Plant disease最新文献

The recent expansion of cotton acreage in the semi-arid Northern High Plains of Texas has raised concerns about the potential widespread distribution of Verticillium dahliae, the causal agent of Verticillium wilt, into these areas. These concerns were primarily driven by the use of lower seeding rates; lower summer air temperatures; the absence of completely resistant cultivars; and the region's proximity to the Southern High Plains, where the pathogen is endemic. This study was conducted to assess Verticillium wilt risk, based on microsclerotia density, in the Northern High Plains. Soil samples were collected from 26 cotton fields across 10 counties, and viable microsclerotia in 40 cm³ of soil per field were quantified using a plating assay with semi-selective media. Microsclerotia were detected in 88.4% of fields: 38.5% of fields were categorized as high risk (microsclerotia/cm³ ≥ 10), 23.1% as moderate risk (3 < microsclerotia/cm³ ≤ 9.9), 26.9% as low risk (0 < microsclerotia/cm³ ≤ 3), and 11.5% showed no detectable risk (microsclerotia = 0). All isolates/phylotypes tested belonged to the defoliating pathotype. Management recommendations tailored to the risk categories are discussed. The detection of microsclerotia in 88.4% of the fields surveyed, with 38.5% categorized as high risk, indicates a concerning level of inoculum and highlights the need for continued surveillance and further research on phenotypic and genotypic characterisation.

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.

Intensive fungicide regimes are commonly used on Buxus spp. in the United States to manage boxwood blight (BWB), a plant disease caused by Calonectria pseudonaviculata (CPS). BWB causes losses in both nursery production and landscapes. The disease is often found within boxwood canopies, where achieving adequate spray coverage and penetration is difficult. The efficacy of the systemic triazole fungicide flutriafol (Fungicide Resistance Action Committee group 3) was evaluated over time by detached leaf assays. The efficacy of several concentrations of flutriafol against three CPS isolates and at several spore concentrations was assessed in the lab. Flutriafol was also applied by drench or sprench (portmanteau of spray and drench, a high-volume foliar application with substantial soil wetting) to container- or field-grown boxwood plants. The triazole fungicide propiconazole, which was previously shown to be efficacious against BWB, and no-fungicide water application were included as control treatments. Leaves of boxwood 'Common', 'Winter Gem', 'Green Velvet', or 'Suffruticosa' were collected periodically, challenged with CPS conidia, and rated for percent symptomatic area over 14-day incubations. In general, lower disease incidence and severity developed on leaves collected from fungicide-treated plants than on leaves from water-treated control plants regardless of the application method. Flutriafol provided protection from CPS infection on leaves from drench-treated boxwood for at least 20 weeks. However, there was a delay of 1 to 4 weeks observed between fungicide application and maximum efficacy depending on treatment and trial. This delay was shorter among leaves from plants treated with higher flutriafol doses or via sprench applications.

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.

Fusarium head blight (FHB) is a devastating fungal disease in wheat, causing significant yield losses and deterioration of grain quality under severe conditions. In this study, a genome-wide association study was conducted with 448 accessions using genotyping data generated by the 660K SNP array. Nine relatively stable FHB resistance loci were identified on chromosomes 1B, 1D, 2D, 5B, 7A, and 7B. Each QTL accounted for 4.1 to 10.4% of the phenotypic variation. Among them, QFhb.nwafu-7BS and QFhb.nwafu-7BL are novel loci. Polymorphisms of the flanking AQP marker AX-94527414 were developed for QFhb.nwafu-7BL, which could be useful for marker-assisted selection of FHB resistance. Correlation analysis indicated that variation in FHB response was independent of plant height, spike length, and uppermost internode length across the three environments. These results offer new resistance resources for FHB resistance breeding and insights for marker-assisted selection and gene cloning.

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.

Pea seed-borne mosaic virus (PSbMV) poses a major threat to global pulse production. This virus, transmitted through seeds, can spread within fields via insect vectors, especially pea aphids (Acyrthosiphon pisum), in a nonpersistent manner. To mitigate the risks associated with PSbMV, it is crucial to plant virus-free seeds, detect the virus at an early stage, and implement effective control measures for the vectors, given that most commercial pulse cultivars are vulnerable to the virus. This study designed and assessed multiple primers for PCR-based virus detection and demonstrated their capability to identify PSbMV isolates in infected plant tissues. The primers successfully detected PSbMV in dried plant tissues and in aphids collected from infected plants, even after being stored at room temperature for up to 3 months. Furthermore, a hydrolysis probe-based assay was developed, and its effectiveness for quantitative PCR (qPCR), digital PCR (dPCR), and droplet digital PCR (ddPCR) was evaluated. Our results showed high sensitivity and linearity of the assay, capable of detecting PSbMV at concentrations as low as 22 copies per reaction mix using digital PCRs. Our findings underscore the effectiveness of the developed primers and assay for the rapid and sensitive detection of PSbMV isolates in a variety of plant tissues, aphids, and seed samples, offering improved tools for disease monitoring and management in agricultural settings.