Development Of Fungicide Resistance Research Articles

Postharvest biocontrol of green mold (Penicillium digitatum) in citrus by Bacillus velezensis strain S161 and its mode of action

Green mold caused by Penicillium digitatum is a major postharvest disease of citrus that can result in significant losses during storage. Synthetic chemical fungicides typically used to control this disease have raised potential concerns regarding environmental pollution, human health, and the development of fungicide resistance. Biological control of postharvest diseases has been demonstrated to be an effective alternative to chemical control. In the present study, we investigated the postharvest biocontrol efficacy of Bacillus velezensis strain S161 against P. digitatum and its potential mechanisms of action. Results indicated that a cell-free supernatant (CFS) obtained from liquid culture of S161 strongly inhibited the mycelial growth, spore germination, and germ tube elongation of P. digitatum in vitro. The CFS effectively protected citrus fruit against P. digitatum, providing 95.6 % control. Further investigations revealed that the CFS degraded and ruptured hyphal membranes and spores and induced the excessive accumulation of reactive oxygen species (ROS) in hyphal cells resulting in oxidative damage. CFS exposure also resulted in the downregulation of genes associated with spore germination, growth, reproduction, and virulence. antiSMASH analysis of biosynthetic gene clusters (BGCs) in B. velezensis indicated that B. velezensis possesses several core clusters, encoding the synthesis of surfactin, bacillomycin D, fengycin, bacilysin, bacillibactin, macrolactin, difficidin, bacillaene, and amylocycicin. Further analysis using Liquid Chromatography Tandem Mass Spectrometry (LC-MS) revealed the presence of four of these metabolites (surfactin, iturin, fengycin, and bacillibactin) in the CFS of B. velezensis. Additional bioassays conducted in sealed plates revealed that volatile organic compounds (VOCs) produced by S161 also inhibited the growth of P. digitatum. A total of 24 VOCs were found to be produced by S161 using headspace solid-phase microextraction/gas chromatography-mass spectrometry (HS-SPME/GC-MS). The identified VOCs were mainly ketones and alcohols. Collectively, our results indicate that B. velezensis strain S161 is an effective biocontrol agent of P. digitatum on citrus and inhibits pathogen germination and growth through a range of mechanisms, including the downregulation of genes associated with spore germination and growth, induction of oxidative stress, and the antimicrobial activity of VOCs.

Multiple and multidrug resistance in Botrytis cinerea: molecular mechanisms of MLR/MDR strains in Greece and effects of co-existence of different resistance mechanisms on fungicide sensitivity.

Botrytis cinerea is a high-risk pathogen for fungicide resistance development. Within the fungal populations, strains have developed multiple mutations in different target genes leading to multiple resistance (MLR) or mutations associated with overexpression of efflux transporters leading to multidrug resistance (MDR). These types of resistance are a major threat, and their successful management is a major challenge. The current study was initiated to a) determine frequencies of MLR/MDR strains in populations originating from several crops, b) identify the types of MDR that occur in Greece, and c) determine interactions between MLR and MDR at the level of sensitivity to botryticides. The frequencies of MLR/MDR phenotypes were determined in 515 isolates subjected to bioassays using discriminatory concentrations of thiophanate-methyl, iprodione, cyprodinil, fenhexamid, boscalid, fluopyram, fludioxonil, pyraclostrobin, and tolnaftate. Interestingly, 7.8% and 31.3% of isolates from strawberry and rootstock seedlings were resistant to every single fungicide class, while MDR phenotypes from strawberries, rootstocks, and tomatoes accounted for 26%, 87%, and 13.4%, respectively. The MLR and MDR isolates were further molecularly analyzed regarding genes erg27, sdhB, Bcpos5, and Mrr1, responsible for resistance to fenhexamid, boscalid and fluopyram, cyprodinil, and MDR, respectively. The different mutations' presence was determined along with a new mutation in Mrr1 leading to MDR. MDR isolates were characterized as MDR1 or MDR1h based on the presence of a 3-bp deletion in Mrr1. MDR1h was predominant in isolates from rootstocks and MDR1 from tomatoes and strawberries, whereas the most frequent target-site mutations were F412S (erg27), H272R (sdhB), and L412F (Bcpos5). To determine whether the accumulation of target-site mutations along with MDR mutations exhibits an additive effect concerning fungicide resistance, the sensitivity of isolates possessing the predominant target-site mutations was calculated in both the presence and the absence of MDR-associated mutations. EC50 in cyprodinil and boscalid increased to about twofold in the presence of MDR mutations, while there was no difference for fenhexamid. In conclusion, MLR/MDR frequencies are notably high in heavily treated crops in Greece, and the combination of MLR and MDR mutations leads to even higher fungicide resistance levels, highlighting the importance of resistance management.

