Alternative Fungicide Research Articles

Evaluating Alternative Fungicides for Effective Management of Rice Blast Disease: Inhibitory Effects on Pyricularia oryzae Cavara

Tricyclazole has been a successful solution for managing rice blast for over three decades. However, the continuous use of this fungicide has led to the development of resistance and the accumulation of tricyclazole residues within rice grains, prompting a ban on its usage in India. In response to this pressing issue, the present study aims to evaluate the efficacy of alternative fungicides in controlling the growth of Pyricularia oryzae, the causal agent of rice blast. The study employed a comprehensive approach, assessing the performance of various fungicides, including picoxystrobin, hexaconazole, isoprothiolane, kresoxim methyl, pyraclostrobin, tebuconazole, kitazin, and zineb, at varying dosage levels (100%, 75%, and 50% of the recommended dose). The findings of this investigation indicated that hexaconazole, isoprothiolane, kitazin, and zineb exhibited a 100% inhibition of P. oryzae growth across all tested doses. Pyraclostrobin also demonstrated a 100% inhibition at the highest dose, although its effectiveness decreased slightly at lower doses. In contrast, picoxystrobin and kresoxim methyl did not exhibit significant effectiveness in controlling the growth of the rice blast pathogen. These results provide valuable insights into the potential alternatives to tricyclazole for managing rice blast when used either alone or in combination at reduced doses.

Efficiency and resistance risk of flusilazole against northern corn leaf blight caused by Setosphaeria turcica

Northern corn leaf blight (NCLB) infected by Setosphaeria turcica is a devastating disease of corn worldwide. Flusilazole is a broad-spectrum triazole fungicide. However, its resistance risk and field efficiency in controlling NCLB are still unknown. The present research evaluated the antifungal activity of flusilazole against 101 S. turcica isolates, and their EC50 values ranged from 0.0013 to 0.0466 μg/mL, with a mean of 0.0157 μg/mL. Seven S. turcica mutants resistant to flusilazole were obtained from two wild-type isolates by fungicide adaptation. After 10 consecutive transfers on PDA medium without fungicide, their resistance decreased. Cross-resistance was not existed between flusilazole and fluazinam, pyraclostrobin, amobam, epoxiconazole, or fluxapyroxad. Compared to the wild-type isolates, seven flusilazole-resistant mutants showed reduced biological fitness. No point mutation was detected, however, over-expression of StCYP51 and StatrD genes were detected in the resistant mutants. In addition, in the field experiment, flusilazole exhibited over 85 % efficacy against NCLB, significantly higher than amobam. In summary, these results suggested that the resistance risk of S. turcica to flusilazole was low, and the over-expression of StCYP51 and StatrD might be related to the flusilazole resistance against S. turcica. Flusilazole showed great potential as an alternative fungicide for controlling NCLB.

Optimizing fungicide programs for peanut leaf spot management in Southeast Alabama: A case for reducing chlorothalonil use

Early leaf spot (caused by Passalora arachidicola) and late leaf spot (Nothopassalora personata) are the most damaging fungal diseases of peanuts (Arachis hypogaea L.) in the southeastern United States. Producers rely heavily on single-site fungicides, which pose a moderate to high risk for resistance development. To mitigate this risk, chlorothalonil, the predominate multi-site fungicide used to manage leaf spot diseases in peanuts, is the backbone of leaf spot spray programs. However, the future availability of chlorothalonil in agriculture is at risk due to regulatory decisions and toxicity issues. Thus, this study was undertaken to evaluate the efficacy of copper sulfate, dodine, and sulfur alone or in combination with other single-site fungicides against leaf spot diseases as chlorothalonil alternatives as well as their influence on yield. Under low disease pressure, all the alternative fungicide programs provided statistically similar leaf spot control when compared to chlorothalonil alone. In contrast, under high disease pressure in 2022, dodine alone and dodine + penthiopyrad did not significantly decrease leaf spot severity when compared to the nontreated control. Additionally, dodine alone and the 2022 premium fungicide program had significantly higher leaf spot severity when compared to chlorothalonil alone under favorable weather patterns for rapid disease development. Sulfur + copper sulfate significantly reduced leaf spot severity as compared to chlorothalonil alone only in 2022. All other remaining fungicide programs provided statistically similar control as chlorothalonil alone. Overall, dodine, sulfur, and copper sulfate have potential to serve as alternatives to chlorothalonil in leaf spot fungicide spray programs in peanuts.

