Development Of Fungicide Resistance Research Articles

Fungicide Sensitivity Survey of Pecan Scab in Texas Pecan Orchards

A fungicide sensitivity survey of pecan scab ( Venturia effusa) from eight different locations in seven pecan orchards in Texas was conducted during the summer of 2021. Using a rapid fungicide sensitivity assay based on single discriminatory concentrations, sensitivities to five fungicides (dodine, fentin hydroxide, thiophanate-methyl, propiconazole, and tebuconazole) were evaluated. Pecan orchards with frequent fungicide use tended to have greater levels of reduced sensitivities to demethylation inhibitor (propiconazole and tebuconazole; >40% of conidial germination at 1 µg/ml of active ingredient) and fentin hydroxide fungicides (>64% of conidial germination at 3 µg/ml of active ingredient) compared to those with fewer fungicide applications in the past. All populations tested in this survey exhibited a high level of resistance to the thiophanate-methyl fungicide but no resistance to dodine. Thiophanate-methyl did not inhibit conidial germination for six scab populations, while dodine consistently inhibited conidial germination for scab populations tested at the discriminatory concentration. The cytochrome b gene was sequenced for determining mutations associated with quinone outside inhibitor (QoI) fungicides. The mutation that results in a substitution of glycine 137 to serine (G137S) in the cytochrome b gene and is related to high resistance to QoI was not found in the representative isolates of scab populations tested in this survey. Our findings are the first report of fungicide resistance development in Texas pecan orchards. Information about fungicide sensitivities of scab populations in orchards will help pecan producers to prepare proper fungicide treatment plans.

Evaluation of Reduced Fungicide Applications for Disease Management in Cold-Climate Wine Grapes in Wisconsin.

Cold-climate wine grapes are produced on 8,000 ha in the North Central region of the United States. Wisconsin has experienced considerable growth, with a 26% increase in acreage since 2017. Chemical management of fungal diseases in cold-climate, interspecific hybrid grapes mirrors that of traditional Vitis vinifera cultivars despite significant differences in disease susceptibility. Most cold-climate cultivars display disease tolerance or resistance to key pathogens such as Plasmopara viticola (downy mildew), Erysiphe necator (powdery mildew), and Phyllosticta ampelicida (black rot). Current fungicide programs in Wisconsin's cold-climate grape industry underutilize genetic resistance, resulting in overreliance on at-risk fungicides and an increased threat of fungicide resistance development. In vineyard trials, the impacts of a reduced fungicide application number compared to current grower "Standard" programs was assessed for disease incidence and severity for five diseases: anthracnose, black rot, downy mildew, Phomopsis cane and leaf spot and powdery mildew. In 2022, with moderate disease pressure at both vineyard sites, there were no significant differences observed when fewer fungicides (six or five applications vs. four applications) were applied. In 2023, higher disease incidence was observed in the "Standard" spray program at one study location which received a greater number of fungicide applications. In both years, grape cultivar was a significant factor with the 'LaCrosse' displaying greater average disease severity than the 'St. Pepin' in both the "Standard" and "Reduced" Programs. These findings present a promising opportunity for cold-climate grape growers to reduce the number of fungicide applications while maintaining disease control and marketable yield.

Nighttime Applications of Germicidal UV Light to Suppress Cercospora Leaf Spot in Table Beet.