SP-141 targets Trs85 to inhibit rice blast fungus infection and functions as a potential broad-spectrum antifungal agent

Rice blast is a devastating disease worldwide, threatening rice production and food security. The blast fungus Magnaporthe oryzae invades the host via the appressorium, a specialized pressure-generating structure that generates enormous turgor pressure to penetrate the host cuticle. However, owing to ongoing evolution of fungicide resistance, it is vitally important to identify new targets and fungicides. Here, we show that Trs85, a subunit of the transport protein particle III complex, is essential for appressorium-mediated infection in M. oryzae. We explain how Trs85 regulates autophagy through Ypt1 (a small guanosine triphosphatase protein) in M. oryzae. We then identify a key conserved amphipathic α helix within Trs85 that is associated with pathogenicity of M. oryzae. Through computer-aided screening, we identify a lead compound, SP-141, that affects autophagy and the Trs85–Ypt1 interaction. SP-141 demonstrates a substantial capacity to effectively inhibit infection caused by the rice blast fungus while also exhibiting wide-ranging potential as an antifungal agent with broad-spectrum activity. Taken together, our data show that Trs85 is a potential new target and that SP-141 has potential for the control of rice blast. Our findings thus provide a novel strategy that may help in the fight against rice blast.

Assessing the Baseline Sensitivity of Predominant Soil-Borne Pathogens against Carbendazim

Fungicide resistance is reducing the effectiveness of fungicides in controlling plant diseases, leading to increase crop losses and the need for alternative control strategies. Addressing this issue requires careful fungicide use and the development of new management approaches. The main objective of present study was to determine the baseline sensitivity and development of fungicide resistance in predominant soil-borne pathogens against carbendazim at various concentrations. It was observed that the EC50 of Fusarium oxysporum and Macrophomina phaseolina was 9.970 and 16.294 µg ml-1, respectively. The baseline sensitivity of both fungi was determined based on the inhibition percentage at which the pathogen showed sensitivity. Repeated transfer of these cultures at same concentrations for some generations showed the progressive decline in growth inhibition across generations resulting in the development of fungicide resistance. These studies have demonstrated that overreliance on certain fungicides can lead to the development of resistant fungal strains, compromising the efficacy of disease management. This emphasizes alternative use of fungicides with different mode of action or following integrated disease management strategies to mitigate fungicide resistance and sustainably protect crops.

The cotton charcoal rot causal agent, Macrophomina phaseolina, biological and chemical control.

The fungus Macrophomina phaseolina causes charcoal rot disease (CRD) in cotton, whose symptoms develop in the late stages of growth and result in wilting and death. Despite significant research efforts to reduce disease incidences, effective control strategies against M. phaseolina are an ongoing scientific effort. Today's CRD control tends toward green options to reduce the chemicals' environmental footprint and health risks. Here, different Trichoderma species were examined separately and in combination with Azoxystrobin (AS) in semi-field open-enclosure pots and a commercial field throughout a full season. In the pot experiment, the T. asperellum (P1) excelled and led to improvement in growth (13%-14%, day 69) and crops (the number of capsules by 36% and their weight by 78%, day 173). The chemical treatment alone at a low dose had no significant impact. Still, adding AS improved the effect of T. longibrachiatum (T7507) and impaired P1 efficiency. Real-time PCR monitoring of the pathogen DNA in the plants' roots at the harvest (day 176), revealed the efficiency of the combined treatments: T. longibrachiatum (T7407 and T7507) + AS. In a commercial field, seed dressing with a mixture of Trichoderma species (mix of P1, T7407, and Trichoderma sp. O.Y. 7107 isolate) and irrigation of their secreted metabolites during seeding resulted in the highest yields compared with the control. Applying only AS irrigation at a low dose (2,000 cc/ha), with the sowing, was the second best in promoting crops. The molecular M. phaseolina detection showed that the AS at a high dose (4,000 cc/ha) and the biological mix treatments were the most effective. Reducing the AS chemical treatment dosages by half impaired its effectiveness. Irrigation timing, also studied here, is proven vital. Early water opening during the late spring suppresses the disease outburst and damages. The results demonstrated the benefits of CRD bio-shielding and encouraged to explore the potential of a combined bio-chemo pest control approach. Such interphase can be environmentally friendly (reducing chemical substances), stabilize the biological treatment in changing environmental conditions, achieve high efficiency even in severe CRD cases, and reduce the development of fungicide resistance.