Inhibitory Activities of Five Fungicides on Alternaria suffruticosae and Their Field Control Efficacy Against Tree Peony Black Spot.

Tree peony black spot (TPBS), mainly caused by Alternaria suffruticosae, is a common leaf disease on the ornamental peony, which poses a great threat to the flower buds in the current year and the flowering quality in the next year. However, there is only one fungicide registered for the control of this disease, difenoconazole. In order to avoid the severe problem of pathogen resistance caused by long-term use of difenoconazole, it is necessary to screen more chemical fungicides for the prevention and control of TPBS. In this study, the biological activities of flutolanil, phenamacril, pyraclostrobin, and boscalid on mycelial growth, conidial germination, germ tube elongation, and sporulation quantity of A. suffruticosae were determined, and the field control efficacy was tested to evaluate the preventive and therapeutic activities. Difenoconazole was used as a control simultaneously. The results showed that pyraclostrobin had the strongest inhibitory effects on the conidial germination, mycelium growth, germ tube elongation, and sporulation quantity, with the average EC50 values of 0.0517, 0.5343, 0.0008, and 0.8068 μg/ml, respectively. The inhibitory activity of flutolanil on the four developmental stages of A. suffruticosae was weaker than that of the other three fungicides. Compared with flutolanil, boscalid, the other succinate dehydrogenase inhibitor, had more strong inhibitory effects on the mycelial growth and sporulation quantity, with the average EC50 values of 3.8603 and 1.4760 μg/ml, respectively. Phenamacril had a moderate inhibitory level and had more inhibitory activity on conidial germination and germ tube elongation, with the average EC50 values of 31.5349 and 5.2597 μg/ml, respectively. All of the four fungicides had no significant effects on the shape of spores and germ tubes. The control fungicide difenoconazole had the strongest inhibitory activity on mycelial growth, and the average EC50 value was only 0.3297 μg/ml. However, its inhibitory activity on the other three growth stages was not high. In the field trials, pyraclostrobin had high control efficacy on TPBS even at low concentrations, reaching a minimum of 62.6293%, which was higher than that of difenoconazole. The other three fungicides had higher control efficacy at high concentrations but decreased significantly at low concentrations. Considering the dosage and control efficacy, pyraclostrobin was the first choice for the control of TPBS. Pyraclostrobin is the preferred alternative fungicide to difenoconazole for the prevention and control of TPBS in production.

Antifungal Activity and Putative Mechanism of HWY-289, a Semisynthetic Protoberberine Derivative, against Botrytis cinerea.

The emergence of resistant pathogens has increased the demand for alternative fungicides. The use of natural products as chemical scaffolds is a potential method for developing fungicides. HWY-289, a semisynthetic protoberberine derivative, demonstrated broad-spectrum and potent activities against phytopathogenic fungi, particularly Botrytis cinerea (with EC50 values of 1.34 μg/mL). SEM and TEM imaging indicated that HWY-289 altered the morphology of the mycelium and the internal structure of cells. Transcriptomics revealed that it could break down cellular walls through amino acid sugar and nucleotide sugar metabolism. In addition, it substantially decreased chitinase activity and chitin synthase gene (BcCHSV) expression by 53.03 and 82.18% at 1.5 μg/mL, respectively. Moreover, this impacted the permeability and integrity of cell membranes. Finally, HWY-289 also hindered energy metabolism, resulting in a significant reduction of ATP content, ATPase activities, and key enzyme activities in the TCA cycle. Therefore, HWY-289 may be a potential candidate for the development of plant fungicides.

