Plant Pathology Journal最新文献

Podosphaera xanthii is an obligate biotrophic fungus responsible for powdery mildew disease in cucurbits. Its strict host dependency has hindered genomic studies due to challenges in isolating pure fungal DNA. In this study, we present a high-quality genome assembly of P. xanthii Race 1 using PacBio HiFi reads, Illumina short reads, and RNA-seq data, combined with stringent in silico filtering to remove host and microbial contaminants. The final assembly spans 151.7 Mbp across 67 scaffolds with 80.04% repeat content and 7,452 predicted genes. Functional annotation revealed effector-related features and gene categories consistent with biotrophic lifestyles. Comparative analyses with other P. xanthii genomes exposed variable contamination levels, underscoring the importance of strict data curation. Our work provides a reliable genomic reference for P. xanthii, enabling future research on pathogenicity, evolution, and host interactions in powdery mildew fungi and contributing to broader understanding of obligate biotrophic adaptation.

Burkholderia glumae, the causal agent of bacterial panicle blight and seedling rot (BSR), is a growing threat to rice production, yet effective and sustainable control measures remain limited. In this study, we evaluated Bacillus velezensis JBCS608 (JBCS608) as a promising biocontrol agent for the management of BSR in rice plants. Treatment with JBCS608 at an optimal concentration of 1 × 10⁸ CFU/mL significantly reduced disease severity, achieving a control efficacy of up to 68.9%. The strain exhibited broad-spectrum antagonistic activity, inhibiting the growth of multiple seed-borne bacterial pathogens, including B. glumae, Burkholderia gladioli, and Burkholderia plantarii, as well as fungal pathogens such as Fusarium moniliforme. In addition to disease suppression, JBCS608 promoted rice seedling growth, likely through the production of indole-3-acetic acid and siderophores, and phosphate-solubilizing activity. For practical applications, we developed both talc-based wettable powder and molasses humic acid liquid formulations using JBCS608 endospores. Both formulations exhibited biocontrol efficacy comparable to that of fresh bacterial cells and maintained high cell viability for over 6 months under cold storage conditions. Collectively, our results indicate that JBCS608 is a potent and eco-friendly biocontrol and plant growth-promoting agent with strong potential for commercial use in the integrated management of BSR in rice.

To better understand the diversity of viral pathogens in Türkiye, a major exporter of cereals in Europe, we performed high-throughput sequencing of total RNA from maize plants collected in the Trakya region. Certain maize plants exhibiting mosaic and mottle symptoms, gathered from Tekirdağ province in Trakya, yielded large numbers of reads corresponding to the genome of a divergent strain of a comovirus, which corresponds to turnip ringspot virus (TuRSV), a recognized species of the genus Comovirus. This finding is unexpected because all known comoviruses infect only dicotyledonous species, and the known host range of TuRSV has been limited to plants in the Brassicaceae family. The nearly complete and partial nucleotide sequences of the bipartite genome of the maize isolate, as named TuRSVTR59, consist of 6,027 nt TuRSV-TR59 RNA1 and 3,920 nt TuRSV-TR59 RNA2, excluding poly (A) tails. RNA1 and RNA2 each encode a single ORF of 1,860 and 1,096 codons, respectively. Phylogenetic analysis demonstrated that TuRSV-TR59 from Türkiye clustered with other TuRSV isolates from diverse hosts and regions, showing highest identity to isolates from Germany, Czech Republic, and Croatia (80.56-77.77% and 92.09-90.50% nucleotide and amino acid sequence identities, respectively). The ability of TuRSV-TR59 isolate to infect maize was confirmed by reverse transcription polymerase chain reaction. Surveys in the Tekirdağ province of Türkiye, done in 2022-2025, revealed that 2 out of 145 maize samples (1.38%) and 8 out of 116 canola samples (6.89%) were found infected with TuRSV. This is the first report of a comovirus in maize from a monocotyledonous plant species.