Target and non-target site mechanisms of fungicide resistance and their implications for the management of crop pathogens.

Fungicides are indispensable for high-quality crops, but the rapid emergence and evolution of fungicide resistance have become the most important issues in modern agriculture. Hence, the sustainability and profitability of agricultural production have been challenged due to the limited number of fungicide chemical classes. Resistance to site-specific fungicides has principally been linked to target and non-target site mechanisms. These mechanisms change the structure or expression level, affecting fungicide efficacy and resulting in different and varying resistance levels. This review provides background information about fungicide resistance mechanisms and their implications for developing anti-resistance strategies in plant pathogens. Here, our purpose was to review changes at the target and non-target sites of quinone outside inhibitor fungicides (QoIs), methyl-benzimidazole fungicides (MBCs), demethylation inhibitor fungicides (DMIs), and succinate dehydrogenase inhibitor fungicides (SDHIs) and to evaluate if they may also be associated with a fitness cost on crop pathogen populations. The current knowledge suggests that understanding fungicide resistance mechanisms can facilitate resistance monitoring and assist in developing anti-resistance strategies and new fungicide molecules to help solve this issue. This article is protected by copyright. All rights reserved.

The antifungal activity of trans‐cinnamic acid and its priming effect in apple in response to Valsa mali

AbstractValsa mali causes Valsa canker, one of the most destructive diseases on apple trees, leading to severe losses for the apple industry in China. Considering the development of fungicide resistance and the harmful effects of chemical residues, it is urgent to identify alternatives to control this disease. Trans‐cinnamic acid (t‐CA), a compound with good antibacterial, antitumour and anti‐inflammatory properties, is widely used in food, medicine and other industries. However, the antifungal activity of t‐CA against V. mali and its regulatory role in apple defence against biotic stresses are unclear. Based on a metabolomic assay, we found that Malus yunnaensis (Valsa canker‐resistant) twigs infected with V. mali dramatically accumulated t‐CA. Exogenous application of t‐CA effectively inhibited V. mali growth on potato dextrose agar. The EC50 value of t‐CA inhibiting mycelial growth was 200 μg/mL. Malus prunifolia (Valsa canker‐susceptible) leaves and twigs pretreated with t‐CA had significantly enhanced V. mali resistance. The t‐CA application increased salicylic acid but reduced jasmonic acid levels in leaves and twigs. Moreover, the contents of phenolic acids and flavonoids increased in t‐CA‐treated samples. In addition, t‐CA increased the activities of phenylalanine ammonia‐lyase, β‐1,3‐glucanase and chitinase. These results indicate that t‐CA plays a significant role in inhibiting V. mali growth and priming apple defence.

Influence of cultivar, environmental conditions, and fungicides on development of Phytophthora root rot and wilt on red raspberry

