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In the ongoing arms race between rice and Magnaporthe oryzae, the pathogen employs effectors to evade the immune response, while the host develops resistance genes to recognise these effectors and confer resistance. In this study, we identified a novel Pik allele, Pik‐W25, from wild rice WR25 through bulked‐segregant analysis, creating the Pik‐W25 NIL (Near‐isogenic Lines) named G9. Pik‐W25 conferred resistance to isolates expressing AvrPik‐C/D/E alleles. CRISPR‐Cas9 editing was used to generate transgenic lines with a loss of function in Pik‐W25‐1 and Pik‐W25‐2, resulting in loss of resistance in G9 to isolates expressing the three alleles, confirming that Pik‐W25‐induced immunity required both Pik‐W25‐1 and Pik‐W25‐2. Yeast two‐hybrid (Y2H) and split luciferase complementation assays showed interactions between Pik‐W25‐1 and the three alleles, while Pik‐W25‐2 could not interact with AvrPik‐C, ‐D, and ‐E alleles with Y2H assay, indicating Pik‐W25‐1 acts as an adaptor and Pik‐W25‐2 transduces the signal to trigger resistance. The Pik‐W25 NIL exhibited enhanced field resistance to leaf and panicle blast without significant changes in morphology or development compared to the parent variety CO39, suggesting its potential for resistance breeding. These findings advance our knowledge of rice blast resistance mechanisms and offer valuable resources for effective and sustainable control strategies. Summary statement: We employed BSA‐seq to identify a novel Pik allele, Pik‐W25, from the wild rice WR25. Pik‐W25 can recognise AvrPik‐C, ‐D, or ‐E alleles and trigger resistance. Notably, the Pik‐W25 NIL showed enhanced field resistance to leaf and panicle blast without significant morphological or developmental differences. These findings advance our knowledge of rice blast resistance mechanisms and offer valuable resources for effective and sustainable rice blast control strategies. [ABSTRACT FROM AUTHOR]

Magnaporthe oryzae is one of the most destructive pathogens that threaten rice production around the world. Previous studies mainly focus on pathogenic mechanism of M. oryzae during infection on rice at leaf stage. However, the pathogenic mechanism of M. oryzae infection on panicle tissue is not well understood. In the present study, we performed RNA sequencing (RNA-seq) to study gene expression patterns of M. oryzae during infection at leaf stage and at panicle stage, respectively. The differentially expressed genes (DEGs) of M. oryzae in the infected leaf and panicle tissues were analyzed. Gene ontology (GO) enrichment analysis of DEGs revealed that M. oryzae genes involved in the biological processes were different at leaf and panicle stages. Furthermore, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of DEGs indicates that genes related to individual and important pathways may function at different infection stages. In particular, CAZymes carbohydrate esterases (CEs), carbohydrate-binding modules (CBMs), and glycoside hydrolases (GHs) may play important roles during M. oryzae infection on rice leaves, while glycosyltransferases (GTs) and GHs may play important roles during infection at rice panicle stage. Further analysis of effectors (BAS3, BAS113, BAS162, MoCDIP4, and MoHEG13) and their homologous genes suggest that they are involved in host defense suppression. Our findings provide insights into understanding the infection mechanisms of M. oryzae for rice leaf blast and panicle blast disease. [ABSTRACT FROM AUTHOR]

