Plant disease最新文献

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.

White leaf spot (Neopseudocercosporella capsellae) poses a significant threat to canola (rapeseed, Brassica napus) production globally, particularly in Australia. Histological studies were undertaken under controlled environment room conditions on triazine-tolerant (TT) cultivars Crusher TT with moderate resistance and Thunder TT with high susceptibility to white leaf spot, to determine how atrazine and the timing of its application affect (i), the disease severity as measured by the percentage of leaf yellowed area , (ii), the rate of conidial germination, (iii), the rate of conidial collapse, (iv), the germ tube length in germinating conidia, and (v), the morphological transformation from multi-celled hyphae or conidia into numerous single-celled blastospores (yeast phase). For each cultivar, two atrazine treatments were used which result in the highest and lowest levels of disease suppression under hyphal inoculation and infection as previously determined. Across 21 days, the percentage of leaf yellowed area of both cultivars was significantly reduced by atrazine application, the rate of conidial germination was reduced, both germ tube length of germinating conidia and subsequent morphological transformation into single-celled blastospores were also reduced, while the rate of collapse of conidia was increased. Notably, in the absence of atrazine, conidial infection resulted in greater percentage of leaf yellowed area as compared with hyphal infection and was strongly associated with more extensive morphological transformation of geminating conidia into single-celled blastospores. It was evident that the formation of single-celled blastospores through morphological transformation is a determining factor for the comparative pathogenicity differences between conidial versus hyphal inoculum, highlighting the significance of this morphological transformation in the pathogenesis of N. capsellae. These findings not only provide new understanding of atrazine-pathogen interactions under controlled conditions but have laid the foundation for future studies and opportunities to further explore potential dimorphism-targeted fungicidal strategies, and to utilize this system as a model for herbicide-pathogen interactions.

Flowering cherries (Prunus subgenus Cerasus) are important street and ornamental trees in Taiwan. Gummosis disease is commonly observed on their trunks and branches, yet the causal agents remain poorly defined. In this study, fungal pathogens were isolated from diseased trees in northern Taiwan and identified through multilocus phylogenetic analysis and pathogenicity assays. Phylogenetic analysis based on internal transcribed spacer, elongation factor 1-α, and β-tubulin sequences revealed three associated species: Botryosphaeria dothidea, Lasiodiplodia thailandica, and L. theobromae. Artificial inoculation confirmed that all three species caused gummosis and internal wood discoloration and produced abundant pycnidia on stems of Prunus campanulata seedlings. To explore chemical control options, eight fungicides representing six modes of action were tested for inhibitory effect and systemic activity. Carbendazim, tebuconazole, propiconazole, and pyraclostrobin strongly inhibited mycelial growth of Lasiodiplodia spp. and B. dothidea (EC₅₀ < 1 mg kg^-1); while fluxapyroxad was highly effective against Lasiodiplodia spp. but not B. dothidea. Root tip-immersion and stem-injection translocation assays indicated good acropetal mobility of carbendazim, tebuconazole, propiconazole, isoprothiolane, and fluxapyroxad, and basipetal transport of tebuconazole, propiconazole, and pyraclostrobin. In greenhouse trials with tebuconazole by five different application methods, preventive stem injection consistently provided the best protection, markedly reducing disease severity, internal discoloration, and pathogen colonization. Topical application (stem painting) required the lowest fungicide input and was effective in suppressing external symptoms. Overall, this study clarifies the etiology of fungal gummosis disease in flowering cherries in Taiwan and demonstrates fungicide application strategies with potential for broader management of fungal trunk diseases in urban landscapes.

Apple scab, caused by Venturia inaequalis, requires regular fungicide applications to achieve adequate disease control. Multi-site fungicides such as mancozeb and captan are integral to chemical management programs due to resistance concerns. To reduce reliance and mitigate regulatory concerns with multi-site fungicides, there has been increased demand for more sustainable solutions. We attempted to use disease forecasting to enhance potential for alternative programs replacing multi-site fungicides with biopesticides to manage apple scab in plantings of cvs. Jonagold and Empire apples. Programs included: untreated control, 'grower-standard' program of conventional multi-site fungicides alternated with single-site fungicides on a calendar schedule, a program where biopesticides alternated (in place of multi-sites) with single-sites on calendar schedule, several programs where biopesticide alternated (in place of multi-sites) with single-sites timed using one of three different disease forecasting tools (NEWA, RIMpro, or Weather services). Programs were carried out for standard and extended season management trials. Disease incidence on terminal leaves and fruit was rated at the end of the season; mean incidence was calculated and analyzed. In all years of the study on 'Jonagold' apples, we observed no significant differences (P > 0.05) among management programs suggesting that integrated programs would be viable and that any forecasting-based timing used in our study can be just as effective as a calendar schedule. For the cv. 'Empire' apples, which are more susceptible to apple scab, the extended season program with NEWA based applications provided the best control. Despite the promising results using biopesticides instead of multi-site fungicides, we can't be certain whether the multi-sites fungicides or biopesticides were effective rotational partners are simply not needed without additional studies without additional controls. Regardless, something is needed to provide a modicum of coverage and ensure fungicide resistance management during low-risk periods, and biopesticides are one of the more environmentally responsible means. However, our results provide a cultivar dependent framework for developing management programs without multi-site fungicides using disease forecasting, while achieving better disease control and ensuring fresh market yields.