Inhibitory effect and action mechanism of citral against black rot in pitaya fruit

Blackspot, caused by Alternaria alternata, is a significant postharvest disease in pitaya. Currently, there are limited effective fungicides to manage this disease. This study aimed to evaluate the antifungal activity of citral against the blackspot pathogen and to determine the protective effect of citral on pitaya. Our results demonstrated that citral effectively curtailed the mycelial growth and spore germination of Alternaria alternata, with a minimum inhibitory concentration (MIC) of 0.6 μL/mL. Observations under a light microscope revealed that citral-treated hyphae displayed characteristics such as sparseness, roughness, twisting, shriveling, and irregular internode separation, along with prominent vacuolation. Propidium iodide and 2,7-Dichlorodi-hydrofluorescein diacetate staining results revealed that the mycelia from the MIC citral-treated group emitted robust fluorescence, with the average fluorescence intensities being 4.03 and 8.09 times higher than the control group, respectively. Furthermore, citral treatment resulted in a decline in the lipid content and dry weight of the hyphae, increased nucleic acid and protein leakage, enhanced exosporial conductivity, and augmented superoxide dismutase (SOD) and catalase (CAT) enzyme activities. Additionally, it fostered the accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA). Fruit damage inoculation assays indicated that an appropriate concentration of citral (1/2 MIC, MIC) could notably diminish the fruit spot diameter expansion. Thus, citral shows promise as a potential alternative fungicide for managing postharvest black rot in pitaya.

Evaluation of fungicidal efficacy of free and nano-encapsulated chitosan against <i>Aspergillus flavus</i> isolated from rice (<i>Oryza sativa</i>) seed

Grains are exposed to contamination by mycotoxins, both in the field and during storage. Aflatoxins produced by Aspergillus species are the most harmful and carcinogenic mycotoxins in grains. Synthetic fungicides are widely used for the control of mycotoxigenic fungi in grains. However, rising public awareness about the toxicological effects of fungicides on human health necessitates the development of non-toxic bio-fungicides. In this connection, reports have shown that chitosan synthesized from shell waste has the potential to serve as an alternative fungicide. Therefore, this study investigated the fungicidal efficacy of free and nano-encapsulated chitosan against aflatoxigenic fungus (Aspergillus flavus). High molecular weight chitosan was purchased, and the in-vitro antifungal efficacy of chitosan against A. flavus was tested using the food poisoning method. Nano-encapsulated chitosan was synthesized using the ionic gelation method, the particle size was determined, and invitro inhibition against A. flavus was investigated. The results revealed that nano-encapsulated chitosan with particle sizes of 525.4 nm, 468.3 nm, and 711.7 nm were obtained. In-vitro mycelial A. flavus growth inhibition of 100% was recorded at 1.5% and 2.0% of free chitosan, while at 0.5% and 1.0% of free chitosan, 45% and 75% inhibition were observed, respectively. Nano-encapsulated chitosan with particle size (nm) of 525.4, 468.3, and 711.7 at 0.50% recorded 61%, 84% and 87% inhibition, respectively. However, at 0.25%, the rate of inhibition was 64%, 78% and 67%, respectively. This study showed that free chitosan and nano-encapsulated chitosan are potential antifungal agents for the control of A. flavus.

Anti-fungal activity of a novel succinate dehydrogenase inhibitor pydiflumetofen against Bipolaris maydis

