Phytopathology最新文献

Insect vectors are increasingly recognized as overlooked drivers of postharvest disease spread. Ceratocystis fimbriata, the causal agent of sweetpotato black rot, can spread rapidly in postharvest environments. Previous work established that Drosophila hydei can acquire viable C. fimbriata propagules both externally and internally, identifying this fly as a potential vector in storage facilities. Here, we expand on that finding by testing whether vector density influences disease transmission and by developing molecular diagnostic assays to improve pathogen detection. Transmission assays were conducted with four fly densities (10, 30, 50, and 80 flies) exposed to inoculum sources and then transferred to clean targets (sterile agar and uninfected sweetpotatoes, with and without wounds). Transmission occurred regardless of fly density, indicating that even small populations are sufficient to spread the inoculum, although incidence was significantly higher in wounded roots. To complement these assays, we standardized qPCR assays using dual-quencher probes targeting two C. fimbriata-specific markers (T3G9 and T5G26). Pathogen DNA was detected in both flies and asymptomatic roots, with the more sensitive marker identifying latent infections that were not visible through symptoms. Together, these results demonstrate that D. hydei vectors C. fimbriata in a density-independent manner, that wounding increases the success of infection, and that qPCR diagnostics can detect transmission events that are overlooked by visual assessment. These findings provide new epidemiological insight into postharvest black rot and support integrated management strategies that combine vector suppression with molecular surveillance.

The MYB transcription factor family is one of the largest gene families in plants and plays critical roles in how plants respond to biotic and abiotic stresses. However, the functions of MYB members in high-temperature seedling plant (HTSP) resistance in wheat to Puccinia striiformis f. sp. tritici (Pst) are not well understood. Previously, TaMYB73, an MYB transcription factor, was identified through an RNA-sequencing study of the wheat cultivar Xiaoyan 6 under infection by Pst. In this work, we characterized the molecular function of TaMYB73. The expression TaMYB73 was upregulated following Pst inoculation and high-temperature treatment. Silencing TaMYB73 resulted in an increased number and size of uredinia, a downregulation of salicylic acid (SA)-responsive genes TaPR1 and TaPR2, and a compromised HTSP resistance to Pst. Conversely, transient overexpression of TaMYB73 in wheat enhanced resistance to Pst by reducing fungal biomass and upregulating TaPR1 and TaPR2. The induction of TaMYB73 by SA and its regulation of SA-responsive genes suggest that it may play a role in the SA signaling pathway. Subcellular localization assays confirmed that TaMYB73 is located in the nucleus. Furthermore, yeast two-hybrid, bimolecular fluorescence complementation, and luciferase complementation assays demonstrated that TaMYB73 can form homodimers. Taken together, our findings establish TaMYB73 as a positive regulator of HTSP resistance in wheat. This work provides important insights into the molecular mechanisms of wheat HTSP resistance to Pst and offers strategies for improving wheat's resistance to this pathogen.

Cotton is a major crop in the southern United States, where Meloidogyne incognita is the most damaging nematode pathogen. Recently, two emerging root-knot nematode species, M. floridensis and M. enterolobii, have been detected in Georgia, raising concerns about their impact on current cotton cultivars. To address this, we evaluated the susceptibility of 12 commercial cotton cultivars to M. enterolobii, M. floridensis, and M. incognita under greenhouse conditions. The susceptible tomato cultivar 'Rutgers' was included as a positive control. Three-week-old cotton plants were individually inoculated with 5,000 eggs of a single nematode species and arranged in a randomized complete block design with six replications. Shoot and root biomass, gall severity, total egg count, and reproduction factor (RF) were assessed. Seven cultivars were resistant (RF < 1) to M. floridensis, and six were confirmed to be resistant to M. incognita. However, none was resistant to M. enterolobii. Among the three species, M. enterolobii caused the most severe galling and highest nematode reproduction, underscoring its aggressive nature and ability to overcome resistance mechanisms effective against other species. This is the first report to systematically compare and assess cotton cultivar responses to M. floridensis and M. enterolobii, providing critical insight into the species-specific susceptibility of these popular modern cultivars. These findings reveal a major vulnerability in current commercial cultivars and emphasize the urgent need to screen diverse genetic material for novel resistance to M. enterolobii, a rapidly emerging threat to cotton production in the southeastern United States.