Phytophthora root rot and wilt (PRRW), caused by Phytophthora rubi and potentially other species of Phytophthora, is a destructive disease of raspberry in Canada and worldwide. In this study, trials were conducted over multiple years (2019–2022) in two fields, with pathogen (P. rubi) inoculated (PI) and naturally infested (NI) fields, to evaluate foliar and soil applied fungicides with different modes of action and application timings to manage PRRW. In addition, PRRW progress was also monitored in one PI field and four NI fields. In PI field plots, PPRW foliage and wilting symptoms appeared 6–8 weeks later and disease index was significantly (p < 0.0042) lower in the cultivar ‘Cascade Bounty’ than the cultivars ‘Meeker’ and ‘Tulameen’, indicating that ‘Cascade Bounty’ showed field tolerance to the disease. The efficacy of foliar fungicides (fosetyl-Al and phosphites) and soil-applied fungicides (oxathiapiprolin, metalaxyl-m, and cyazofamid) were assessed on susceptible cultivars at both sites. In PI plots, the fungicide treatments significantly enhanced (p = 0.01 to < 0.0001) numbers of primocanes and floricanes, as well as weight, percent witling index, and fruit yield of floricanes. Soil application of a tank mix or rotation of oxathiapiprolin and metalaxyl-m, and alternating these products with cyazofamid, was more effective compared to other fungicides in reducing PRRW and improving plant vigor. Our study identified effective fungicide treatment options for PRRW, allowing growers to alternate new chemistries with currently registered fungicides to reduce the risk of fungicide resistance development.

Microbes in Management of Fungal Diseases of Grape

In India, grapes are commercially cultivated in the state of Maharashtra and some districts of Karnataka and Tamil Nadu which are characterized by warm, humid and intermittently wet or cloudy weather. Viticulture practices and grape pathology in these tropical regions is vastly different from that in temperate regions, necessitating greater emphasis on microbial interventions for disease management. Three fungal diseases namely, downy mildew, powdery mildew and anthracnose are the major threat to sustainable viticulture and cause great economic loss to growers. The high susceptibility of commercial grape varieties, presence of abundant inoculum in vineyards, and favourable weather for most part of the year, have a cumulative effect and disease outbreaks occur in a very short span of time. Dependence on chemicals alone has led to increase in cost of cultivation, development of fungicide resistance in pathogens, and presence of fungicide residues at harvest; apart from environmental concerns on continued and high use of fungicides. The use of naturally occurring microbes for biological control of diseases and also for induction of systemic resistance in susceptible grape varieties against these diseases is a safer and sustainable option. Worldwide researchers are searching for efficient microbes for management of grape diseases in vineyards and postharvest and this article is a compilation of their work.

Modelling quantitative fungicide resistance and breakdown of resistant cultivars: Designing integrated disease management strategies for Septoria of winter wheat.

Plant pathogens respond to selection pressures exerted by disease management strategies. This can lead to fungicide resistance and/or the breakdown of disease-resistant cultivars, each of which significantly threaten food security. Both fungicide resistance and cultivar breakdown can be characterised as qualitative or quantitative. Qualitative (monogenic) resistance/breakdown involves a step change in the characteristics of the pathogen population with respect to disease control, often caused by a single genetic change. Quantitative (polygenic) resistance/breakdown instead involves multiple genetic changes, each causing a smaller shift in pathogen characteristics, leading to a gradual alteration in the effectiveness of disease control over time. Although resistance/breakdown to many fungicides/cultivars currently in use is quantitative, the overwhelming majority of modelling studies focus on the much simpler case of qualitative resistance. Further, those very few models of quantitative resistance/breakdown which do exist are not fitted to field data. Here we present a model of quantitative resistance/breakdown applied to Zymoseptoria tritici, which causes Septoria leaf blotch, the most prevalent disease of wheat worldwide. Our model is fitted to data from field trials in the UK and Denmark. For fungicide resistance, we show that the optimal disease management strategy depends on the timescale of interest. Greater numbers of fungicide applications per year lead to greater selection for resistant strains, although over short timescales this can be oset by the increased control oered by more sprays. However, over longer timescales higher yields are attained using fewer fungicide applications per year. Deployment of disease-resistant cultivars is not only a valuable disease management strategy, but also oers the secondary benefit of protecting fungicide effectiveness by delaying the development of fungicide resistance. However, disease-resistant cultivars themselves erode over time. We show how an integrated disease management strategy with frequent replacement of disease-resistant cultivars can give a large improvement in fungicide durability and yields.

