Plant disease最新文献

This study investigated the effects of near-ambient ozone (O₃) and future predicted CO₂ concentrations on disease severity and progress of leaf rust (LR) on wheat, caused by Puccinia triticina Eriks. (Pt). Four winter wheat cultivars (Coker 9553, NC Neuse, Jamestown, and NuEast) with differential LR resistance were assessed for their O₃ responses to four O₃ treatments (sub-ambient, 50, 75, and 100 ppb O₃) in continuously stirred tank reactors (CSTRs) located in the greenhouse. Ozone-induced foliar symptoms on the cultivars were either absent or negligible at a near-ambient ozone concentration (50 ppb), but all cultivars showed visible injury symptoms at high O₃ concentrations. The effects of long-term near-ambient O₃ (50 ppb) and elevated CO₂ (570 ppm) on disease severity and disease components were also assessed on flag leaves after plants were inoculated with Pt race 'MBTNB' at GS 39-40 Zadoks in outdoor-plant environment chambers (OPECs). Infection was initiated by aerosol application of urediniospores following dew formation on leaves under high humidity conditions in the OPECs. Rust resistant cultivar NuEast did not exhibit LR symptoms under gas treatments. Near-ambient O₃ singly or combined with elevated CO₂ (570 ppm) increased disease severity and pustule size, and accelerated pustule formation on the susceptible cultivar Coker 9553. However, elevated CO₂ alone had no significant effect on disease severity. This study suggests that the interactive effect of greenhouse gases on wheat rust diseases could lead to enhanced rust epidemics.

Rice viral diseases are emerging threats to tropical agroecosystems, yet their spatiotemporal dynamics and transmission ecology remain poorly understood. From 2021 to 2023, systematic field surveys were conducted across 13 rice-growing regions of Hainan Island, China, to assess virus incidence, diversity, and vector associations. Six known rice viruses were detected via RT-PCR, and virome profiling was performed using rRNA-depleted transcriptome sequencing. Brown planthopper (Nilaparvata lugens, BPH) abundance and virus-carrying rates were measured to evaluate their association with Rice ragged stunt virus (RRSV) outbreaks. Virus incidence varied markedly across ecological zones and seasons: the semi-arid to semi-humid transitional zone showed the highest infection rates (~45%), while humid and mountainous areas showed minimal detection. Incidence peaked in summer and autumn and was significantly higher in late-season rice. Virome analysis identified 18 RNA viruses, including nine novel species, spanning multiple viral families. Twelve viruses were detected in BPH and seven in rice, with RRSV being the most prevalent in both. Correlation analysis revealed a strong association between RRSV incidence and BPH virus-carrying rate (R² = 0.40, P < 0.001), but not with vector abundance. These results underscore the ecological and vector-related drivers of rice virus epidemics in tropical systems and support viruliferous vector monitoring as a tool for disease forecasting.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating wheat disease worldwide. We dissected the genetic basis of adult-plant resistance (APR) to stripe rust in a recombinant inbred line (RIL) population derived from the cross Tianmin 668 × Jingshuang 16. Following inoculation with prevalent Pst races CYR32, CYR33, and CYR34, phenotypic evaluation across three growing seasons revealed quantitative inheritance of the resistance with high heritability. Seven APR QTL were identified. The resistant parent Tianmin 668 contributed three QTL on chromosomes 2AS, 2BS, and 2BL. The most stable QTL, QYrtj-2AS explaining 9.39-16.73% of the phenotypic variance, was confirmed to be Yr17 using 2NS-specific markers and whole-genome resequencing. The susceptible parent Jingshuang 16 also contributed four QTL, including QYrtj-3BS (Yr30) and QYrtj-6BS. These QTL explained 14.15-15.06% and 12.78-13.66% of the phenotypic variance, respectively, but exhibited less environmental stability than Yr17. Pyramiding QYrtj-2AS (Yr17) with the two additional QTL from Tianmin 668 on chromosome 2B reduced the maximum disease severity by 33%, demonstrating significant additive effects. These results demonstrate the value of both major-effect QTL, such as QYrtj-2AS (Yr17) and QYrtj-2BL, and environmentally responsive QTL derived even from susceptible parents for breeding. This study provides valuable genomic resources and molecular markers for pyramiding durable stripe rust resistance in wheat.

