Search Results (274)

Cucurbit crops—including cucumber (Cucumis sativus), watermelon (Citrullus lanatus), and melon (Cucumis melo)—are of major economic and nutritional importance worldwide. Yet their productivity and quality are severely compromised by foliar fungal diseases, particularly powdery mildew (PM), downy mildew (DM), and target leaf spot (TLS). While PM and DM have been extensively studied, TLS has emerged as an increasingly prevalent and damaging disease in key production regions, yet it remains comparatively understudied—especially with respect to its molecular basis and comparative pathobiology relative to PM and DM. Current reliance on chemical fungicides is hampered by escalating pathogen resistance and concerns over residual toxicity, whereas conventional breeding approaches face inherent limitations in pyramiding durable, broad-spectrum resistance against multiple pathogens. In this context, cucumber has emerged as a pivotal model species for dissecting foliar disease resistance mechanisms in cucurbits, supported by a high-quality reference genome, extensive resequencing datasets, diverse germplasm collections, and an efficient Agrobacterium-mediated transformation system. Despite these advantages, existing reviews predominantly address PM or DM resistance in isolation; comprehensive syntheses integrating TLS resistance advances—and critically, cross-disease comparisons of genetic architecture, transcriptional reprogramming, and defense signaling—are notably scarce. Furthermore, the translational pipeline—from gene discovery and functional validation to deployment in marker-assisted or genome-edited breeding—lacks systematic evaluation. Here, we provide a focused, cucumber-centered review that (i) synthesizes recent progress in mapping QTLs and GWAS loci, and characterizing key resistance-associated gene families (such as NLRs, RLKs, PR genes) conferring resistance to PM, DM, and TLS; (ii) integrates transcriptomic, epigenomic, and proteomic evidence to delineate conserved versus pathogen-specific host responses; (iii) highlights breakthroughs and unresolved questions in TLS resistance research, including the roles of novel susceptibility factors and non-canonical immune regulators; and (iv) critically assesses bottlenecks in translating resistance genes into practical breeding outcomes—such as linkage drag, functional redundancy, and genotype-by-environment interactions—and proposes empirically grounded strategies for accelerating molecular design of multi-disease-resistant cultivars. Collectively, this review aims to bridge fundamental insights with applied breeding goals, offering a conceptual and strategic framework for integrated management of foliar fungal diseases and the development of durable, broad-spectrum resistance in cucurbits. Full article

Sunflower downy mildew, caused by Plasmopara halstedii, remains one of the most destructive diseases worldwide. The genetic diversity of P. halstedii populations continues to challenge resistance breeding efforts. This study evaluates the effectiveness of key resistance genes against P. halstedii isolates collected in Hungary. Eight isolates were tested using the sunflower differential lines HA-335, RHA-419, and RHA-340, with the resistance genes Pl6, Pl_Arg, and Pl8, respectively. Disease development was assessed by observing sporulation and symptoms including stunting, chlorosis, damping-off, and abnormal development at three time points after inoculation. Plant height was also measured to evaluate growth responses. The Pl6 resistance gene (HA-335) did not provide effective protection against any of the tested isolates, indicating that Pl6 does not confer reliable resistance against the Hungarian isolates examined in this study. The resistance conferred by Pl8 was not uniformly effective against the Hungarian isolates tested. This study provides the first report of Pl8-virulent P. halstedii isolates identified in both Hungary and Central Europe. The resistance gene Pl_Arg (RHA-419) conferred resistance to all tested P. halstedii isolates. These findings highlight the changing virulence profiles of P. halstedii populations in Hungary, emphasizing the need for ongoing pathogen monitoring and strategic use of resistance genes. Full article

