Plant disease最新文献

Pear decline, caused by 'Candidatus Phytoplasma pyri', has emerged in Chilean pear orchards in recent years. While several Cacopsylla species are potential vectors of 'Ca. P. pyri', the disease's full epidemiological cycle remains uncertain. Cacopsylla bidens, present in Chilean orchards, has recently been reported as a vector. This study conducted year-long surveys in two commercial pear orchards across different Chilean regions, capturing C. bidens in zones with 'Ca. P. pyri'-infected pear trees. All developmental stages were collected, with peak abundances occurring in March and April. Outside the study zones, C. bidens were found in pine trees but not in adjacent cultivated areas. Two seasonal morphotypes, summer and winter forms, were identified. Molecular analysis detected 'Ca. P. pyri' in a high proportion of insects, with maximum infection rates in March and April. These findings advance our understanding of 'Ca. P. pyri' spatial and temporal dynamics and its potential role in 'Ca. P. pyri' spreading under Chilean field conditions.

Durian (Durio zibethinus) is an economically important tropical fruit endemic to Southeast Asia. Hainan is a new region for durian cultivation. Foliar diseases of durian were common at all durian orchards during field surveys carried out from October 2023 to October 2024 in Hainan, China. In this study, Fusarium species associated with durian foliar disease in Hainan (China) were studied based on multilocus phylogenetic analyses using translation elongation factor 1-α (tef1), partial RNA polymerase second largest subunit (RPB2), and calmodulin (CaM). Six Fusarium species including F. pernambucanum, F. sulawesiense, F. hainanense, F. irregulare, F. mangiferae and F. concentricum were identified. Pathogenicity tests showed that all six species were pathogenic to detached wounded and unwounded durian leaves except F. irregulare, which only induced visible symptoms on wounded durian leaves. The findings from this study expand the pathogenic fungal species on durian as this is the first report of these Fusarium spp. causing durian leaf disease worldwide.

Crown rust, caused by Puccinia coronata f. sp. avenae (Pca), remains a persistent threat to oat production in Australia. To monitor recent shifts in virulence and population structure, 30 Pca isolates collected during the 2024 growing season across major Australian oat-producing regions were analysed. Virulence analysis of 30 isolates using 52 oat differential lines identified 25 unique races that were not detected in previous years. Whole-genome sequencing of 28 of these isolates were analysed in the context of a broader historical Australian and international genomic datasets including isolates from Taiwan, South Africa, USA. Results confirmed the uniqueness of the Australian Pca population and revealed well-established genotypic lineages persisting over multiple years, with L18 and L16 being dominant. Notably, L16 was again present in Western Australia after being undetected in 2023, while L18 maintained its prevalence for a third consecutive season. Beyond these dominant groups, phylogenetic analysis and a k-mer containment analysis also identified a novel and genetically distinct lineage, designated as L19, represented by one isolate collected in WA. To add to the characterisation of lineage L19, we recorded virulence phenotypes on a small collection of current commercial cultivars. These findings enhance understanding of Pca diversity and emphasise the importance of surveillance approaches that integrate phenotypic and genomic surveillance.

Xanthomonas arboricola pv. pruni (XAP) causes bacterial spot of peach. Current disease management in the southeastern USA mainly relies on routine applications of copper and oxytetracycline (OTC), but copper-tolerant and OTC-resistant XAP have been reported in South Carolina (SC) peach orchards. To study the prevalence and persistence of copper-tolerant and OTC-resistant XAP, a survey was conducted across seven SC and Georgia peach orchards/farms annually during 2021 to 2024. Of the 1,741 XAP isolates collected, 4.4% were copper sensitive; 24.3%, 65.5%, and 5.8% were copper-tolerant up to 150 (LCT150), 175 (LCT175), and 200 µg/ml of copper sulfate pentahydrate, respectively. All the OTC-resistant isolates (24.9% of the population) came from the three conventional SC orchards and contained tetC. In the same orchards, trees with OTC-resistant isolates had significantly higher bacterial spot incidence and severity on both fruit and leaves than the other trees, while higher bacterial leaf spot incidence was observed on trees with LCT175 vs. LCT150 XAP, suggesting potential negative impact of OTC resistance and copper tolerance on the chemical spray programs. In each orchard, bacterial spot incidence, severity, and defoliation increased over time within each season, but the percentage of the resistant/tolerant XAP population remained similar. Regardless of the spray programs utilized, copper-tolerant and OTC-resistant XAP populations have been consistently recovered from the sampled trees across years. Season-long chemical spray programs are still valuable for this disease, but the prevalence and persistence of copper-tolerant and OTC-resistant XAP emphasizes the need for resistance management and development of novel disease management strategies.

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.