BLAST DISEASE A MAJOR THREAT TO FOOD SECURITY: A REVIEW OF PATHOGEN AND STRATEGIES TO CONTROL

Rice blast is caused by the fungi Magnaporthe oryzae, which belongs to the group Ascomycota. The disease cycle of rice blast begins with the infection of the plant tissue by the spores of the pathogen. The spores can be carried by wind, water, and insects, and can infect the plant at any growth stage, from seedling to the heading stage. Once the spore lands on the plant tissue, they germinate and penetrate the tissue through a specialized structure called appressoria. Inside the plant tissue, the fungus grows and produces lesions that appear as small grayish-white spots on the leaves, collar, neck, and panicle of the plant. Under favorable conditions, the lesions can enlarge rapidly, causing complete crop failure. The epidemiology of rice blasts is influenced by various factors, such as temperature, humidity, rainfall, wind, and varietal susceptibility. The pathogen can survive in the soil and plant debris for several months, providing a potential source of infection for the next crop. Several management strategies have been developed to control rice blasts, including cultural, botanical, nutrient management, biotechnological, and chemical methods. Chemical methods such as fungicides can be used to control the disease, but their use should be judicious to avoid the development of fungicide resistance and environmental pollution.

Knockdown of Bmp1 and Pls1 Virulence Genes by Exogenous Application of RNAi-Inducing dsRNA in Botrytis cinerea

Botrytis cinerea is a pathogen of wide agronomic and scientific importance partly due to its tendency to develop fungicide resistance. Recently, there has been great interest in the use of RNA interference as a control strategy against B. cinerea. In order to reduce the possible effects on non-target species, the sequence-dependent nature of RNAi can be used as an advantage to customize the design of dsRNA molecules. We selected two genes related to virulence: BcBmp1 (a MAP kinase essential for fungal pathogenesis) and BcPls1 (a tetraspanin related to appressorium penetration). After performing a prediction analysis of small interfering RNAs, dsRNAs of 344 (BcBmp1) and 413 (BcPls1) nucleotides were synthesized in vitro. We tested the effect of topical applications of dsRNAs, both in vitro by a fungal growth assay in microtiter plates and in vivo on artificially inoculated detached lettuce leaves. In both cases, topical applications of dsRNA led to gene knockdown with a delay in conidial germination for BcBmp1, an evident growth retardation for BcPls1, and a strong reduction in necrotic lesions on lettuce leaves for both genes. Furthermore, a strongly reduced expression of the BcBmp1 and BcPls1 genes was observed in both in vitro and in vivo experiments, suggesting that these genes could be promising targets for the development of RNAi-based fungicides against B. cinerea.

Risk Evaluation of Benzovindiflupyr Resistance of Verticillium dahliae Population in Maine.

Verticillium dahliae causes Verticillium wilt, resulting in significant losses to potato production. Benzovindiflupyr, a succinate dehydrogenase inhibitor, effectively controls V. dahliae. However, frequent applications of the chemical may expedite the development of fungicide resistance in the pathogen population. To evaluate the risk of benzovindiflupyr resistance, 38 V. dahliae strains were obtained from diseased potatoes in Maine. The sensitivity of the field population was determined based on effective concentration for 50% inhibition (EC50), which ranged from 0.07 to 11.28 μg ml-1 with a median of 1.08. Segregated clusters of EC50 values indicated that Maine V. dahliae populations have developed benzovindiflupyr resistance. By exposing conidia of V. dahliae to a high concentration of benzovindiflupyr, 18 benzovindiflupyr-resistant mutants were obtained. To examine their fitness, the mutants were continuously subculture-transferred for up to 10 generations. Mycelial growth, conidial production, competitiveness, pathogenicity, and cross resistance of the 10th generation mutants were examined. Results showed that 50% of the resistant mutants retained an adaptive level in mycelial growth, and 60% maintained conidial production similar to their parents. Pathogenicity did not change for any of the mutants. No cross resistance was detected between benzovindiflupyr and either azoxystrobin, boscalid, fluopyram, or pyrimethanil. Thus, the resistance risk in V. dahliae to benzovindiflupyr should be considered in Maine potato production.

Strong Resistance to Early and Late Leaf Spot in Peanut-Compatible Wild-Derived Induced Allotetraploids.