Eugenol exhibits a broad spectrum of antimicrobial activities and fungicide efficacy against crop diseases. However, the antifungal mechanisms of eugenol remain incompletely understood. In this study, we assessed the inhibitory activity of eugenol against several phytopathogenic fungi and found it to be particularly effective against Botrytis cinerea. The half-maximal effective concentration for inhibiting the hyphal growth of B. cinerea was determined to be 72.11 µg/ml. Eugenol exhibited a significant inhibition effect of 66.72 and 43.62% against gray mold on tomato fruits and leaves at the 1,500.0 µg/ml dose. Micromorphological analysis revealed that eugenol induced abnormalities in hyphal structures, including disrupted cell membranes and unclear organelle boundaries. Transcriptomic analysis indicated that differentially expressed genes in hyphae treated with eugenol were primarily enriched in processes related to lipid metabolism, transmembrane transport, and electron transfer activity. Molecular docking studies suggested that eugenol may bind to oleate delta-12 desaturase (FAD2) with a low free energy of -9.9 kcal/mol. Assays of cell membrane permeability and hyphal staining confirmed that eugenol disrupts the cell membrane, resulting in leakage of hyphal contents. A quantitative PCR assay showed that eugenol significantly altered the expression of genes involved in lipid metabolism. Compared with the wild type, the fad2 mutant displayed slower hyphal growth rates and became less sensitive to the effects of eugenol. This study demonstrates that eugenol targets FAD2 and disrupts cell membrane integrity, thereby inhibiting the proliferation of B. cinerea. Several formulations of eugenol, including feneptamidoquin or meridianin C, exhibit stronger inhibitory effects, offering promising potential for the control of gray mold.

Osthole exhibits strong inhibitory activity against phytopathogenic fungi; however, its antifungal mechanism remains unclear. This study assessed osthole's inhibitory effects on several phytopathogenic fungi, revealing a half-maximal effective concentration of 73.03 μg/ml against the hyphal growth of Botrytis cinerea. Micromorphological analysis showed that osthole caused abnormalities in the hyphae, including unclear organelle boundaries and organelle dissolution. Integrated transcriptomic and metabolomic assays and correlation analysis indicated that osthole induced differentially expressed genes and differentially abundant metabolites, which were enriched particularly in the pathways of glyoxylate and dicarboxylate metabolism, tyrosine metabolism, glycerophospholipid metabolism, fructose and mannose metabolism, citrate cycle, biosynthesis of unsaturated fatty acids, and ABC transporters. Molecular docking and molecular dynamics simulation assays demonstrated that osthole binds stably to amidase, a key enzyme in energy metabolism, with a relatively lower binding energy of -8.5 kcal/mol compared with osthole's analogs, suggesting that amidase may be a potential target protein in the fungus. A microscale thermophoresis assay indicated that the dissociation constant (Kd) value for osthole binding to amidase was significantly lower compared with that of osthole's analog 7-methoxycoumarin. Overall, this study demonstrates that osthole disrupts energy metabolism, nitrogen metabolism, substance transport, and the metabolism of the hyphal cell wall and cell membrane, potentially targeting the amidase of B. cinerea. These findings highlight the potential of osthole for controlling gray mold.

Xylella fastidiosa (Xf) is the etiological agent of Pierce's disease (PD), a major threat to viticulture worldwide. The Xf prtA^- mutant, characterized by its planktonic phenotype and absence of biofilm formation, has been previously labeled as hypervirulent due to its aggressive symptomatology in the PD-susceptible Vitis vinifera 'Thompson Seedless'. This study challenges the hypervirulent concept by demonstrating that a diverse range of grapevine accessions, especially the PD line U0505, exhibited resistance to Xf prtA^-. Our findings suggest that different resistance mechanisms are present against the planktonic and biofilm phenotypes of Xf, as represented by the prtA^- Xf mutant and the wild-type Temecula1 Xf strain, respectively. This study underscores the complexity of host-pathogen interactions and highlights the importance of multiple host defense mechanisms in countering specific virulence strategies of Xf. The resistance assessed in the U0505 line against Xf prtA^- infection provides valuable insights into potential genetic and molecular targets for breeding PD-resistant grapevine cultivars and developing effective disease management strategies.

Fusarium crown rot (FCR), caused by Fusarium pseudograminearum, poses a significant threat to global wheat production. To elucidate the mechanisms driving FCR prevalence under drought and saline conditions and the distinct geographic distributions of 3-acetyl-deoxynivalenol (3AcDON) and 15-acetyl-deoxynivalenol (15AcDON) populations, this study investigated the biological characteristics of 40 F. pseudograminearum strains. These characteristics included conidiation capacity, pathogenicity, and responses to temperature, drought, and salt stress under simulated laboratory conditions. The results indicated no significant differences in conidial production or seedling pathogenicity between the two populations. Optimal mycelial growth occurred at 20 to 25°C, with the 15AcDON population exhibiting larger growth than the 3AcDON population, except at 15°C. Moderate drought stress significantly enhanced mycelial growth, particularly in the 15AcDON population, which showed significantly larger colony diameters than the 3AcDON population at 20 to 35% PEG6000 concentrations. Both populations showed strong tolerance to osmotic stress (1 M sorbitol) and moderate salt stress (1 M NaCl), though no genotype-specific differences were observed under these conditions. These findings highlight the role of temperature and drought in shaping the geographic distribution of F. pseudograminearum populations and provide insights into the environmental adaptability of the fungus, offering a scientific basis for predicting FCR epidemics under global climate change.