Southern corn leaf blight (SCLB) is a disease caused by Bipolaris maydis. Pydiflumetofen is a novel succinate dehydrogenase inhibitor (SDHI) fungicide. However, its inhibitory activity against B. maydis has not been investigated in depth. In this study, mycelial growth rate and spore germination methods were used to establish a baseline for the sensitivity of 102 B. maydis strains collected from five regions of China to pydiflumetofen. The results showed that pydiflumetofen exhibited strong inhibitory activity against B. maydis. The EC50 values ranged from 0.0292 to 0.5207 μg/mL and from 0.0115 to 0.4883 μg/mL, with the average EC50 values of 0.2050 ± 0.1779 μg/mL and 0.1858 ± 0.0994 μg/mL for inhibition of mycelial growth and spore germination, respectively. After treatment with pydiflumetofen, the apical branching of mycelia increased significantly, and morphological changes such as twisting, deformation, rupture, and shriveling of mycelia and spores were observed. In addition, it significantly increased cell membrane permeability and decreased succinate dehydrogenase (SDH) activity and adenosine triphosphate (ATP) content. Moreover, the SDH gene expressions were changed, in which MbSdhB, MbSdhC and MbSdhD expressions were significantly upregulated, except for MbSdhA expression, which was significantly downregulated. In detached leaf experiments, pydiflumetofen showed strong protective and curative effects against B. maydis, superior to the same concentration of prochloraz and pyraclostrobin, and its protective effect was better than its curative effect. The field trials showed that the control efficacy of pydiflumetofen at 225 g/hm2 was >70% and its control efficacy at 300 g/hm2 reached 81.77%, which was significantly higher than that of pyraclostrobin and epoxiconazole at the same dosage. After 1:1 mixing of pydiflumetofen with the above control agents, the control efficacies of these mixtures at the same dosage increased compared to the use of a single agent. All the above results demonstrated that pydiflumetofen exhibits excellent inhibitory activity against B. maydis and good control of SCLB, suggesting that it could be used as an alternative fungicide for the control of SCLB.

Dodine as an alternative to chlorothalonil in the control of leaf spot diseases in peanut

AbstractPeanut (Arachis hypogaea L.) is susceptible to leaf spot diseases caused by the fungi Nothopassalora personata and Passalora arachidicola, which can decrease yield substantially. Chlorothalonil is one of the most widely used fungicides to control these diseases but was recently banned in the European Union due to toxicity to amphibians and fish. Dodine is an alternative fungicide with a similar range of activity. However, information about its impact on the peanut physiology is lacking. The objectives of this study were to assess the effect of dodine on leaf photosynthesis, yield, and pod quality of peanut and evaluate the potential of dodine as a replacement of chlorothalonil in the control of leaf spot diseases. A 3‐year field experiment was conducted using Georgia‐06G. Treatments consisted of chlorothalonil at 0.86 kg a.i. ha−1 (high rate), chlorothalonil at 0.43 kg a.i. ha−1 (low rate), dodine at 0.68 kg a.i. ha−1 (high rate), and dodine at 0.34 kg a.i. ha−1 (low rate). Photosynthetic efficiency was altered by fungicide in only a few instances, and a clear trend was not observed. The high rate of dodine resulted in the least defoliation caused by leaf spot of all fungicide treatments. Pod maturity, yield, and grading parameters were not affected by fungicide. Overall, dodine did not impact negatively the photosynthetic activity, pod quality, and yield of peanut. Moreover, this chemistry was efficient in controlling leaf spot diseases under heavy disease pressure; therefore, dodine is a potential replacement of chlorothalonil in the control of leaf spot diseases in peanut.

Replacing Mancozeb with Alternative Fungicides for the Control of Late Blight in Potato.

Mancozeb (MZ) is a broadly used fungicide for the control of plant diseases, including late blight in potatoes caused by the oomycete Phytophthora infestans (Mont.) De Bary. MZ has been banned for agricultural use by the European Union as of January 2022 due to its hazards to humans and the environment. In a search for replacement fungicides, twenty-seven registered anti-oomycete fungicidal preparations were evaluated for their ability to mitigate the threat of this disease. Fourteen fungicides provided good control (≥75%) of late blight in potted potato and tomato plants in growth chambers. However, in Tunnel Experiment 1, only three fungicides provided effective control of P. infestans in potatoes: Cyazofamid (Ranman, a QiI inhibitor), Mandipropamid (Revus, a CAA inhibitor), and Oxathiapiprolin + Benthiavalicarb (Zorvek Endavia, an OSBP inhibitor + CAA inhibitor). In Tunnel Experiment 2, these three fungicides were applied at the recommended doses at 7-, 9-, and 21-day intervals, respectively, totaling 6, 4, and 2 sprays during the season. At 39 days post-inoculation (dpi), control efficacy increased in the following order: Zorvec Endavia > Ranman > Revus > Mancozeb. Two sprays of Zorvec Endavia were significantly more effective in controlling the blight than six sprays of Ranman or four sprays of Revus. We, therefore, recommend using these three fungicides as replacements for mancozeb for the control of late blight in potatoes. A spray program that alternates between these three fungicides may be effective in controlling the disease and also in avoiding the build-up of resistance in P. infestans to mandipropamid and oxathiapiprolin.