Plasmopara viticola (Pv), the causal agent of downy mildew, is one of the most damaging pathogens affecting grapevine. Current control strategies largely depend on copper-based fungicides and synthetic chemicals, raising increasing concerns related to environmental sustainability and pathogen resistance. This study evaluated the efficacy of a novel Saccharomyces cerevisiae extract (U) as an inducer of resistance in the grapevine–Pv interaction. Microscopic observations revealed the ability of U to inhibit Pv spread over the leaf. Additionally, biochemical and molecular responses were analyzed in grapevine leaves subjected to four treatments: plants treated only with water (U⁻/Pv⁻; i.e., control) or U (U⁺/Pv⁻), inoculated with Pv (U⁻/Pv⁺), or both treated with U and then inoculated with Pv (U⁺/Pv⁺). Fully expanded leaves were sampled at 2-, 5-, 24-, and 72-h post inoculation (hpi). In U⁺/Pv⁻ leaves, jasmonic, salicylic and abscisic acid (JA, SA, and ABA), as well as hydrogen peroxide (H₂O₂) increased at 2 hpi (+44, +33, +38%, and 3-fold, respectively), accompanied by upregulation of pr1 (2-fold higher than control, respectively), suggesting the capacity of U to trigger the plant alert system. In U⁻/Pv⁺ leaves, peaks of JA and H₂O₂ occurred at 24 hpi (+40% and 4-fold higher than control), followed by marked ethylene emissions and upregulation of pr1 and pr2 (i.e., genes associated with Pv defense; around 2-fold, averagely) at 72 hpi, confirming the progression of infection. In contrast, U⁺/Pv⁺ leaves showed stronger peaks of H₂O₂ at both 2 and 5 hpi (7-fold and +58%, respectively), together with SA accumulation and upregulation of pr1, pr2, eds1, and chit1b at 72 hpi (more than 2-fold), suggesting a priming effect of U. Overall, U effectively enhanced grapevine defense responses and limited Pv development, highlighting its potential as a sustainable disease management strategy. Full article

Botrytis cinerea and Plasmopara viticola, the causal agents of grey mold and downy mildew, respectively, are two major grapevine pathogens whose control largely relies on synthetic fungicides, raising environmental and health concerns. Plant-derived secondary metabolites, particularly flavonoids involved in plant defense, represent promising sustainable alternatives. Among them, sakuranetin, a flavanone aglycone known for its antifungal activity in rice, remains poorly explored for grapevine protection. In this study, sakuranetin was purified from cherry branches (48 mg) and structurally characterized using UHPLC-ESI-QTOF-MS and NMR analyses. Its antifungal activity against B. cinerea and P. viticola was evaluated through in vitro, in vivo and in planta assays. For B. cinerea, our results showed a significant in vitro inhibition of mycelium growth, with EC₅₀ values of 16.43 mg·L⁻¹, while no protection of detached berries was observed. Against P. viticola, sakuranetin has no effect on the release of zoospores, but there is a total inhibition of spore germination at 1 mg·L⁻¹ in vitro, confirmed in vivo on a foliar disc. In planta, no significant protection is observed at 25 mg·L⁻¹, even if some targeted defense genes are induced. Further studies are needed to determine the best concentration of sakuranetin to use to manage B. cinerea and P. viticola in planta. Full article

Muskmelon (Cucumis melo L.) is an economically important crop that remains highly susceptible to destructive fungal diseases, including gummy stem blight, downy mildew, Fusarium wilt, and anthracnose. Although fungicides and resistant cultivars are widely used, reliance on chemical control raises concerns regarding environmental safety, food quality, and the emergence of fungicide-resistant pathogen populations. Consequently, microbial biopesticides, particularly Bacillus species, have attracted increasing attention as sustainable alternatives. In this study, muskmelon plants exhibiting leaf wilting, chlorosis, and stem yellowing were collected from Guangming Farm in Wufeng, Taichung, Taiwan, and associated pathogens were isolated from stem tissues and identified to determine the causal agent of these symptoms. In addition, the biocontrol efficacy of Bacillus subtilis strain MCLB2 against melon fruit rot, as well as its underlying mechanisms, was evaluated. Pathogenicity assays confirmed that isolate F01 was the causal agent. Based on morphological characteristics and internal transcribed spacer (ITS) sequence analysis, this isolate showed 99.8% identity to Fusarium pernambucanum URM 7559 (GenBank accession no. NR_163754), and phylogenetic analysis further placed it within the Fusarium incarnatum-equiseti species complex (FIESC). Antagonistic assays demonstrated that B. subtilis MCLB2 significantly inhibited mycelial growth and suppressed the spore germination of F. pernambucanum. In addition, culture filtrates of strain MCLB2 effectively reduced Fusarium-induced fruit rot in melon and disrupted fungal cellular respiration. Liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis revealed that the strain produced surfactin-family lipopeptides. In conclusion, B. subtilis MCLB2 exhibits potential as a sustainable biocontrol agent for managing Fusarium fruit rot in melon, likely through surfactin-mediated disruption of fungal cellular respiration. Full article