Cinnamon essential oil (CEO) exhibits antimicrobial activity in a dose-dependent manner, offering potential for controlling plant bacterial diseases. This study investigated the effects of CEO on Xanthomonas euvesicatoria pv. euvesicatoria 173, the causal agent of pepper bacterial spot disease. Treatment with an EC50 dose of CEO significantly altered bacterial culturability and protein expression profiles. Proteomic analyses revealed that, relative to untreated control, a TonB-dependent receptor and a Clp protease were upregulated, and ATP-binding cassette transporter proteins were downregulated in the CEO-exposed X. euvesicatoria. Quantitative real-time PCR confirmed that TonB and Clp proteases abundance positively correlated with transcriptional upregulation of their corresponding genes. Our findings suggest that CEO disrupts cellular homeostasis by targeting key membrane functions. Further investigation is required to elucidate how key changes in transport and proteolytic systems contribute to the control by CEO of the plant pathogen, X. euvesicatoria.

Producing virus-free planting materials is fundamental to sustainable fruit tree cultivation, particularly for high-value crops such as apple (Malus domestica) and grapevine (Vitis vinifera). Given the systemic and persistent nature of most plant viruses and viroids, effective elimination remains a major challenge within a tissue culture-based propagation system. Therefore, this review aims to provide a comprehensive overview of conventional virus elimination strategies-including thermotherapy, meristem and shoot tip culture, chemotherapy, and electrotherapy-while highlighting their respective strengths and limitations. Concurrently, advancements in virus detection technologies have significantly enhanced the sensitivity, speed, and precision of virus indexing, enabling the early detection of low-titer or latent infections in plantlets cultured in vitro. Besides eradication strategies, increasing attention is directed toward virus inhibition approaches. RNA interferencebased methods and plant-derived antiviral agents demonstrate promising antiviral activity in tissue-cultured apples and grapevines, offering chemical-free and ecofriendly alternatives. These biologically based inhibition strategies are particularly well-suited for integration into existing micropropagation systems. Collectively, this review emphasizes the importance of combining conventional sanitation methods with next-generation diagnostics and innovative biological inhibition technologies to develop robust, scalable, and sustainable protocols for virus-free certification.

We developed a rapid and efficient TaqMan-based realtime reverse transcription quantitative PCR (RT-qPCR) assay for the detection and quantification of viruses infecting fruit trees, including blackberry chlorotic ringspot virus (BCRV), blueberry shock virus (BlShV), and plum pox virus (PPV). The detection limits for each virus were 40 copies (BCRV), 500 copies (BlShV), and 40 copies (PPV), respectively. Two primer-probe sets were selected for each virus, with amplification efficiencies ranging from 90-110%. High specificity was confirmed against other viruses or viroids sharing the same host plants. Multiplex detection of BCRV, BlShV, and PPV was achieved by using FAM and Cy5 fluorescent dyes. All sets maintained high efficiency and sensitivity with varying amounts of RNA extracted from the woody branches of the host plant. This assay will be useful for rapid and accurate diagnosis of plant virus diseases, especially in quarantine stations where leaf tissue is often unavailable upon import.

Root-knot nematodes (RKNs, Meloidogyne spp.) are significant threats to global agriculture because their host range is broad, and therefore, their adverse effects on crop productivity are substantial. Cladosporium sphaerospermum PQ394940 was isolated from egg masses of RKNs infecting eggplant and examined for its ability as a bioagent against the M. javanica. In an in vitro assay, the fungus effectively inhibited egg hatch (95.3%) and increased the mortality percent of secondstage juveniles (J2s, 73.3%) through direct parasitism. Moreover, after observation, the fungus showed a capacity for paralyzing eggs and juveniles under a compound microscope. Fungal culture filtrate (CF) has been examined against egg hatch and J2s mortality. Data revealed that CF can increase J2s mortality percent and suppress egg hatching. In the seed germination test, C. sphaerospermum PQ394940 significantly increased eggplant seed germination compared with control treatment. Fungus has been identified by amplifying ribosomal internal transcribed spacer (ITS-rDNA) using ITS4 and ITS5 primer pairs. A fragment with 570-580 bp was amplified and the result of rDNA sequencing was recorded in GenBank (PQ394940). Under greenhouse conditions, C. sphaerospermum PQ394940 significantly promoted eggplant growth. Moreover, fungus significantly reduced M. javanica reproduction and root galling. Additionally, fungus significantly reduced the root gall index, egg mass index, and reproductive factor. Thus, C. sphaerospermum PQ394940 is considered larvicidal and ovicidal, can also be added to the soil as a bio-fertilizer. As highlighted in this study, C. sphaerospermum PQ394940 will be useful in integrated pest management, improving crop productivity, and decreasing environmental impact.

