Plant pathogens employ a diverse array of effectors to facilitate host colonisation, including evolutionarily conserved core effectors. In this study, we identified MoPce1, a CAP/PR-1 domain-containing protein widely distributed among fungal species, as a key virulence factor in Magnaporthe oryzae. Among 72 putative core effectors (PCEs), MoPce1 was found to be essential for pathogenicity but dispensable for asexual development. It localises to biotrophic interfacial complex (BIC) in invasive hyphae (IHs) and to the cytoplasm in Nicotiana benthamiana leaves and rice protoplasts. Ectopic expression of a signal peptide-deleted variant of MoPCE1 (MoPCE1Δsp) in rice compromised blast resistance and suppressed the reactive oxygen species (ROS) burst. Notably, MoPce1 lacks the conserved cysteine residues essential for sterol-binding in the CAP domain, suggesting its potential association with a novel ligand. Further investigation revealed that MoPce1 interacts with rice catalase OsCATC, specifically via the C1 fragment (231-360 aa). Disruption of OsCATC (oscatc) enhanced rice blast resistance and triggered a stronger ROS burst. Collectively, our results indicate that MoPce1 targets OsCATC to disrupt ROS homeostasis and suppress host immunity, thereby facilitating infection.

Plants utilize reactive oxygen species (ROS) as key defense signals, whereas pathogens have evolved mechanisms to disrupt ROS homeostasis. However, plant factors that directly counteract pathogen-derived ROS-scavenging effectors remain elusive. Here, we identified cysteine-rich receptor-like secreted protein 1 (OsCRRSP1) as a positive regulator of rice resistance to Magnaporthe oryzae. OsCRRSP1 expression is strongly induced upon pathogen infection; genetic analyses showed that knockout mutants are more susceptible, whereas overexpression enhances resistance. OsCRRSP1 directly interacts with both the fungal catalase MoCatB and the rice catalase OsCatB and inhibits their H2O2-degrading activities, leading to reduced catalase activity and enhanced ROS accumulation. Consequently, OsCRRSP1 overexpression elevates H2O2 levels, whereas MoCatB overexpression suppresses ROS accumulation and promotes disease development. These findings uncover a previously unrecognized OsCRRSP1-MoCatB/OsCatB module that fine-tunes ROS homeostasis to strengthen rice immunity and provides a promising molecular target for resistance breeding.

SUMMARY Plants deploy a sensor repertoire, usually NLRs, to perceive pathogen effectors and activate executor NLR-triggered immunity. Here we reveal that rice HMA proteins function as sensors detecting the Magnaporthe oryzae MAX effector AvrPigm to trigger broad-spectrum blast resistance mediated by the CNL PigmR. AvrPigm is conserved with multiple copies in blast genomes and targets HMA proteins, facilitating HMA translocation into the cytoplasm. Cryo-EM structure of the HPP04 HMA reveals a filament-like oligomer with ssDNA/RNA bound inside the filament, which display cyclic nucleotide synthase activity to generate 2′,3′-cNMP in a CNL-dependent manner. We further discovered that the LRR domains of the executor CNLs perceive 2′,3′-cNMP to mount immunity. Our study thus establishes an unrecognized immunity mode with a distinct repertoire of sensor receptors that produce signaling molecules that are perceived by the LRR domains of executor NLRs to mediate immunity, shedding new light on the sensor-executor conception and immune activation in plants. Highlights HMA proteins and CNL receptors form a new sensor-executor mode in plant immunity Cryo-EM reveals the filament-like structure of HMA-ssRNA/ssDNA HMA proteins are cyclic nucleotide synthetases to generate 2′,3′-cNMP LRR domains of CNLs perceive 2′,3′-cNMP to mediate immunity