Diseases like downy mildew (DM) and powdery mildew (PM) are characterized by whitish symptoms on leaves of many plant species. Hyperspectral imaging (HSI) has been successfully used for the detection and identification of various diseases associated with different symptoms. Proximal HSI (400–1000 nm) was tested under controlled conditions for its potential to differentiate among whitish disease symptoms on leaves of apple and grapevine due to DM, PM, and a non-melanized mutant of apple scab at the leaf and tissue (microscopic) level. Spectral traits were analyzed by using difference spectra and spectral ratios, spectral vegetation indices like NDVI, and average brightness and half NIR increase introduced here and were confirmed by supervised spectral angle mapper classification. Although similar, spectral signatures of whitish symptoms were significantly different and could be used for spectral separation of diseases; differences were greater on the tissue level than on the leaf level. However, disease detection and differentiation were affected by spectral differences between plant species, leaf sides, the variability of symptoms in space and time, and the integrity of superficial pathogen structures. In the case of similar disease symptoms, additional spectral information on the effects of pathogens on plant metabolism, e.g., leaf water patterns, supports spectral differentiation of leaf diseases. Full article

Background/Objectives: Downy mildew, caused by Peronosclerospora and Sclerophthora species, is a major constraint to maize production in tropical and subtropical regions, with yield losses of 30–100%. This systematic review synthesised evidence on methods used to screen maize for downy mildew resistance and assessed their effectiveness, reliability, and associated markers. Methods: PubMed, Google Scholar, ScienceDirect, and CAB Abstracts were searched (last searched 22 October 2025) for English-language studies (1990–2025) evaluating phenotypic or molecular screening methods. Risk of bias was assessed using the RoB 2 framework. Narrative synthesis was conducted following a protocol registered on the Open Science Framework. Results: Twelve studies met the inclusion criteria, predominantly from India and Cambodia. Spreader row systems (seven studies) and conidial spray inoculation (six studies) were the most common field methods, while the glasshouse sandwich technique generated the highest disease pressure. Cross-method correlations were strong (r = 0.92–0.99), and heritability estimates ranged from 0.50 to 0.97. QTL mapping identified resistance loci on chromosomes 2, 3, and 6, with chromosome 6 stable across multiple pathogen species. Evidence certainty was moderate for method effectiveness and low for molecular markers. Conclusions: Established phenotypic screening methods reliably discriminate resistant germplasm; however, standardised protocols, broader geographic validation, and independent molecular marker confirmation are needed. Full article

Downy mildew, caused by Plasmopara viticola, is a devastating disease that threatens global grape production, with chemical control remaining the most effective management strategy. However, the repeated application of fungicides has led to widespread resistance in P. viticola populations, while data on the resistance of P. viticola to metalaxyl (MET), cymoxanil (CYM), and cyazofamid (CYA) in China remain limited. In this study, the resistance status of P. viticola to these three fungicides was evaluated across 9 major grape-growing regions in China using leaf-disc bioassays, and potential cross- and multi-resistance patterns were assessed. The majority of isolates (127/233) exhibited either lower resistance (33.48%) or moderate resistance (21.03%) to MET based on the minimum inhibitory concentration (MIC) of 10 μg/mL and 100 μg/mL. Baseline sensitivity profiles for CYM and CYA were established as 8.69 ± 0.64 μg/mL and 0.42 ± 0.05 μg/mL, respectively, using 170 and 137 isolates. The total resistance frequency of P. viticola to CYM was 29.42% (21.18% low resistance, 8.24% moderate resistance), while that to CYA was 28.47% (18.25% low resistance, 9.49% moderate resistance, 0.73% high resistance). A weak but significant positive correlation was detected between CYM and CYA sensitivities (r = 0.193, p = 0.0196), and 13 isolates exhibited resistance to both fungicides, indicating potential multi-resistance risk. Significant regional differences in resistance profiles were observed among populations (p < 0.05), and no overall fitness penalties were detected. These findings highlight the necessity of region-specific and integrated resistance management strategies for sustainable control of grape downy mildew in China. Full article

Frequent rainfall during the ripening season in Shaanxi’s grape-growing regions increases the incidence of downy mildew and black rot. In recent years, rain-shelter cultivation has reduced the incidence of these diseases; however, it has been associated with frequent powdery mildew outbreaks that severely compromise fruit quality and yield. To mitigate powdery mildew under rain-shelter conditions, we characterized disease dynamics and evaluated “bio-based” or “microbial-derived” pesticide control strategies. A large number of studies have shown that rain shelter cultivation can significantly change the microclimate. This study found that changes in microclimate affect the incidence pattern of powdery mildew, and there are significant differences in the resistance of different grape varieties to powdery mildew. A prediction model based on microclimate showed that 15-day accumulated growing degree days (GDD15; base 10 °C) before disease onset were positively correlated with the disease index (r = 0.860), whereas relative humidity was negatively correlated (r = −0.637); a multiple regression including both variables explained 81.4% of the variance. In biopesticide screening, blasticidin S and polyoxin inhibited spore germination by >95%. In-shelter efficacy varied among cultivars, and biopesticide effects on fruit quality were also cultivar dependent. For example, blasticidin S increased total phenol and anthocyanin contents in Cabernet Sauvignon but reduced phenolic accumulation in Chardonnay. Full article

