Continuous cropping often results in stunted plant growth and a higher incidence of soil-borne diseases. Soil microbial communities play a crucial role in promoting plant growth, maintaining plant health, and enhancing plant resistance to various diseases. This study examines the impact of continuous cropping on chili root rot and explores the contribution of soil microbial communities to alleviating this issue. The results revealed that prolonged continuous cropping significantly altered the composition of the rhizosphere bacterial community. High-throughput sequencing analysis indicated a marked increase in the abundance of Fusarium pathogens, accompanied by a significant decline in antagonistic bacteria from the genera Bacillus and Pseudomonas. LEfSe analysis showed that Bacillus and Pseudomonas were the core bacterial biomarkers in chili continuous cropping soil, which were successfully isolated and demonstrated significant antagonistic effects against Fusarium solani. Utilizing these antagonistic bacteria, nine different synthetic communities (SynComs) were constructed. Among them, the T7 SynCom exhibited excellent biocontrol efficacy. It effectively suppressed the pathogen, reduced the incidence of root rot, and enhanced systemic induced resistance by activating the plant immune-associated pathways, including the MAPK signaling pathway, ethylene signaling pathway, and pathways mediated by jasmonic acid and salicylic acid. These findings offer new insights into using functional SynComs as a sustainable agricultural solution and open new avenues for overcoming the challenges posed by continuous cropping.[Formula: see text] Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
Historically, Fusarium oxysporum f. sp. fragariae (Fof), the causal agent of Fusarium wilt in strawberry, has been a major problem for strawberry production in California but has been largely absent in the rest of the United States. During the growing seasons of 2023 to 2025, independent detections of Fof were made on strawberry plants exhibiting symptoms of Fusarium wilt in the eastern U.S. states of Florida, North Carolina, New York, Connecticut, and Virginia. Sixteen isolates were obtained from symptomatic plants across this region, and a subset (n = 14) were confirmed to be Fof by pathogenicity testing, morphological characterization, PCR diagnostics, and whole-genome sequencing. Specifically, these tests demonstrated that all tested isolates were virulent on susceptible (fw1) strawberry cultivars but not on resistant (FW1) cultivars, classifying them as race 1. Although all isolates tested positive with the more recently developed Fof-specific PCR assay by Burkhardt et al. (2019), many (43.75%) failed detection with the commonly used Suga et al. (2013) assay. Comparative genomics revealed that these isolates represent at least three distinct phylogenetic clades (Y1, Y2, and the putative Y10), suggesting multiple independent introductions rather than a single dissemination event. The genetic diversity of the eastern U.S. Fof populations and their likely origin from nursery stock highlight the need for more robust diagnostics, certified clean planting stock, and region-specific resistance trials to manage Fusarium wilt beyond California.
Robusta coffee (Coffea canephora) production in tropical regions is increasingly constrained by fungal diseases associated with complex pathogen interactions and favorable environmental conditions. This study investigated symptom diversity, pathogen composition, pathogenicity, and environmental drivers associated with fungal infections in Robusta coffee plantations in southern Thailand. Field surveys were conducted in three commercial plantations located in Thung Lan Subdistrict, Khlong Hoi Khong District, Songkhla Province, Thailand, during February-July 2025. A total of 90 coffee trees were assessed using a stratified sampling approach, and disease symptoms affecting leaves, branches, flowers, and fruits were recorded. Nineteen representative disease symptoms were identified and grouped into major disease categories, including dieback complex, fruit rot/lesion complex, and leaf spot complex. The dieback complex exhibited the highest disease incidence and severity (65.4 ± 5.2% incidence; 58.7 ± 4.3% severity), followed by fruit rot/lesion complex (42.7 ± 4.8% incidence; 36.5 ± 3.8% severity) and leaf spot complex (38.2 ± 3.9% incidence; 29.8 ± 2.7% severity). A total of 10 morphologically distinct fungal isolates were recovered from symptomatic tissues. Molecular analyses identified Fusarium falciforme (95.41%), Lasiodiplodia/Diplodia sp. (99.37%), Lasiodiplodia theobromae (99.79%), and Lasiodiplodia sp. (81.35%). Pathogenicity assays demonstrated that all representative isolates induced disease symptoms on detached Robusta coffee leaves. Among them, F. falciforme showed the highest aggressiveness, producing lesions up to 4.73 cm within 7 days after inoculation. Environmental monitoring further indicated that elevated humidity and moderate temperature during the rainy season favored fungal disease development. These findings demonstrate that fungal diseases in Robusta coffee are driven by multi-pathogen interactions shaped by humid tropical environments, providing an important basis for integrated disease management and sustainable coffee production under changing climatic conditions.