RNA demethylation plays an important role in diverse biological processes. Intriguingly, RNA demethylation has not been reported in bamboo, which is known for its rapid growth. PheALKBH9, an m6A demethylase in bamboo, was stably transformed into rice and increased its susceptibility to rice blast disease. Heterologous expression of PheALKBH9 reduced the overall m6A modification levels in rice. Using HyperTRIBE (Targets of RNA-binding proteins Identified By Editing), we identified evolutionarily conserved PheALKBH9 target RNAs in both rice and Moso bamboo. Overexpression of PheALKBH9 led to higher protein expression and shorter poly(A) tails. Notably, PheALKBH9 directly bound to CCR4-associated factor1 (CAF1G) and poly(A)-binding genes (PABPC1 and PABPC2), potentially modulating poly(A) tail lengths. In addition, PheALKBH9 also bound to and removed m6A modifications from Perox4, JAZ7, and METS2, key players in plant immunity, suggesting that PheALKBH9 plays a role in plant disease resistance. In summary, our study unveils a previously unknown role of PheALKBH9-mediated m6A demethylation in response to blast disease and provides insights into its mechanisms in monocotyledonous plants.

The vacuole degrades and recycles endocytic and autophagic cargos, while the retromer complex sorts cargos from the endosomes to the trans-Golgi network or the plasma membrane, thus preventing unnecessary vacuolar degradation. However, whether the retromer complex regulates vacuolar proteolytic system during autophagic substrate degradation remains unclear. This study demonstrates that the retromer complex regulates both general and selective autophagy by ensuring the delivery of vacuolar protease(s) into the vacuole lumen in the rice blast fungus Magnaporthe oryzae. The central retromer subunit, MoVps35, transports the serine protease MoPrb1 from the endosomes to the vacuole lumen. Deletion of MoVPS35 or any other retromer component prevents the transport of MoPrb1-GFP into the vacuole lumen. Consistently, ΔMoprb1 mutant shows similar defects as the retromer mutants, including failure of autophagy-dependent conidiation and plant infection. Additionally, mutation of the catalytic residues of MoPrb1 (Asp 192, His 224 and Ser 390) reduces autophagy flux. Furthermore, MoVps35 also interacts with another aspartyl protease MoPep4 via MoPrb1. Loss of MoPEP4 leads to abnormal micro-autophagy (pexophagy) but not to fungal development and pathogenicity. Overall, this study demonstrates a crucial role of the retromer complex in the regulation of macro- and micro-autophagy by different vacuolar proteases in M. oryzae.

The Elongator complex is conserved in a wide range of species and plays crucial roles in diverse cellular processes. We have previously shown that the Elongator protein PoElp3 was involved in the asexual development, pathogenicity, and autophagy of the rice blast fungus. In this study, we further revealed that PoElp3 functions via tRNA-mediated protein integrity. Phenotypic analyses revealed that overexpression of two of the tRNAs, tK(UUU) and tQ(UUG) could rescue the defects in ΔPoelp3 strain. TMT-based proteomic and transcriptional analyses demonstrated that 386 proteins were down-regulated in ΔPoelp3 strain compared with wild type strain Guy11, in a transcription-independent manner. Codon usage assays revealed an enrichment of Glutamine CAA-biased mRNA in the 386 proteins compared with the 70-15 genome. In addition to those reported previously, we also found that PoErp9, a sphingolipid C9-methyltransferase, was down-regulated in the ΔPoelp3strain. Through an ILV2-specific integration of PoERP9-GFP into the wild type and ΔPoelp3 strain, we were able to show that PoErp9 was positively regulated by PoElp3 translationally but not transcriptionally. Functional analyses revealed that PoErp9 was involved in the fungal growth, conidial development, pathogenicity, and TORrelated autophagy homeostasis in Pyricularia oryzae. Taken together, our results suggested that PoElp3 acts through the tRNA-mediated translational efficiency to regulate asexual development, pathogenicity, sphingolipid metabolism, and autophagy in the rice blast fungus.

