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1.
Brown rot, caused by Moniliniafructicola (G Wint) Honey, is a serious disease of peach in all commercial peach production areas in the USA, including South Carolina where it has been primarily controlled by pre-harvest application of 14-alpha demethylation (DMI) fungicides for more than 15 years. Recently, the Qo fungicide azoxystrobin was registered for brown rot control and is currently being investigated for its potential as a DMI fungicide rotation partner because of its different mode of action. In an effort to investigate molecular mechanisms of DMI and Qo fungicide resistance in M fructicola, the ABC transporter gene MfABC1 and the alternative oxidase gene MfAOX1 were cloned to study their potential role in conferring fungicide resistance. The MfABC1 gene was 4380 bp in length and contained one intron of 71 bp. The gene revealed high amino acid homologies with atrB from Aspergillus nidulans (Eidam) Winter, an ABC transporter conferring resistance to many fungicides, including DMI fungicides. MfABC1 gene expression was induced after myclobutanil and propiconazole treatment in isolates with low sensitivity to the same fungicides, and in an isolate with high sensitivity to propiconazole. The results suggest that the MfABC1 gene may be a DMI fungicide resistance determinant in M fructicola. The alternative oxidase gene MfAOX1 from M fructicola was cloned and gene expression was analyzed. The MfAOX1 gene was 1077 bp in length and contained two introns of 54 and 67 bp. The amino acid sequence was 63.8, 63.8 and 57.7% identical to alternative oxidases from Venturia inaequalis (Cooke) Winter, Aspergillus niger van Teighem and A nidulans, respectively. MfAOX1 expression in some but not all M fructicola isolates was induced in mycelia treated with azoxystrobin. Azoxystrobin at 2 microg ml(-1) significantly induced MfAOX1 expression in isolates with low MfAOX1 constitutive expression levels.  相似文献   

2.
Luo CX  Schnabel G 《Phytopathology》2008,98(2):230-238
The ability to develop fungicide resistance was assessed in Monilinia fructicola isolates with different fungicide sensitivity phenotypes by adapting mycelium and conidia to increasing concentrations of selective fungicides and UV mutagenesis. Results showed that adaptation to Quinone outside inhibitor (QoI) fungicide azoxystrobin and sterol demethylation inhibitor (DMI) fungicide propiconazole was more effective in conidial-transfer experiments compared to mycelial-transfer experiments. DMI-resistant (DMI-R) isolates adapted to significantly higher doses of azoxystrobin in both, mycelial- and conidial-transfer experiments compared to benzimidazole-resistant (BZI-R) and sensitive (S) isolates. Adaptation to propiconazole in conidial-transfer experiments was accelerated in BZI-R isolates when a stable, nonlethal dose of 50 microg/ml thiophanate-methyl was added to the selection medium. One of two azoxystrobin-resistant mutants from DMI-R isolates did not show any fitness penalties; the other isolate expired before further tests could be carried out. The viable mutant caused larger lesions on detached peach fruit sprayed with azoxystrobin compared to the parental isolate. The azoxystrobin sensitivity of the viable mutant returned to baseline levels after the mutant was transferred to unamended medium. However, azoxystrobin resistance recovered quicker in the mutant compared to the corresponding parental isolate after renewed subculturing on medium amended with 0.2 and 1 microg/ml azoxystrobin; only the mutant but not the parental isolate was able to adapt to 5 microg/ml azoxystrobin. In UV mutagenesis experiments, the DMI-R isolates produced significantly more mutants compared to S isolates. All of the UV-induced mutants showed stable fungicide resistance with little fitness penalty. This study indicates the potential for QoI fungicide resistance development in M. fructicola in the absence of a mutagen and provides evidence for increased mutability and predisposition to accelerated adaptation to azoxystrobin in M. fructicola isolates resistant to DMI fungicides.  相似文献   