Rice blast is the devastating disease, caused by Magnaporthe oryzae, and presents a significant challenge to rice production impacting leaves, nodes, stems, necks, and panicles throughout the growing season. To enhance sustainable rice production and effective disease management, it is crucial to continuously monitor rice blast incidence and race diversity. An increase in the incidence of rice blast disease in Korea in 2020 and 2021 has been reported, leading to a decline in rice production, particularly in Jeonbuk, where both leaf and panicle blast were prevalent. In this study, the incidences of rice leaf blast and panicle blast were monitored nationwide from 2020 to 2022 and race diversity and pathogenic characteristics of 754 rice blast isolates collected from leaves and necks were identified. Among these, 633 isolates of race distribution were identified according to the resistant reactions of the Korean differential race system. Applying the Korean differential race system, the isolates were categorized into 40 different unique Korean races distinguishing the ability to cause disease in Japonica-type and Indica-type cultivars. Moreover, pathotypes analysis of 556 isolates using the monogenic resistance lines showed that most of the evaluated isolates reveal incompatible reactions to monogenic lines carrying resistance genes Pita-CP1, Piz-t, and Piz-5. The similarity of the pathotypes among the isolates was analyzed based on the disease reactions of the monogenic resistance lines and 28 isolates were selected as a standard representative set considering their viability, high virulence, dominant Korean races, and different reactions to resistance genes. This comprehensive study aims to inform the development of durable blast protection and provide valuable insights for breeding broad-spectrum-resistant rice cultivars.

Pecan (Carya illinoensis) is a major economic crop in Mexico. The states of Chihuahua and Sonora contribute approximately 80% to the national production. Recently, symptoms of trunk diseases, including necrotic lesions in the xylem, cankers, dieback, and shoot blights, have been observed in pecan orchards in Sonora. This study aimed to determine the presence and identity of fungi responsible for these symptoms. A survey was conducted between 2021 and 2022 in eleven orchards near Hermosillo, Sonora. Fungi were isolated from necrotic tissue on PDA medium, yielding around 150 isolates. Based on colony morphology, 50 isolates were selected for molecular characterization using the translation elongation factor 1 alpha (tef1-α) gene, the nuclear ribosomal DNA-internal transcribed spacer (ITS), and, for some isolates, the β-tubulin gene. The fungi identified included Pseudofusicoccum stromaticum, Lasiodiplodia exigua, L. brasiliensis, Diaporthe caatingaensis, Eutypellla microtheca, and several Fusarium spp. The optimal growth temperature for most isolates was 30°C, with none exhibited growth at 40°C, although some Lasiodiplodia and Pseudofusicoccum isolates showed limited growth at 37°C. Following pathogenicity studies, the Lasiodiplodia species produced the largest lesions on pecan cv. Wichita, followed by P. stromaticum, while D. caatingaensis and E. microtheca exhibited intermediate virulence. The least virulent were D. caatingaensis and Fusarium spp. isolates. This study contributes to understanding the phytosanitary status of pecan orchards in Mexico and lays the groundwork for developing management strategies to control these fungi.

Although the pathogen Fusarium proliferatum is responsible for soybean root rot, the mechanisms underlying its pathogenicity remain unclear. We detected limited soybean resistance to six F. proliferatum strains isolated from China. To elucidate the mechanisms underlying F. proliferatum pathogenicity, we conducted RNA sequencing analysis of the F. proliferatum isolate Fp6-1 during the mycelial and infection stages. Transcriptome sequencing analysis identified 10 significantly upregulated candidate effector molecules; these were selected for subsequent transcriptional pattern analysis. Bioinformatics analysis predicted 80 candidate effectors that were cysteine-rich, contained signal peptides, lacked transmembrane domains, and were secreted extracellularly. The conserved domains, pathogenicity, and functions of these candidate effectors were assessed. Pathogen host interaction database comparisons demonstrated that 44 of the candidate effectors were associated with virulence. Among these, 12 were upregulated during the infection stage and contained the pectate lyase, Hce2, FKBP-C, abhydrolase, DUF196, SGNH hydrolase, CE4 superfamily, ZnMc pappalysin-like, GH16 Streptomyces laminarinase-like, MhpC, and glyco-hydro-11 domains. The majority of the predicted candidate effectors were upregulated during F. proliferatum infection. Given that domestic soybean cultivars resistant to F. proliferatum are scarce in China, this study provides invaluable resources for subsequent functional analyses and guidance for future soybean breeding efforts.

Citrus yellow vein clearing virus (CYVCV, Potexvirus citriflavivenae), an emerging pathogen that poses a threat to citrus production worldwide. To address this threat, three reverse transcription quantitative polymerase chain reaction (RT-qPCR) detection assays were developed and validated using all currently available public sequences and in-house high-throughput sequencing data from recent CYVCV detections in California, following guidelines for quantitative and qualitative real-time PCR experiments. Among the RT-qPCR assays tested, the CYVCV-4 outperformed others in analytical sensitivity, specificity, and diagnostic accuracy, demonstrating high amplification efficiency. The CYVCV-4 assay targets the RNA-dependent RNA polymerase gene of CYVCV and demonstrated high specificity by avoiding cross-reactivity and accurately identifying infected, non-infected, and non-target citrus pathogens. Its superior performance is attributed to optimized primer and probe design, enabling specific hybridization to the target sequence while minimizing non-specific amplification. The assay's robustness, inter-assay and intra-assay variation, and reproducibility were thoroughly validated across multiple labs, varying reaction conditions, and different qPCR instruments. Recent detections of CYVCV in California underscore the need for rapid and reliable diagnostics to protect citrus production and germplasm. The development and validation of the CYVCV-4 assay demonstrate its effectiveness through comprehensive testing, supporting its use in citrus diagnostic labs, quarantine programs, and field surveys, ultimately enhancing CYVCV management efforts. This development highlights the opportunity for plant diagnostics to adopt harmonized validation practices through frameworks like the Diagnostic Assay Validation Network, crucial for national programs, such as the National Clean Plant Network, which depend on validated assays to ensure clean plant systems and agricultural biosecurity.