Iminoctadine tris (albesilate) resistance in Geotrichum citri-aurantii and its management

The bis-guanidine fungicide iminoctadine tris (albesilate) (ITA) is widely used to control citrus sour rot pathogen Geotrichum citri-aurantii but its resistance status in the orchards is still unclear. In the present study, ITA resistance in G. citri-aurantii was assessed and resistance mechanisms and its alternative fungicides were explored. ITA resistance frequency in field isolates of G. citri-aurantii collected between 2018 and 2020 from orchards in China was 6.2%. Consecutively culturing on potato dextrose agar (PDA) for 10 generations showed that ITA resistance for field resistant isolates was relatively stable, whereas resistance for the laboratory induced resistant isolates declined by 53.9%. The competitive ability on citrus fruit for resistant isolates was substantially lower than that of the sensitive isolates. Resistance mechanism studies showed that an ATP-binding cassette (ABC) gene (EVM0003677) and two major facilitator superfamily (MFS) genes (EVM0000087 and EVM0003101) might be involved in ITA resistance only in the induced resistant isolates but not in the field resistant isolates. Bioassay of 26 fungicides found that the demethylation inhibitor fungicides metconazole and propiconazole, and the dinitro-aniline fungicide fluazinam were highly effective to ITA-sensitive isolates of G. citri-aurantii and their EC50 values were 0.33, 0.56, and 0.54 mg/L, respectively. The protective control efficacies of ITA, propiconazole, metconazole, and fluazinam all at 400 mg/L were 100%, 60.4%, 33.9%, and 18.5%, respectively. No positive cross resistance was detected between ITA and metconazole, propiconazole or fluazinam. The mixture of ITA and propiconazole at the mass ratio of 9:8 had a synergistic co-toxicity factor of 26. These results have significant implications for our awareness of ITA resistance in orchards and its management.

Antifungal Properties of Nanosilver Clay Composites Against Fungal Pathogens of Agaricus bisporus

AbstractThis study aimed to determine the possible control of selected pathogenic and competitive fungi of A. bisporus by three nanosilver clay composites and establish the effective concentrations of the composites for inhibiting pathogens. Nanosilver (AgNPs) clay (zeolite, montmorillonite, and palygorskite) composites were synthesized by a microwave‐assisted surface functionalization technique, and various techniques characterized the products. Zeolite and montmorillonite composites showed uniformly distributed spherical AgNPs with an average size of 3.33 nm and 2.85 nm, respectively, whereas palygorskite presented agglomerated and unevenly distributed AgNPs. The influence of the various composites on 9 fungi, including strains of T. aggressivum f. aggressivum, L. fungicola, C. dendroides, and Mycogone sp., was determined in vitro at different concentrations. At 10 mg/mL, AgNP‐zeolite and AgNP‐montmorillonite inhibited 8 out of 9 pathogens, while AgNP‐palygorskite only inhibited 1 pathogen. The nanosilver clay composites tested against A. bisporus revealed no adverse effects on mycelial growth at any concentrations tested. This study confirms that AgNP‐zeolite and AgNP‐montmorillonite composites have effective antifungal properties and can be used as alternative fungicides against mushroom pathogens without affecting A. bisporus growth. However, further investigation is required to unravel the mechanism of selective antifungal activity observed in this study.