In 2024 fall, symptoms of leaf blade and petiole spots were observed on strawberry plants 'Rociera FNM' and 'Marisma FNM'. In 450 randomly selected plants from 3 nurseries of Segovia province (Spain) 3.5% of incidence was recorded. Lesions on the leaf were reddish-brown with yellowish halos and became necrotic. Dark brown lesions with defined edges were noted on petioles. Affected tissue sections were excised, rinsed with 0.1% Tween 20, submerged in 70% ethanol (20 s), followed by 1% NaOCl (60 s), and then placed onto potato dextrose agar (Condalab, Madrid, Spain) with 50 mg/l of streptomycin sulphate. Plates were incubated at 28°C under darkness. From 6 crowns and 2 petioles 8 isolates (Di 3 to Di 10) were obtained from different pycnidia via single conidia isolation. Colonies had petal-shaped margins. Hyphae were initially hyaline, later developing an orange coloration in the center of the colony, and black conidiomata were visible two weeks post-incubation. Conidiomata were ellipsoidal to globose. Single-celled conidia were brown, ellipsoidal with slightly mucronate apices, narrowly truncated bases and smooth walls. This morphology was consistent with Coniella sp. as described by Álvarez et al. (2016). Isolates were stored in 50% glycerol solution at -80ºC. Genomic DNA was extracted from the 8 selected isolates. The internal transcribed spacer (ITS) region, translation elongation factor 1-alpha (TEF1), and large subunit ribosomal RNA (LSU) were amplified using the primer pairs ITS1/ITS4 (White et al. 1990), EF728/EF986 (Carbone and Kohn 1999), and LR0R/LR7 (Chethana et al. 2017), respectively. Sequence alignments performed in MEGA v11.0 (Tamura et al. 2021) showed that all isolates were identical across the three analyzed loci. Sequences of Di6 and Di10 isolates were deposited in GenBank. BLASTn analyses revealed that ITS (PX663172, PX663173), TEF1 (PX666006, PX666007), and LSU (PX663628, PX663629) sequences showed 100% identity with C. fragariae strain CBS 198.18 for ITS and 99% and 100% identity with strain CBS 167.84 for TEF1 and LSU, respectively. A concatenated phylogenetic tree was constructed with representative Coniella species and outgroup sequences from NCBI GenBank (Chethana et al., 2017) and confirmed the identity. Pathogenicity test was conducted using isolates Di6 and Di10. Inoculation with each isolate was performed by spraying 25 mL of a conidial suspension (5 x 104 conidia/mL) onto 5 plants of 'Rociera FNM'. Control plants were sprayed with sterile water. The assay was carried out twice. After inoculation, plants were covered with a plastic bag and kept in darkness for two days. Growth chamber was maintained at 25±2°C with 12-h photoperiod. Identical symptoms to the initially observed appeared on inoculated plants 6 days post-inoculation. Both isolates exhibited comparable severity (proportion of symptomatic leaf area) 20 days after inoculation. An assay was also performed on 'Marismas FNM', giving the same results. Fungal colonies re-isolated from the lesions had the same morphology and ITS, TEF-1 and LSU sequences of the inoculated isolates, thereby fulfilling Koch's postulates. In Switzerland and Great Britain C. fragariae has previously been isolated from strawberry plants (Rigotti et al. 2003; Jones and Baker, 2007). To our knowledge, this is the first report of C. fragariae on strawberry in Spain. Monitoring of the pathogen is essential since it can spread through asymptomatic plants into strawberry’s nurseries and fields.
Trichoderma hamatum T2 is an antagonistic fungus with biocontrol potential. In this study, single-factor experiments combined with response surface methodology were employed to optimize liquid fermentation conditions for T2, in order to enhance its inhibitory efficacy against Neofusicoccum laricinum, the causal pathogen of larch shoot blight. Using Rose Bengal medium as the basal medium, key fermentation factors, including carbon source, nitrogen source, inorganic salts, and culture conditions, were optimized. Under the optimized fermentation conditions, the sterile fermentation filtrate of T. hamatum T2 exhibited an inhibition rate of 78.8% against N. laricinum, compared with 28.0% obtained using the unoptimized PDA medium. In pot experiments, T2 treatment reduced disease incidence from 76.67% to 16.67%, with a control efficacy of 78.26%. In field trials, the control efficacies were 53.33% in 2024 and 60.26% in 2025. Following pathogen inoculation, T2 treatment significantly increased POD and SOD activities in larch needles, and promoted the accumulation of flavonoids and total phenols. T2 treatment also elevated GR activity, as well as the contents of non-structural carbohydrates, soluble sugars, starch, and proline. Response surface methodology effectively optimized the fermentation conditions of T2. This fungus enhances host resistance by inducing the plant antioxidant system and secondary metabolism, exhibiting promising potential for the biological control of larch shoot blight.