Cercospora leaf spot (CLS), caused by the hemibiotrophic fungus Cercospora beticola, is a destructive disease affecting table beet. Multiple applications of fungicides are needed to reduce epidemic progress to maintain foliar health and enable mechanized harvest. The sustainability of CLS control is threatened by the rapid development of fungicide resistance, the need to grow commercially acceptable yet CLS-susceptible cultivars, and the inability to manipulate agronomic conditions to mitigate disease risk. Nighttime applications of germicidal UV light (UV-C) have recently been used to suppress several plant diseases, notably those caused by ectoparasitic biotrophs such as powdery mildews. We evaluated the efficacy of nighttime applications of UV-C for suppression of CLS in table beet. In vitro lethality of UV-C to germinating conidia increased with increasing dose, with complete suppression at 1,000 J/m2. Greenhouse-grown table beet tolerated relatively high doses of UV-C without lethal effects despite some bronzing on the leaf blade. A UV-C dose >1,500 J/m2 resulted in phytotoxicity severities greater than 50%. UV-C exposure to ≤750 J/m2 resulted in negligible phytotoxicity. Older (6-week-old) greenhouse-grown plants were more susceptible to UV-C damage than younger (2- and 4-week-old) plants. Suppression of CLS by UV-C was greater when applied within 6 days of C. beticola inoculation than if delayed until 13 days after infection in greenhouse-grown plants. In field trials, there were significant linear relationships between UV-C dose and CLS control and phytotoxicity severity, and a significant negative linear relationship between phytotoxicity and CLS severity at the final assessment. Significant differences between UV-C doses on the severity of CLS and phytotoxicity indicated an efficacious dose near 800 J/m2. Collectively, these findings illustrate significant and substantial suppression by nighttime applications of UV-C for CLS control on table beet, with potential for incorporation in both conventional and organic table beet broadacre production systems.

Testing the efficacy of a newly released fungicide, Sphaerex, for control of Fusarium Head Blight in wheat

Fusarium head blight (FHB) is a destructive disease of wheat and other small-grain cereals. FHB causes reduction in crop yield due to pre-mature bleaching of spikes. Additionally, it deteriorates the crop quality due to the production of mycotoxins. An integrated management strategy is needed to effectively manage this disease. One of the most important strategies in the FHB management toolbox is chemical control. Fungicides start losing their efficacy over time due to the development of fungicide resistance in the pathogens. This necessitates the development and testing of new fungicides with multiple active ingredients or modes of action. In this 3-year study, we evaluated the effectiveness of a new fungicide with multiple active ingredients, Sphaerex (a proprietary mix of metconazole and prothioconazole) in an FHB-susceptible soft red winter wheat cultivar, Shirley in the eastern United States. Sphaerex provided significantly better control over untreated plots for FHB Incidence, FHB Severity, and DON content across all three years. The level of control of FHB and DON by Sphaerex was found to be similar to that provided by other standard FHB fungicides. The yield of the fungicide-treated plots was statistically similar to that of the untreated plots.

Trichothecene mycotoxin profiling of Fusarium graminearum isolates from wheat and maize, and the baseline sensitivity to pydiflumetofen and other fungicides

Fusarium graminearum is the most important pathogen of maize and winter wheat in Canada, resulting in yield loss and mycotoxin contamination. Fungicides are essential to manage F. graminearum in cereal crops. Until pydiflumetofen became commercial, the only available fungicides were triazoles, limiting the potential to manage fungicide resistance. Fusarium graminearum isolates were surveyed from wheat, grain maize and overwintering maize stalks in southern Ontario. Chemotype and the baseline sensitivity to pydiflumetofen were determined in addition to sensitivity to common fungicides used to control F. graminearum. Fusarium graminearum has several strains producing different trichothecenes called chemotypes. In Ontario, 73.3% of the F. graminearum isolates were 3ANX chemotypes producing 7α-hydroxy, 15-deacetylcalonectrin, in addition to 15-acetyldeoxynivalenol and deoxynivalenol; the remaining isolates were 15ADON chemotypes producing only 15-acetyldeoxynivalenol and deoxynivalenol. Chemotype was not affected by isolate source (wheat grain, maize grain, maize stalks) nor by location. All isolates were sensitive to pydiflumetofen and fungicide products containing pydiflumetofen. The mean EC50 for isolates exposed to pydiflumetofen was 0.05 µg mL−1 (range 0.01–0.10 µg mL−1). The mean EC50 for isolates exposed to Miravis®Ace (containing pydiflumetofen and propiconazole), Miravis®Neo 300SE (containing pydiflumetofen, azoxystrobin and propiconazole), Caramba® (containing metconazole), Proline® (containing prothioconazole) and Prosaro (containing prothioconazole and tebuconazole) was 0.06, 0.13, 0.18, 0.05, 3.75 and 0.30 µg mL−1, respectively. These data will be useful in monitoring the development of fungicide resistance.