Magnaporthe oryzae (syn. Pyricularia oryzae), the causative agent of devastating crop diseases, exhibits remarkable genomic plasticity that contributes to its adaptability and pathogenicity. Individual M. oryzae strains may contain supernumerary mini-chromosomes, which are dispensable and highly repetitive. Here, we explored the stability of two mini-chromosomes of a Lolium strain isolated in the US, TF05-1, in which one mini-chromosome contains sequences nearly identical to the mini-chromosome of the wheat isolate B71 from Bolivia. The discordance of their phylogenetic relationships based on genomic polymorphisms in core chromosomes and polymorphisms in mini-chromosomes indicated horizontal transfer of the mini-chromosome. Contour-clamped homogeneous electric field (CHEF) karyotyping and genome sequencing analysis found variation in numbers and sizes of mini-chromosomes among asexual monoconidial progeny of TF05-1. Optimization of a fluorescence in situ hybridization (FISH) protocol enabled single-cell karyotyping and revelation of drastic cellular variation in numbers of mini-chromosomes. In addition, rearrangement within mini-chromosomes occurred frequently in the TF05-1 progeny. We characterized an intrachromosomal rearrangement presumably mediated by a palindrome repeat. The rearrangement resulted in a 300-kb deletion and a 900-kb duplication. We found that, in contrast to Long Terminal Repeat (LTR) retrotransposons in core chromosomes, LTR retrotransposons in mini-chromosomes were more recently inserted, less methylated, and with higher G + C content. The data indicated that most LTR retrotransposons in mini-chromosomes retain high activity and have yet to be silenced by fungal genome defense mechanisms such as repeat-induced point mutation, which may contribute to highly dynamic mini-chromosome content in fungi.

Many pathogenic fungi display 'two-speed genome', with the fast-evolving genomic compartments enriched with repetitive sequences, particularly the transposons, which have been shown to drive the variation of pathogenicity-associated genes. Supernumerary chromosomes (SCs) are known to facilitate genomic variation in fungal pathogens, but their specific role in such processes remains understudied. In this study, we assessed the transferability of SCs between asexual Magnaporthe oryzae strains during co-culture and co-infection, and investigated their role in genome reconstruction through experimental evolution assays. We found that SCs could be horizontally transferred between M. oryzae strains and revealed frequent structural variations facilitated by SCs, including deletions, duplications, translocations, and SC-core chromosome recombinations during and after horizontal transfer. Remarkably, all observed intra- and inter-chromosome rearrangements were confined to core chromosome ends and SCs, indicating a robust role of SCs in facilitating genetic exchange within fast-evolving genomic compartments. Additionally, SC carrying the avirulence gene AvrPikE modulates M. oryzae virulence against Pikh rice through horizontal transfer, loss of whole SC, and segmental deletions. Our findings establish SCs as critical players in shaping the diversity and dynamics of the pathogenic fungal genomes, highlighting them as a cradle for the variation of pathogenicity-associated genes.

The fungal pathogens exhibit diverse genome architecture, which facilitates the host adaptation. Although increasing high-quality genomic data enable insights into the genome architecture of many fungal pathogens during the last decades, genomic features of many fungal species are still not fully characterized. Here, we identified a Pyriculariaceae family fungal strain Xenopyricularia zizaniicola JB-1 causing the leaf spot disease on Zizania latifolia and revealed its distinct genome compartment features. The fungal strain JB-1 was identified as X. zizaniicola based on the Koch's postulate, conidial morphology, and phylogenetic analysis. Using 2.51 Gb PacBio HiFi sequencing data, the JB-1 genome was assembled into nine contigs, five of which contain telomeric repeats at both ends. The genome size is 40,888,459 bp with an N50 of 6,431,016 bp, and a total of 9,894 protein-coding genes were predicted. BUSCO assessment demonstrated high completeness, with 754 (99.47%) of the 758 BUSCO orthologs identified as complete. The absence of both repeat-rich regions at chromosome ends and preferential residing of pathogenicity-associated genes (PAGs) in the repeat-rich regions indicated a genome compartment dissimilar to the "two-speed genome" commonly observed in Pyricularia oryzae, indicating a distinct evolution drive of the PAGs in X. zizaniicola strain JB-1. Additionally, the JB-1 genome encodes fewer PAGs compared to other members of family Pyriculariaceae. These findings provide valuable genomic resources of family Pyriculariaceae and will facilitate future studies on host-pathogen interactions and the development of effective disease management strategies for X. zizaniicola.IMPORTANCEThe family Pyriculariaceae includes notorious pathogens that annually result in significant agricultural losses. The genome architecture of plant fungal pathogens reflects their evolutionary adaptation to host-pathogen interactions. However, limited knowledge exists regarding the genomic features of other species within family Pyriculariaceae, particularly those associated with the economically important crop Zizania latifolia. In this study, we assembled the first high-quality genome of Xenopyricularia zizaniicola strain JB-1, which infects Z. latifolia, and revealed its distinct genome architecture. We provide evidence that the distribution pattern of pathogenicity-associated genes in X. zizaniicola strain JB-1 closely resembles the "one-speed genome" structure, which contrasts with Pyricularia oryzae. Our findings provide valuable resources for genomic studies within family Pyriculariaceae and contribute to our understanding of the adaptive evolution of pathogens to their hosts.