The expanding U.S. crop production of urdbean (Vigna mungo L. Hepper.), a protein-rich East Asian legume (Gowda et al. 2013), presents a unique opportunity to document Vigna pathogens. In August 2022, small chlorotic foliar lesions with brown to black centers and yellow halos were observed on urdbean accession lines PI518264 and PI377394 in a field plot of 0.006 hectares in Boone County, IA. Disease incidence ranged from 30% to 75% of affected plots. Symptomatic leaves with >10% lesion severity were collected for analysis. Leaf surfaces were disinfected with a 5% NaOCl wash, rinsed with autoclaved distilled water, and sectioned into 1 x 1 mm fragments containing infected tissue. Fragments were placed on Potato Dextrose Agar (PDA) and incubated at room temperature under ambient light. After 7-14 days, orange to red velvety colonies emerged. Mycelia were transferred to Water Agar for 2 days, then hyphal-tipped and transferred to PDA. Plates were incubated at room temperature for 7-14 days, and five representative isolates were selected for morphological and molecular identification. The isolates exhibited velvety mycelium ranging from orange to brown, with an orange pigment diffusing into the PDA. After 14-21 days, black sporodochia formed, producing globular conidia measuring 15-20 µm. Based on morphology, the isolates E_A2, and E_EHB were identified as Epicoccum sp. DNA was extracted using 50 µl of Prepman Ultra Sample Reagent (Applied Biosystems, Foster City, California, USA). The rDNA internal transcribed spacer (ITS), large subunit (LSU), RNA polymerase II second largest subunit (RPB2), actin (ACT), β-tubulin 2 (TUB2), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) regions were amplified by PCR using the primer pairs ITS-1F/ITS-4, ITS5/TW13 FRPB2-5F/FRPB2-7R, ACT-512F/ACT-783R, Bt2A/Bt2B, and GDF/GDR, respectively. Phylogenetic trees of concatenated sequences, the best fit-partition scheme, and substitution models were selected by PartionFinder2 (Lanfear et al. 2016) and Bayesian Inference done by MrBayes 3.2 (Ronquist et al. 2012) both integrated in Phylosuite v2 (Zhao et al. 2025) with all its dependencies. Sequences were deposited in GenBank (accession nos. PZ357005:PZ357006, PZ437652:PZ437653, PZ452804:PZ452805, PZ787846:PZ787847, PZ452811:PZ452812, and PZ787844:PZ787845). To confirm the pathogenicity of the Epicoccum strains, 10 urdbean plants from accessions PI518264 and PI377394 were grown in 10 x 10 cm pots with professional greenhouse potting mix (Sungrow, Agawam, MA) under standard greenhouse conditions. At 25 days (V2 growth stage), plants were inoculated with a spore suspension (10 6 conidia/mL) sprayed twice, two days apart. Control plants received autoclaved distilled water. Inoculated plants were covered with plastic domes for 96 h, misted every 4-8 h, and kept in darkness for 24 h post-inoculation. After dome removal, plants were placed into a growth chamber (25ºC, 16 h light cycle, 85% RH) for 7-30 days. One week post-inoculation, brown to red spots appeared on inoculated leaves, while controls remained symptom-free. Epicoccum tobaicum was reisolated from symptomatic tissue with a 78% frequency, confirming its role as the pathogen. Studies have reported E. tobaicum (syn. E. layuense) as a brown leaf spot-causing on hosts such as Camellia sinensis (Chen et al. 2020), and Avena sativa (Jeong et al. 2023). Epicoccum tobaicum belongs to E. nigrum complex species and was formally described as a new species within the genus Epicoccum in 2017 (Chen et al. 2017). This is the first report of E. tobaicum causing disease on urdbean in the U.S., posing a potential threat to crop productivity.
Blueberries (Vaccinium spp.), economically important fruit crops with rich nutritional properties, have been extensively cultivated in China in recent years (Zhou et al. 2025). In November 2023 to March 2024, blossom blight was observed on blueberries in plastic tunnels in Honghe Hani and Yi Autonomous Prefecture (23.68° N, 102.77° E), Yunnan, China. The disease incidence ranged from 8% to 14%. Infected blueberry petals showed necrotic lesions and covered with a brownish mold layer under high humidity. Some blossoms shriveled and remained adherent to the fruit, with stunted fruit development. Symptomatic blossom blight samples were excised from lesion margins, surface-sterilized with 75% ethanol for 45 seconds, rinsed three times with sterile distilled water, then placed onto 25% lactic acid-supplemented potato dextrose agar (PDA). After incubating at 25°C for 3 days, hyphal tips from the colony margins growing out of diseased tissues were transferred onto fresh PDA. Seven morphologically similar isolates were obtained. The colonies were subcircular with abundant aerial mycelia at 25°C, being dark gray on PDA and light gray on oatmeal agar (OA) at 7 days post inoculation (dpi). Isolate JSLMG6-1 was randomly selected for identification and pathogenicity assay, with mycelial growth rates of 9.6 and 5.3 mm/d on PDA and OA at 25°C, respectively. For sporulation, it was incubated on V8 agar at 25°C in darkness for 5 days, followed by continuous UV irradiation at 25°C for another 9 days. Pycnidial conidiomata were globose to subglobose, 71.1-124.6 μm in diameter, ostiolate, with walls of