3.
ABSTRACT The fitness and the dynamics of demethylation inhibitor fungicide (DMI) sensitivity in isolates of Monilinia fructicola sensitive (no growth at 0.3 mg/liter propiconazole) and resistant (>/=50% relative growth at 0.3 mg/liter propiconazole) to propiconazole were investigated. Overall, there was no considerable compromise in the fitness of resistant isolates compared to sensitive isolates of M. fructicola at the time of collection. Resistant and sensitive isolates differed in their sensitivity to propiconazole (P < 0.001) and incubation period (P = 0.044), but not in latent period, growth rate, spore production, and spore germination frequency (P > 0.05). Consecutive transferring on potato dextrose agar had an impact on conidia production, conidial germination, and growth rate (P < 0.0001). Consecutive transferring also had an impact on propiconazole sensitivity in resistant isolates. In the resistant isolates, sensitivity to propiconazole increased (R(2) = 0.960, P = 0.0034) within the first eight transfers. Similarly, sensitivity to propiconazole increased by 273% over the course of 34 months in cold storage in propiconazole-resistant isolates. Our results show that propiconazole resistance is unstable in vitro and that standard subculturing and cold storage procedures impact propiconazole sensitivity of resistant isolates. The instability of propiconazole resistance in M. fructicola may have important implications for disease management in that a reversion to propiconazole sensitivity could potentially occur in the absence of DMI fungicide pressure in the field.  相似文献   

4.
BACKGROUND: Septoria leaf blotch is the most important disease of wheat in Europe. To control this disease, fungicides of the 14α‐demethylase inhibitor group (DMIs) have been widely used for more than 20 years. However, resistance towards DMIs has increased rather quickly in recent years. The objective of this study was to evaluate, on plants and under controlled conditions, the protective and curative efficacy of the DMI fungicide prothioconazole against three current isolates of M. graminicola, chosen to belong to different DMI‐resistant phenotypes. Fungicide efficacy was assessed by visual symptoms and by quantitative real‐time polymerase chain reaction (PCR). RESULTS: With a protective fungicide application, prothioconazole was always effective against each isolate. This was in accordance with the EC50 results. However, curative efficacy differed between the isolates. It remained at a good level, between 60 and 70% against one isolate, whereas it was strongly affected by late applications from 7 days post‐inoculation with the two other isolates. CONCLUSION: A protective application of prothioconazole in wheat crops could be the best strategy to keep a high efficacy against Septoria leaf blotch. Copyright © 2011 Society of Chemical Industry  相似文献   

5.
In late 2003, nine populations of Sclerotinia homoeocarpa in Ontario Canada (seven of which had been previously sampled in early 1994, prior to the registration of sterol demethylation-inhibiting (DMI) fungicides for turf disease control in Canada) were sampled and tested for sensitivity to propiconazole. Four of the nine populations had not been treated with DMI fungicides during the intervening years, and isolates from these locations were sensitive to propiconazole (geometric mean EC50 values of 0·005–0·012 µ g mL−1, compared with 0·005–0·008 µ g mL−1 for the original 1994 populations). Among the five populations from 2003 that had been exposed to DMI fungicides, mean EC50 values were significantly greater, ranging from 0·020 to 0·048 µ g mL−1. A significant correlation of determination was found between estimated number of fungicide applications and log EC50 ( R 2 = 0·832, P  = 0·0001), and the equation predicted that 42·3 applications of propiconazole would be needed to bring a sensitive population (EC50 < 0·01  µ g mL−1) to a resistant level (EC50 > 0·10  µ g mL−1). Fungicide sensitivity vs. duration of fungicide efficacy was also tested, and it was found that isolates with decreased sensitivity were able to more quickly overcome the inhibitory effects of fungicide application, reducing the duration of control from 3 weeks to 2 weeks.  相似文献   

