 80.51 kg. The skeleton hyphae from the basidiocarp are grayish to grayish-red in color, septate, and 1.41–2.75 μm in diameter, with frequently dichotomous branched and broadly ellipsoid basidiospores. The basidiospores are monocellular, ellipsoid, with round ends or one slightly pointed end, brown–gray in color, and measured 6.52–10.26 μm × 4.68–7.17 μm (n = 30). When cultured for 9 days at 25 ± 2 °C on PDA, the colony was white, ellipsoid or oval, with slightly ragged edges, measured Φ58.26 ± 3.05 mm (n = 5), and the growth rate = 6.47 mm/day; prosperous blast-spores formed after culturing for 21 days, making the colony surface powdery-white. The mycelia were septate, hyaline, branching at near-right angles, measured Φ1.28–3.32 μm (n = 30), and had some connections. The blast-spores were one-celled, elliptic or barley-seed shaped, and measured 6.52–10.26 μm × 4.68–7.17 μm (n = 30). Its rDNA-ITS, TEF1α and RPB2 sequences amplified through PCR were 602 bp, 550 bp and 729 bp, respectively. Blast-n comparison with these sequences showed that ZHM1939 was 99.67–100% identical to related strains of Ganoderma mutabile. A maximum likelihood phylogenic tree using the concatenated sequence of rDNA-ITS, TEF1α and RPB2 was constructed and it showed that ZHM1939 clustered on the same terminal branch of the phylogenic tree with the strains Cui1718 and YUAN 2289 of G. mutabile (Bootstrap support = 100%). ZHM1939 could grow on all the 15 original inoculum substrates tested, among which the best growth was shown on substrate 2 (cornmeal 40 g, sucrose 10 g, agar 20 g), with the fastest colony growth rate (6.79 mm/day). Of the five propagation substrates tested, substrate 1 (wheat grains 500 g, gypsum powder 6.5 g and calcium carbonate 2 g) resulted in the highest mycelium growth rate (7.78 mm/day). Among the six cultivation substrates tested, ZHM1939 grew best in substrate 2 (cottonseed hulls 75 g, rice bran 12 g, tree leaves 5 g, cornmeal 5 g, lime powder 1 g, sucrose 1 g and red soil 1 g) with a mycelium growth rate of 7.64 mm/day. In conclusion, ZHM1939 was identified as Ganoderma mutabile, which is a huge mushroom and rare medicinal macrofungus resource. The original inoculum substrate 9, propagation substrate 1 and cultivation substrate 2 were the most optimal substrates for producing the original propagation and cultivation inocula of this macrofungus. This is the first report on successful growing conditions for mycelial production, but basidiocarp production could not be achieved. The results of the present work establish a scientific foundation for further studies, resource protection and application development of G. mutabile. Full article

Rice blast, caused by Magnaporthe oryzae, significantly threatens global rice production. Disease control is complicated by the pathogen’s high genetic diversity, which is driven by heterothallic recombination between opposite mating types that underlies variation. However, mechanisms governing sexual reproduction in this fungus remain poorly characterized, largely due to the absence of reliable methods for scalable ascospore progeny production. In this study, we established two novel mating methods, namely Conidial Mixing Mating (CMM) and Hyphal Segments Mixed Mating (HMM). Both methods employed optimized suspensions (5 × 10⁴ conidia/mL or equivalent hyphal density) mixed at 1:1 ratios, incubated under standardized conditions: 20 °C with a 12 h/12 h photoperiod. We characterized perithecia, asci, and ascospore morphology using fluorescence microscopy, paraffin sectioning, cryo-scanning electron microscopy, and transmission electron microscopy. Furthermore, both methods enabled phenotypic characterization of sexual reproduction-deficient mutants, including ΔMopmk1 and ΔMoopy2. In conclusion, we established two efficient methods for investigating M. oryzae sexual reproduction, providing foundational tools to advance studies of sexual mechanisms, pathogenicity evolution, and genetic variation. Full article

Rice blast is one of the main diseases of rice, causing severe economic losses to agricultural production; thus, the search for blast resistance is a top priority for rice breeding. When challenged by the blast causal fungus Magnaporthe oryzae the expression level of OsMAPKKK69 gene in rice cultivar Nipponbar was found to increase significantly. Such an induction was also found in a different genetic material, cultivar Shufanggaonuo, indicating that OsMAPKKK69 plays an important role in blast disease response. However, the function of OsMAPKKK69 remains unclear. In this study, wild type ZH11 was selected as the background material to investigate the expression and functions of OsMAPKKK69 in rice disease resistance by constructing knockout mutants. The results showed that OsMAPKKK69 is mainly expressed in four-week-old shoots and localized in cell membrane, cytoplasm, and nucleus. The two allelic knockout mutants, osmapkkk69-1 and osmapkkk69-2, were more resistant to M. oryzae and bacterial blight Xanthomonas oryzae pv. Oryzae (Xoo). Further agronomic trait analysis revealed that the osmapkkk69-1 and osmapkkk69-2 mutants had reduced plant height, smaller grain size, a significant increase in tillering number, but also a significant increase in yield per plant. Our results show that OsMAPKKK69 is involved in the immune response of rice by negatively regulating the resistance to rice blast and blight diseases, and in regulating important agronomic traits. This study lays a foundation for revealing the molecular mechanism of OsMAPKKK69 in the immune response to rice diseases and provides novel genetic resources for rice breeding. Full article