Combined interaction of fungicides binary mixtures: experimental study and machine learning-driven QSAR modeling

Fungicide mixtures are an effective strategy in delaying the development of fungicide resistance. In this research, a fixed ratio ray design method was used to generate fifty binary mixtures of five fungicides with diverse modes of action. The interaction of these mixtures was then analyzed using CA and IA models. QSAR modeling was conducted to assess their fungicidal activity through multiple linear regression (MLR), support vector machine (SVM), and artificial neural network (ANN). Most mixtures exhibited additive interaction, with the CA model proving more accurate than the IA model in predicting fungicidal activity. The MLR model showed a good linear correlation between selected theoretical descriptors by the genetic algorithm and fungicidal activity. However, both ML-based models demonstrated better predictive performance than the MLR model. The ANN model showed slightly better predictability than the SVM model, with R2 and R2cv at 0.91 and 0.81, respectively. For external validation, the R2test value was 0.845. In contrast, the SVM model had values of 0.91, 0.78, and 0.77 for the same metrics. In conclusion, the proposed ML-based model can be a valuable tool for developing potent fungicidal mixtures to delay fungicidal resistance emergence.

Synthesis and Antifungal Activities of Novel Griseofulvin Derivatives as Potential Anti-Phytopathogenic Fungi Agents.

The extensive and repeated application of chemical fungicides results in the rapid development of fungicide resistance. Novel antifungal pesticides are urgently required. Natural products have been considered precious sources of pesticides. It is necessary to discover antifungal pesticides by using natural products. Herein, 42 various griseofulvin derivatives were synthesized. Their antifungal activities were evaluated in vitro. Most of them showed good antifungal activity, especially 3d exhibited a very broad antifungal spectrum and the most significant activities against 7 phytopathogenic fungi. In vivo activity results suggested that 3d protected apples and tomatoes from serious infection by phytopathogenic fungi. These proved that 3d had the potential to be a natural product-derived antiphytopathogenic fungi agent. Furthermore, docking analysis suggested that tubulin might be one of the action sites of 3d. It is reasonable to believe that griseofulvin derivatives are worth further development for the discovery of new pesticides.

Assessing the predictability of fungicide resistance evolution through in vitro selection

Plant pathogens are highly adaptable, and have evolved to overcome control measures including multiple classes of fungicides. More effective management requires a thorough understanding of the evolutionary drivers leading to resistance. Experimental evolution can be used to investigate evolutionary processes over a compressed timescale. For fungicide resistance, applications include predicting resistance ahead of its emergence in the field, testing potential outcomes under multiple different fungicide usage scenarios or comparing resistance management strategies. This review considers different experimental approaches to in vitro selection, and their suitability for addressing different questions relating to fungicide resistance. When aiming to predict the evolution of new variants, mutational supply is especially important. When assessing the relative fitness of different variants under fungicide selection, growth conditions such as temperature may affect the results as well as fungicide choice and dose. Other considerations include population size, transfer interval, competition between genotypes and pathogen reproductive mode. However, resistance evolution in field populations has proven to be less repeatable for some fungicide classes than others. Therefore, even with optimal experimental design, in some cases the most accurate prediction from experimental evolution may be that the exact evolutionary trajectory of resistance will be unpredictable.

Increasing the tolerance of Trichoderma harzianum T-22 to DMI fungicides enables the combined utilization of biological and chemical control strategies against plant diseases

Demethylase inhibitors (DMIs) targeting CYP51 proteins in fungi are often used for plant disease management. Trichoderma harzianum, a widely used biocontrol agent, however, is sensitive to DMIs. This negates their combined use as a strategy in practices. Increasing the tolerance of T. harzianum to DMIs represents a feasible solution to this problem. In this regard, the overexpression of a CYP51B variant in Mycosphaerella graminicola (MgCYP51B-v) conveys increased tolerance to DMIs. Molecular docking indicated a distinct decrease in the affinity of MgCYP51B-v with DMIs. Since CYP51B proteins are conserved in M. graminicola and T. harzianum, we attempted to increase DMI tolerance in T. harzianum by heterologously expressing MgCYP51B-v. A series of T. harzianum mutants were obtained that were able to develop colonies on tebuconazole-amended medium. Two representative mutants were selected for further studies that confirmed that they were resistant to tebuconazole with resistance factors (RFs) of approximately 10.0. The mutants maintained a similar level of resistance after ten rounds of subculture without fungicide, indicating that the fungicide resistance was stably inherited. The mutants also exhibited increased tolerance to other DMIs, including metconazole, ipconazole, hexaconazole, and prochloraz. Further assessment indicated that the DMI resistance in the mutants did not have any impact on their fitness. The improved compatibility between T. harzianum and DMIs enables the utilization of a combined strategy in which these disease control agents are used together. Such a strategy has the potential to provide synergistic disease control and prevent or delay the development of fungicide resistance.

