Plant disease最新文献

Sudden death syndrome (SDS), primarily caused by Fusarium virguliforme, threatens soybean (Glycine max) production across the United States and Ontario, Canada. SDS thrives in cool, wet soils, with post-planting rainfall exacerbating disease, making pre-planting management strategies like resistant cultivars and seed treatments crucial. This study evaluated biological and chemical seed treatments on resistant and susceptible soybean cultivars across 14 locations in 2022 and 15 locations in 2023. Data collection included final stand counts, root rot severity, foliar SDS severity index (FDX), and yield. Trials were categorized into high (FDX ≥ 10%) or low (FDX < 10%) disease severity locations based on the non-treated control (NTC). In high disease locations, cultivar and seed treatment significantly (P ≤ 0.01) influenced FDX, root rot, and yield. The base+fluopyram and base+fluopyram+natamycin treatment reduced FDX by 6.7% and increased yield by 288.5 kg/ha over the non-treated. The resistant cultivar reduced FDX by 9.7% and root rot by 2.1%, while increasing yield by 247.7 kg/ha relative to the susceptible cultivar. Under low disease pressure, cultivar selection remained significant, with resistance reducing FDX by 2.4% and root rot by 0.8%, and improving yield by 445.5 kg/ha. In contrast, the effects of seed treatment were not significant in the low disease severity environments. No seed treatments reduced FDX or root rot and only base+fluopyram and base+fluopyram+natamycin increased yield (+254 to 301 kg/ha) compared to the non-treated in the low disease severity environments. Cultivar resistance remains the most effective SDS management strategy, with seed treatments providing significant benefits under high disease pressure.

Sclerotinia sclerotiorum, the causal agent of Sclerotinia stem rot (SSR), is a fungal pathogen of soybean that can lead to yield losses of over 11 million bushels in the northern United States. While resistant cultivars can reduce SSR impacts, limited research has focused on early-maturity soybean lines adapted to the Northern Great Plains due to the lack of appropriate check lines. The primary objective was to screen early-maturity soybean lines and identify those showing consistent responses to different S. sclerotiorum isolates. In this study, we screened 193 diverse soybean lines from the United States Department of Agriculture (USDA) germplasm collection from varying maturity groups (MGs), ranging from 000 to I. Under greenhouse conditions, these lines were inoculated with a highly aggressive isolate of S. sclerotiorum, and the lesion length development was recorded at three independent time points post-inoculation. Relative Area Under Disease Progress Curve (RAUDPC) values were generated to evaluate resistance ratings. High resistance was observed in 39% of MG 000 lines, 13.8% of MG 00 lines, and 3.8% of MG 0 lines. Representative resistant, moderately resistant, and susceptible lines were subsequently evaluated against four S. sclerotiorum isolates of differing aggressiveness (WI-20, WI-43, WI-15, and WI-3). Significant line × isolate interactions were observed (P < 0.0001), but PI 194639 and PI 548649 displayed consistent resistance or susceptibility across isolates, respectively. These findings demonstrate the importance of screening with multiple S. sclerotiorum isolates and the identification of potential early-maturity soybean check lines for future SSR resistance evaluations.

Soybean cyst nematode (SCN, Heterodera glycines) is one of the most yield-limiting nematodes in soybean production. Application of synthetic nematicides is a critical component in the integrated management of SCN in China. However, resistance has developed in SCN to conventional nematicides, leading to the failure of these nematicides in some fields. It is pivotal for the soybean industry to develop new nematicides that can achieve sustainable nematode control. Seed treatment is a promising control approach. Fluopyram is widely used to control various plant-parasitic nematodes (PPNs); however, it is currently not registered as a seed treatment in China for use in controlling SCN. In this study, the efficacy of fluopyram as a seed treatment to manage SCN was evaluated through in vitro tests, greenhouse experiments, and field trials. In vitro tests showed that fluopyram caused a high mortality of H. glycines second-stage juveniles (J2s), with 50% lethal concentration (LC50) value of 0.96 mg/L that was superior to abamectin. In greenhouse experiments, compared with the untreated control, seed treatment with fluopyram at 0.15 mg active ingredient (a.i.)/seed provided significant SCN control, while maintaining excellent soybean root length and shoot fresh weight, better than the commercially available seed treatment with a 35.6% formulation of abamectin + carbendazim + thiram at 10 mL/kg seed. Moreover, in split-root experiments, fluopyram treatment at 0.15 mg a.i./seed reduced number of J2s inside the roots by 65.3% and induced resistance to SCN. Fluopyram also enhanced activities of phenylalanine ammonia-lyase (PAL) and peroxidase (POD), which was associated with the increased expressions of the defense-related genes GmNPR1-1, GmSAMT1 and GmACS9b. In two consecutive years of field trials, fluopyram seed treatment at 0.15 mg a.i./seed exhibited significant control of SCN. Compared to the control, it reduced numbers of cysts on the roots, cysts in the soil, and nematode juveniles inside the roots by 57.5%, 52.2%, 63.6% in 2023, and 63.7%, 57.2%, 67.9% in 2024, respectively. These results indicated that fluopyram not only exhibited strong nematicidal activity against H. glycines but also induced systemic resistance in soybean. In summary, fluopyram seed treatment has the potential to manage SCN in the field and warrants further studies.

Pea (Pisum sativum L.) is a cool-season annual legume crop cultivated globally. It is increasingly integrated into cereal-based rotations across Mediterranean agroecosystems, raising concerns about plant-parasitic nematodes (PPNs) that affect both legumes and subsequent crops. This study establishes the prevalence, diversity, and abundance of PPNs in a novel cropping system in southern Spain, where pea is introduced into cereal rotations. Nematode community structure in the surveyed fields is strongly influenced by intensive tillage practices and the desiccation tolerance of certain species, which facilitates their persistence through the dry summer season. The dominant PPNs affecting pea crops are Pratylenchus spp., with P. mediterraneus frequently occurring in mixed infections alongside closely related species such as P. thornei, P. neglectus, and P. crenatus. Given the absence of molecular tools specifically designed for P. mediterraneus, we developed a species-specific qPCR assay targeting P. mediterraneus and its close relative P. thornei. The newly developed qPCR assay was validated for specificity and sensitivity, and successfully applied to nematode communities extracted from pea root tissues. This molecular tool enables precise detection and quantification of P. mediterraneus and P. thornei, even in complex mixtures, offering a robust resource for nematode diagnostics and integrated management in legume-based cropping systems.

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.