In-silico prediction, characterization, molecular docking and dynamic simulation studies for screening potential fungicides against leaf rust of Triticum aestivum

Triticum aestivum is an important crop worldwide, which is a large source of food grain. T.aestivum demands on developed countries will grow every year, this increase in the demand is profoundly serious especially in the light climate change which would lead to a 29% reduction in final productivity. Rust fungus attacks the T.aestivum, specifically newly planted T.aestivum plants, which block the vascular system, stun, and finally damage grain and tillers. In present study we predict the 3D structure then find the binding pocket and conserved domains for MAPkinase-1 of Puccinia triticina. After that, screen the FungiPAD, PubChem, NPAtlas databases by physicochemical properties, docking, clustering, ADME (Absorption, distribution, metabolism, and excretion) and PAINS (pan assay interference compounds) filter analysis. Through this screening process screen the nine compounds, which are benzovindiflupyr, furametpyr, isopyrazam, fenaminstrobin, and flumorph from Fungicide database: zoxamide, vinclozolin, pentachloronitrobenzene, and dithianon from PubChem database, based on the binding energy, clustering, ADME and PAINS analysis. All these nine compounds bind in the same pocket and show the same pattern of interaction. Among these nine compounds, select the two compounds (PubChem:122087 (-6.96 kcal/mol) and FDBD02904 (-8.62 kcal/mol)) based on binding energy for 100 ns MD simulation and free energy calculation. MD simulation shows stability throughout the simulation, and it shows the sable interaction when compounds bind to the MAPKinase 1 protein which may help to protein kinase pathways in plant defense response. This result helps to design alternative fungicide against the wheat rust disease. Communicated by Ramaswamy H. Sarma

Ascochyta blight in North Dakota field pea: the pathogen complex and its fungicide sensitivity.

Worldwide, Ascochyta blight is caused by a complex of host-specific fungal pathogens, including Ascochyta pisi, Didymella pinodes, and Didymella pinodella. The application of foliar fungicides is often necessary for disease management, but a better understanding of pathogen prevalence, aggressiveness, and fungicide sensitivity is needed to optimize control. Leaf and stem samples were obtained from 56 field pea production fields in 14 counties in North Dakota from 2017 to 2020 and isolates were collected from lesions characteristic of Ascochyta blight. Based on fungal characteristics and sequencing the ITS1-5.8S-ITS2 region, 73% of isolates were confirmed to be D. pinodes (n = 177) and 27% were A. pisi (n = 65). Across pathogens, aggressiveness was similar among some isolates in greenhouse assays. The in vitro pyraclostrobin sensitivity of all D. pinodes isolates collected from 2017 to 2020 was lower than that of the three baseline isolates. Sensitivity of 91% of A. pisi isolates collected in 2019 and 2020 was lower than the sensitivity of two known sensitive isolates. Resistance factors (Rf) from mean EC50 values of pyraclostrobin baseline/known sensitive isolates to isolates collected from 2017 to 2020 ranged from 2 to 1,429 for D. pinodes and 1 to 209 for A. pisi. In vitro prothioconazole sensitivity of 91% of D. pinodes isolates collected from 2017 to 2020 was lower than the sensitivity of the baseline isolates and 98% of A. pisi isolates collected from 2019 to 2020 was lower than the sensitivity of the known sensitive isolates. Prothioconazole Rf ranged from 1 to 338 for D. pinodes and 1 to 127 for A. pisi. Based on in vitro results, 92% of D. pinodes and 98% of A. pisi isolates collected displayed reduced-sensitivity/resistance to both fungicides when compared to baseline/known sensitive isolates. Disease control under greenhouse conditions of both pathogens provided by both fungicides was significantly lower in isolates determined to be reduced-sensitive or resistant in in vitro assays when compared to sensitive. Results reported here reinforce growers desperate need of alternative fungicides and/or management tools to fight Ascochyta blight in North Dakota and neighboring regions.

Baseline Pydiflumetofen Sensitivity of Fusarium pseudograminearum Isolates Collected from Henan, China, and Potential Resistance Mechanisms.

