In vitro sensitivity of Verticillium fungicola to selected fungicides

Twenty isolates of Verticillium fungicola var. fungicola collected from diseased fruit-bodies of Agaricus bisporus from prochloraz-treated crops, were exposed to a range of concentrations of six chemicals (benomyl, chlorothalonil, formaldehyde, iprodione, prochloraz-Mn-complex and prochloraz + carbendazim) in vitro. EC₅₀ values were determined for each fungus-fungicide combination. All isolates were more sensitive to prochloraz-Mn-complex (EC₅₀ values less than 5 mg 1^–1) than to the remainder fungicides, and only seven isolates were moderately sensitive (EC₅₀ values between 5 and 50 mg 1^–1) to prochloraz + carbendazim. All isolates were moderately sensitive to formaldehyde, whereas the majority of isolates were very resistant to the other three fungicides (benomyl, chlorothalonil and iprodione).     

Incidence,identification and pathogenicity of Cladobotryum mycophilum,causal agent of cobweb disease on Agaricus bisporus mushroom crops in Spain

Between 2008 and 2011, outbreaks of cobweb were observed in commercial white button mushroom (Agaricus bisporus) crops in Castilla‐La Mancha (Spain). In the last 3 years, the presence of the disease has notably increased resulting in serious economic losses. Based on morphological and genetic analyses, the casual agent of cobweb was identified as Cladobotryum mycophilum. A. bisporus mushroom crops were surveyed over a 2‐year period to estimate the incidence of cobweb. The presence of the disease was detected in 32% of the mushroom crops observed, being of particular concern in autumn (44% of crops infected) and winter (37%). As regards the casing material, the percentage of crops affected by cobweb was 34% in crops using mineral casing and 29% in those cased with a peat‐based casing, with no statistical relationship between the casing and the presence of cobweb. Two cropping trials inoculated with C. mycophilum were set up to evaluate the pathogenicity of the causal agent of cobweb in three peat‐based casings (C1, C2 and C3). The effect of cobweb on mushroom productivity was evaluated by comparing mushroom production and the cobweb patches detected in the casing soil. The decrease in total yield of mushrooms attributed to cobweb reached 12.9% with C2, and the crop area colonised by cobweb reached a final percentage of 36% with C3.     

Reduced sensitivity of tomato early blight pathogen (Alternaria solani) isolates to protectant fungicides,and implication on disease control

The sensitivity of Alternaria solani isolates to the fungicides mancozeb and chlorothalonil was evaluated, to determine if inadequate disease management by these fungicides could be attributed to reduced sensitivity of A. solani isolates to these fungicides. The sensitivity of 60 isolates of A. solani was assessed using the inhibition of radial mycelial growth (RG) method, using fungicide concentrations of 0, 1.0, 10, 100, 500 and 1000 μg a.i ml^?1 medium. EC₅₀ was calculated for each isolate and fungicide combination. The EC₅₀ values of different A. solani isolates to mancozeb ranged from 9.05 to 712.65 μg ml^?1. EC₅₀ values of different isolates to chlorothalonil ranged from 4.25 to 849.4 μg ml^?1. The percentage of isolates with reduced sensitivity was 46.7 and 53.3% for mancozeb and chlorothalonil, respectively. Results of the in vivo tests demonstrated decline in disease control by the two fungicides with the reduced-sensitivity isolates compared to the sensitive ones.     

Baseline sensitivity and efficacy of fluopyram against Botrytis cinerea from table grape in Italy