The Elongator complex is conserved in a wide range of species and plays crucial roles in diverse cellular processes. We have previously shown that the Elongator protein PoELp3 was involved in the asexual development, pathogenicity, and autophagy of the rice blast fungus. In this study, we further revealed that PoElp3 functions via tRNA-mediated protein integrity. Phenotypic analyses revealed that overexpression of two of the tRNAs, tK(UUU) and tQ(UUG) could rescue the defects in ΔPoelp3 strain. TMT-based proteomic and transcriptional analyses demonstrated that 386 proteins were down-regulated in ΔPoelp3 strain compared with wild type strain Guy11, in a transcription-independent manner. Codon usage assays revealed an enrichment of Glutamine CAA-biased mRNA in the 386 proteins compared with the 70-15 genome. In addition to those reported previously, we also found that PoErp9, a sphingolipid C9-methyltransferase, was down-regulated in the ΔPoelp3 strain. Through an ILV2-specific integration of PoERP9-GFP into the wild type and ΔPoelp3 strain, we were able to show that PoErp9 was positively regulated by PoElp3 translationally but not transcriptionally. Functional analyses revealed that PoErp9 was involved in the fungal growth, conidial development, pathogenicity, and TOR-related autophagy homeostasis in P. oryzae. Taken together, our results suggested that PoElp3 acts through the tRNA-mediated translational efficiency to regulate asexual development, pathogenicity, sphingolipid metabolism, and autophagy in the rice blast fungus.

Magnaporthe oryzae, a filamentous heterothallic ascomycete fungus that serves as the causative agent of rice blast disease, is globally distributed in rice-growing regions. Populations shaped by environmental factors and human intervention play important roles in the formation of genetic structure. In this study, population structures and spatiotemporal dynamics were investigated based on large-scale whole genomic sequences of rice-infecting M. oryzae around the world. By analyzing these genetic structures, we identified divergent clades that crossed geographic boundaries. While we observed associations between the isolates and their geographic origins, we also found that there were frequent migration events occurring across Asia in main rice cultivation regions. Within Asia, China was the migration origin, facilitating gene flows to Japan and South Korea. Since the 1970s, the genetic diversity of M. oryzae populations in China has also shown a steadily increasing trend, continuing through to the 2020s. Additionally, our analysis of the evolutionary history of Asian M. oryzae populations provided insights into the population expansion that has taken place in recent decades. Overall, our findings indicate that human-mediated gene flows played a pivotal role in shaping the genetic structure of M. oryzae.

