Plant disease最新文献

Pythium soft rot in ginger is caused by Pythium myriotylum, leading to significant reductions in ginger yields. In this study, a loop-mediated isothermal amplification (LAMP) detection method was established for Py. myriotylum in infected ginger plants and infested soil. The Py. myriotylum genome was compared with the genomes of seven additional oomycete species to obtain species-specific sequences. LAMP primer sets were designed and assessed at temperatures from 58°C to 68°C and tested for their specificity. Furthermore, the sensitivity of the screened primer set was evaluated, and the detection limit was 1 pg of Py. myriotylum genomic DNA (gDNA) in a 25-µl reaction volume. LAMP was used to detect Py. myriotylum zoospores in solution (1×10²/ml), vermiculite (1×10²/g), and soil (1×10⁴/g). A rapid and portable gDNA extraction method from ginger seedlings and rhizomes using solid-phase reversible immobilization beads for purification was adopted. The LAMP assay could reliably detect Py. myriotylum in artificially inoculated diseased ginger seedlings and rhizosphere vermiculite. The portable gDNA extraction method coupled with the LAMP assay facilitates point-of-care pathogen detection, requiring 2 to 3 hours for eight samples, greatly reducing the time needed for Py. myriotylum detection of Pythium soft rot in ginger.

Luffa acutangula and Momordica charantia, known for their edible and medicinal value, are economically important cucurbitaceous vegetable crops cultivated globally. Gummy stem blight, primarily caused by Stagonosporopsis species, is a devastating disease on cucurbits, resulting in significant economic losses. Although occurrence of gummy stem blight on L. acutangula and M. charantia has been reported previously, the pathogen responsible for the disease on these two crops has not been clearly identified because of the taxonomical nomenclature changes. During the period from 2018 to 2024, diseases resembling gummy stem blight were commonly observed on L. acutangula and M. charantia in Guangdong Province of China, with a disease incidence for L. acutangula of 13.5 to 21.7% in Guangzhou and 13.5 to 25.0% in Huizhou and a disease incidence for M. charantia of 20.0 to 30.0% in Guangzhou and 16.7 to 26.7% in Huizhou. Samples of symptomatic leaves, stems, and fruits were collected, and 52 fungal isolates with similar colony morphology were obtained. The initial identification of these isolates was based on cultural and morphological characteristics, which placed them in Stagonosporopsis. Subsequently, they were identified as S. citrulli with multilocus phylogenetic analyses using the ribosomal DNA internal transcribed spacer and portions of the β-tubulin, chitin synthase I, and calmodulin genes. Pathogenicity tests were conducted on leaves and fruits of L. acutangula, M. charantia, and Cucumis sativus with representative isolates of S. citrulli. These isolates produced lesion symptoms on L. acutangula and M. charantia similar to the disease symptoms in the field. Furthermore, they were also pathogenic to C. sativus. The same pathogen was reisolated from lesions of inoculated plants to fulfill Koch's postulates. To our knowledge, this study is the first report identifying S. citrulli as the causal agent of gummy stem blight on L. acutangula and M. charantia in China.

Fusarium dry rot (FDR) is a major postharvest disease of potatoes, causing significant economic losses worldwide. This study investigated the morphological and molecular diversity of Fusarium species causing dry rot in the San Luis Valley (SLV), Colorado. Potato tubers exhibiting characteristic dry rot symptoms were sampled during the 2023 and 2024 growing seasons. Fusarium species were isolated, characterized morphologically and molecularly, and identified as Fusarium oxysporum, F. sambucinum, F. clavum, and F. solani. Colony morphology, macroconidia, microconidia, and chlamydospore formation were analyzed to classify isolates into four distinct groups. Molecular characterization using internal transcribed spacer, rpb2, and tef markers confirmed species identity, supported by sequencing and phylogenetic analysis that grouped isolates into well-defined clades. Radial growth assessments demonstrated significant differences among species over time, with F. sambucinum exhibiting the fastest growth. Pathogenicity assays on three potato cultivars revealed varying virulence, with F. solani causing the most severe infections in cultivars tested. This study represents the first documented occurrence of F. oxysporum, F. sambucinum, F. clavum, and F. solani as causal agents of FDR in Colorado. Furthermore, F. clavum is a novel species associated with potato dry rot, not previously reported in the United States. The integration of molecular and traditional techniques underscores the genetic and morphological diversity of Fusarium spp. in the SLV and highlights their pathogenic potential. These findings provide a foundation for future research to mitigate the economic impacts of FDR and ensure the viability of potato production in Colorado and beyond.