6.
Four hundred and thirty-five isolates of Sclerotinia homoeocarpa from eight populations in southern Ontario were tested for sensitivity to the demethylation-inhibiting (DMI) fungicides, propiconazole, myclobutanil, fenarimol and tebuconazole. The isolates were collected in summer 1994 just prior to legal DMI fungicide use on turfgrass in Ontario. There were wide variations in sensitivities, and seven of the eight populations were very sensitive to the fungicides. Based on mean EC50 and the distribution of DMI sensitivity, one population near the U.S. border was suspected of having been previously exposed to DMI fungicide. Pairwise comparisons of EC50 values for the different fungicides showed low to moderate correlations between fungicides. EC50 values of myclobutanil and propiconazole had the best correlation, followed by the pair of tebuconazole and fenarimol. Other pairwise comparisons were not statistically significant except for a barely significant relationship between EC50 values of myclobutanil and tebuconazole. For field populations of plant pathogens, cross-resistance to different DMI fungicides may not be as strong as conventionally thought. The data collected here will allow comparison to subsequent years to look for detectable shifts in S. homoeocarpa sensitivity to DMI fungicides as they become more frequently used in Ontario.  相似文献   

7.
Monilia yunnanensis was recently identified as a new species causing brown rot of peach in China. Sterol 14α-demethylase inhibitors (DMIs) continue to be important in the management of brown rot of Monilinia spp. worldwide. Tebuconazole and triadimefon are two kinds of DMI fungicides that may be used for brown rot control in China. To establish the baseline sensitivity of M. yunnanensis to these two DMI fungicides, 203 M. yunnanensis single spore isolates were collected. Measurements of sensitivity to the two fungicides were based on inhibition of mycelial growth. For both fungicides, the sensitivity distribution was a unimodal curve, with an EC50 range (the effective concentration to inhibit mycelial growth by 50 %) of 0.0001–0.0644 μg/ml for tebuconazole and 0.2311–1.7477 μg/ml for triadimefon. The M. yunnanensis isolates were obtained from orchards where DMI fungicides have not been used for peach brown rot control, thus the fungicide sensitivity distribution established in this study can be considered as the baseline for monitoring the resistance development in M. yunnanensis once the DMI fungicides are used to control peach brown rot.  相似文献   

8.
Demethylation inhibitor (DMI) fungicides are used to control brown rot in stone fruit worldwide. However, their specific mode of action can select resistant isolates of Monilinia fructicola. Monilinia fructicola resistant to DMI fungicides are associated with a fitness cost in the absence of selective pressure, indicating that the sensitive population can be re-established when discontinuing the fungicide in the field. This work aimed to build up the sensitive population of M. fructicola after discontinuing the use of tebuconazole for successive crop seasons. The sensitivity of M. fructicola to tebuconazole was assessed in four commercial peach orchards in Paraná and São Paulo States from 2012/13 to 2015/16. Different fungicide programmes were used and DMI fungicides were discontinued from 2013/14. The sensitivity of M. fructicola to tebuconazole was assessed by a mycelial growth assay in vitro and by determining the frequency of the G461S mutation in the MfCYP51 gene. The isolates from Paraná had high sensitivity to the fungicide across all seasons and the frequency of the G461S mutation remained below 5%. The isolates from São Paulo were highly resistant in the 2012/13 season; however, there was a gradual decline until 2015/16. In addition, the G461S mutation frequency in Sao Paulo State was about 80% in the 2012/13 season, but reduced until it was completely undetectable in 2015/16. These results provide evidence that resistance can be managed in orchards with high selective pressure to tebuconazole after discontinuing the use of the fungicide for at least 3 years.  相似文献   

9.
BACKGROUND: The long‐term preservation of interesting phenotypes in plant pathogenic fungi allows for follow‐up studies in the future. Twelve storage approaches were investigated to determine their effects on instability of propiconazole resistance for three demethylation inhibitor (DMI) fungicide‐resistant and two DMI‐sensitive isolates of Monilinia fructicola. They included mycelium in PDA slants under mineral oil, in PDA plugs under 10% glycerol, on dried filter paper and conidia on silica gel, each stored for 36 weeks at 4, ? 20, and ? 80 °C. RESULTS: None of the storage approaches prevented the rapid decline of EC50 values for propiconazole in the three resistant isolates, and no significant differences were found among storage approaches (P = 0.787) or between storage approaches and consecutive transfers (P = 0.053). Most of the decline in resistance occurred during the first 4 weeks of storage. The DMI resistance‐associated genetic element Mona, located in the immediate upstream region of the MfCYP51 gene, was still present in the three resistant isolates after 36 weeks of storage and weekly transfers. Furthermore, the Mona element and a portion of the MfCYP51 gene, which encodes the target enzyme for DMIs, did not reveal signs of DNA methylation. Resistance to propiconazole was partially regained in resistant isolates after two growth cycles on fresh peach fruit. CONCLUSIONS: Obtained data indicate that the decline of DMI resistance in M. fructicola cannot be prevented using commonly employed storage methods at various temperatures. The number of consecutive transfers and the storage duration prior to fungicide sensitivity tests in M. fructicola should be indicated in scientific papers. Copyright © 2011 Society of Chemical Industry  相似文献   