Within Phytophthora alni, an invasive pathogen of alders (Alnus spp.), three species have been identified. The most frequent and pathogenic species is P. × alni. It has a variable intraspecific structure, with dominance of the Pxa-1 genotype and the presence of dozens of rare genotypes (in most cases derived from Pxa-1). Its local populations are highly variable, and their population structure and development remain unknown. We compared two sets of strains isolated from identical sites during the epidemic (2005 to 2010) and post-epidemic (2020 to 2024) phases of the disease in the Vltava River basin (Czech Republic) and studied them using microsatellite marker analysis and fitness tests (sporangia production, growth, and virulence). We acquired 151 P. × alni isolates of 23 multilocus genotypes. We found that during the post-epidemic phase, genetic diversity decreased, and the dominance and incidence of the Pxa-1 genotype increased. Only the dominant genotype (Pxa-1) was repeatedly isolated from the same sites, whereas the rare genotypes were replaced. During the post-epidemic phase, both the incidence of rare genotypes and the degree of their derivation from Pxa-1 decreased. The rare genotypes had lower fitness than Pxa-1 (the more changes there were, the worse the fitness was). These results allow us to hypothesize the evolution of local populations of P. × alni in Europe, as the most pathogenic genotype, Pxa-1, will also prevail during the late phases of the disease, and the risk of further damage to the surviving host populations will persist.

Xanthomonas arboricola pv. pruni (Xap) is a well-known phytopathogenic bacterium responsible for bacterial spot in Prunus species. Although cherry has historically been listed as a potential host for this pathogen, the occurrence of Xap bacterial spot in cherry is rare. In the present study, two bacterial strains isolated from cherry in Montenegro and initially identified as Xap were subjected to genomic and pathogenicity analyses. The results showed substantial genetic divergence, along with distinct phenotypic profiles, between these strains and reference Xap strains known to be pathogenic in Prunus. These findings are consistent with recent studies reporting the existence of nonpathogenic, less virulent, or atypical strains of X. arboricola that had previously been misidentified as Xap due to limitations of previous diagnostic methods. The results, together with the historically low number of verified Xap infections in cherry and evidence that some strains may have been misidentified or confused with nonpathogenic or misclassified strains, contribute to the hypothesis that cherry may not be a highly relevant natural host for Xap and should therefore be reevaluated. This could have implications for monitoring strategies, risk assessment, and regulatory measures concerning Xanthomonas management in cherry cultivation. [Formula: see text] Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Field performance of winter wheat genotypes with quantitative resistance to Stagonospora nodorum blotch (SNB) is influenced by genotype-by-environment interactions (GEIs). This phenomenon explains why cultivars may perform inconsistently across environments, affecting decisions on locally adapted genotypes. Further, GEIs can also affect risk assessment when cultivar disease reaction is used as a model predictor under the assumption of stable responses across environments. Thus, this study investigated GEI effects on four disease metrics: final disease severity (SEV), relative area under disease progress stairs (rAUDPS), time to 50% disease incidence (T₅₀), and the apparent rate of disease increase (ω), describing SNB epidemics of 18 commercial soft red winter wheat cultivars planted in 18 environments in North Carolina from 2021 to 2024. Linear mixed models with various variance-covariance structures for random effects were used to analyze the disease data, and a third-order factor analytic model provided the best fit to the data across the metrics examined. Type B genetic correlation ([Formula: see text]), broad-sense heritability ([Formula: see text]), overall cultivar performance (OP), and global stability (expressed as root mean square deviation [RMSD]) were estimated using model outputs and the factor analytic selection tool method. For SEV, rAUDPS, and T₅₀, values of [Formula: see text] ranged from -0.15 to 0.99, with most environment pairs exhibiting high [Formula: see text] values, indicating an agreement in cultivar rankings, although some low [Formula: see text] values revealed rank instability and non-crossover GEI. Based on OP and RMSD, 'USG 3230' was the top-performing and most stable cultivar, whereas 'TURBO' and 'SH7200' were more unstable cultivars. Cultivar reaction classes derived from OP exhibited consistent class-level means of marginal predictions across environments with varying GEIs, supporting their utility as indicators of SNB susceptibility in risk assessment models. However, the presence of minor non-crossover GEI effects suggests that incorporating environmental drivers of GEI into SNB risk models could enhance prediction accuracy.