Do Growers Using Solo Fungicides Affect the Durability of Disease Control of Growers Using Mixtures and Alternations? The Case of Spot-Form Net Blotch in Western Australia.

Growers often use alternations or mixtures of fungicides to slow down the development of resistance to fungicides. However, within a landscape, some growers will implement such resistance management methods, whereas others do not, and may even apply solo components of the resistance management program. We investigated whether growers using solo components of resistant management programs affect the durability of disease control in fields of those who implement fungicide resistance management. We developed a spatially implicit semidiscrete epidemiological model for the development of fungicide resistance. The model simulates the development of epidemics of spot-form net blotch disease, caused by the pathogen Pyrenophora teres f. maculata. The landscape comprises three types of fields, grouped according to their treatment program, with spore dispersal between fields early in the cropping season. In one field type, a fungicide resistance management method is implemented, whereas in the two others, it is not, with one of these field types using a component of the fungicide resistance management program. The output of the model suggests that the use of component fungicides does affect the durability of disease control for growers using resistance management programs. The magnitude of the effect depends on the characteristics of the pathosystem, the degree of inoculum mixing between fields, and the resistance management program being used. Additionally, although increasing the amount of the solo component in the landscape generally decreases the lifespan within which the resistance management program provides effective control, situations exist where the lifespan may be minimized at intermediate levels of the solo component fungicide. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Variety mixtures of winter wheat: a general status and national case study

Food and feed production worldwide heavily relies on wheat (Triticum aestivum). However, current agricultural practices face numerous challenges including a shortage of land for cultivation, a desire to reduce the use of chemical pesticides and fertilizers, and the development of resistance towards employed pesticides and virulence towards host resistance in the most widely grown varieties. In this paper, we demonstrate based on the literature that cultivating wheat variety mixtures generally leads to increased yield and yield stability across years and environments, reduced severity of multiple diseases, and a decreased risk of lodging before harvest compared to the cultivation of pure stands. Moreover, mixtures may delay fungicide resistance development and increase genetic diversity, ultimately prolonging the durability of resistance genes. Furthermore, growing mixtures may lower the risk of crop failure due to more extreme weather events and lead to better utilization of water and nutrients. We discuss a Danish case study advocating the cropping of wheat varieties in mixtures as an example of how variety mixtures can be utilized in integrated pest management strategies. The study shows that if all involved stakeholder groups promote the adoption of variety mixtures, a major uptake by farmers can be reached, potentially reducing the dependency on pesticides in current cropping schemes.

Two-Year Survey of Botrytis Fruit Rot Levels in Commercial Strawberry Fields in California with and without Fungicide Applications

ABSTRACT Botrytis fruit rot (BFR) causes significant losses in-field and postharvest in strawberries and is mainly managed by fungicides. Strategically applying fungicides only during wet and cool periods would reduce fungicide resistance development and grower costs. A survey of BFR levels in field-grown strawberries with and without fungicide applications was conducted in Santa Maria, California. Weather data were collected to calculate the BFR risk factor using Florida’s Strawberry Advisory System (StAS). There were no significant differences between fungicide and no-fungicide treatments for in-field and postharvest BFR incidence in 2021 and in-field BFR incidence in 2022, while the no-fungicide treatment showed higher postharvest BFR incidence in 2022. Average in-field BFR incidence for fungicide and no-fungicide treatments was 2.6% and 2.5% for 2021 and 3.0% and 3.7% for 2022. Average postharvest BFR incidence for fungicide and no-fungicide treatments was 1.8% and 2.0% for 2021 and 0.6% and 1.5% for 2022. BFR risk factor was significantly associated with BFR incidence in 2021, but not in 2022. StAS predicted a 50% and 44% fungicide application reduction in 2021 and 2022 compared to grower standard treatments. These results indicate the potential of reducing fungicide use without compromising BFR control in California strawberry production.