Early (ELS) and late leaf spots (LLS) are two of the most destructive diseases in peanut (Arachis hypogaea). They can cause severe plant defoliation and tremendous yield loss in the absence of fungicide applications. The high costs of fungicides, their potential for deleterious effects on the environment, the tightening of regulations, and the development of fungicide resistance call for additional management strategies to mitigate both diseases. The use of resistant cultivars is an economical way to manage these diseases, but there are limited sources of leaf spot resistance available in cultivated peanuts. Wild peanut species are excellent sources of resistance, but because of the ploidy level, they do not produce fertile progeny when crossed with peanut. To circumvent this, induced allotetraploids were developed so that resistance traits can be introgressed from wild species into peanut. Here we screened 13 induced allotetraploids (BatDur1, BatDur2, BatSten1, GregSten1, IpaCor1, IpaCor2, IpaDur1, IpaDur2, IpaDur3, IpaVillo1, MagDur1, MagSten1, and ValSten1) against ELS and LLS using a detached leaf bioassay to characterize various components of resistance and identify genotypes that can be used for breeding. Strong associations were detected between the measured components of disease resistance (r = 0.91 to 1.0; P < 0.001) and between ELS and LLS bioassays (r = 0.81 to 0.91; P < 0.001). Induced allotetraploids, particularly those derived from A. stenosperma, exhibited fewer and smaller lesions with limited sporulation and reductions in disease progression in both bioassays. Interestingly, allotetraploids derived from the B-genome peanut progenitor A. ipaënsis were almost as susceptible as cultivated genotypes. The overall results reveal several sources of foliar disease resistance that can be used in breeding programs for ELS and LLS resistance.[Formula: see text] Copyright © 2023 The Author(s). This is an open-access article distributed under the CC BY 4.0 International license.

First Report of In Vitro Insensitivity to Fluazinam of Clarireedia jacksonii Causing Dollar Spot of Turfgrass on New England Golf Courses

Dollar spot, caused by the newly renamed ascomycete fungus Clarireedia spp., contributes to the aesthetic and functional damage and ultimate death of turfgrass. Fluazinam, a protective fungicide belonging to the 2,6-dinitroaniline chemical group, has proven to be one of the most efficacious fungicide classes of managing a variety of turfgrass diseases, including dollar spot, due to its low risk for fungicide resistance as a broad-spectrum fungicide. Dollar spot isolates collected from six New England golf courses with suspected resistance to multiple fungicide classes had shown reduced sensitivity to fluazinam using a mycelial growth inhibition assay. This is the first report of reduced sensitivity to fluazinam in dollar spot field isolates in the United States. Briefly, in vitro sensitivity assays of 22 isolates collected from 12 golf courses and UMass turf research facilities showed that reduced fluazinam sensitivity of isolates was detected on six golf courses since 2017, demonstrating that fungi with higher exposure to fluazinam tend to develop reduced sensitivity over time. To date, there is no reported field resistance of fluazinam in C. jacksonii. However, the findings highlight the need for ongoing monitoring of in vitro and field sensitivity to fluazinam in C. jacksonii, as well as emphasizing judicious use of fluazinam in managing dollar spot disease to delay the development of fungicide resistance.

First Report of Resistance to Pyraclostrobin in Pseudocercospora spp. from Blackberry (Rubus fruticosus) in Georgia, United States

Pseudocercospora leaf spot is frequently observed in blackberry production in the southeastern United States. To manage the impacts of leaf spot diseases, blackberry growers in the southeastern United States typically rely on the application of single-site fungicides, including the quinone outside inhibitors (QoIs) (FRAC 11) pyraclostrobin and azoxystrobin. In recent years, despite the regular application of chemical fungicides to manage leaf spots, blackberry growers and extension personnel in Georgia have noticed relatively poor control of these diseases. To investigate potential control failures due to fungicide resistance development, Pseudocercospora were isolated from symptomatic leaves collected from blackberry ( Rubus fruticosus) in five commercial fields in southeastern Georgia. Using a mycelial growth inhibition assay, isolates were screened for resistance to pyraclostrobin. Among the 13 isolates tested, 12 were determined to be resistant to the fungicide. Subsequent sequencing of the cytochrome b gene indicated the presence of the G143A mutation in all fungicide-resistant isolates. The identification of fungicide resistance in 12 of 13 isolates and 4 of 5 examined commercial blackberry sites in Georgia suggests that resistance to this fungicide may be prevalent among Pseudocercospora on blackberry in Georgia and that future fungicide resistance monitoring efforts in Georgia blackberry plantings may be warranted. This represents the first report of QoI fungicide resistance in Pseudocercospora spp. from blackberry.