Accurate and timely diagnostics are essential for plant disease control, but one challenge is the emergence of new isolates with genomic variation, which limits the binding capabilities of PCR primers and serological antibodies. Triticum mosaic virus (TriMV) and wheat streak mosaic virus (WSMV) are two economically impactful viruses that infect wheat in the US Great Plains. We found that primers traditionally used to detect these are unreliable for Colorado isolates, with 33 of 105 samples tested between 2021-2025 with false negative discrepancies for one or both viruses. We compared all available genomes and developed new universal WSMV and TriMV primers within higher regions of conservation across these genomes. With qPCR, we found that these diagnostic primer pairs were 16% more efficient than the established primers for WSMV, and 18% more efficient for TriMV. Both were 16% more sensitive in detecting viral loads, had higher specificity for the associated viruses (E-values near zero), low specificity for the wheat genome (E-values = 1.9-7.5), and universally detected Colorado isolates. To improve throughput for multiple samples, we subsequently designed a sensitive and specific multiplex PCR bioassay to detect both viruses in a single reaction. Finally, we developed a colorimetric loop-mediated isothermal amplification (LAMP) bioassay to detect WSMV and/or TriMV, using either RNA or cDNA as the genomic template. The LAMP bioassay was reliable, specific, and highly sensitive, consistent with our PCR diagnostic results. Overall, our modified primers and new LAMP assay will serve as improved tools to reliably detect new virus isolates.

Epidemiology and management of aphid-transmitted yellow dwarf viruses (YDVs) have received international attention in small grain crops over the past century. However, focused research regarding YDV management in grass seed production systems, including perennial ryegrass (Lolium perenne L.), is limited. An integrated pest management program is needed to reduce the impact of the aphid-YDV complex in perennial grass seed crops. The objectives of the study were to evaluate the effects of nitrogen fertilizer rate, and the timing and frequency of foliar insecticide applications on aphid abundance, YDV disease incidence, and seed yield in two perennial ryegrass cultivars in small-plot field trials from 2021 to 2024. Trade-offs in economic returns across treatment combinations and YDV detection using remote sensing were also observed. Aphid and natural predator densities varied across foliar insecticide treatments. The high nitrogen rate increased YDV incidence across three field seasons in both cultivars. Seed yield and economic returns were greatest for the less susceptible cultivar when fully protected with one insecticide treatment per season (autumn, spring, and summer). A higher-than-recommended nitrogen rate did not increase seed yield across treatment combinations in first-year stands; however, an increase was observed in second- and third-year stands when YDV infection averaged >50%. Selecting resistant cultivars and reducing aphid populations during the autumn and spring aphid flights is critical for maximizing seed yield potential in perennial ryegrass. Furthermore, a lower nitrogen rate can be used in first-year stands to save input costs with no impact on seed yield potential.

Seed rot and damping-off of alfalfa (Medicago sativa L.) is caused by a soilborne disease complex resulting in thin initial stands of plants with continuing damage during wet soil conditions decreasing forage yields and winter survival. Apron (metalaxyl) and Apron XL (mefenoxam) have been used on alfalfa seeds for decades to reduce damping-off and early season root rot. Although several other anti-oomycetes (oomicides) and fungicides are labeled for use on alfalfa seeds, there is little information on their efficacy against specific pathogens or the disease complex. Our objective was to test chemical seed treatments to identify those with broad antimicrobial activity to aid in establishing alfalfa stands where pathogen complexes are present. First, 10 products were tested for mycelial growth inhibition of nine alfalfa pathogens. The two most promising, EverGol Energy and Intego Solo, were active against Globisporangium ultimum, Pythium irregulare, P. sylvaticum, P. paroecandrum, Aphanomyces euteiches, and Phytophthora medicaginis. Protection of seedlings in agar plate bioassays and infested soil assays against G. ultimum and Pythium species by EverGol Energy was like that of Apron XL, whereas Intego Solo was not effective. The EverGol Energy seed treatment provided modest protection in bioassays with A. euteiches and P. medicaginis for susceptible cultivars, although it did not improve protection for resistant cultivars. Combined seed treatments did not improve seedling health in single pathogen bioassays or experiments with naturally infested field soil with multiple pathogens. Seed treatments with Apron and Apron XL were the most effective in providing partial protection against the disease complex in field soil. These results suggest that greater resistance is needed for managing the disease complex.

Plant viruses cause significant damage to crops, yet research on them remains limited, leading to an underestimation of plant viral diversity. This study constructed an up-to-date atlas of plant viruses by integrating data from public databases and further established the Plant Virus Database (PVD, freely available at http://computationalbiology.cn/PlantVirusBase/#/) for storing and organizing these viruses. The PVD contained 3,353 virus species and 9,010 virus-plant host interactions, more than double of those reported in previous studies. Among these, 1,986 viruses are capable of infecting crops. With few exceptions, most plant viruses were observed to infect only a limited number of plant hosts, and vice versa, indicating that the plant virome is still underestimated. Comparative analysis of viromes in monocots and eudicots, as well as plants from tropical and temperate regions, revealed significant differences in virome composition. Analysis of virus host ranges demonstrated that dsDNA viruses exhibit broader host ranges compared to other virus groups. However, biological characteristics such as whether viruses are enveloped, genome size, or transmission mode (horizontal or vertical) showed no or weak associations with the host range of plant viruses. Overall, this study not only provides a valuable resource for further research on plant and crop viruses but also enhances our understanding of the genetic diversity of plant viruses and their interactions with hosts.

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.