Dynamic transposition of transposable elements (TEs) in fungal pathogens has significant impact on genome stability, gene expression, and virulence to the host. In Magnaporthe oryzae, genome plasticity resulting from TE insertion is a major driving force leading to the rapid evolution and diversification of this fungus. Despite their importance in M. oryzae population evolution and divergence, our understanding of TEs in this context remains limited. Here, we conducted a genome-wide analysis of TE transposition dynamics in the 11 most abundant TE families in M. oryzae populations. Our results show that these TEs have specifically expanded in recently isolated M. oryzae rice populations, with the presence/absence polymorphism of TE insertions highly concordant with population divergence on Geng/Japonica and Xian/Indica rice cultivars. Notably, the genes targeted by clade-specific TEs showed clade-specific expression patterns and are involved in the pathogenic process, suggesting a transcriptional regulation of TEs on targeted genes. Our study provides a comprehensive analysis of TEs in M. oryzae populations and demonstrates a crucial role of recent TE bursts in adaptive evolution and diversification of the M. oryzae rice-infecting lineage. IMPORTANCE:Magnaporthe oryzae is the causal agent of the destructive blast disease, which caused massive loss of yield annually worldwide. The fungus diverged into distinct clades during adaptation toward the two rice subspecies, Xian/Indica and Geng/Japonica. Although the role of TEs in the adaptive evolution was well established, mechanisms underlying how TEs promote the population divergence of M. oryzae remain largely unknown. In this study, we reported that TEs shape the population divergence of M. oryzae by differentially regulating gene expression between Xian/Indica-infecting and Geng/Japonica-infecting populations. Our results revealed a TE insertion-mediated gene expression adaption that led to the divergence of M. oryzae population infecting different rice subspecies.

Magnaporthe oryzae is a filamentous heterothallic ascomycete fungus globally distributed in rice-growing regions and serves as the causative agent of rice blast disease. Populations shaped by environmental factors and human intervention play important roles in the formation of genetic structure. In this study, population structures and spatiotemporal dynamics were investigated based on the large-scale whole genomic sequences of rice-infecting M. oryzae around the world. By analyzing the genetic structures, we identified divergent clades that crossed geographic boundaries. While we observed associations between the isolates and their geographic origins, we also found that there were frequent migration events occurring worldwide. The populations in Asia demonstrated the highest genetic diversity due to the continent’s history of rice domestication, followed by separate gene flows to Africa, North America, South America and Europe. Within Asia, China was the migration origin, facilitating gene flows to Japan and South Korea. Additionally, our analysis of the evolutionary history of global M. oryzae populations provided insights into the population expansion that has taken place in recent decades. Overall, our findings indicate that human-mediated gene flows played a pivotal role in shaping the genetic structure of M. oryzae.

Abstract Magnaporthe oryzae(syn.Pyricularia oryzae), the causative agent of devastating crop diseases, exhibits remarkable genomic plasticity that contributes to its adaptability and pathogenicity. IndividualM.oryzaestrains may contain supernumerary mini-chromosomes, which are dispensable and highly repetitive. Here, we explored the stability of two mini-chromosomes of aLoliumstrain isolated in the US, TF05-1, in which one mini-chromosome contains sequences nearly identical to the mini-chromosome of the wheat isolate B71 from Bolivia. The discordance of their phylogenetic relationships based on genomic polymorphisms in core chromosomes and polymorphisms in mini-chromosomes indicated horizontal transfer of the mini-chromosome. Karyotyping analysis and genome sequencing analysis found variation in numbers and sizes of mini-chromosomes among asexual monoconidial progeny of TF05-1. Rearrangement within mini-chromosomes occurred frequently in the TF05-1 progeny. We characterized an intrachromosomal rearrangement presumably mediated by a palindrome repeat. The rearrangement resulted in a 300-kb deletion and a 900-kb duplication. The susceptibility to structural variation in mini-chromosomes may be associated with repetitive features and the high activity of transposable elements in mini-chromosomes, in which many intact retrotransposons were recently inserted, largely unmethylated, and likely have yet to be silenced by fungal genome defense mechanisms such as repeat-induced point mutation.