pale brown to dark brown textural angularis. Conidia were short cylindrical or slightly reniform, straight to slightly curved, nonseptate, hyaline, mearing 7.3-17.2 × 2.6-5.0 μm (mean 10.3 × 3.7 μm). The morphological characteristics were similar to those of Stagonosporopsis caricae (Aveskamp et al. 2010; Bracale et al. 2020; Zhang et al. 2023). DNA fragments of internal transcribed spacer (ITS), calmodulin (CAL), chitin synthase I (CHS), and β-tubulin (BTUB) were amplified and bidirectionally sequenced (Han et al. 2026). The sequences were deposited in GenBank (accession nos. PX904963, PX905966-PX905968). Bayesian inference phylogeny based on concatenated ITS, CAL, CHS, and BTUB sequences showed that the isolate JSLMG6-1 clustered together with four previously reported strains of S. caricae, including CBS 102399, CBS 248.90, PS1-1, and RV16 (Stewart et al. 2015), and formed an independent clade supported by a posterior probability value of 1. Thus, the isolates from blueberry blossom blight samples were identified as S. caricae. Pathogenicity tests were conducted on unwounded blueberry blossoms, fruits, and leaves of tissue-cultured plantlets using 5-mm mycelial plugs of JSLMG6-1 (controls: PDA plugs). Inoculated materials were incubated at 25°C under a 14/10 h photoperiod with >80% relative humidity. Six replicates per treatment, the experiment was repeated twice. Necrotic lesions developed at all inoculated sites on blossoms (4 dpi), fruits (10 dpi), and leaves (10 dpi), while PDA controls remained healthy. S. caricae was re-isolated from diseased tissues and confirmed by morphological and molecular identification. To our knowledge, this is the first report of S. caricae causing blueberry blossom blight in China. S. caricae could also be a potential pathogen of blueberry fruit rot and leaf spot. This study is crucial for the diagnosis and management of blueberry diseases.
Nepeta cataria (catnip; Lamiaceae) is a perennial herb naturalized in Europe, Asia, and North America. It is cultivated as a medicinal and ornamental plant and is valued for attracting pollinators, repelling certain insect pests, and its attractiveness to cats (Gomes et al., 2020). During the fall of 2019 and 2020, powdery mildew was observed on multiple catnip cultivars at the Rutgers University Snyder Research Farm, Pittstown, NJ. The disease was again observed from January 2025 onward on greenhouse-grown catnip at Rutgers University, New Brunswick, NJ. Symptoms consisted of white powdery colonies on adaxial and abaxial leaf surfaces and petioles that coalesced into large patches. Severely infected leaves became chlorotic, necrotic, papery, and prematurely defoliated. Disease incidence was 100% on catnip plants with an average disease severity of 60% leaf area affected. Morphological characteristics of isolate CR-1 isolated from catnip 'CS75', were consistent with Golovinomyces spp. (Braun and Cook, 2012). Hyphae were hyaline, 5–8 μm wide, with slightly nipple-shaped appressoria. Conidiophores measured 55–145 × 10–14 μm. Foot cells measured 50–100 μm and were mostly curved at the base. Conidia (n = 30) were catenescent, ellipsoid to doliiform, produced in chains of 3–5, and measured 25.2–40.0 × 15.6–26.2 μm. Fibrosin bodies and chasmothecia were not observed. To confirm identification, the internal transcribed spacer (ITS) and large ribosomal subunit (28S) rDNA regions were amplified using JumpStart Taq Ready Mix (Millipore Sigma) with primers ITS5/P3 and LSU1/LSU2 (Bradshaw and Tobin, 2020). ITS amplicons were purified (Monarch DNA Gel Extraction Kit, New England Biolabs), re-amplified with PM5G/PM6G (Scholler et al., 2016), and sequenced. Sequences were deposited in GenBank under the accessions PZ595194 (ITS) and PZ595195 (28S). Blast searches showed 99-100% identity with Golovinomyces spp. (GenBank: ITS: AB769437.1; GenBank:28S: LC076831.1). Concatenated ITS and 28S sequences were aligned with members of the Golovinomyces biocellatus complex (Scholler et al., 2016; Takamatsu et al., 2013). Maximum-likelihood analysis in MEGA12 (Kumar et al., 2024) placed isolate CR-1 within the Golovinomyces monardae clade with 95% bootstrap support. A voucher specimen was deposited in the U.S. National Fungus Collections, USDA-ARS, Beltsville, MD (accession no. BPI 937340). To fulfill Koch's postulates, infected catnip 'CS75' leaves were pressed onto healthy 'CS75' leaves. Ten plants were inoculated, and ten non-inoculated plants served as controls. Plants were maintained in an indoor grow room at 23°C, 50% relative humidity, and a 14-h photoperiod. Powdery mildew developed on inoculated plants within 6–8 days, whereas control plants remained symptomless. The reisolated powdery mildew was sequence and morphologically identical to the original isolate. The pathogenicity assay was repeated twice with similar results. G. monardae has previously been reported on mountain mint and spearmint (Lamiaceae) in the United States (Klingeman et al., 2018; Rajmohan et al., 2019). Catnip may serve as an inoculum reservoir for economically important mint crops, making accurate species identification important for disease management. To our knowledge, this is the first report of G. monardae causing powdery mildew on catnip in the United States.