Succinate dehydrogenase inhibitor (SDHI) fungicides constitute a relatively recent fungicide class registered for the treatment of grey mould on grapevine in Italy. The sensitivity profile to a novel compound fluopyram was established for a set of 203 Botrytis cinerea isolates collected from Sicilian vineyards within 2009–2012 prior its introduction into market. In addition, its performances were compared in in vitro and in vivo assays with other registered SDHI fungicide boscalid, to evaluate their frequency distributions EC₅₀ values and cross‐resistance patterns. Results of the article showed that EC₅₀ values for fluopyram ranged from 0.05 to 1.98 µg mL^?1. Although EC₅₀ values of boscalid ranged from 0.01 to 89.52 µg mL^?1, no cross‐resistance relationship was observed between the two fungicides (r = 0.003; P = 0.964) within our B. cinerea population. On further confirming these data, boscalid failed in controlling grey mould infections when boscalid‐resistant isolates were inoculated on grape berries whereas fluopyram exhibited a good efficacy against the same isolates. This study represents the first report on the baseline sensitivity to fluopyram within B. cinerea population from Sicilian table grape vineyards in Italy, and it clearly shows the lack of cross‐resistance in vitro and in vivo between fluopyram and boscalid for the field pathogen isolates. These results provided useful information for managing of fungicide resistance suggesting that fluopyram could be a valid alternative to boscalid for the control of grey mould of table grape.     

Synthesis and Antifungal Activities of Trichodermin Derivatives as Fungicides on Rice

Twenty new trichodermin derivatives, 2a – 5 , containing alkoxy, acyloxy, and Br groups in 4‐, 8‐, 9‐, 10‐ and 16‐positions were synthesized and characterized. The antifungal activities of the new compounds against rice false smut (Ustilaginoidea virens), rice sheath blight (Rhizoctonia solani), and rice blast (Magnaporthe grisea) were evaluated. The results of bioassays indicated that the antifungal activities were particularly susceptible to changes at 4‐, 8‐, and 16‐positions, but low to changes at 9‐ and 10‐positions. Most of these target compounds exhibited good antifungal activities at the concentration of 50 mg l^?1. Compound 4 (9‐formyltrichodermin; EC₅₀ 0.80 mg l^?1) with an CHO group at 9‐position displayed nearly the same level of antifungal activity against Ustilaginoidea virens as the commercial fungicide prochloraz (EC₅₀ 0.82 mg l^?1), while compound 3f ((8R)‐8‐{[(E)‐3‐phenylprop‐2‐enoyl]oxy}trichodermin; EC₅₀ 3.58 and 0.74 mg l^?1) with a cinnamyloxy group at C(8) exhibited much higher antifungal activities against Rhizoctonia solani and Magnaporthe grisea than the commercial fungicides prochloraz (EC₅₀ 0.96 mg l^?1) and propiconazole (EC₅₀ 5.92 mg l^?1), respectively. These data reveal that compounds 3f and 4 possess high antifungal activities and may serve as lead compounds for the development of fungicides in the future.     

Trichoderma species on Agaricus bisporus farms in Serbia and their biocontrol

Twenty Trichoderma isolates were collected on 13 Serbian Agaricus bisporus farms and one in Bosnia and Herzegovina during 2006–2010. Twelve isolates were classified into five species by standard mycological studies and ITS1/ITS4 sequence analyses, namely Trichoderma atroviride, Trichoderma koningii, Trichoderma virens, Trichoderma aggressivum f. europaeum and Trichoderma harzianum. Eight isolates were not identified to the species level but were shown to be related to T. harzianum. The isolates of T. harzianum exhibited the highest virulence to the harvested A. bisporus pilei and T. virens and T. aggressivum f. europaeum the lowest. Antifungal activity of two biofungicides based on Bacillus subtilis and tea tree oil and the fungicide prochloraz manganese were tested in vitro to all Trichoderma isolates. Prochloraz manganese and B. subtilis were highly toxic to all tested Trichoderma isolates, their ED₅₀ values were below 0.3 and 1.3 mg L^?1, respectively. Tea tree oil did not exhibit a significant antifungal activity (ED₅₀ = 11.9–370.8 mg L^?1). The effectiveness of biofungicides was evaluated against T. harzianum in a mushroom growing room, and they were applied alone or in combination with the fungicide at a respective proportion of 20:80%. Prochloraz manganese showed higher effectiveness than both tested biofungicides or their respective mixtures. The biofungicide based on B. subtilis demonstrated greater effectiveness in preventing disease symptoms than tea tree oil. B. subtilis combined with the fungicide revealed less antagonism in effectiveness against pathogen than tea tree oil.     