Understanding Phakopsora pachyrhizi in soybean: comprehensive insights, threats, and interventions from the Asian perspective.

Soybean (Glycine max L.) is an important crop in Asia, accounting for 17% of global soybean cultivation. However, this crop faces formidable challenges from the devastating foliar disease, Asian Soybean Rust (ASR), caused by Phakopsora pachyrhizi, a biotrophic fungus with a broad host range, causing substantial yield losses (10-100%) in Asia. This comprehensive review consolidates knowledge on ASR, encompassing its impact, historical perspectives, genetic diversity, epidemic drivers, early detection, risk assessment, and sustainable management strategies of ASR in the region. ASR has expanded globally from Asia, reaching Africa and Americas, driven by wind-dispersed urediniospores. Genetic diversity studies reveal the complexity of P. pachyrhizi, with distinct populations exhibiting varying virulence patterns. Factors affecting ASR epidemics in Asia include host susceptibility, landscape connectivity, climate, and environmental conditions. Understanding the interplay of these factors is essential for early intervention and control of ASR in soybean fields. Effectively managing ASR can exploit the utilization of diverse intervention strategies, encompassing disease forecasting, automated early detection, disease resistance, fungicide application, and biological control. A pivotal aspect of successful, sustainable disease management lies in reducing the ASR pathogen virulence and preventing it from developing fungicide resistance, while the highpoint of effectiveness in disease control is attained through a synergistic approach, integrating various strategies. In summary, this comprehensive review provides insights into multifaceted approaches that contribute to the development of sustainable and economically impactful soybean production in the face of the persistent threat of ASR in Asia.

Evaluation of Spinach Cultivars for Resistance to Stemphylium Leaf Spot (Stemphylium vesicarium) and White Rust (Albugo occidentalis)

Stemphylium leaf spot, caused by Stemphylium vesicarium, and white rust, caused by Albugo occidentalis, can cause significant losses in spinach production. Management of these foliar diseases of spinach has become increasingly challenging with the development of fungicide resistance in some pathogen populations, high planting density and overhead irrigation used for baby leaf spinach production, and the fact that >60% of fresh market spinach production in the United States is certified organic. To identify spinach cultivars with resistance to Stemphylium leaf spot and white rust, a field trial was performed near Crystal City, TX, USA, in 2021 (79 cultivars), 2022 (87 cultivars), and 2023 (63 cultivars). Each year, the plants were inoculated with S. vesicarium and rated for disease severity. Plants were also rated for white rust severity that resulted from natural infection during the 2021 and the 2022 trials. During each trial, 11% to 27% of the cultivars were identified as resistant to Stemphylium leaf spot, and another 29% to 48% had moderately resistant reactions. In contrast, only 5 of 79 cultivars (6%) in the 2021 trial did not develop symptoms of white rust, and all 87 cultivars evaluated in the 2022 trial had symptoms of white rust. Although there was no significant correlation between mean Stemphylium leaf spot ratings and mean white rust ratings during these trials, the cultivars Colusa, Kodiak, PV-1569, and PV-1664 displayed resistant or moderately resistant responses to both diseases in at least two trials. Therefore, processing and fresh market spinach growers have resistant cultivars from which to select to reduce the economic impacts of Stemphylium leaf spot and white rust.