Astragalus membranaceus (Fisch.) Bge. (Fabaceae), an important medicinal plant widely cultivated in China, is valued for its roots, which are extensively used in traditional medicine. In August 2023, a red core disease was observed in commercial A. membranaceus fields in Sanying Town, Guyuan City, Ningxia Hui Autonomous Region, China (36°32′N, 106°24′E). Affected plants showed no visible symptoms on the root surface, whereas internal tissues exhibited distinct reddish-brown discoloration. The disease occurred throughout the growing season. In a surveyed field of approximately 1 ha, disease incidence reached about 40%, with a disease severity of approximately 70%. Symptomatic roots were collected and cut into 5-cm segments. Root pieces were surface-sterilized in 75% ethanol for 1 min, followed by 1.5% sodium hypochlorite for 3 min, rinsed three times with sterile distilled water, and aseptically split longitudinally. Tissues were placed onto Luria–Bertani (LB) agar and incubated at 37°C for 24 h. Four bacterial isolates were consistently obtained. A representative isolate, designated EMM901, was selected for further characterization. Colonies on LB agar were circular, yellow, and mucoid. Cells were rod-shaped, Gram-negative, and measured approximately 0.40–0.52 × 1.12–1.69 μm. Biochemical tests showed positive reactions for glucose utilization, cellulase activity, yellow pigment production, and growth at 37°C, whereas methyl red reaction, gelatin liquefaction, and Gram staining were negative. Based on morphological and biochemical characteristics, the isolate was preliminarily identified as Pantoea sp. For molecular identification, the 16S rRNA gene and a partial gyrB gene of strain EMM901 were amplified and sequenced. The resulting sequences were deposited in GenBank under accession numbers PZ055100 (16S rRNA gene) and PX789892 (partial gyrB gene). Phylogenetic analyses based on the 16S rRNA and gyrB gene sequences showed that strain EMM901 clustered with reference strains of Pantoea agglomerans in GenBank, confirming its taxonomic identity. Pathogenicity was assessed using a needle-inoculation assay. A bacterial suspension of EMM901 (1×10⁸ CFU/mL) was injected into healthy, unwounded roots of A. membranaceus seedlings. Control plants were inoculated with sterile distilled water. Inoculated seedlings were maintained in a greenhouse at 25 °C with 65–70% relative humidity. Typical red core symptoms identical to those observed in the field developed in inoculated plants within 7–10 days, whereas control plants remained symptomless. The pathogenicity test was repeated twice with consistent results. The bacterium was re-isolated from symptomatic roots (Fig. 3), and its morphological traits and DNA sequences were identical to those of the original isolate, thereby fulfilling Koch’s postulates. Pantoea agglomerans has been reported to cause diseases on various plant hosts (Fan et al. 2022; Zhang et al. 2022; Yan et al. 2024; Sepúlveda et al. 2023). To our knowledge, this is the first report of red core disease of A. membranaceus caused by Pantoea agglomerans in China. Identification of the causal agent provides a basis for disease diagnosis and management for Astragalus production.
Demethylase inhibitor (DMI) fungicides have been implicated in the emergence of triazole-resistant Aspergillus fumigatus (TRAF) in agricultural environments. To assess whether propiconazole (a triazole DMI) application exerts selective pressure for TRAF, field trials were conducted in strawberry and snap bean crop production systems. Three different treatments (T1, four (strawberry) three (snapbean) applications; T2, two (strawberry) one (snapbean) applications; and T3, no application) were applied at labelled rates. Soil samples were collected at baseline and after each fungicide application and screened for A. fumigatus and TRAF isolates. Linear mixed-effects models revealed no significant alteration in A. fumigatus counts (colony forming units/gram of soil) across treatment intensities, indicating that propiconazole application did not impact overall A. fumigatus population levels. Significant variation was noted across time points, though without a consistent trend. Four putative TRAF isolates were recovered from propiconazole field trials and one from the control field; all exhibited resistance to tebuconazole and propiconazole, with cross-resistance to medical triazoles. Multiplex qPCR assay using commercial AsperGenius kit identified two isolates harboring TR34/L98H environmental mutation in the cyp51A gene, while three isolates were identified as A. fischeri, which belongs to Aspergillus Section Fumigati. Despite the abundant presence of A. fumigatus in strawberry and snap bean compost samples, no TRAF were recovered at any sampling stage. These findings suggest that while propiconazole use does not significantly alter A. fumigatus population dynamics, further investigations are required into environmental selection pressures and resistance mechanisms.
