Biological activity of triazole fungicides towards Botrytis cinerea
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Botrytis cinerea Pers. ex Fr., the causal agent of grey mould, is one of the most ubiquitous plant pathogens. The fungus is of high economic importance in various major crops and during transport and storage of agricultural products. Protectant fungicides such as chlorothalonil, dichlofluanid, folpet or thiram are widely used for disease control. Since their introduction in the 1960S/1970s, systemic fungicides such as the benzimidazoles or dicarboximides have been used extensively. However, their effectivity is severely hampered by a rapid development of resistance to these fungicides.Antifungal activity of N1-substituted azoles was discovered in the late 1960s. Since then, a large number of azole derivatives have been developed as agricultural fungicides and antimycotics. The mode of action of these azoles is based on inhibition of the cytochrome P450-dependent sterol 14α-demethylase (P450 14DM ), an enzyme of the sterol pathway. By now, sterol demethylation inhibitors (DMIs) comprise about 35 commercial products and represent the most important group of systemic fungicides. DMI fungicides are commonly applied in control of rusts, powdery mildews and scabs. Only few of them are registered for control of B. cinerea . This is ascribed to a limited field performance for which the reasons are not evident. A replacement of dicarboximides or benzimidazoles by DMI fungicides would be attractive, since DMIs have a number of advantages over other fungicides including a relatively low resistance risk.The aim of the study described in this thesis is to identify factors involved in the limited field performance of DMI fungicides towards B. cinerea . The study is restricted to the largest group of DMIs, the triazoles. Before presenting results obtained in this study a literature review on the biology and control of B. cinerea , the mode of action and mechanisms involved in selective fungitoxicity of DMI fungicides, and factors responsible for discrepancies in laboratory and field pesticide performance is given ( chapter 1 ). Biological activity of triazoles towards B. cinerea was investigated in vitro with cell-free assays ( chapters 3 - 4 ) and toxicity assays ( chapters 3 - 7) and in vivo on different hosts ( chapter 5 ).The first step in the research presented in this thesis was the development of a cell-free assay for sterol synthesis from the model fungus Penicillium italicum ( Moniliaceae ) according to a method described for Aspergillus fumigatus ( chapter 2 ). Subsequently, the method developed was adopted for Botrytis cinerea ( chapter 3). This assay was used to study the relationship between chemical structure and biological activity of commercial and experimental triazoles and stereoisomers of cyproconazole,SSF-109 and tebuconazole towards B. cinerea ( chapter 4 ). On basis of these experiments intrinsic inhibitory activity of triazoles towards P450 14DM of the target pathogen was determined. in following experiments, factors which influence In vivo activity or field performance were Investigated. In vivo activity of triazole fungicides towards B. cinerea was tested on foliar-sprayed tomato plants and diptreated grape berries, and compared with that of selected benzimidazoles and dicarboximides ( chapter 5 ). in this context was also studied whether biological compounds could specifically antagonize activity of triazoles ( chapter 5 ). Variation in triazole sensitivity of the pathogen population was studied for field isolates (121) of B. cinerea collected during 1970 - 1992 in Europe and israel ( chapter 6 ). in this survey less sensitive populations were detected. A putative mechanism of resistance to DMI fungicides in field isolates with a relatively low sensitivity to DMIs was studied and compared with that operating in laboratory-generated DMI-resistant mutants ( chapter 7 ). Effects of inhibitors of mitochondrial respiration and multisite-inhibiting fungicides on accumulation of tebuconazole were tested to evaluate their potency as candidate compounds in synergistic mixtures with DMIs ( chapter 7 ). The development of synergistic mixtures may improve biological activity of DMI fungicides in control of B. cinerea.Keywords:
Chlorothalonil
Myclobutanil
Pyrimethanil
Azole