Xylella fastidiosa (Xf) is a quarantine plant pathogen in the European Union, recognized as a high-priority pest due to its devastating cultural and economic impact on crops, ornamental plants, and landscape vegetation. The development and implementation of reliable, sensitive, and specific diagnostic methods for Xf detection are critical to ensure the production and trade of healthy plant material and to facilitate effective control measures, primarily aimed at eradication. Despite the availability of numerous detection protocols, their diagnostic parameters remain not precisely defined, and no universally accepted gold standard protocol exists. This study compared the global accuracy and performance of six molecular assays using almond samples collected from naturally infected almond trees in the Alicante Demarcated Area, Spain. Additionally, the study evaluated the influence of plant sample type (leaf petioles versus woody chips) on diagnostic accuracy. Harper-qPCR and Li-qPCR assays demonstrated the highest sensitivity, with detection limits as low as 2.8 to 3 fg of Xf DNA. Droplet digital PCR (ddPCR) exhibited excellent sensitivity for woody chip samples, while Li-qPCR showed superior specificity across both tissue types. In contrast, recombinase polymerase amplification displayed lower detection limits and reproducibility compared with qPCR-based methods. Bayesian latent class models indicated that combining Harper-qPCR and Li-qPCR for petioles, or Harper-qPCR and ddPCR for wood samples, optimized diagnostic reliability by reducing false negatives, which is critical in buffer zones under eradication while maintaining high specificity. These findings emphasize the need for tailoring diagnostic protocols to the epidemiological context, balancing sensitivity and specificity to optimize surveillance schemes for Xf and to support effective phytosanitary management strategies.[Formula: see text] Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Trichoderma afroharzianum, the causal agent of Trichoderma ear rot, is an emerging pathogen of maize (Zea mays L.). It was recently reported as a maize pathogen in Germany, France, and in Italy. In 2023, nine seed lots from three farms in Northern Italy were tested for their phytosanitary conditions, revealing infection rates of up to 71% with Trichoderma spp. All seed lots showed symptoms of Trichoderma ear rot infection, and 26 out of 50 isolates were identified as T. afroharzianum. The study confirmed that T. afroharzianum infects maize seeds causing severe disease. Thirteen isolates from infected seeds were used to design species-specific primers on the translation elongation factor 1α gene and to develop a SYBR Green quantitative PCR to detect and quantify T. afroharzianum in maize seeds. The assay was validated following EPPO standard PM 7/98 guidelines, assessing analytical sensitivity, specificity, selectivity, repeatability, and reproducibility. The specificity of the method was validated using 19 T. afroharzianum strains and 16 nontarget species, including Trichoderma species belonging to the T. harzianum species complex. Only target DNA produced positive amplifications. Analytical sensitivity was tested using serial dilutions of T. afroharzianum DNA, revealing a detection limit of 50 fg, even in the presence of maize seed DNA. The assay enables specific and sensitive detection of target DNA in asymptomatic samples, providing a valuable tool for early target detection and quantification during seed certification.

Disease surveillance is a keystone of human, animal, and plant health. It contributes to the prevention and management of epidemics. Over the past two decades, several methodological frameworks have been developed for the evaluation of human and animal health surveillance systems, but such approaches are still lacking in plant health. Here, we aimed at providing one of the first evaluations of a plant pest surveillance system. We applied the semi-quantitative OASIS method, already successfully used for the evaluation of centralized surveillance in animal health, to the French surveillance system of sharka, a viral disease of Prunus trees. A four-member evaluation team conducted semi-directed interviews with 29 professionals covering the different institutions and functions involved in this surveillance system. The evaluation showed that the main strength of the current system is its organization into well-performing regional units that enable adjusting the national surveillance strategy for the application of locally relevant control measures. The main opportunities for improvement were related to system coordination and science-based exploitation of the surveillance data for long-term disease control. We have provided a proof of concept that there is no other obstacle than vocabulary issues to the transposition of the OASIS method to plant diseases, which opens up the possibility to assess other surveillance systems and thus enables to improve their efficiency.

Root-lesion nematodes (Pratylenchus spp.) are significant agricultural pests worldwide. From January 2021 to January 2023, 365 root and rhizosphere soil samples were collected in key soybean-producing regions, revealing a new species, Pratylenchus brasiliensis sp. nov., in Brazil's agricultural frontier. Identification employed a polyphasic approach, integrating microscopy, morphometric analyses, and multigene phylogenetics. Molecular species delineation targeted the D2-D3 expansion segments of the 28S rRNA gene, the internal transcribed spacer (ITS) rRNA region, and cytochrome oxidase I (COXI) mitochondrial DNA. Females of P. brasiliensis sp. nov. RE 614.25 to 671.98 μm long and 26.42 to 27.34 μm wide, with a ventrally curved body, four lateral lines, a well-developed spermatheca, a vulva at 77 to 81% body length, and a conical tail with 19 to 25 annuli. The labial region features three annuli and a robust stylet (17 to 18 μm) with anchor-shaped basal knobs. Males are shorter (450 to 550 μm), with curved spicules (15 to 17 μm) and a bursa extending over the tail. Molecular analysis confirmed P. brasiliensis sp. nov. as closely related to P. bolivianus, P. curvicauda, and P. vandenbergae. Pathogenicity tests demonstrated its ability to cause necrotic lesions and gallery formation in soybean roots, with reproduction factors > 1 in major Brazilian soybean cultivars, emphasizing its agricultural threat. The discovery emphasizes the need for surveillance and the development of management strategies to mitigate its impact on soybean yield. Further studies are needed to explore its host range and identify resistance sources in soybean cultivars.