Fungal diseases severely threaten global agriculture, while conventional chemical fungicides face increasing restrictions due to environmental and safety concerns. In this study, we isolated a soil-derived Bacillus stercoris strain, DXQ-1, exhibiting strong antagonistic activity against plant pathogenic fungi, notably Magnaporthe oryzae, the causal agent of rice blast. Scanning electron microscopy revealed that DXQ-1 disrupts fungal hyphae and inhibits conidial germination, with a 24 h crude broth treatment reducing germination to 83.33% and completely blocking appressoria formation. LC-MS-based metabolomic analysis identified key antifungal components, including lipids (35.83%), organic acid derivatives (22.15%), and small bioactive molecules (e.g., Leu-Pro, LPE 15:0). After optimizing fermentation conditions (LB medium, pH 7.0, 28 °C, 48 h), the broth showed >90% inhibition against M. oryzae and Nigrospora oryzae and retained high thermal (68 °C, 1 h) and UV (4 h) stability. Field trials demonstrated effective disease control and significant promotion of rice growth, increasing plant height (17.7%), fresh weight (53.3%), and dry weight (33.3%). These findings highlight DXQ-1 as a promising biocontrol agent, offering a sustainable and effective alternative for managing fungal diseases in crops. Full article

Rice blast disease, caused by the ascomycete fungus Magnaporthe oryzae (syn. Pyricularia oryzae), poses a severe threat to global rice production. Southern China, a major rice-growing region characterized by diverse agroecological conditions, faces substantial challenges from blast disease, yet our understanding of the genetic structure of M. oryzae populations in this region remains limited. Here, we analyzed 885 M. oryzae strains from 18 nurseries across four rice ecological regions in Southern China using a panel of genome-wide SNP markers. Phylogenetic and principal component analyses revealed three distinct clonal lineages: lineage I (58.19%), lineage II (21.36%), and lineage III (20.45%). Lineage I exhibited a broader geographic distribution compared to the other two lineages. Host-adapted divergence was observed across rice subspecies, with lineage III predominantly associated with japonica growing-regions, while lineages I and II mainly colonized indica rice-growing regions. Genetic diversity exhibited significant spatial heterogeneity, with the nucleotide diversity (π) ranging from 0.17 in South China to 0.32 in the Middle–Lower Yangtze River region, reflecting differential cropping systems. The predominantly negative Tajima’s D values across populations suggested recent expansion or selective sweeps, likely driven by host resistance pressures. High genetic differentiation between lineage I and other lineages contrasted with low divergence between lineages II and III, indicating distinct evolutionary trajectories. Furthermore, an uneven distribution of mating types among three genetic lineages was observed, suggesting limited sexual recombination within clonal lineages. The information obtained in this study may be beneficial in devising suitable strategies to control rice blast disease in Southern China. Full article

Magnaporthe oryzae (M. oryzae) is a phytopathogenic fungus that inflicts damage on vital crops, particularly rice. Its asexual reproduction leads to the generation of numerous conidia, which is a critical factor contributing to the prevalence of rice blast disease. However, the molecules regulating the asexual reproduction of M. oryzae are unknown. In our study, to identify the molecules capable of regulating the asexual reproduction of M. oryzae, compositions of the complete medium (CM) were screened. Results showed that acid-hydrolyzed casein (AHC) could remarkably promote conidial production. One M. oryzae conidiation inducer was isolated from AHC using high-performance liquid chromatography (HPLC) under the guidance of bioassay. Its structure was further elucidated as a decapeptide compound (pyroGlu-EQNQEQPIR) by LC-MS/MS, chemical synthesis, and conidium-inducing assays, named M. oryzae conidiation inducer decapeptide (MCIDP). MCIDP could significantly promote the conidiation of M. oryzae and two other filamentous ascomycetes (Botrytis cinerea and Fusarium graminearum). The Mps1 MAPK cascade signaling pathway is crucial for conidiation, and the effect of MCIDP on this pathway was investigated to elucidate the mechanism underlying conidiation enhancement. qRT-PCR analysis demonstrated that MCIDP could remarkably upregulate the gene expression within the Mps1 MAPK cascade signaling pathway, especially the WSC2, WSC3, PKC1, MKK1, MPS1, and MIG1. Furthermore, the ΔMowsc1, ΔMowsc2, ΔMowsc3, and ΔMomid2 mutant strains were constructed. Bioassay results showed that MCIDP failed to promote conidial formation and hyphal growth in these mutant strains. These findings indicate that MCIDP promotes conidiation of M. oryzae by modulating the Mps1 MAPK signaling pathway. Full article