The mixture of kresoxim‐methyl and boscalid,an excellent alternative controlling grey mould caused by Botrytis cinerea

Grey mould, caused by the fungus Botrytis cinerea, is one of the most destructive diseases in greenhouses for which serious fungicide resistance has developed. Between 2003 and 2005, 213 isolates of B. cinerea from two geographical regions were characterised for baseline sensitivity to kresoxim‐methyl. In the absence of salicylhydroxamic acid (SHAM), the mean 50% effective concentration (EC₅₀) values were 6.67 ± 0.61 (mean ± SD) and 0.37 ± 0.10 mg L^?1 during growth and germination, respectively. In the presence of 100 mg L^?1 SHAM, baseline sensitivities were distributed as unimodal curves with mean EC₅₀ values of 2.38 ± 0.21 and 0.28 ± 0.09 mg L^?1 for inhibiting growth and inhibiting germination, respectively. The mixture of kresoxim‐methyl and boscalid showed good control efficacy against strawberry grey mould disease. After the mixture was extensively used on strawberry for 2 years, 50 isolates were collected and determined for their sensitivity to kresoxim‐methyl and boscalid, respectively. The mean EC₅₀ of germination inhibition by boscalid was 0.39 ± 0.08 mg L^?1. The mean EC₅₀ of germination inhibition by kresoxim‐methyl was 0.26 ± 0.07 mg L^?1 in the presence of 100 mg L^?1 SHAM. Sensitivities of B. cinerea to both kresoxim‐methyl and boscalid did not show any significant decrease. These results suggest that their mixture is a satisfactory alternative candidate for management of grey mould disease in greenhouses.     

Activity of Ten Fungicides against Phytophthora capsici Isolates Resistant to Metalaxyl

Pepper Phytophthora blight (PPB), caused by Phytophthora capsici, is an important disease of pepper in China. The extensive application of metalaxyl has resulted in widespread resistance to this fungicide in field. This study has evaluated the activities of several fungicides against the mycelial growth and sporangium germination of metalaxyl‐sensitive and metalaxyl‐resistant P. capsici isolates by determination of EC₅₀ values. The results showed that the novel carboxylic acid amide (CAA) fungicide mandipropamid exhibited excellent inhibitory activity against PPB both in vitro and in vivo, with averagely EC₅₀ values of 0.075 and 0.004 μg/ml in mycelial growth and sporangium germination, respectively, and over 88% efficacy in controlling PPB. The other three CAA fungicides also provided over 70% efficacy in controlling PPB. The mycelial growth was less sensitive to quinone outside inhibitor (QoI) fungicides azoxystrobin and trifloxystrobin than that of sporangium germination in P. capsici isolates. However, azoxystrobin and trifloxystrobin provided over 80% efficacy in controlling PPB. It was noted that propamocarb and cymoxanil did not exhibit activity against the mycelial growth or sporangium germination of P. capsici isolates in the in vitro tests, with over 70% efficacy in controlling PPB. The new fungicide mixture 62.5 g/l fluopicolide + 625 g/l propamocarb (trade name infinito, 687.5 g/l suspension concentrate (SC)) produced over 88% efficacy in controlling PPB caused by both metalaxyl‐sensitive and metalaxyl‐resistant isolates. The data of this study also proved that there was obviously no cross‐resistance between metalaxyl and the other tested fungicides. Therefore, these fungicides should be good alternatives to metalaxyl for the control of PPB and management of metalaxyl resistance.     

The influence of fungicides on Arthrobotrys oligospora in simulated putting green soil

Plant‐parasitic nematodes are destructive pests in bentgrass putting greens. Few chemical or nonchemical approaches for nematode management exist. Studies were conducted to determine: the in vitro tolerance of the nematophagous fungus Arthrobotrys oligospora, to the fungicides chlorothalonil and myclobutanil used to manage diseases on putting greens; the concentration of fungicides obtained from simulated putting green soil; and the ability of the fungus to reduce populations of the ring nematode, Criconemella ornata. Both fungicides reduced in vitro hyphal growth and germination of conidia above 10 mg kg^‐1. Soil concentrations of chlorothalonil were less than 5 mg kg^‐1 and concentrations of myclobutanil were below detection limits. Nematode populations were not affected by A. oligospora in simulated greens but nematode populations were lowest in pots inoculated with A. oligospora and receiving fungicide treatments. Results of these studies indicate that applications of chlorothalonil and myclobutanil used to manage fungal diseases of bentgrass may not adversely affect A. oligospora; however, the fungus may not reduce nematode populations below desired thresholds.     