Biorational Fungicides to Manage Cucurbit Powdery Mildew on Winter Squash in New York

Cucurbit powdery mildew (CPM) is one of the most common foliar diseases of winter squash grown in New York. Conventional fungicides remain the primary method for managing CPM. However, increasing consumer demand for organic produce and concerns about both environmental safety and fungicide resistance development have driven research to identify alternative management strategies. Biorational fungicides, including biologicals, botanicals, and minerals, are increasingly available for certified organic production but are generally considered less effective at managing CPM than conventional products. Copper-containing pesticides approved for use in organic production are effective, but concerns about nontarget effects are driving exploration of alternative biorational solutions for CPM. Further research is warranted to validate and expand management strategies for organic cucurbit production. In this study, we evaluated 9 and 10 biorational fungicides to reduce CPM on winter squash in field trials in 2021 and 2022, respectively. The treatment that consistently and most effectively reduced disease severity was Kocide 3000-O (copper hydroxide) followed by Theia ( Bacillus subtilis) and Regalia plus Stargus ( Reynoutria sachalinensis plus B. amyloliquefaciens). The developmental product Curezin (copper zinc) and the adjuvant Dyne-Amic (alkylphenol ethoxylate) also significantly reduced disease compared with the untreated control in 2022. No differences in yield were observed in either year. We conclude that copper-based biorational fungicides most effectively managed CPM compared with other biological and botanical products evaluated, followed by Theia and Regalia plus Stargus. Knowledge gained from this study can inform current CPM management practices and the development of future tools for IPM strategies.

Sensitivity of the Causal Agent of Northern Leaf Blight of Corn, Exserohilum turcicum, to the Demethylase-Inhibiting Fungicide Flutriafol

Fungicides including active ingredients in the demethylation inhibitor group (Fungicide Resistance Action Committee Group 3) are used to manage corn diseases such as northern corn leaf blight, caused by Exserohilum turcicum. This study assessed the level of sensitivity to the demethylation-inhibiting fungicide flutriafol on a population of 81 E. turcicum isolates collected from across the United States in 2020. Sensitivity to flutriafol for E. turcicum was assessed using fungicide-amended media to determine the effective concentration needed to limit hyphal growth by 50%. The mean absolute EC50 values of the overall population calculated using the four-parameter log-logistic and Weibull2 four-parameter models were 2.1881 and 3.2643 µg/ml, respectively. The growth of most isolates ( n = 70, 86.4%) was completely inhibited by 1 µg/ml of flutriafol. However, the growth of seven isolates (8.6%) was only completely inhibited at 10 or 100 µg/ml, and complete inhibition was not observed at 100 µg/ml for four isolates (4.9%). These results suggest that there may be isolates of E. turcicum in the United States that are resistant to flutriafol. Additional fungicide sensitivity screening is critical to monitor the development of fungicide resistance in U.S. populations of E. turcicum.

Fungicide-Resistant Botrytis in Forest Nurseries May Impact Disease Control in Norway Spruce.

Gray mold, caused by Botrytis spp., is a serious problem in Norway spruce seedling production in forest nurseries. From 2013 to 2019, 125 isolates of Botrytis were obtained from eight forest nurseries in Norway: 53 from Norway spruce seedlings, 16 from indoor air, 52 from indoor surfaces, and four from weeds growing close to seedlings. The majority of isolates were identified as B. cinerea, and over 60% of these were characterized as Botrytis group S. B. pseudocinerea isolates were obtained along with isolates with DNA sequence similarities to B. prunorum. Fungicide resistance was assessed with a mycelial growth assay, and resistance was found for the following: boscalid (8.8%), fenhexamid (33.6%), fludioxonil (17.6%), pyraclostrobin (36.0%), pyrimethanil (13.6%), and thiophanate-methyl (50.4%). Many isolates (38.4%) were resistant to two to six different fungicides. A selection of isolates was analyzed for the presence of known resistance-conferring mutations in the cytb, erg27, mrr1, sdhB, and tubA genes, and mutations leading to G143A, F412S, ΔL497, H272R, and E198A/F200Y were detected, respectively. Detection of fungicide resistance in Botrytis from Norway spruce and forest nursery facilities reinforces the necessity of employing resistance management strategies to improve control and delay development of fungicide resistance in the gray mold pathogens.[Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Investigating the effectiveness of ginger and turmeric extracts on common soil-borne pathogens affecting plants