Downy mildew (Plasmopara viticola) poses a major and recurring threat to Greek viticulture, yet existing point-based forecasting models require in-vineyard stations, limiting scalability in fragmented landscapes. This study introduces a spatially explicit model (MeteoGrape) using one fully equipped reference meteorological station plus eight distributed sensors across an 85 km² area in Kavala, Greece. The model is structured in three phases. In Phase A, a single reference station was paired with eight low-cost distributed sensors to reconstruct hourly temperature and relative humidity data through regression correction and radial basis function interpolation, generating a 342-cell grid at 0.005° resolution. During Phases B and C, deterministic epidemiological rules were applied to simulate oospore development, with accumulated degree-hours and humidity exposure converted into spatial risk classifications. Cross-validation (leave-one-sensor-out) confirms meteorological reliability. The model captured an elevated risk period beginning on 16 May, preceding the regional advisory bulletin (23 May), and mapped the spatial distribution of accumulated risk through late May. Validation supports temporal consistency at the regional scale, while fine-scale spatial accuracy is identified as a subject for future field-based evaluation. The framework demonstrates the feasibility of extending established point-based disease models into spatially explicit risk maps under limited meteorological infrastructure. Full article

Downy mildew of hops represents a serious disease affecting hops production in all growing regions. Disease management is primarily based on the application of fungicides at regular intervals based on a short-term forecasting methodology that is essential for evaluating the occurrence of theoretical infections. To enable a more reliable assessment of the pathogen’s presence in a given area, spore traps capturing airborne Pseudoperonospora humuli sporangia can be utilized. The use of quantitative real-time PCR (qRT-PCR) for the detection of sporangia collected by these traps allows for the elimination of laborious and time-consuming microscopic counting. Among four tested P. humuli-specific nuclear DNA sequences, an effective qRT-PCR detection method was developed based on the c127233.5e3 sequence. This detection approach was used for the quantification of sporangia from volumetric spore trap samples collected in situ under field conditions at three selected localities in Bohemia and Moravia during the 2021–2022 period. The obtained results were compared with the short-term forecasting method of the downy mildew (HDM) weather index (I) based on meteorological data. The overall course of the HDM weather index (I) closely correlated with the occurrence of sporangia: after reaching the maximum HDM weather index (I) value, the highest sporangium detection was observed with a time delay of 1–2 weeks at all the monitored sites. The results corresponded well with data obtained from volumetric spore traps in Germany, and the qRT-PCR method proved to be fully comparable to light microscopy. The combination of volumetric spore traps and qRT-PCR can significantly improve the precision of short-term forecasting systems for P. humuli infection, thereby enabling more efficient fungicide application programs in hops protection and contributing to a better understanding of the pathogen’s dispersal dynamics. Full article

Mediterranean greenhouses commonly rely on passive climate control techniques to reduce dependence on energy-intensive systems. This study was conducted in Almería (Spain) in a multi-span greenhouse divided into two sectors: a West sector equipped with a double-roof system using a pink sunlight spectrum photoconverter film combined with an increased natural ventilation surface, and an East control sector with standard ventilation and a calcium carbonate-whitened roof. The effects of this integrated passive climate management configuration on the development of naturally occurring fungal diseases were evaluated in tomato (Solanum lycopersicum L.), pepper (Capsicum annuum L.), and cucumber (Cucumis sativus L.). Powdery mildew (Leveillula taurica) and early blight (Alternaria linariae) were observed in tomato; powdery mildew in pepper; and downy mildew (Pseudoperonospora cubensis), powdery mildew (Podosphaera xanthii), and gummy stem blight (Stagonosporopsis spp.) in cucumber. Across crop cycles, the sector combining double roofing and enhanced ventilation consistently exhibited lower disease severity for powdery mildew, downy mildew, and gummy stem blight compared with the control sector. In contrast, early blight did not show a clear or consistent response to the greenhouse configuration. Overall, the results indicate that the combined use of a double-roof system with a sunlight spectrum photoconverter film and increased natural ventilation can contribute to improved microclimate regulation and reduced fungal disease pressure under Mediterranean greenhouse conditions. This integrated passive approach may therefore represent a useful complementary component of sustainable disease management strategies in protected horticulture. Full article