Rice blast caused by Magnaporthe oryzae pathotype is the worst disease that leads to serious food insecurity globally. Understanding rice blast disease pathogenesis is therefore essential for the development of a blast disease mitigation strategy. Reverse phosphorylation mediated by phosphatases performs a vital function in the activation of diverse biological mechanisms within eukaryotic. However, little has been reported on the roles of PP2Cs in the virulence of blast fungus. In this current work, we deployed functional genomics and biochemical approaches to characterize type 2C protein phosphatase MoPtc6 in blast fungus. Deletion of MoPTC6 led to a drastic reduction in conidiophore development, conidia production, hyphal growth, and stress tolerance. Western blotting assay demonstrated that the phosphorylation level of MoOsm1 was decreased while MoMps1 was increased in the MoPtc6 deletion mutant, and comparative transcriptome assay revealed a higher number of expressed genes between mutant and wild type. Localization assay confirmed that MoPtc6 is sub-localized in the cytoplasm of mycelia, spores, and in the appressoria of M. oryzae. Furthermore, disruption of MoPTC6 impaired appressoria turgor pressure and glycogen utilization; more findings revealed attenuation of hyphal penetration and virulence upon deletion of MoPTC6. Generally, present findings suggested the role of MoPtc6 in the growth and virulence of M. oryzae. Full article

Rice blast caused by the ascomycete fungus Magnaporthe oryzea is one of the most widespread and destructive rice diseases worldwide. The most economical and effective strategy for controlling rice blast is the rational use and promotion of disease-resistant varieties. To enhance disease resistance, it is essential to analyze the resistance levels of rice varieties and the role of resistance (R) genes. To investigate blast resistance, R gene distribution, and their contributions in japonica rice, 287 varieties were evaluated through artificial inoculation. PCR detection was also performed using specific primers for eleven R genes. The results showed that 24.4% of the varieties exhibited moderate resistance (MR), indicating an overall moderate resistance level. The frequency of R genes varied significantly: Pib was the most prevalent (89.2%), followed by Pi5 (73.5%), Pita (62.4%), Pia (54.4%), Pikh (48.4%), Pik (41.1%), Pi9 (35.5%), Pizt (23.7%), Pit (10.8%), and Pi1 (10.5%). No Pigm was detected. Among these, Pik, Pi9, Pizt, and Pita contributed most significantly to disease resistance, with contributions of 42.4%, 38.2%, 38.2%, and 33.5%, respectively. The number of R genes detected in the tested varieties ranged from 0 to 9, with most varieties containing more than three genes. The highest proportion of resistant varieties was observed in those carrying six genes. The most common R gene combinations in resistant varieties were ‘Pib + Pita + Pi5 + Pikh + Pik + Pi9’ and ‘Pizt + Pib + Pita + Pia + Pi5 + Pik + Pi9’. In conclusion, these findings provide valuable insights into the breeding and utilizing blast-resistant japonica rice varieties in Anhui Province. Full article

The avirulence (AVR) genes of the filamentous ascomycete fungus Magnaporthe oryzae (M. oryzae) are known to mutate rapidly under a higher selection pressure, allowing the pathogen to evade recognition by rice resistance (R) genes. Understanding the geographic distribution and natural variation of AVR genes is critical for the rational utilization and prolonging of the effectiveness of R genes. In this study, a total of 1060 M. oryzae strains collected from 19 rice blast nurseries in 13 provinces across southern China were subjected to presence/absence variation (PAV), genetic variation, and virulence analyses of the AVR-Pita1 gene. PCR amplification results indicated that AVR-Pita1 was present in only 57.45% of the blast strains, with significant geographic variation in distribution frequency. Specifically, the highest frequency (100%) was observed in strains from Chengmai, Hainan, while the lowest (1.79%) was observed in strains from Baoshan, Yunnan. A sequencing analysis identified 29 haplotypes of AVR-Pita1, characterized by insertions, deletions, and base substitutions. A phylogenetic analysis indicated that haplotypes of AVR-Pita1 identified in this study were clustered into one clade. A further amino acid sequence analysis of these haplotypes led to the identification of 25 protein variants. Notably, four haplotypes of AVR-Pita1 exhibited pathogenicity toward its corresponding rice R gene, PtrA. Additionally, we performed allele profiling of Ptr in a collection of elite parental lines that are widely used in rice breeding in southern China and found that the functional Ptr alleles (PtrA, PtrB, and PtrC) accounted for over 70%. Full article