Synthesis and Fungicidal Activities of New 1,2,4‐Triazolo[1,5‐a]pyrimidines

A series of new acetohydrazone‐containing 1,2,4‐triazolo[1,5‐a]pyrimidine derivatives were designed and synthesized for the purpose of searching for novel agrochemicals with higher fungicidal activity. Their in vitro fungicidal activities against Rhizoctonia solani were evaluated, and the most promising compound, 2‐[(5,7‐dimethyl[1,2,4]triazolo[1,5‐a]pyrimidin‐2‐yl)sulfanyl]‐2′‐[(2‐hydroxyphenyl)methylidene]acetohydrazide ( 2‐17 ), showed a lower EC₅₀ value (5.34 μg ml^?1) than that of commercial carbendazim (EC₅₀=7.62 μg ml^?1). Additionally, compound 2‐17 was also found to display broad‐spectrum fungicidal activities, and its EC₅₀ value (4.56 μg ml^?1) against Botrytis cinereapers was very similar to that of carbendazim. Qualitative structure–activity relationships (QSARs) of the synthesized compounds were also discussed.     

Development of novel 2-substituted acylaminoethylsulfonamide derivatives as fungicides against Botrytis cinerea

Botrytis cinerea is an economically important fungal pathogen with a host range of over 200 plant species. Unfortunately, gray mold disease caused by B. cinerea has not been effectively controlled because of its high risk for fungicide resistance development. As a part of our ongoing efforts to develop novel sulfonamides as agricultural fungicides against Botrytis cinerea, we introduced 2-aminoethanesulfonic acid (taurine) substructure, designed and synthesized a series of novel 2-substituted acylaminoethylsulfonamides. The newly synthesized sulfonamides were evaluated in vitro and in vivo for their fungicidal activity against Botrytis cinerea, of which the 2-ethoxyacetylamide derivative (V-A-12, EC₅₀ = 0.66 mg·L⁻¹) exhibited the highest potency in vitro and superior fungicidal activity compared with procymidone (EC₅₀ = 1.06 mg·L⁻¹). In vivo bioassay indicated that compound V-A-12 could be effective for the control of tomato gray mold. Moreover, the structure-activity relationship of these sulfonamides was analyzed by establishing a three-dimensional quantitative structure-activity relationship (3D-QSAR) model, which can provide guidance for the development of sulfonamides as fungicides. Finally, the effeicacy of sulfonamide derivatives was again verified in the activity evaluation against resistant Botrytis cinerea strains. These results further enhance the development value of 2-substituted acylaminoethylsulfonamides to control the tomato gray mold.     

Antiviral activity of Distictella elongata (Vahl) Urb. (Bignoniaceae), a potentially useful source of anti-dengue drugs from the state of Minas Gerais, Brazil

Aims: To investigate the in vitro antiviral activity of Distictella elongata (Vahl) Urb. ethanol extracts from leaves (LEE), fruits (FEE), stems and their main components. Methods and Results: The antiviral activity was evaluated against human herpesvirus type 1 (HSV‐1), murine encephalomyocarditis virus (EMCV), vaccinia virus Western Reserve (VACV‐WR) and dengue virus 2 (DENV‐2) by the 3‐(4, 5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) colorimetric assay. LEE presented anti‐HSV‐1 [EC₅₀ 142·8 ± 5·3 μg ml^?1; selectivity index (SI) 2·0] and anti‐DENV‐2 activity (EC₅₀ 9·8 ± 1·3 μg ml^?1; SI 1·5). The pectolinarin ( 1 ) isolated from LEE was less active against HSV‐1 and DENV‐2. A mixture of the triterpenoids ursolic, pomolic and oleanolic acids was also obtained. Ursolic and oleanolic acids have shown antiviral activity against HSV‐1. A mixture of pectolinarin ( 1 ) and acacetin‐7‐O‐rutinoside ( 2 ) was isolated from FEE and has presented anti‐DENV‐2 activity (EC₅₀ 11·1 ± 1·6 μg ml^?1; SI > 45). Besides the antiviral activity, D. elongata has disclosed antioxidant effect. Conclusions: These data shows that D. elongata has antiviral activity mainly against HSV‐1 and DENV‐2, besides antioxidant activity. These effects might be principally attributed to flavonoids isolated. Significance and Impact of the Study: Distictella elongata might be considered a promising source of anti‐dengue fever phytochemicals.     