Fusarium wilt (FW), caused by Fusarium oxysporum f. sp. lycopersici (Fol), is one of the most devastating diseases in tomato crops. None of the succinate dehydrogenase inhibitor (SDHI) fungicides is registered for the control of FW of tomatoes in China. In this study, the inhibitory activities of 12 SDHI fungicides against Fol were determined in vitro, and the results showed that pydiflumetofen and cyclobutrifluram exhibited excellent inhibitory activities, with inhibition rates of approximately 75.63 to 87.25% at a concentration of 1 μg ml^-1. Bixafen, fluopyram, isopyrazam, and benzovindiflupyr exhibited weak inhibitory activities, with inhibition rates of approximately 45.68 to 75.00% at a concentration of 20 μg ml^-1. Penflufen, sedaxane, isofetamid, boscalid, thifluzamide, and carboxin exhibited very poor inhibitory activities, with inhibition rates of approximately 13.45 to 61.73% at a concentration of 50 μg ml^-1. Forty pydiflumetofen-resistant mutants of Fol were obtained, and the point mutation of FoSDHC1 was associated with resistance of Fol to pydiflumetofen. Three FoSDHC1 deletion mutants were obtained, and FoSDHC1 deletion mutants exhibited no significant differences in vegetative growth, conidiation, and virulence but exhibited increased sensitivities toward all SDHI fungicides tested except thifluzamide and boscalid compared with the wild-type strain. These results indicated that FoSDHC1 regulated the sensitivity of Fol to most SDHI fungicides.

In 2022, an outbreak of apparent Fusarium wilt raised concern because the disease has historically been sporadic and infrequent. Previous studies reported that the primary causal agent of this disease in the United States is Fusarium oxysporum f. sp. nicotianae, but the identity of other Fusarium spp. responsible for Fusarium wilt and root rot and their pathogenicity have not been thoroughly investigated. To identify Fusarium species associated with the recent disease outbreak in flue-cured tobacco, 36 symptomatic plants with apparent one-sided wilting were sampled from 14 fields in Virginia and North Carolina. Forty-seven obtained isolates showed colony morphology typical of Fusarium spp. on potato dextrose agar (PDA) medium. Fifteen isolates representing colony variations on PDA were further selected for microscopic examination and molecular identification using the translation elongation factor 1-alpha (tef1-α) gene. Phylogenetic analysis of tef1-α nucleotide sequences identified nine Fusarium species representing five distinct species complexes: Fusarium incarnatum-equiseti (six isolates), F. oxysporum (three isolates), F. solani (three isolates), F. fujikuroi (two isolates), and F. tricinctum (one isolate). The pathogenicity of each isolate was assessed on flue-cured tobacco cultivar K326 seedlings at the six-leaf stage in greenhouse inoculation experiments with or without wounding. All 15 Fusarium isolates were pathogenic, causing root rot, leaf necrosis, and reduced growth parameters compared with the control treatment. The diversity of Fusarium species associated with Fusarium wilt of tobacco and the variability in aggressiveness among Fusarium species within the same species complex or belonging to different Fusarium species complexes provide a theoretical basis for future research on the epidemiology of Fusarium disease in tobacco and integrated disease management strategies to reduce disease development and severity.

Verticillium dahliae, a soilborne fungal pathogen, infects and causes wilt symptoms in dicot but not monocot plants. The precise sequence of events when V. dahliae infects monocots remains unclear. In this study, we confirmed on several different hosts that V. dahliae can cause typical Verticillium wilt symptoms on dicots but not on monocots. Scanning electron microscopic and transmission electron microscopic studies indicate that V. dahliae germinates, expands, and initially penetrates both cotton (dicot) and maize (monocot) roots. While V. dahliae has been previously shown to colonize the root cortex in monocots, our work clearly revealed that the pathogen penetrates into the xylem but is unable to survive in the maize roots during early stages of colonization. Rather, the conidia and mycelia break down in maize, and remains of shrunken cells persist in the roots. Collectively, our results provide new clues on the sequence of events that occur when V. dahliae infects monocots versus dicots and may underlie Verticillium wilt symptoms on dicots but not on monocots.