Fusarium crown rot (FCR), caused by Fusarium pseudograminearum, is one of the most important diseases impacting wheat production in the Huanghuai region, the most important wheat-growing region of China. The current study found that the SDHI fungicide pydiflumetofen, which was recently developed by Syngenta Crop Protection, provided effective control of 67 wild-type F. pseudograminearum isolates in potato dextrose agar, with an average EC50 value of 0.060 ± 0.0098 μg/ml (SE). Further investigation revealed that the risk of fungicide resistance in pydiflumetofen was medium to high. Four F. pseudograminearum mutants generated by repeated exposure to pydiflumetofen under laboratory conditions indicated that pydiflumetofen resistance was associated with fitness penalties. Mutants exhibited significantly (P < 0.05) reduced sporulation in mung bean broth and significantly (P < 0.05) reduced pathogenicity in wheat seedlings. Sequence analysis indicated that the observed pydiflumetofen resistance of the mutants was likely associated with amino acid changes in the different subunits of the succinate dehydrogenase target protein, including R18L and V160M substitutions in the FpSdhA sequence; D69V, D147G, and C257R in FpSdhB; and W78R in FpSdhC. This study found no evidence of cross-resistance between pydiflumetofen and the alternative fungicides tebuconazole, fludioxonil, carbendazim, or fluazinam, which all have distinct modes of action and could therefore be used in combination or rotation with pydiflumetofen to reduce the risk of resistance emerging in the field. Taken together, these results indicate that pydiflumetofen has potential as a novel fungicide for the control of FCR caused by F. pseudograminearum and could therefore be of great significance in ensuring high and stable wheat yields in China.

Comparative Study Between Alternative Fungicides and Traditional Fungicides Alone and Combined in Management Banana Root Rot

Comparative Study Between Alternative Fungicides and Traditional Fungicides Alone and Combined in Management Banana Root Rot

Application of phyto-fabricated zinc oxide nanoparticles to diminish brown spot of pear whilst maintaining its quality.

Pyrus communis is a common fruit of temperate region, its domestication and origin is at two different points, Asia and China. Pear fruits bearing brown spot symptoms were picked, and pathogen was isolated and poured on Potato Dextrose Agar (PDA) media. On basis of molecular and molecular analyses, this isolated pathogen was identified as Alternaria alternata. Zinc oxide nanoparticles (ZnO NPs) were prepared from Theveti peruviana leaf extract and were characterized through various techniques Fourier Transform Infrared Spectroscopy (FTIR) analysis of prepared ZnO NPs depicted the presence of agents responsible for stabilization and reduction such as alkenes, alkynes, nitro compounds, alkyl halides, aromatic compounds and aliphatic amines. X-ray diffraction (XRD) analysis confirmed the size (27 nm) and crystalline nature of ZnO NPs. Scanning electron microscopy (SEM) depicted the irregular shape of the prepared ZnO NPs. Mass percentage of zinc (79.84%) and oxygen (20.16%) was depicted using Energy Dispersive X-Ray (EDX) analysis. The in vitro and in vivo antifungal activity (A.F) of prepared NPs against A. alternata was confirmed by poisoned food technique and wound inoculation method. On the basis of which it was concluded that 1.0 mg/mL concentration of ZnO NPs could effectively inhibit A. alteranata growth and minimize the risk of brown spot of pear. SEM images of A. alternata under 1 mg/mL NPs showed the deformation in morphology of A. alternata. ZnO NPs also aided in the preservation of its various organoleptic and biochemical properties. The high percentage of soluble solids, firmness, ascorbic acid and sugars demonstrated its high quality. It has been concluded that 1 mg/mL ZnO NPs can effectively control brown spot of pear while maintaining its quality. In addition, the method might be applied to control emerging diseases in an ecofriendly way to meet the global food demand. RESEARCH HIGHLIGHTS: Isolation and characterization of pathogen causing brown spot in pear. Pathogenicity of A. alternata was checked on healthy fruits. Thevetia peruviana leaf extract was used for the synthesis, characterization and antifungal assay of ZnO Nanoparticles. Green synthesized nanoparticles can be economically effective alternative fungicide for the large scale in agriculture fields.