Effects of wheat foliar fungicides on the aphid endoparasitoid Aphidius rhopalosiphi DeStefani-Perez (Hym., Aphidiidae) on glass plates and on plants

Abstract: The side-effects of several fungicides used in wheat to control disease at heading growth stage were assessed on the aphid parasitoid Aphidius rhopalosiphi by tests conducted in the laboratory on glass plates and in the greenhouse on young wheat plants. Very few formulations containing only one active ingredient (carbendazim, cyproconazole or epoxyconazole) or combinations of two (carbendazim + cyproconazole, carbendazim + hexaconazole) were harmless to A. rhopalosiphi in the glass-plate tests. There was no apparent synergism between fungicides tested in combinations. The parasitoid mortalities in tests carried out on plants were less and chlorothalonil, epoxyconazole, fenpropidin, fenpropimorph, flusilazole, flutriafol, prochloraz, tebuconazole, tridemorph and a number of combinations (carbendazim + flutriafol, chlorothalonil + cyproconazole, epoxyconazole + tridemorph, chlorothalonil + hexaconazole, chlorothalonil + flutriafol, cyproconazole + prochloraz, epoxyconazole + fenpropimorph, fenpropimorph + propiconazole, propiconazole + tridemorph, triadimenol + tridemorph) were harmless or only slightly harmful to the aphid parasitoid. Several combinations (carbendazim + epoxyconazole, carbendazim + fenpropimorph, carbendazim + flusilazole, carbendazim + tebuconazole, chlorothalonil + fenpropimorph, chlorothalonil + flusilazole, fenpropimorph + fenpropidin, fenpropimorph + prochloraz, fenpropidin + propiconazole, fenpropidin + tebuco nazole, tebuconazole + triadimenol) were toxic for wasps on plants. The parasitoid mortalities were less on plants than on glass plates but the wasps spent less time on treated leaves and in some cases parasitism of aphids was reduced to a large extent. These results suggest that in addition to study of the direct effects of pesticides on beneficial insects (mortalities, reduction of fertility) their effects on the behaviour of the insects should also be studied. Products that induced a repellent effect need further testing in field or semi-field conditions. However, many fungicide combinations that have little or no effect on A. rhopalosiphi can protect wheat against a wide range of diseases and the results obtained in this study indicate that an appropriate and effective protection of wheat at earing growth stage can be achieved with products that have no effects on aphid parasitoids.     

In vitro and In vivo Effects of Some Fungicides against the Chickpea Blight Pathogen, Ascochyta rabiei

The effects of various fungicides on mycelial growth and spore germination of Ascochyta rabiei were determined by incorporating them into potato dextrose agar and measuring colony diameter and observing colony growth and spore germination at 20 ± 2°C. Eight fungicides prevented spore germination of the pathogen at concentrations of 0.125–2 μg/ml, three hindered mycelial growth at 2–4 μg/ml and seven failed to inhibit mycelial growth even at 128 μg/ml. The reference fungicide for the pathogen, chlorothalonil, stopped conidial germination at low rates but did not prevent mycelial growth at 128 μg/ml. Thirteen fungicides were tested against seed infections of the pathogen, and benomyl + thiram, carbendazim and carbendazim + chlorothalonil seed treatments gave more than 85% inhibition on both vacuum‐infiltrated and naturally infected seeds. Coating the seeds with polymers did not increase the effectiveness of fungicides. Three fungicides; (azoxystrobin, chlorothalonil and mancozeb), gave the highest protection in the field but protection decreased with increased inoculum pressure. Addition of humic acid to fungicide suspensions did not affect their performance.     