Rice blast, caused by Pyricularia oryzae, is one of the most destructive rice diseases worldwide. Using resistant rice varieties is the most cost-effective way to control the disease, and it is crucial to analyze the resistance level and the resistance genes distribution of the main varieties. In this study, we collected 119 rice main varieties in Jiangsu province and evaluated the resistance to leaf and panicle blast and found that indica rice was more resistant to rice blast than japonica rice. Moreover, we detected the distribution of 14 resistance genes (R genes) in the 119 varieties. The distribution frequencies of three R genes, Pish, Pit, and Pia, were higher than 80%, and the Pigm had the lowest distribution frequency (1.68%), followed by Pi2 (15.18%) and Pi5, Piz-t (24.37%). Combined with the multiple stepwise regression and the resistance contribution rate, eight major R genes Pita, Pi5, Pi9, Pib, Pb1, Pikm, Piz-t, and Pi2 significantly affected the resistance of rice, and we also found that six gene combinations with 100% resistance contribution rate could effectively increase the resistance of rice varieties. In summary, monitoring the resistance level of rice varieties and analyzing their resistance genes were beneficial for rice resistance breeding. [ABSTRACT FROM AUTHOR]

The rice blast, caused by the hemibiotrophic plant pathogen Magnaporthe oryzae, is a devastating disease that threatens rice crop production worldwide. The molecular interactions that underlie the rice-M. oryzae interaction have received much attention. However, genome-wide research focusing on alternative splicing (AS) has not been well-studied in rice—M. oryzae interactions. AS in plants leads to diverse proteomes without an expansion in gene numbers to regulate cellular processes during abiotic or biotic stress. The Pi21 gene negatively regulates rice resistance to M. oryzae infection, and thus the Pi21-RNAi silenced transgenic line (#241) exhibits partial but durable resistance. We compared the AS landscape in #241 and "Nipponbare" (Nip) during interacting with M. oryzae Guy11, and the alternative 3′ splice-site (A3SS) is the most common AS type. GO enrichment analysis of #241-specific differentially alternatively spliced genes (DASGs) revealed that WRKY transcription factors (TFs), bHLH TFs, F-box protein with leucine rich repeats, AAA-type ATPase, and protein kinase were enriched in the GO terms "response to jasmonate acid (JA)" and "ethylene (ET)" at 24 h post-inoculation (hpi). At 48 hpi, one #241-specific DASG, ubiquitin gene (Os08g0295000), was predicted to be involved in endoplasmic reticulum (ER) stress. In silico analysis combined with PCR amplification confirmed that multiple isoforms are produced by Os08g0295000 and a skipped exon (SE) event results in isoform switching during interaction with M. oryzae. Protein–protein interaction (PPI) network analysis predicted that Os08g0295000-encoding proteins may interact with SNARE protein Q9LGF8 (Uniprot ID) to cooperatively regulate rice's response to M. oryzae. This study uncovered the AS profile of rice in response to M. oryzae, which will help to explore the linkage between AS and durable rice resistance. [ABSTRACT FROM AUTHOR]

Rice blast, caused by Pyricularia oryzae, is one of the most destructive rice diseases worldwide. It is essential to understand the population structure and race distribution of P. oryzae for the prevention and control of rice blast. This study collected 1584 isolates across Jiangsu province from 2003 to 2017 to determine race diversity, common and dominant race structures, and resistance profiles using eight parameters from the Chinese differential cultivars (CDC) entries. Race diversity analysis indicated that the race diversity of 1584 isolates in Jiangsu province increased from 2003 to 2006 and fluctuated steadily from 2007 to 2017. Common race structure analysis showed that the common race structure of the isolates fluctuated wildly on an annual basis. Moreover, the race ZG1 was the dominant race, suggesting that the most commonly grown rice varieties in Jiangsu are highly adaptive to race ZG1. In addition, due to a higher level (>85%) of resistance to the population of isolates from 2003 to 2017, Tetep may be conformed as the most promising donor of blast resistance for resistance breeding in Jiangsu province. In summary, it is beneficial to control rice blast by continuous monitoring of the population structure and distribution of P. oryzae with the monogenic germplasm entries and by maintaining a diversity of rice varieties. [ABSTRACT FROM AUTHOR]