The balance of microbial communities in an ecosystem is the most important factor representing its healthy state, even when immigrant microorganisms, such as biological control agent, are introduced into agricultural fields. Thus, this study aimed to investigate the potential of the antagonistic bacterium KPB25 (Bacillus altitudinis) as a biological control agent against fire blight by analyzing the changes in the epiphytic and endophytic bacterial communities of apple tree leaves following treatment. The KPB25 treatment resulted in increased community richness and diversity in endophytic bacteria. Conversely, in epiphytic bacteria, community diversity decreased after treatment. Beta-diversity analysis revealed that the endophytic community formed distinct clusters following KPB25 treatment, indicating a shift in the community structure. Relative abundance analysis of the endophytic and epiphytic communities highlighted that some bacterial families, which increased in abundance following KPB25 treatment, oxidized sugars into organic acids or produced antibiotics, potentially creating an environment that makes it difficult for Erwinia amylovora to survive when attempting to infect its host. These findings suggest that KPB25 interacts with certain microbial taxa within apple trees, contributing to the regulation and alteration of the microbial community in a manner that promotes an environment unfavorable for E. amylovora. Overall, KPB25 may have enhanced certain microbial groups within the endophytic residual bacterial community of apple leaves that contribute to fire blight suppression, with minor structural changes but significant shifts in microbial diversity.

Rice brown spot, caused by Bipolaris oryzae, typically occurs during the rice harvest season and can cause substantial yield losses. In 2023-2024, this disease emerged in rice cultivation areas of Korea. However, the population structure and genetic diversity of B. oryzae isolates remain unclear. Such information is necessary to effectively target and control rice brown spot. Thus, this study aimed to investigate the population structure of 50 B. oryzae isolates collected from the leaves, neck, and panicles of rice infected with brown spot through random amplified polymorphic DNA analysis. Among 140 primers tested, 30 were selected and applied, of which 5 exhibited significant polymorphisms among the isolates. The generated dendrogram revealed five clades with 92% similarity. Group A was the most predominant, comprising 84.0% of the total isolates (42/50), followed by Group C (8.0%, 4/50). Groups B, D, and E each contained one isolate (2%). These isolates were collected from the southern region of Korea and exhibited high genetic similarity (>95%). Two strains from Group A (F1305 and F1318) and one each from Groups B (F1248), C (F1253), D (F1317), and E (F1409) were selected and tested for their mycological characteristics and pathogenicity. Compared with the other strains, F1253, F1317, and F1409 exhibited higher conidial production and caused larger diseased leaf areas in the pathogenicity tests. These results suggest that the B. oryzae isolates that caused rice brown spot in 2023 are genetically homogeneous. This study may serve as a basis for developing targeted control strategies against brown spot.

Bipolaris oryzae, the causal agent of rice brown spot, is a necrotrophic fungus that produces phytotoxic secondary metabolites, yet its genomic basis of pathogenicity remains incompletely defined. We sequenced six South Korean B. oryzae isolates and analyzed them together with publicly available genomes from Bipolaris and related Pleosporaceae, covering 37 Bipolaris isolates across eight species. Phylogenomics based on singlecopy orthologs confirmed the monophyly of Bipolaris and resolved B. oryzae as a distinct lineage. Comparative analyses showed that B. oryzae has a moderately reduced secretome and fewer candidate pathogenicity gene families relative to B. maydis and B. sorokiniana, while retaining a conserved core enriched in carbohydrate and amino acid metabolism. We identified 48 secondary metabolite biosynthetic gene clusters in B. oryzae F1253 and, critically, localized the ophiobolin biosynthetic gene cluster to pseudochromosome 2. The cluster contains conserved core genes, oblA to oblD, which are broadly retained across Bipolaris, and exhibits interspecies variation in synteny and copy number associated with repeat element insertions. These findings reveal the genomic architecture underlying metabolic specialization and toxin biosynthesis in B. oryzae. They also provide actionable targets and markers for management, including diagnostics for oblA to oblD, screening of rice germplasm for ophiobolin tolerance, and RNAi-based suppression of ophiobolin biosynthesis under climate-related stress.