Potential agronomic options for energy-efficient sugar beet-based bioethanol production in northern Japan

Sugar beet (Beta vulgaris L. subsp. vulgaris) is deemed to be one of the most promising bioethanol feedstock crops in northern Japan. To establish viable sugar beet‐based bioethanol production systems, energy‐efficient protocols in sugar beet cultivation are being intensively sought. On this basis, the effects of alternative agronomic practices for sugar beet production on total energy inputs (from fuels and agricultural materials during cultivation and transportation) and ethanol yields (estimated from sugar yields) were assessed in terms of (i) direct drilling, (ii) reduced tillage (no moldboard plowing), (iii) no‐fungicide application, (iv) using a high‐yielding beet genotype, (v) delayed harvesting and (vi) root+crown harvesting. Compared with the conventional sugar beet production system used in the Tokachi region of Hokkaido, northern Japan, which makes use of transplants, direct drilling and no‐fungicide application contributed to reduced energy inputs from raising seedlings and fungicides, respectively, but sugar (or ethanol) yields were also reduced by these practices, to a greater equivalent extent than the reductions in energy inputs. Consequently, direct drilling (6.84 MJ L^?1) and no‐fungicide application (7.78 MJ L^?1) worsened the energy efficiency (total energy inputs to produce 1 L of ethanol), compared with conventional sugar beet production practices (5.82 MJ L^?1). Sugar yields under conventional plow‐based tillage and reduced tillage practices were similar, but total energy inputs were reduced as a result of reduced fuel consumption from not plowing. Hence, reduced tillage showed improved energy efficiency (5.36 MJ L^?1). The energy efficiency was also improved by using a high‐yielding genotype (5.23 MJ L^?1) and root+crown harvesting (5.21 MJ L^?1). For these practices, no major changes in total energy inputs were noted, but sugar yields were consistently increased. Neither total energy inputs nor ethanol yields were affected by extending the vegetative growing period by delaying harvesting.     

Selection of a Suitable Medium to Determine Sensitivity of Monilinia fructicola Mycelium to SDHI Fungicides

Succinate dehydrogenase inhibitor (SDHI) fungicides are important tools to control preharvest and postharvest brown rot of stone fruits. In this study we determined the mycelial growth rate of Monilinia fructicola isolates on various media and picked the three that allowed the fastest growth to assess the sensitivity of mycelium to SDHI fungicides boscalid, fluopyram, and penthiopyrad. Minimal medium (MM) supported mycelial growth the best and yielded lowest EC₅₀ values for three SDHI fungicides. EC₅₀ values corresponded with disease incidence data obtained from detached fruit assays. Penthiopyrad had significantly greater intrinsic activity in vitro compared to fluopyram at the α = 0.05 level and compared to boscalid at the α = 0.1 level. However, detached fruit assays revealed that this ‘advantage’ did not carry over in vivo. In conclusion, MM appears to be the best medium currently available to assess the sensitivity of M. fructicola mycelium in vitro.     

Physiological and biochemical response of potato (Solanum tuberosum L. cv. Kara) to O3 and antioxidant chemicals: possible roles of antioxidant enzymes

An Egyptian cultivar of potato (Solanum tuberosum L. cv. Kara) was grown in the field at two locations in northern Egypt: a ‘rural’ and a ‘suburban’ site, from October 2000 and November 2002. The antiozonant ethylenediurea (EDU) and the fungicide chlorothalonil (1,3‐benzenedicarbonitrile‐2,4,5,6 tetrachloroisophthalnitrile) were applied as a foliar spray to plants at both sites. It was found that foliar injury symptoms were reduced greatly in plants treated with EDU and/or chlorothalonil, and the yield of treated plants was higher than that of the untreated ones, with the EDU having a greater protection than chlorothalonil. Antiozonant (EDU) and fungicide (chlorothalonil) combination sprays were even more effective in reducing O₃ injury. Moreover, the percentage of protection was higher in the rural area than in the suburban one, and this was associated with higher levels of O₃ recorded in the rural area. The response to O₃, EDU, and chlorothalonil of the leaf antioxidant scavenger system was examined. Antiozonant‐treated plants had the highest reduced glutathione/oxidised glutathione ratio. The results suggest that EDU and chlorothalonil do not act directly as antiozonant to inhibit O₃ injury but act through maintaining some antioxidant enzymes during O₃ exposure. To the best of knowledge, this is the first report demonstrating the marked enhancement of yield and plant oxidative enzymes by fungicides as a mechanism of protecting plants against noxious oxidative stress from the environment in the developing world.     