Grapevine downy mildew is a major disease in vineyards all around the world, caused by the oomycete Plasmopara viticola (Berk. & M. A. Curtis) Berl. & De Toni. Normally, its control depends almost exclusively on chemical and copper-based fungicides, especially in high-incidence areas with high relative humidity and mild temperatures. However, the European Union is determined to reduce the application of these phytochemicals by at least 50% by 2030, forcing winegrowers to seek alternative low-input strategies for proper sanitary maintenance. Basic substances (BSs), described in European Regulation (EC) 1107/2009, stand out as promising alternatives, but their molecular mechanism of action remains mostly unknown. In this context, this study analyzed the genetic effect in grapevine plants of several commercial products composed of BSs (chitosan, soy lecithin, Equisetum arvense and Salix cortex). All products exhibited promising results, triggering the induction of similar defence mechanisms, which included pathogenesis-related proteins (PRs), involved in direct pathogen repression; stilbenes, capable of producing antimicrobial compounds such as resveratrol and pterostilbene; several hormones, including oxylipins, ethylene, salicylic acid and terpenes, mediating immune signalling; and genes related to structural features of the plant, such as lignin, callose, cellulose and cuticular wax, constituting a first physiological barrier against P. viticola. Disease severity reduction differed among treatments, with Salix cortex showing the highest efficacy (58%), followed by BABA (38%) and LESOY (35%), while LECI and CHIT had minor effects (<9%). Gene expression analyses revealed that Salix cortex modulated the highest percentage of genes (41%), followed by natural infection without treatment (32%), LESOY (27%), BABA (26%), LECI (23%) and CHIT (23%). In terms of defence mechanisms, Salix cortex promoted the most pathways, LESOY induced eight, BABA and LECI seven and CHIT five. Overall, these results indicate that BSs can modulate several defence pathways in grapevine, supporting their potential use as sustainable alternatives for controlling downy mildew. Full article

Cucumber downy mildew, caused by the obligate parasitic oomycete Pseudoperonospora cubensis [(Berkeley & M. A. Curtis) Rostovzev], is a major threat to global cucumber production. Effective disease management relies on rapid and accurate pathogen detection. However, due to the specialized parasitic nature of P. cubensis, conventional methods are often laborious, low-throughput and inadequate, necessitating the development of a new approach for high-throughput sporangia counting. To address this limitation, we developed a rapid, high-throughput flow cytometry (FCM) assay for the direct quantification of P. cubensis sporangia. The optimal staining protocol involved adding 30 µL of 1000× diluted SYBR Green I to 500 µL of sporangial suspension and incubating at room temperature for 20 min. The flow cytometry parameters were set to a high sample loading speed with a 30-s acquisition time. Instrumental settings included an FL1 (green fluorescence) threshold of 8 × 10⁴ and an SSC (side scatter) threshold of 3 × 10⁵, with low gain. Validation against hemocytometer counts revealed a strong positive correlation (r = 0.8352). The assay demonstrated high reproducibility, with relative standard deviations (RSDs) ranging from 1.96–9.84%, and a detection limit of 1–10 sporangia/µL. Operator-dependent variability ranged from 8.85% to 18.79%. These results confirm that the established flow cytometry assay is a reliable and efficient tool for P. cubensis quantification, offering considerable potential for improving cucumber downy mildew monitoring and control strategies. Full article

Volatile organic compounds (VOCs) produced by Medicinal Aromatic Plants (MAPs) are bioactive signaling molecules that play key roles in plant defense, acting against pathogens and triggering resistance responses. Intercropping with VOC-emitting MAPs can therefore enhance disease resistance. This study investigated VOCs emitted by sage (Salvia officinalis) as potential resistance inducers in grapevine (Vitis vinifera) against Plasmopara viticola, the causal agent of downy mildew, under consociated growth conditions. Sage and grapevine plants were co-grown in an airtight box system for 24 or 48 h, after which grape leaves were inoculated with P. viticola. Disease assessments were integrated with grapevine leaf metabolic profiling to evaluate responses to VOC exposure and pathogen infection. Untargeted and targeted metabolomic analysis revealed that sage VOCs consistently reprogrammed grapevine secondary metabolism, without substantial differences between 24 and 48 h exposures. Lipids, phenylpropanoids, and terpenoids were markedly accumulated following VOC exposure and persisted following inoculation. Correspondingly, leaves pre-exposed to sage VOCs exhibited a significant reduction in disease susceptibility. Overall, our results suggest that exposure to sage VOCs induces signaling and metabolic reprogramming in grapevine. Further research should elucidate how grapevines perceive and integrate these signals, as well as the broader processes underlying MAP VOC-induced defense, and evaluate their translation into sustainable viticultural practices. Full article