Summary: Pyricularia oryzae is a multi‐host pathogen causing cereal disease, including the devastating rice blast. Panicle blast is a serious stage, leading to severe yield loss. Thirty‐one isolates (average 4.1%) were collected from the rice panicle lesions at nine locations covering Jiangsu province from 2010 to 2017. These isolates were characterized as Pyricularia sp. jiangsuensis distinct from known Pyricularia species. The representative strain 18‐2 can infect rice panicle, root and five kinds of grasses. Intriguingly, strain 18‐2 can co‐infect rice leaf with P. oryzae Guy11. The whole genome of P. sp. jiangsuensis 18‐2 was sequenced. Nine effectors were distributed in translocation or inversion region, which may link to the rapid evolution of effectors. Twenty‐one homologues of known blast‐effectors were identified in strain 18‐2, seven effectors including the homologues of SLP1, BAS2, BAS113, CDIP2/3, MoHEG16 and Avr‐Pi54, were upregulated in the sample of inoculated panicle with strain 18‐2 at 24 hpi compared with inoculation at 8 hpi. Our results provide evidences that P. sp. jiangsuensis represents an addition to the mycobiota of blast disease. This study advances our understanding of the pathogenicity of P. sp. jiangsuensis to hosts, which sheds new light on the adaptability in the co‐evolution of pathogen and host. [ABSTRACT FROM AUTHOR]

Panicle blast, caused by the fungus Magnaportheoryzae (syn. Pyricularia oryzae), directly contributes to yield loss in the field. The effects of panicle development stage and temperature on panicle blast were studied and the infection process of M. oryzae in panicles was visualized. Rice panicles at different development stages from three rice cultivars were inoculated with a conidial suspension in vitro. The rice cultivar Lijiangxintuanheigu was highly susceptible to panicle blast at 5 days postinoculation (dpi) when the pulvinus distance was 15–20 cm. Nanjing 9108 was moderately susceptible to panicle blast when the pulvinus distance was 8–10 cm, but Yliangyou 800 was resistant. The effect of temperature on panicle blast was determined under 22–35 °C temperature treatments. Inoculated panicles placed at temperatures of 28 and 30 °C showed the highest lesion grade based on lesion length at 5 dpi. The infection process of M. oryzae in rice panicles was observed by confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM). M. oryzae initially formed the appressorium to invade through the epidermis of rice panicles at 24 hours postinoculation (hpi). As the disease progressed, the invasive hyphae formed dense mycelial networks in the inner parenchyma cells at 60 hpi. Our results will contribute to the understanding of panicle development stage and temperature effects on panicle blast and improve resistance evaluation methods. Additionally, visualization of the infection process by CLSM and TEM are valuable methods to observe M. oryzae invasive hyphae inside rice panicle cells. [ABSTRACT FROM AUTHOR]

Summary: The biotrophic fungal pathogen Ustilaginoidea virens causes rice false smut, a newly emerging plant disease that has become epidemic worldwide in recent years. The U. virens genome encodes many putative effector proteins that, based on the study of other pathosystems, could play an essential role in fungal virulence. However, few studies have been reported on virulence functions of individual U. virens effectors. Here, we report our identification and characterization of the secreted cysteine‐rich protein SCRE1, which is an essential virulence effector in U. virens. When SCRE1 was heterologously expressed in Magnaporthe oryzae, the protein was secreted and translocated into plant cells during infection. SCRE1 suppresses the immunity‐associated hypersensitive response in the nonhost plant Nicotiana benthamiana. Induced expression of SCRE1 in rice also inhibits pattern‐triggered immunity and enhances disease susceptibility to rice bacterial and fungal pathogens. The immunosuppressive activity is localized to a small peptide region that contains an important 'cysteine‐proline‐alanine‐arginine‐serine' motif. Furthermore, the scre1 knockout mutant generated using the CRISPR/Cas9 system is attenuated in U. virens virulence to rice, which is greatly complemented by the full‐length SCRE1 gene. Collectively, this study indicates that the effector SCRE1 is able to inhibit host immunity and is required for full virulence of U. virens. [ABSTRACT FROM AUTHOR]