Rice blast can affect different plant organs, including leaves and necks. Leaf blast epidemics mainly occur in the early, vegetative stage of crop growth, whereas neck blast appears after heading, when disease severity on leaves in general is declining and low. This typical sequence therefore leads to questioning the extent to which airborne inoculum originating from diseased leaves contributes to neck infection. Two microfield experiments were conducted to address this question. Leaf blast epidemics with differing onset times were artificially generated on two susceptible varieties (Co39 and IR50). In each microfield, the upper parts of 22 tillers (boot and flag leaf) were bagged at booting stage for three weeks, resulting in a physical protection of the neck nodes from airborne inoculum. Neck blast was assessed immediately after the bag removal. Levels of leaf and neck blast were higher in the first than in the second experiment. In both experiments, leaf blast dynamics displayed an increase, a plateau, then a decrease in disease severity; both leaf and neck blast levels were higher in Co39 than in IR50, and were highest when epidemic onset on leaves was early (at seedling); and neck blast was observed in protected panicles, but its average incidence (28%) was about half of that on un-protected panicles. These results suggest the concomitant occurrence of neck infection from airborne propagules, as well as from within-tiller, non-airborne disease transmission. These results and their potential implications for disease management are discussed in the context of epidemiological hierarchies from plant to landscape.
Cold-hardy interspecific hybrid grapevines (CIHG; Vitis spp.) have expanded grape production in Northern regions of the United States, but mature vineyards in the upper Midwest are increasingly showing grapevine trunk disease-like symptoms, including cordon dieback, skipped spurs, stunted shoots, and vascular discoloration. Previous surveys recovered Fusarium spp. at high frequency from symptomatic CIHG tissues, but their roles as causal agents for vine decline remained unclear. In this study, we characterized Fusarium isolates recovered from symptomatic CIHGs in Iowa vineyards and evaluated their pathogenicity on grapevines and barley. Phylogenetic analysis of concatenated tef1 and rpb2 sequences resolved 88 CIHG-associated Fusarium isolates into 13 species-level lineages across four species complexes, with most isolates belonging to the F. sambucinum species complex and clustering within the F. graminearum clade. Representative isolates of F. graminearum, F. nanum, F. oxysporum, and F. sporotrichioides caused vascular lesions on both CIHG ‘Itasca’ and V. vinifera ‘Chardonnay’, with descriptively greater lesion lengths observed on ‘Itasca’, particularly at the later sampling time. Over 80 grapevine-associated Fusarium isolates were also evaluated on barley florets and/or seedlings. Approximately 40% of the isolates caused greater than 50% floret infection, and 70% exhibited seedling pathogenicity comparable to or greater than that of the positive control strain F. graminearum PH-1, indicating potential host overlap between grapevines and cereal crops. These findings support Fusarium spp. as causal agents of decline symptoms in CIHGs and suggest that Midwestern vineyards may be exposed to diverse Fusarium populations with relevance to both specialty and cereal crop systems.
Sclerotinia sclerotiorum, the causal agent of white mold, is a globally distributed fungal pathogen responsible for major yield losses in many crops. Spray-induced gene silencing (SIGS) has emerged as a promising alternative for disease control. Building on prior research, this study advanced SIGS by targeting S. sclerotiorum argonaute 2 (SsAgo2), using FF4 (PAZ domain to 5'-PIWI domain) and FF5 (PIWI central domain) fragments which are important regions involved in RNA binding and cleavage. We optimized spray tank mix/dilution in the greenhouse and scaled up dsRNA production using E. coli. The greenhouse results demonstrated that dsRNA with nanosheets significantly inhibited white mold disease on tomato and N. benthamiana compared to empty vector control (p = 0.03 and 0.004, respectively). To evaluate off-target effects, SIGS was tested on Botrytis cinerea, a related necrotrophic pathogen. No significant differences in lesion size were observed between SsAgo2 dsRNA-treated and water-treated Nicotiana benthamiana leaves. Gene ontology analysis of differential expressions in sunflower leaves revealed no significant differences between SsAgo2-FF4 or SsAgo2-FF5 compared to control. Field trials in 2024 demonstrated effectiveness. Parameters assessed included disease severity, wet weight, head width, and seed weight. Area under the disease progress curve (AUDPC) analysis revealed that dsRNA sprays, applied before and after manual inoculation or during natural infection, significantly reduced infection levels with p < 0.1 as the cut off. Sunflower fresh weight increased by 104.4 g (p = 0.04) and 96.7 g (p = 0.07), while head width increased by 2.5 cm (p = 0.03) and 1.5 cm (p = 0.10), respectively. This report demonstrates that the dsRNA mixture has potential to incorporate SIGS into field applications for the management of white mold disease.