Characterization and fitness of Fusarium graminearum mutants resistant to fluazinam

AbstractFusarium head blight (FHB), predominately caused by ascomycete Fusarium graminearum sensu stricto, is a devastating fungal disease of cereal crops worldwide. In this study, baseline sensitivity of F. graminearum s. str. to fluazinam was established using 100 isolates that were collected from Anhui and Jiangsu provinces of China in 2009 and 2018. The EC50 values of fluazinam on mycelial growth inhibition ranged from 0.0211 to 0.1097 μg/mL and the mean EC50 was 0.0601 ± 0.0191 μg/mL, which indicated that fluazinam had a strong inhibitory effect on mycelial growth of F. graminearum s. str. To acquire fluazinam‐resistant (FluR) mutants, one wild‐type strain (PH‐1, with assembled genome) and another four fluazinam‐sensitive (FluS) isolates randomly selected from the above‐mentioned population were domesticated with fluazinam or mutagenized by ultraviolet light in vitro. As a result, 45 FluR mutants were obtained with resistance frequencies of 0.68% (domestication) and 8 in 10−8 (mutagenesis), respectively. Of the 45 FluR mutants, 11 were selected to determine the biological fitness. Based on data of radial mycelial growth, asexual and sexual reproduction, response to environmental stresses, pathogenicity and deoxynivalenol production, all the tested mutants suffered from a fitness penalty. Additionally, slightly positive cross‐resistance was observed between the combination of fluazinam and tebuconazole, pyraclostrobin, or pydiflumetofen, but not phenamacril or carbendazim. Therefore, a low‐to‐moderate risk of development of F. graminearum s. str. resistant to fluazinam was suggested, indicating that fluazinam could be a good alternative fungicide against the FHB in the field.

Biocontrol efficacy of endophytic Trichoderma spp. in fresh and dry powder formulations in controlling northern corn leaf blight in sweet corn

Seventy-three endophytic Trichoderma spp. obtained from healthy corn leaves collected in the central and northeast parts of Thailand were evaluated for their biocontrol activity against northern leaf blight disease due to Exserohilum turcicum. Among them, T. asperellum KUFA0702, KUFA0703, T. hamatum KUFA0706, T. harzianum KUFA0710, and T. harzianum KUFA0713 showed promising biocontrol efficacy against the disease under laboratory and greenhouse conditions; thus, they were selected for control efficacy evaluation under field conditions using their fresh and dry powder formulations. The results found that the fresh formulation of each Trichoderma strain displayed better biocontrol effects than their dry formulation. In field trials, the application of fresh formulation of T. harzianum KUFA0710 displayed the best disease reduction at 55.70%, while its dry formulation caused 47.46% disease reduction followed by T. harzianum KUFA0713 at 49.92% and 43.84% disease reduction when applied as fresh and dry formulations, respectively. The antagonistic activities of Trichoderma spp. included fast growth with high competition for space and nutrients and production of antifungal crude extracts. Moreover, all Trichoderma strains showed compatibility fungicides at recommendation rate with azoxystrobin (1000 ppm) and difenoconazole + azoxystrobin (500 ppm). These fungi can serve as alternative fungicides or be combined with fungicides for integrated pest management.

Identification of Pathogens Causing Alfalfa Fusarium Root Rot in Inner Mongolia, China

Alfalfa Fusarium Root Rot (AFRR) is a serious soil-borne disease with a complex pathogenicity. Diseased samples suspected of AFRR were collected from Hohhot, Ordos, Hulunbeier, Chifeng, and Bayannur in Inner Mongolia, China, leading to 317 isolates. The isolates were identified as Fusarium acuminatum, F. solani, F. equiseti, F. incarnatum, F. oxysporum, F. avenaceum, F. verticillioides, F. proliferatum, F. falciforme, F. tricinctum, F. virguliforme, and F. redolens, and the results of pathogenicity testing showed that 12 Fusarium species could cause alfalfa root rot. Among these, F. verticillioides, F. falciforme, and F. virguliforme have not previously been reported to cause AFRR in China. Although the population structure of the pathogens differed in different regions, the dominant pathogenic species was F. acuminatum. Fungicide toxicity tests showed that seven fungicides inhibited F. acuminatum, of which fludioxonil, kresoxim-methyl, and triadimefon were found to be strongly toxic towards F. acuminatum with EC50 values of 0.09, 2.28, and 16.37 μg/mL, respectively, suggesting that these could be used as alternative fungicides for the control of AFRR. The results of this study can provide a theoretical basis for exploring the occurrence and epidemiology of alfalfa root rot and strategies for its control.