Magnaporthe oryzae (syn. Pyricularia oryzae), the causative agent of devastating crop diseases, exhibits remarkable genomic plasticity that contributes to its adaptability and pathogenicity. Individual M. oryzae strains may contain supernumerary mini-chromosomes, which are dispensable and highly repetitive. Here, we explored the stability of two mini-chromosomes of a Lolium strain isolated in the US, TF05-1, in which one mini-chromosome contains sequences nearly identical to the mini-chromosome of the wheat isolate B71 from Bolivia. The discordance of their phylogenetic relationships based on genomic polymorphisms in core chromosomes and polymorphisms in mini-chromosomes indicated horizontal transfer of the mini-chromosome. Karyotyping analysis and genome sequencing analysis found variation in numbers and sizes of mini-chromosomes among asexual monoconidial progeny of TF05-1. Rearrangement within mini-chromosomes occurred frequently in the TF05-1 progeny. We characterized an intrachromosomal rearrangement presumably mediated by a palindrome repeat. The rearrangement resulted in a 300-kb deletion and a 900-kb duplication. The susceptibility to structural variation in mini-chromosomes may be associated with repetitive features and the high activity of transposable elements in mini-chromosomes, in which many intact retrotransposons were recently inserted, largely unmethylated, and likely have yet to be silenced by fungal genome defense mechanisms such as repeat-induced point mutation. ### Competing Interest Statement SL is the co-founder of Data2Bio, LLC. Other authors claim no competing interest.

The genomes of the fungus Magnaporthe oryzae that causes blast diseases on diverse grass species, including major crops, have indispensable core-chromosomes and may contain supernumerary chromosomes, also known as mini-chromosomes. These mini-chromosomes are speculated to provide effector gene mobility, and may transfer between strains. To understand the biology of mini-chromosomes, it is valuable to be able to detect whether a M. oryzae strain possesses a mini-chromosome. Here, we applied recurrent neural network models for classifying DNA sequences as arising from core- or mini-chromosomes. The models were trained with sequences from available core- and mini-chromosome assemblies, and then used to predict the presence of mini-chromosomes in a global collection of M. oryzae isolates using short-read DNA sequences. The model predicted that mini-chromosomes were prevalent in M. oryzae isolates. Interestingly, at least one mini-chromosome was present in all recent wheat isolates, but no mini-chromosomes were found in early isolates collected before 1991, indicating a preferential selection for strains carrying mini-chromosomes in recent years. The model was also used to identify assembled contigs derived from mini-chromosomes. In summary, our study has developed a reliable method for categorizing DNA sequences and showcases an application of recurrent neural networks in predictive genomics.

Fungi from the Pyricularia genus cause blast disease in many economically important crops and grasses, such as wheat, rice, and Cenchrus grass JUJUNCAO. Structure variation associated with the gain and loss of effectors contributes largely to the adaptive evolution of this fungus towards diverse host plants. A telomere-to-telomere genome assembly would facilitate the identification of genome-wide structural variations through comparative genomics. Here, we report a telomere-to-telomere, near-complete genome assembly of a Pyricularia penniseti isolate JC-1 infecting JUJUNCAO. The assembly consists of eight core chromosomes and two supernumerary chromosomes, named mini1 and mini2, spanning 42.1 Mb. We annotated 12,156 protein-coding genes and identified 4.54% of the genome as repetitive sequences. The two supernumerary chromosomes contained fewer genes and more repetitive sequences than the core chromosomes. Our genome and results provide valuable resources for the future study in genome evolution, structure variation and host adaptation of the Pyricularia fungus.

Endoplasmic reticulum (ER) is an enclosed three-dimensional eukaryotic membrane network composed of flattened sacs. Fusion of homologous membranes to the ER membrane is essential for the maintenance of this network structure. In yeast, ER membrane fusion is mediated by Sey1p, whose paralogues function distinctly in different species. In this study, we investigated the biological functions of MoSEY1 in the devastating rice blast fungus Magnaporthe oryzae by functional genomic approach. Compared to wild type, deletion of MoSEY1 considerably decreased the growth and conidia production of M. oryzae. Additionally, the absence of MoSEY1 delayed appressorium formation and invasive hyphae growth. The appressorium function was also impaired in ΔMosey1 mutant. Subcellular localization analysis revealed that MoSey1 is localized at the ER. The ΔMosey1 mutant showed augmented sensitivity to ER stress. Additionally, we found that MoSey1 regulated the unfolded protein response, autophagy, and protein secretion in M. oryzae. In conclusion, our study unveiled the involvement of MoSey1 in the development, pathogenesis, and ER functions in M. oryzae.