Foliar fungicides remain a cornerstone of disease management in modern crop production systems, yet their field performance can be inconsistent and difficult to predict. While fungicide efficacy is often attributed to product choice and application timing, environmental conditions may alter spray deposition, uptake, movement within plants, host physiology, and pathogen development. As agricultural systems face increasing climatic variability, understanding how environmental factors affect foliar fungicides is critical for reliable disease control and yield protection. This review examines the mechanistic basis of fungicide-plant interactions, including mode of action, uptake, redistribution, and effects on plant metabolism and defense. It also synthesizes current knowledge on how environmental stress modifies foliar fungicide performance across field crop systems, focusing on the roles of temperature, leaf wetness, rainfall, humidity, solar radiation, drought, and wind in influencing fungicide retention, absorption, redistribution, and persistence. Evidence from diverse agricultural systems demonstrates that environmental conditions can enhance or diminish fungicide effectiveness and, in some cases, mask poor fungicide performance or create the illusion of effective disease control. This review highlights practical strategies to improve fungicide reliability under challenging conditions. By clarifying how environmental factors interact with plant and fungicide biology, this review provides a foundation for interpreting field outcomes and guiding future efforts to improve fungicide reliability under variable agroecosystem conditions.
Pholiota conissans is an economically important edible mushroom in China; however, its production has been severely impacted by cobweb disease during the fruiting stage, leading to substantial yield losses. In this study, a fungal pathogen was identified as the causal agent of cobweb disease. The strains were isolated from infected fruiting bodies collected in November 2021 and were identified as a new species Cladobotryum hypsigum sp. nov., based on morphological characteristics and a multi-locus phylogenetic analysis of four gene regions (ITS, RPB1, RPB2, and TEF). Pathogenicity tests were conducted by inoculating healthy mushrooms with a spore suspension of representative isolates. The resulting symptoms were consistent with those observed in cultivation settings, and the same pathogen was successfully re-isolated, thus fulfilling Koch’s postulates. Biological characterization indicated that the optimal conditions for mycelial growth were a temperature of 25°C and pH 5. Sucrose and yeast extract were the most suitable carbon and nitrogen sources, respectively. In vitro fungicide sensitivity assays, performed using the hyphal growth inhibition method against six common fungicides, demonstrated that Carbendazim was the most effective agent. The IC50 values for Carbendazim were 0.7742 µg/mL for the pathogen and 4.827 µg/mL for the host mushroom, indicating significant selectivity. These findings provide a scientific basis for developing effective strategies to manage cobweb disease in P. conissans cultivation.
Cercospora leaf blight (CLB) is the most devastating foliar disease of soybean in the US Gulf South, causing significant economic impacts throughout the growing region. The sole causal agent of CLB was thought to be Cercospora kikuchii, but we now recognize that the disease is predominantly caused by Cercospora cf. flagellaris and Cercospora cf. sigesbeckiae in North America. However, a lack of information about the spatial population dynamics of the causal agents and the disease cycle, including the most important sources of inoculum, hinders the development of new and effective management tools. Species-specific detection/quantification assays are a first step towards addressing these epidemiological knowledge gaps. By quantifying pathogen presence both spatially and temporally, we can better elucidate the disease cycle and identify targets for developing precise disease management tools. A TaqMan quantitative polymerase chain reaction (qPCR) assay was developed for C. kikuchii prior to the discovery that C. cf. flagellaris and C. cf. sigesbeckiae are the principal causal agents, but we found the assay was not species-specific, detecting both C. kikuchii and C. cf. flagellaris. Therefore, new TaqMan qPCR assays were developed for C . cf. flagellaris, C. cf. sigesbeckiae, and C. kikuchii by leveraging comparative genomics. The assays were species-specific and had a detection limit of ~3-7 pg/µl DNA, which corresponded to approximately 100 conidia. PCR efficiencies were between 93-105% for genomic DNA and 83-110% for conidial samples, depending on the assay. These assays can be used for the quantification of CLB pathogens to ultimately guide effective CLB disease management.
Yam (Dioscorea spp.) is an economically important tuber crop in China, yet the identity, relative abundance, and molecular characterization of the dominant endoparasitic nematode taxa constraining its production remain insufficiently documented. Rhizosphere soil (n = 110) and yam tubers (n = 48) were sampled from nine localities across Jiangxi and Shandong provinces between April 2020 and January 2021. Community structure was quantified using prominence value (PV), mean population density (MPD), and frequency of occurrence (FO). Morphological identification used standard taxonomic keys and light microscopy for the primary focal taxon, Pratylenchus coffeae. Species-level confirmation employed PCR amplification of the internal transcribed spacer (ITS) and D2-D3 expansion segment of 28S ribosomal DNA (rDNA), followed by Bayesian phylogenetic inference, with full morpho-molecular characterization applied to P. coffeae as the principal endoparasitic taxon and supporting molecular confirmation provided for co-occurring taxa. Three primary endoparasitic taxa were recovered: Pratylenchus coffeae was the most abundant and prominent endoparasitic nematode recovered from yam tubers, followed by M. incognita, with R. reniformis recovered at comparatively low abundance; P. coffeae likewise dominated the rhizosphere soil community. At the aggregate level, Pratylenchus coffeae was the most prominent endoparasitic nematode across surveyed Chinese yam systems, surpassing M. incognita in both prominence value and frequency of occurrence. However, dominance patterns varied between provinces: P. coffeae was overwhelmingly prevalent in Jiangxi, while M. incognita dominated in Shandong. Thus, no single species is the principal endoparasite across both provinces. This study delivers the first molecularly verified baseline for the prominent endoparasitic nematode complex of Chinese yams, providing a replicable diagnostic framework for surveillance, phytosanitary monitoring, and integrated pest management.