Camphor tree leaves are a valuable source of essential oils, but their yield is severely threatened by anthracnose caused by Colletotrichum fioriniae and C. siamense. To develop an eco-friendly alternative to chemical pesticides, we isolated a strain of Burkholderia pyrrocinia, designated DLL-114, from camphor tree roots. DLL-114 exhibited strong antagonistic activity against both pathogens, and inoculation assays demonstrated that it significantly reduced lesion areas while maintaining leaf greenness. Moreover, DLL-114 showed broad-spectrum antifungal activity against several crop pathogens, with its antifungal effects mediated by multiple antagonistic pathway. Whole-genome sequencing using Illumina and PacBio platforms revealed an 8.36 Mb genome comprising three circular chromosomes and two plasmids, with a GC content of 66.12%. The genome encodes 7,739 protein-coding genes and 21 secondary metabolite biosynthetic gene clusters, only one of which showed complete similarity to a known cluster. Notably, biosynthesis operons for gluconic acid, pyrrolnitrin, catecholate siderophores, and ornibactin were identified. This genomic features, together with metabomic evidence, suggest that DLL-114 is a promising candidate for the production of bioactive secondary metabolites and a potential biocontrol agent for sustainable agriculture.

Diverse climatic environments lead to distinct ecological conditions in different rice planting regions, resulting in a wide variety of Magnaporthe oryzae (rice blast fungus) populations that frequently adapt and vary to suit their specific ecological niches. Understanding the diversity of M. oryzae populations across different ecological planting zones is fundamental for controlling rice blast disease. This study systematically investigated the population structure, distribution of avirulence (Avr) genes, and pathogenicity of M. oryzae using 174 monosporic isolates collected in 2021 from three counties in Hunan Province: Xinhua, Longhui, and Liuyang. The results indicated that while the number of physiological races in the three locations was similar, the dominant physiological races differed significantly. Overall, the resistance gene Pikm exhibited the highest resistance frequency. Additionally, genes like Pik, Pikp, and Pizt showed good resistance against pathogen populations in some ecological zones. Resistance frequencies varied dramatically across different ecological environments, indicating differing practical value for specific resistance genes in different ecological regions. Representative isolates from each location were screened and used to test the resistance of locally main cultivated varieties. The results revealed significant differences in the proportion of varieties resistant to the pathogen populations from the three locations. These findings provide a data basis for resistance breeding and the rational distribution of rice varieties across different ecological regions in Hunan Province.

Kiwifruit bacterial canker (KBC), caused by Pseudomonas syringae pv. actinidiae (Psa), threatens global kiwifruit production. Traditional control methods face challenges like bacterial resistance and environmental issues. In this study, four lytic phages (pSM43, pGZ41, pWA51, and pSO21) were isolated and characterized using Psa M228 as the host bacterium. Notably, the phage pGZ41 represents a novel phylogenetic lineage, and the four-phage cocktail demonstrates significant advantages over previously reported single phages or mixtures in terms of lytic spectrum and resistance management. These phages exhibit distinct structural features and biological properties. Genomic sequencing classified them as double-stranded DNA viruses with genome sizes spanning 38,130 - 100,813 base pairs (bp), encoding 91 to 309 putative opening frames. The complete genome sequences have been deposited in GenBank under accession numbers PX673947 (pSM43), PX673946 (pGZ41), PX673948 (pWA51), and PX673949 (pSO21). The phage cocktail has a significant inhibitory effect on the growth of Psa M228 in vitro, in Arabidopsis thaliana and kiwifruit leaf discs. In vitro tests demonstrated that phage cocktails could effectively suppress bacterial growth and delay the emergence of resistant strains within a short period. In A. thaliana, phages exhibited strong antibacterial capabilities, reducing bacterial load by 4.92 log CFU/g in the treatment group and 4.33 log CFU/g in the prevention group compared to the infected control group. In kiwifruit leaf discs assays, the prevention group treated with phage cocktails exhibited superior efficacy, reducing lesion areas by 3-5 times compared to the treatment group. The significant efficacy in plant models, combined with the high environmental stability of the phages (particularly pGZ41), underscores the strong potential of this phage cocktail as a practical, sustainable, and environmentally friendly biocontrol agent for integrated management of kiwifruit canker in orchard settings.  This multi-level validation suggests these phages as promising biocontrol agents for controlling kiwifruit canker caused by Psa.