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Despite decades of agricultural and urban use of fungicides and widespread detection of these pesticides in surface waters, relatively few data are available on the effects of fungicides on fish and invertebrates in the aquatic environment. Nine fungicides are reviewed in this report: azoxystrobin, boscalid, chlorothalonil, fludioxonil, myclobutanil, fenarimol, pyraclostrobin, pyrimethanil, and zoxamide. These fungicides were identified as emerging chemicals of concern because of their high or increasing global use rates, detection frequency in surface waters, or likely persistence in the environment. A review of the literature revealed significant sublethal effects of fungicides on fish, aquatic invertebrates, and ecosystems, including zooplankton and fish reproduction, fish immune function, zooplankton community composition, metabolic enzymes, and ecosystem processes, such as leaf decomposition in streams, among other biological effects. Some of these effects can occur at fungicide concentrations well below single-species acute lethality values (48- or 96-hour concentration that effects a response in 50 percent of the organisms, that is, effective concentration killing 50 percent of the organisms in 48 or 96 hours) and chronic sublethal values (for example, 21-day no observed adverse effects concentration), indicating that single-species toxicity values may dramatically underestimate the toxic potency of some fungicides. Fungicide modes of toxic action in fungi can sometimes reflect the biochemical and (or) physiological effects of fungicides observed in vertebrates and invertebrates; however, far more studies are needed to explore the potential to predict effects in nontarget organisms based on specific fungicide modes of toxic action. Fungicides can also have additive and (or) synergistic effects when used with other fungicides and insecticides, highlighting the need to study pesticide mixtures that occur in surface waters. For fungicides that partition to organic matter in sediment and soils, it is particularly important to determine their effects on freshwater mussels and other freshwater benthic invertebrates in contact with sediments, as available toxicity studies with pelagic species, mainly Daphnia magna, may not be representative of these benthic organisms. Finally, there is a critical need for studies of the chronic effects of fungicides on reproduction, immunocompetence, and ecosystem function; sublethal endpoints with population and community-level relevance.
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Botrytis
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Chlorothalonil
Propiconazole
Monilinia fructicola
Benomyl
Myclobutanil
Vinclozolin
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Iprodione
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Botrytis cinerea is the pathogen of gray mold disease affecting a wide range of plant hosts, with consequential economic losses worldwide. The increased frequency of fungicide resistance of the pathogen challenges its disease management, and thus the development of alternative control strategies are urgently required. In this study, we showed excellent synergistic interactions between resveratrol and pyrimethanil. Significant synergistic values were recorded by the two-drug combination on the suppression of mycelial growth and conidia germination of B. cinerea. The combination of resveratrol and pyrimethanil caused malformation of mycelia. Moreover, the inoculation assay was conducted on table grape and consistent synergistic suppression of the two-drug combination was found in vivo. Our findings first revealed that the combination of resveratrol and pyrimethanil has synergistic effects against resistant B. cinerea and support the potential use of resveratrol as a promising adjuvant on the control of gray mold.
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Objective)The resistance to pyrimethanil of Botrytis cinerea isolated from diseased grape berries in China was studied. (Method)A total of 104 single conidial isolates of B. cinerea were isolated from diseased grape berries which were collected from vineyards located in 14 different cities or suburban counties in China. The method of mycelial growth inhibition was used to determine the resistance of B. cinerea to anilinopyrimidine fungicides pyrimethanil.(Result)The findings in the current work demonstrated that the resistance frequency of B. cinerea to pyrimethanil was 22.22% to 62.5%. Most of the resistant isolates showed middle resistant or high resistant phenotype, and the resistant frequency of high resistant isolates reached up to 44.23%. Resistance to pyrimethanil of B. cinerea differs in different viticulture climate zones. (Conclusion)Resistance to pyrimethanil of B. cinerea isolated from grape diseased samples in China is commonly present, and the resistant isolates showed cross resistance. Accordingly, the frequency of use of pyrimethanil should be limited in the prevention of grape gray mold, and fungicides such as dicarboximide and carbamates can be used alternatively. It was suggested that novel fungicides or biofungicides should be introduced for the control of grape gray mold.