In September 2025, a total of 15 soybean fields were surveyed in Muan and Gongju, Korea. Irregular leaf blight symptoms were observed in five fields, with approximately 1–10% of soybean plants showing symptoms in each affected field. To isolate the causal pathogen, symptomatic leaf tissue was surface-disinfected with 1% NaOCl for 1 min, rinsed with sterile distilled water, and placed on potato dextrose agar (PDA). The plates were incubated at 20℃ for 7 days, and olive-brown hyphae growing from the tissues were subcultured twice on PDA. Five isolates with similar morphology were obtained from symptomatic leaves, and one representative isolate, DA17-37, was selected for further morphological, molecular, and pathogenicity analyses. The conidia were predominantly oval to ellipsoidal and aseptate, measuring 3.71-6.45 x 1.77-2.83 μm, with a mean size of 5.11 x 2.14 μm (n=30). The ascospores were mostly oval and 1-septate, measuring 12.49-18.25 x 4.13-5.41 μm with a mean size of 15.08 x 4.48 μm (n=30). Additionally, multicellular chlamydospores were observed. Overall, these morphological characteristics were consistent with those of the genus Didymella. To genetically characterize isolate DA17-37, genomic DNA was extracted, and the internal transcribed spacer (ITS), beta-tubulin (tub2), and RNA polymerase II second largest subunit (rpb2) genes were amplified by PCR using the respective primer sets described previously (Gorny et al. 2016; Liu et al. 1999; Woudenberg et al. 2009). The resulting sequences were deposited in GenBank under accession numbers PZ274701, PZ433240, and PZ439292. Maximum likelihood phylogenetic analysis of the concatenated dataset showed that isolate DA17-37 clustered with the reference strains of Didymella americana. To confirm the pathogenicity of isolate DA17-37, a conidial suspension (1 x 10 6 conidia/mL) prepared from 30-day-old PDA cultures grown at 20℃ was sprayed onto 2-week-old potted soybean plants. Control plants were sprayed with sterile distilled water. The inoculated plants were incubated in a dew chamber at 26℃ for 3 days and then transferred to a growth chamber maintained at 26℃ and 70% relative humidity under a 16-h photoperiod. Symptoms first appeared at 7 days post-inoculation (dpi), and representative symptoms showing disease progression were photographed at 14 dpi, whereas the uninoculated control plants remained healthy. To satisfy Koch’s postulates, the same pathogen was re-isolated from symptomatic leaves and identified based on morphology and DNA sequence analysis. Didymella americana has been reported as a causal pathogen of leaf blight on lima bean in the United States. To the best of our knowledge, this is the first report of leaf blight caused by D. americana on soybean in Korea. Continued monitoring is needed to assess the potential spread of this disease in Korea and to support the development of appropriate disease management strategies.
Cytospora canker, primarily caused by Cytospora plurivora D.P. Lawr. L.A. Holland & Trouillas is one of the most destructive diseases of peach (Prunus persica [L.] Batsch), a crop with significant economic and cultural importance in Colorado. Canker pathogens including Cytospora spp. are a major driver of reduced productivity and longevity of orchards worldwide, yet management options are limited. Fungicides can be used to protect pruning wounds from infection but have primarily been tested as hand sprays which are labor intensive and therefore expensive. Air blast sprayers are currently used by growers to manage other diseases and pests and for nutrient applications; however, their efficacy on canker pathogens is not well understood. Additionally, methods for application on woody tissue may differ from foliar sprays. This study evaluated the efficacy of canopy spray applications of captan and lime sulfur in preventing infections on scaffold branches and examined the effects of application timing and axial fan use on spray coverage and uniformity. In spring trials, 3% lime sulfur significantly reduced lesion size by 58% on middle branches and 87% on upper branches, whereas captan (3.5 liters per hectare) showed mixed results. The rate of application may have been insufficient. Minimal lesion development occurred in fall trials, and neither treatment was significantly different from untreated controls. Discrepancies in efficacy across heights were linked to uneven distribution of spray coverage. In coverage trials, spray coverage, as measured by water sensitive paper cards, varied significantly by season, height, and orchard. Greater coverage was achieved on bare trees in spring compared to foliated trees in summer. Axial fan use improved coverage in some cases but decreased it in others. The results from this study will help inform future trials and aid peach growers in developing management programs for Cytospora canker.