Understanding gene regulatory networks is essential to elucidate developmental processes and environmental responses. Here, we studied regulation of a maize (Zea mays) transcription factor gene using designer transcription activator-like effectors (dTALes), which are synthetic Type III TALes of the bacterial genus Xanthomonas and serve as inducers of disease susceptibility gene transcription in host cells. The maize pathogen Xanthomonas vasicola pv. vasculorum was used to introduce 2 independent dTALes into maize cells to induced expression of the gene glossy3 (gl3), which encodes a MYB transcription factor involved in biosynthesis of cuticular wax. RNA-seq analysis of leaf samples identified, in addition to gl3, 146 genes altered in expression by the 2 dTALes. Nine of the 10 genes known to be involved in cuticular wax biosynthesis were upregulated by at least 1 of the 2 dTALes. A gene previously unknown to be associated with gl3, Zm00001d017418, which encodes aldehyde dehydrogenase, was also expressed in a dTALe-dependent manner. A chemically induced mutant and a CRISPR-Cas9 mutant of Zm00001d017418 both exhibited glossy leaf phenotypes, indicating that Zm00001d017418 is involved in biosynthesis of cuticular waxes. Bacterial protein delivery of dTALes proved to be a straightforward and practical approach for the analysis and discovery of pathway-specific genes in maize.

Rice blast is the major disease that threatens rice production in Fujian. Investigation of the variation of avrirulence genes（AVRs） in the field population of rice blast fungus could facilitate the release and rotation of the resistance varieties, and subsequently prevent the burst of rice blast disease caused by the loss of rice blast resistance. We firstly investigated the pathogenicity and genetic variation of a field population consisting of 113 Magnaporthe oryzae monoconidial strains isolated from three different major rice planting regions in Fujian province. For pathogenicity and virulence assays of the strains, spray inoculation was performed using 24 monogenic lines carrying 24 different major blast resistance genes. The results showed that the pathogenicity frequency of strains isolated from Jianyang, Ninghua and Shanghang were ranged from 12.50% to 95.83%, 29.17% to 100% and 4.55% to 86.36%, respectively. All strains showed strong pathogenicity toward the monogenic lines carrying Piks、Pib、Pi3 and Pi12, while strains isolated from Jianyang and Ninghua also showed strong pathogenicigy toward the monogenic lines carrying other 12 resistance genes,including Pia, Pii, Piz, Pita, Pit, Pish, Pi5, Pi7, Pi19, Pi20, Pita2 and Pi11. To investigate the genetic variation of AVR genes in the above strains, we performed genotyping of 8 AVR genes: Avr-Pia, Avr-Pib, Avr-Pik, Avr-Piz-t, Avr-Pii,Avr-Pi9, Avr-Pi54, and Avr-Co39. As expected, Avr-Co39 was absent in all the strains, indicating that all the strains collected in the three regions of Fujian province did not carry the AVR gene. The frequency of Avr-Pib in the 113 strains was also very low（37.17%）. However, the ratio was much higher than that of the functional Avr-Pib（4.32%）, indicating some loss-of-function mutations of Avr-Pib in the Fujian field population. We compared the sequence of selected AVR genes amplified from some field isolates to the reference sequences, and found variation in the promoter region of Avr-Pib, as well as Avr-Pik and Avr-Piz-t. Besides, we also found mutations in the coding region of Avr-Pik and Avr-Pita amplified from some of the Fujian field isolates. Our results suggested that rice cultivars carrying Pi1, Piz5, Pi9, Pik,Pikh and Pikm still could be used in Fujian Province.