Genetic Basis of Pathogen Establishment and Fungicide Resistance of Phylogenetically Relate Pseudocercospora spp. through Comparative Genomics

Cavendish banana is one of the most consumed fruits across countries with demands expected to grow by 2026. The Philippines is one of the top producers of Cavendish bananas, yet is negatively impacted by the Sigatoka disease complex (SDC) caused by three Pseudocercospora spp. – namely, P. musae, P. fijiensis, and P. eumusae. These pathogens are persistent in the field despite various control programs implemented in plantations. Whole genomes of fungi have aided in understanding the interactions of co-occurring pathogens and the emergence of fungicide-resistant populations. This study sought to characterize the underlying basis of Pseudocercospora spp. co-infection by determining possible processes involved during disease establishment and factors associated with fungicide resistance development through an in silico approach. Homology search on disease establishment-related proteins revealed that Pseudocercospora spp. share more similar than unique proteins, suggesting an independent disease establishment process. Meanwhile, the ratio analyses of non-synonymous and synonymous mutations (Ka/Ks) in fungicide resistance-related genes suggest that mutations in sdhB genes exhibit adaptive potential. Furthermore, proteins that are associated with the development of fungicide resistance in other fungal species have been detected among Pseudocercospora spp. Lastly, phylogenetic studies using ribosomal RNA gene cluster showed that Pseudocercospora spp. have shown indications that two Pseudocercospora spp. have diverged from one of these species. The findings of the study elucidate the contributory factors for the co-infection of Pseudocercospora spp. in bananas. Results in the disease establishment study can also be used in developing more effective strategies for SDC control in bananas and provide insights into the epidemiological trajectories of pathogens over time.

Efficacy of Fungicides Used to Manage Downy Mildew in Cucumber Assessed with Multiple Meta-Analysis Techniques.

A nationwide, quantitative synthesis of fungicide efficacy data on management of cucurbit downy mildew (CDM) caused by Pseudoperonospora cubensis is needed to broadly evaluate fungicide performance. Three-level meta-analysis, three-level meta-regression, and network meta-analyses were conducted on data from 46 cucumber (Cucumis sativus) CDM fungicide efficacy studies conducted in the eastern United States retrieved from Plant Disease Management Reports published between 2009 and 2018. Three response variables were examined in each analysis: disease severity, marketable yield, and total yield, from which percent disease control and percent yield return compared with nontreated controls was calculated. Moderator variables used in the three-level meta-analysis or three-level meta-regression included year, disease pressure, number of fungicide applications, and slicing or pickling cucumbers. In the network meta-analysis, fungicides were grouped by common combinations of Fungicide Resistance Action Committee Codes and modes of action. Overall, fungicides significantly (P < 0.001) reduced disease severity and increased marketable and total yields, resulting in a mean 54.0% disease control and 61.9% marketable and 73.3% total yield return. Subgroup differences were observed for several fungicide applications, control plot disease severity, and cucumber type for marketable yield. Based on the meta-regression analysis for disease severity by year, fungicide efficacy has been decreasing from 2009 to 2018, potentially indicating broad development of fungicide resistance over time. Treatments containing quinone inside inhibitors, pyridinylmethyl-benzamides, and protectants and treatments containing oxysterol binding protein inhibitors and protectants most effectively reduced disease severity. The most effective fungicide combinations for disease control did not always result in the highest yield return.