10.
Experiments evaluating the curative and protective effect of sprays of benodanil, bitertanol, oxycarboxin, triadimefon, triforine and propiconazole, and intensive oxycarboxin fog and triforine spray regimes, against chrysanthemum white rust are described. All treatments reduced the disease when applied before symptoms developed but only propiconazole completely prevented disease development. A single spray of propiconazole applied 4–8 days after inoculation was sufficient to eradicate infection. This fungicide was also found to eliminate symptomless infection from cuttings when used as a dip prior to planting, or as two sprays after planting. When sporulation had occurred, three sprays of propiconazole or benodanil killed the telia, but viable telia were still present after three sprays of oxycarboxin, triadimefon or triforine. When applied as single protective sprays none of these fungicides consistently prevented infection, although levels were considerably reduced when application was made 2–3 days before exposure to the disease. Observational trials indicate that although propiconazole has some growth retardant effect it does not appear to present any significant phytotoxicity problems, either as a spray or as soil residue. As a result of this work propiconazole has been successfully used in a statutory eradication campaign against this rust. To avoid the possible development of resistance, it is suggested that its use should be confined to actual outbreaks, or when it is suspected that plants or cuttings may have become infected.  相似文献   

11.
采用菌丝生长速率法和孢子萌发法,分别测定了烟草灰霉病菌对多菌灵、嘧霉胺、异菌脲和丙环唑的敏感性,同时通过离体叶片法评估了这4种杀菌剂对烟草灰霉病的保护和治疗作用。结果表明:4种杀菌剂对烟草灰霉病菌的菌丝生长和孢子萌发均表现出了不同程度的抑制活性,并对灰霉病同时具有保护和治疗作用。其中多菌灵对菌丝生长的抑制活性最强,EC50平均值为0.06 mg/L,其次为丙环唑、嘧霉胺和异菌脲,EC50平均值分别为0.36、0.53和0.60 mg/L;异菌脲和丙环唑对烟草灰霉病菌孢子萌发的抑制活性较强,EC50平均值分别为2.05和2.21 mg/L,其次为嘧霉胺和多菌灵,EC50平均值分别为10.56和131.23 mg/L。异菌脲和多菌灵对灰霉病的保护作用和治疗作用均最强,当药剂质量浓度为200 mg/L时,其对离体叶片的保护和治疗作用防效分别为100%、100%和98.3%、91.8%。研究结果可为烟草灰霉病的科学防治提供依据。  相似文献   

