Plant disease最新文献

Rhizoctonia solani is a soil-borne pathogen with a broad host range and considerable genetic diversity, yet little is known about its population structure in Sweden or Northern Europe. This study presents the most comprehensive survey to date of R. solani and related fungi across major field crops in Sweden, focusing on the southern agricultural region Scania. A total of 202 isolates were collected and characterized using rDNA-ITS sequencing for anastomosis group (AG) identification, geographic mapping, and multivariate analysis. The isolates primarily belonged to multinucleate AG-5 (81), followed by AG-3 (32), AG-2-1 (30), and AG-1 IB and AG-4 HGII (both 13), among other AGs, binucleate isolates, and Waitea species. AG-5 was clearly dominant, particularly on legumes, showing mild aggressiveness on pea and faba bean and high intraspecific ITS diversity. In contrast, AG-4 HGII and AG-2-1 displayed higher virulence, while AG-3 was non-pathogenic on the same hosts. Multivariate analyses revealed crop- and region-specific AG distributions. AG-3 was strongly associated with carrot and potato in Northeastern Scania, whereas across the rest of the region, AG-5 dominated legumes and was also found on sugar beet, together with AG-4 HGII and AG-2-1, while AG-2-1 occurred mainly on Brassicaceae. These findings have direct implications for crop rotation planning and disease management, highlighting potential risks in rotations involving legumes, Brassicaceae, and sugar beet, while rotations with carrot or potato may present lower risk. Overall, this study underscores the ecological complexity of Rhizoctonia in Swedish agroecosystems, emphasizing the need for localized surveillance and tailored management strategies to mitigate disease risk.

Apple Valsa canker, caused by Valsa mali, is a serious disease affecting apple trees. Saprophytic colonization is a crucial stage in the infection process, with spore germination being a prerequisite for this phase. The effects of nutrients, temperature, moisture, pH, and light on the germination of both conidia and ascospores of V. mali were investigated under controlled environmental conditions. The results showed that the germination of V. mali spores requires supplementary nutrients, and compound nutrients are more conducive to spore germination. In distilled water, neither conidia nor ascospores germinated, resulting in a germination rate of 0%. In a sugar solution, the maximum germination rate remained below 75%. However, germination rates reached 100% in media supplemented with bark extract, fruit extract, or potato dextrose (PD) culture medium. The temperature range for conidial germination was 3.1-34.8°C, with an optimum of 25.6°C. Conidial germination required a duration of wetness or relative humidity exceeding 97% to be sustained for at least 7.6 hours. The suitable pH range for conidial germination was 4-8. In contrast, ascospore germination occurred over a broader temperature range of 0.6-41.7°C, with an optimum of 25.6°C. Ascospore germination required a relative humidity above 90% for at least 6.8 hours and was supported by a wider pH range of 4-10. Light significantly inhibited conidial germination but had no observable effect on ascospore germination. These results can be used to construct a prediction model that estimates the amount and timing of V. mali colonization on branch surfaces based on environmental and nutritional conditions. This prediction model can then inform the timing and methods for implementing apple Valsa canker control programs more effectively.

Since 2021, a previously undocumented and economically significant fruit rot disease has emerged on apple (Malus domestica) during cold storage in the Loess Plateau region of China. An unidentified basidiomycetous fungus was consistently isolated from symptomatic fruits across multiple packinghouses. The ITS sequences from these isolates exhibited less than 90% identity with validated fungal species in GenBank. Concatenated multi-locus phylogenetic analysis and whole-genome phylogenomics placed the fungus within a monophyletic clade proposed as a new family (Neocyphellaceae fam. nov.) within the Agaricales order. Pathogenicity assays confirmed the fungus's capacity to consistently induce lesions on pre-wounded apple fruits and leaves. Notably, neither asexual nor sexual sporulation structures were observed on potato dextrose agar (PDA) or any other tested media. The fungus displayed distinct psychrotolerant characteristics. This organism exhibited optimal growth and virulence at 15-20°C, while exhibiting approximately 70% growth inhibition and 50% virulence attenuation at 28°C compared to 20°C. In vitro fungicide sensitivity assays revealed high sensitivity to demethylation inhibitors (DMIs; average EC50 for hexaconazole = 0.029 μg/mL) and quinone outside inhibitors (QoIs; average EC50 for pyraclostrobin = 0.12 μg/mL). The novel taxon was formally described as Neocyphella psychrotropha, and we propose the disease name "apple Neocyphella rot".

Soybean (Glycine max L.) is a globally significant oil crop with a pivotal role in the economic development of nations. In 2023, an unusual outbreak of soybean root rot (SRR) was observed in Harbin, Heilongjiang Province, China. Colletotrichum sojae infects soybean roots, leading to root rot symptoms. Using the tissue isolation method, a total of 22 fungal isolates were obtained, among which five representative pathogenic strains were identified as C. sojae. The remaining 17 strains are common Fusarium oxysporum and Phomopsis species that have been previously reported in the Heilongjiang region. To the best of our knowledge, this is the first report of SRR caused by C. sojae in China. Additionally, C. sojae exhibited a broad host range, causing root rot in most tested legumes, but did not infect maize or mung bean. Fungicide susceptibility assays revealed that C. sojae isolates were most sensitive to prochloraz, with an EC50 value of 0.0031 μg/mL. In two independent greenhouse pot experiments, the average control efficacy of 0.45 mg/mL prochloraz against SRR caused by C. sojae was 81.3%. Our results provide a theoretical foundation for managing SRR in this region and contribute to the development of effective disease control strategies.

Common bunt, caused by Tilletia caries and T. laevis, is a fungal disease of wheat that can cause significant yield and quality losses. Field screening for common bunt is often hampered by environmental factors and limited to one evaluation per year. In contrast, greenhouse screening potentially enables two to three assessments per year. We evaluated three greenhouse inoculation methods and two scoring techniques using two highly susceptible cultivars ('Apogee' and 'Red Bobs') and four moderately susceptible cultivars ('Fielder', 'LCS Star', 'SY Capstone', and 'UI Platinum'). In the first inoculation method, seeds were inoculated with a teliospore suspension and planted on the same day. In the second method, inoculated seeds were allowed to dry and were planted three days later. In the third method, seedlings were inoculated at the three-leaf stage by spraying a teliospore suspension directly onto the leaves. Disease incidence (percentage of infected spikes per plant) and severity (percentage of infected spikelets) were measured at physiological maturity. Seedling inoculation by spraying produced the lowest infection levels across all cultivars, with overall incidence ranging from 7.91 to 19.11% and severity from 5.01 to 13.69%. The two seed inoculation methods showed greater disease symptoms, with incidence ranging from 49.35 to 98.02% and severity from 43.04 to 94.06 %, with no significant differences between the methods. Severity and incidence were correlated (0.95 to 0.97) across the two seed inoculation methods. Thus, the seed inoculation methods were superior to seedling spray inoculation method for the response of wheat germplasm to common bunt infection. This finding was validated with a set of wheat cultivars and differential lines. This study underscores the importance of considering inoculation techniques in screening germplasm to select for common bunt resistance in wheat.

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.

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.

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.

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.