Risk Assessment of the Fungicide Bontima with the Active Substances Cyprodinil and Isopyrazam

Bontima is a new fungicide containing the two active substances isopyrazam and cyprodinil. Bontima is a fungicide against the most important diseases in winter and spring barley. Isopyrazam is a new active ingredient with new mechanisms of action that may delay the development of fungicide resistance in treated crops. &#x0D; The risk assessment was finalized at a meeting May 29, 2012, by the Panel on plant protection products of the Norwegian Scientific Committee for Food Safety (VKM). &#x0D; The Norwegian Food Safety Authority would like, in this regard, an assessment of the following: &#x0D; &#x0D; The fate and behaviour in the environment and the ecotoxicological effects and risks with regard to the properties of Bontima and the active substances. The Panel is particularly asked to look at the following: o The persistence of isopyrazam and its metabolites. o The leaching potential of isopyrazam and its metabolites. &#x0D; &#x0D; VKM’s conclusion is as follows: &#x0D; Fate-related issues &#x0D; Isopyrazam is likely to be persistent in Norwegian soils with an associated risk of accumulation after repeated use. &#x0D; Isopyrazam exhibits low mobility in soil and is not expected to reach groundwater, however the two main metabolites are likely to exceed the EUs drinking water limit of 0.1 \(\mu\)g/L in groundwater. &#x0D; Since drainage and runoff, as well as drift, contributes to concentrations in surface water the risk assessment have to consider all these sources. In the EU DAR step 4 calculations, buffer zones of 20 m have been used to reduce runoff levels contributions by 80 %. VKM does not accept the use of these buffer zone modifications for Norwegian topographic conditions (with e.g. steeper agricultural areas). &#x0D; Risk to the environment &#x0D; There is minimal risk for toxic effects of isopyrazam to terrestrial organisms. &#x0D; For the aquatic compartment, there is a high risk for toxic effects of isopyrazam to aquatic organisms with the proposed application regime. This is based on calculations of runoff without buffer zone modifications, from which the resulting TER calculations show high risk of acute effects on fish and a medium risk of acute effects on invertebrates. A minimal risk for toxic effects was calculated for sediment dwelling organisms, aquatic plants, and algae.

Identification of potential chemical fungicides with diverse groups of active ingredient for controlling late blight of potato in Bangladesh

Potato is the third important food crop in Bangladesh and Bangladesh ranked as third and seventh in Asia and in the world, respectively. But potato production greatly affected by the late blight of potato caused by an oomycete, Phytophthora infestans (Mont.) de Bary worldwide. Application of need-based fungicides is the key factor to control this disease and to avoid development of fungicide resistance in P. infestans. Experiments were conducted in both in vitro and in field condition to evaluate some selected chemical fungicides to identify the best one to control the late blight disease of potato. The results of in vitro test revealed that all the fungicides inhibited the growth of P. infestans by 94% over control. But the results of field experiment conceded that the lowest late blight severity was found in T10 (Curzate M8) (0.49%) followed by T6 (AcrobateMz) (0.52%), T8 (Micra) (0.59%), T7 (Xtramyl) (0.61%), T3 (Daconyl) (0.84%), T5 (Secure) (1.28%), T9 (Sanoxanyl) (1.43%), T1 (Unilax) (1.83%), T2 (TemperM) (2.58%) and T4 (Amiscore) (6.34%) at 71 DAP while the maximum late blight severity (95.33%) was observed in T0 (water as control). The highest yield was obtained in T10 (Curzate M8) (25.94 t/ha) followed by T6 (AcrobateMz) (25.67 t/ha), T5 (Secure) (25.22 t/ha), T7 (Xtramil) (24.61 t/ha), T8 (Micra) (24.61 t/ha) and T9 (Sanoxanil) (23.67 t/ha) which were statistically similar and the lowest (8.39 t/ha) yield was observed in T0 (water as control). The highest Benefit Cost Ratio (BCR) was obtained from when potato plants were sprayed with T10 (Curzate M8) (1.02) following by T7 (Xtramil) (0.99), T8 (Micra) (0.99), T6 (AcrobateMz) (0.92), T9 (Sanoxanil) (0.90), T5 (Secure) (0.89), T1 (Unilax) (0.80), T3 (Daconil) (0.74), T4 (Amiscore) (0.71) and T2 (TemperM) (0.44) compared to control T0 (water as control) (-0.30). The results indicated that application of these fungicides yielded a benefit of Tk. ranged by 0.44 to 1.02 over the investment of Tk. 1.00. Therefore, identification of a number of potential chemical fungicides might be useful in the alternate use of these fungicides against late blight of potato in the field. Asian Australas. J. Biosci. Biotechnol. 2022, 7 (1), 23-35