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By screening the compounding combination of Wuyiencin and chemical agents, this study aims to delay the emergence of chemical agent resistance, and provide a technical reference for scientific and rational fungicides technology. This study investigated the impacts of the antibiotic wuyiencin derived from Streptomyces albulus var. wuyiensis and its combination with pyrimethanil on the inhibition of Botrytis cinerea. Treatment with wuyiencin (≥80 µg mL−1) strongly inhibited the pathogenicity of B. cinerea and activated the plant defense response against B. cinerea. Application of 80–100 µg mL−1 wuyiencin effectively controlled grape gray mold (by 57.6–88.1% on leaves and 46.7–96.6% on fruits). Consequently, the application of 80–100 µg mL−1 wuyiencin effectively mitigated grape gray mold incidence, leading to a substantial reduction in disease symptoms to nearly imperceptible levels. When wuyiencin (at the median effective concentration [EC50]) was combined with pyrimethanil (EC50) at a ratio of 7:3, it exhibited the highest efficacy in inhibiting B. cinerea growth. This combination was significantly more potent (p < 0.05) than using wuyiencin or pyrimethanil alone in controlling gray mold on grape leaves and fruits. Furthermore, the combination effectively delayed resistance development in gray mold. The experimental results show that wuyiencin can delay resistance development by affecting the expression of methionine biosynthesis genes and reducing the activity of the cell wall-degrading enzyme activity.
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Botryotinia fuckeliana (de Bary) Whetzel, anamorph Botrytis cinerea Pers.:Fr. causes severe damages in vineyards on the yield as well as on quality of grapes at harvest. Pyrimethanil (anilinopyrimidine fungicide class) have been used to control grey mould, the disease caused by this pathogen. The anilinopyrimidine were registered in Switzerland in 1995 to control grey mould in grapes. A dual mode of action has been described involving the inhibition of methionine biosynthesis and the inhibition of hydrolytic enzyme secretion. The anilinopyrimidines inhibit mycelial growth of fungus. The intensive use of anilinopyrimidines may result reduced sensitivity and loss of efficacy. Recently, a reduction in sensitivity to anilinopyrimidines in B. cinerea strains was also reported from France. In the last 35 years B. cinerea developed resistance to virtually all the specific fungicides used to control grey mould. Field resistance to benzimidazoles, phenylcarbamates and dicarboximides was detected shortly after their introduction. Therefore, an antiresistance strategy should be introduced for current fungicides as well. This study was initiated to study the resistance of B. cinerea to one of the main important class of modern fungicides, the anilinopyrimidines viz. pyrimethanil. This information will be useful to provide alternative fungicide options to the growers.
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Botrytis cinerea is a necrotrophic pathogen causing a major problem in the export and post-harvest of strawberries. Inappropriate use of fungicides leads to resistance among fungal pathogens. Therefore, it is necessary to evaluate the sensitivity of B. cinerea to various classes of fungicide and to determine the effectiveness of different concentrations of commonly used fungicides. We thus evaluated the effectiveness of six classes of fungicide in inhibiting the growth and development of this pathogen, namely, fludioxonil, iprodione, pyrimethanil, tebuconazole, fenpyrazamine, and boscalid. Fludioxonil was the most effective (EC50 < 0.1 μg/ml), and pyrimethanil was the least effective (EC50 = 50 μg/ml), at inhibiting the mycelial growth of B. cinerea. Fenpyrazamine and pyrimethanil showed relatively low effectiveness in inhibiting the germination and conidial production of B. cinerea. Our results are useful for the management of B. cinerea and as a basis for monitoring the sensitivity of B. cinerea strains to fungicides. Keywords: Botrytis cinerea, fungicide, strawberry
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Fludioxonil
Iprodione
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Azole
Raphanus
Tebuconazole
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