Baseline Sensitivity of Populations of Phytophthora capsici from China to Three Carboxylic Acid Amide (CAA) Fungicides and Sequence Analysis of Cholinephosphotranferases from a CAA‐sensitive Isolate and CAA‐resistant Laboratory Mutants

During 2006–2008, 572 isolates of Phytophthora capsici were collected from seven provinces in China, and their sensitivities to three carboxylic acid amides (CAA), dimethomorph, flumorph and pyrimorph were determined. Of these isolates, 90 isolates without a history of exposure to CAA fungicides (CAAs) were used to set up the baseline sensitivity. Baseline EC₅₀ values ranged from 0.122 to 0.203 (mean ± SD, 0.154 ± 0.022) μg ml^?1 for dimethomorph, from 0.301 to 0.487 (mean ± SD, 0.373 ± 0.043) μg ml^?1 for flumorph and from 0.557 to 0.944 (mean ± SD, 0.712 ± 0.082) μg ml^?1 for pyrimorph, respectively. The other 482 isolates were tested with a single discriminatory dose and were completely inhibited at 0.5 μg ml^?1 of dimethomorph. Four CAA‐resistant mutants were generated by repeated exposure to dimethomorph in vitro. As compared to the parental wild‐type isolate, the four CAA‐resistant mutants showed similar fitness in hyphal growth, sporulation in vitro and pathogenicity in vivo. Mutants resistant to CAAs in the in vitro assay caused visible lesions on pepper stems or roots treated with the recommended dose of dimethomorph. Previous studies upon the mode of action of CAAs suggested that these fungicides maybe inhibit phospholipid biosynthesis and that the primary target could be the cholinephosphotranferase (CPT), which is referred to aminoalcoholphosphotransferases (AAPTs). We sequenced and analyzed two CPT (AAPT1 and AAPT2) genes in P. capsici. Based on the cDNA sequence, we found that the AAPT1 and AAPT2 gene span 1538 and 1459 bp and were interrupted by five and three introns, respectively. There was no difference between the parental wild‐type isolate and the four CAA‐resistant mutants in the amino acid sequences of AAPT1 and AAPT2 gene. So, it was assumed that the resistance to dimethomorph was not due to mutations in the amino acid sequence of these two possible target genes.     

N‐[2‐[(3‐Chlorophenyl)amino]‐phenyl]‐3‐(difluoromethyl)‐1‐methyl‐1H‐pyrazole‐4‐carboxamide: Synthesis,Crystal Structure,Molecular Docking and Biological Activities

In continuation of our previous research on the development of novel pyrazole‐4‐carboxamide with potential antifungal activity, compound SCU2028 , namely N‐[2‐[(3‐chlorophenyl)amino]phenyl]‐3‐(difluoromethyl)‐1‐methyl‐1H‐pyrazole‐4‐carboxamide, was synthesized by new method, structurally characterized by IR, HR‐ESI‐MS, ¹H‐ and ¹³C‐NMR spectra and further identified by single‐crystal X‐ray diffraction. In pot tests, compound SCU2028 showed good in vivo antifungal activity against Rhizoctonia solani (R. solani) and IC₅₀ value of it was 7.48 mg L^?1. In field trials, control efficacy of compound SCU2028 at 200 g.a.i. ha^?1 was 42.30 % on the 7^th day after the first spraying and 68.10 % on the 14^th day after the second spraying, only slightly lower than that of thifluzamide (57.20 % and 71.40 %, respectively). Further in vitro inhibitory activity showed inhibitory ability of compound SCU2028 was 45‐fold higher than that of bixafen and molecular docking of compound SCU2028 to SDH predicted its binding orientation in the active site of the target protein SDH. These results suggested that compound SCU2028 was a potential fungicide for control of rice sheath blight.