Soil-borne viruses have crop production across the world, resulting in lower crop yields, poor crop performance, and rising production costs. Crop production has faced increased threats in recent years, including soil-borne disease epidemics, high chemical fungicide costs and the development of fungicide resistance, climate change, new disease outbreaks, and growing concern for both environmental and soil health. To address these infections, crop producers must implement integrated soil-borne disease control measures. In this work, two plant extracts (ginger and turmeric) were examined in vitro and in vivo for their ability to inhibit soil-borne pathogen mycelia development. Turmeric effectively suppressed the development of two pathogens when added to the two extracted extracts, with 74.59% inhibition against Fusarium sp and 73.49% inhibition against Rhizoctonia sp. Ginger extracts demonstrated a somewhat lower inhibitory activity against Rhizoctonia, with 73.58% inhibition at 50% concentration and 72.15% at 50% concentration. In vivo tests of turmeric extract against Rhizoctonia solani and Fusarium sp. were carried out to further the research. The data showed that using turmeric extract resulted in a substantial reduction in illness severity and incidence in both infections.

Identification of Fungicide Combinations for Overcoming Plasmopara viticola and Botrytis cinerea Fungicide Resistance.

Fungal diseases, including downy mildew (caused by Plasmopara viticola) and gray mold (caused by Botrytis cinerea), significantly impact the marketable yield of grapes produced worldwide. Cytochrome b of the mitochondrial respiratory chain of these two fungi is a key target for Quinone outside inhibitor (QoI)-based fungicide development. Since the mode of action (MOA) of QoI fungicides is restricted to a single site, the extensive usage of these fungicides has resulted in fungicide resistance. The use of fungicide combinations with multiple targets is an effective way to counter and slow down the development of fungicide resistance. Due to the high cost of in planta trials, in silico techniques can be used for the rapid screening of potential fungicides. In this study, a combination of in silico simulations that include Schrödinger Glide docking, molecular dynamics, and Molecular Mechanism-Generalized Born Surface Area calculation were used to screen the most potent QoI and non-QoI-based fungicide combinations to wild-type, G143A-mutated, F129L-mutated, and double-mutated versions that had both G143A and F129L mutations of fungal cytochrome b. In silico docking studies indicated that mandestrobin, famoxadone, captan, and thiram have a high affinity toward WT cytochrome b of Botrytis cinerea. Although the QoIs mandestrobin and famoxadone were effective for WT based on in vitro results, they were not broadly effective against G143A-mutated isolates. Famoxadone was only effective against one isolate with G143A-mutated cytochrome b. The non-QoI fungicides thiram and captan were effective against both WT and isolates with G143A-mutated cytochrome b. Follow-up in silico docking and molecular dynamics studies suggested that fungicide combinations consisting of famoxadone, mandestrobin, fenamidone, and thiram should be considered in field testing targeting Plasmopara viticola and Botrytis cinerea fungicide resistance.

Sensitivity to 12 Fungicides and Resistance Mechanism to Trifloxystrobin, Carbendazim, and Succinate Dehydrogenase Inhibitors in Cucumber Corynespora Leaf Spot (Corynespora cassiicola).

Corynespora cassiicola is the causal agent of cucumber Corynespora leaf spot, which affects many economically important plant species. Chemical control of this disease is hampered by the common development of fungicide resistance. In this study, 100 isolates from Liaoning Province were collected, and their sensitivity to 12 fungicides was determined. All the isolates (100%) were resistant to trifloxystrobin and carbendazim, and 98% were resistant to fluopyram, boscalid, pydiflumetofen, isopyrazam, and fluxapyroxad. However, none were resistant to propiconazole, prochloraz, tebuconazole, difenoconazole, and fludioxonil. The Cytb gene of trifloxystrobin-resistant isolates encoded the G143A mutation, whereas the β-tubulin gene of carbendazim-resistant isolates encoded the E198A and E198A and M163I mutations. Mutations in SdhB-I280V, SdhC-S73P, SdhC-H134R, SdhD-D95E, and SdhD-G109V were associated with resistance to the succinate dehydrogenase inhibitors (SDHIs). Trifloxystrobin, carbendazim, and fluopyram were barely effective on the resistant isolates, whereas fludioxonil and prochloraz were effective on the isolates that were resistant to the quinone outside inhibitors (QoIs), SDHIs, and benzimidazoles. Ultimately, this study demonstrates that fungicide resistance seriously threatens the effective control of Corynespora leaf spot.