12.
Southern corn leaf blight (SCLB) caused by Cochliobolus heterostrophus is a fungal disease that impacts production of corn in China. Fungicides have been the main strategy to manage SCLB. In this study, 276 isolates of C. heterostrophus from seven locations in Fujian Province of China were tested for sensitivity to three demethylation inhibitor (DMI) fungicides. The results indicated that most of the isolates of C. heterostrophus tested were exceptionally sensitive to the three DMI fungicides. Correlation analysis revealed positive association between propiconazole and diniconazole (r?=?0.8145, P?<?0.0001), propiconazole and prochloraz (r?=?0.6190, P?<?0.0001), and diniconazole and prochloraz (r?=?0.5784, P?<?0.0001). However, there was no cross-resistance between these three DMI fungicides and the other six fungicides tested, which included carbendazol, chlorothalonil, mancozeb, iprodione, fluazinam, and pyraclostrobin. In a preventive pot experiment, one spray of 25% propiconazole emulsifiable concentrate (EC) with 250 μg active ingredient (a.i.) mL?1 applied 12 and 24 h before inoculation at the seedling (V6) stage reduced severity of SCLB by 85.60–89.21%. Nevertheless, the curative activity of propiconazole was much weaker (P?<?0.05) than its preventive efficacy. In greenhouse pot assays, one dose of propiconazole at 250 μg a.i. mL?1 was the most efficacious for controlling SCLB at the seedling and tasseling (VT) stages of corn, decreasing severity by 80.31%–84.85%, which was higher (P?<?0.05) compared to diniconazole, prochloraz, and other reference fungicides. Therefore, propiconazole appears to be very effective in reducing SCLB and should be applied as a preventive rather than therapeutic fungicide. Our findings provide essential information on the evolution of DMI resistance in C. heterostrophus in Fujian Province of China and may serve as a guide for early resistance monitoring in the future.  相似文献   

13.
BACKGROUND: Myclobutanil, a demethylation inhibitor (DMI) fungicide, is an important fungicide for controlling apple scab and powdery mildew. Overuse of this fungicide has led to establishment of scab isolates with reduced sensitivity to this fungicide in several countries. Experiments were conducted to determine the sensitivity of the causal agent of apple scab, Venturia inaequalis (Cooke) Winter, to myclobutanil in the UK, in order to assess whether there is a relationship between fungal insensitivity and the number of DMI applications, and establishing whether fungal sensitivity varied greatly within an orchard. RESULTS: Reduced sensitivity of V. inaequalis to myclobutanil was positively related linearly to the number of DMI applications. ED50 values ranged from 0.028 to 1.017 mg L?1 (average = 0.292) for the baseline population, whereas isolates from two other orchards had much greater ED50 values, ranging from 0.085 to 5.213 mg L?1 (average = 1.852). There was significant variation in fungal sensitivity to myclobutanil among fungal isolates from different locations within a single orchard. CONCLUSIONS: Spatial spread of insensitive isolates of V. inaequalis to myclobutanil is likely to be limited in distance. Conidia may be an important source of primary inoculum. Myclobutanil should still be effective for most field isolates, but its use should be strategically integrated with other groups of fungicides. Copyright © 2009 Society of Chemical Industry  相似文献   

14.
BACKGROUND: Succinate dehydrogenase inhibitors (SDHIs) constitute a fungicide class with increasing relevance in crop protection. These fungicides could play a crucial role in successful management of grey mould disease. In the present study the effect of fluopyram, a novel SDHI fungicide, on several developmental stages of Botrytis cinerea was determined in vitro, and the protective and curative activity against the pathogen was determined on strawberry fruit. Furthermore, fungal baseline sensitivity was determined in a set of 192 pathogen isolates. RESULTS: Inhibition of germ tube elongation was found to be the most sensitive growth stage affected by fluopyram, while mycelial growth was found to be the least sensitive growth stage. Fluopyram provided excellent protective activity against B. cinerea when applied at 100 µg mL?1 96, 48 or 24 h before the artificial inoculation of the strawberry fruit. Similarly, fluopyram showed a high curative activity when it was applied at 100 µg mL?1 24 h post‐inoculation, but, when applications were conducted 48 or 96 h post‐inoculation, disease control efficacy was modest or low. The measurement of baseline sensitivity showed that it was unimodal in all the populations tested. The individual EC50 values for fluopyram ranged from 0.03 to 0.29 µg mL?1. In addition, no correlation was found between sensitivity to fluopyram and sensitivity to other fungicides, including cyprodinil, fenhexamid, fludioxonil, iprodione, boscalid and pyraclostrobin. CONCLUSIONS: The obtained biological activity, baseline sensitivity and cross‐resistance relationship data suggest that fluopyram could play a key role in grey mould management in the near future and encourage its introduction into spray programmes. Copyright © 2011 Society of Chemical Industry  相似文献   

15.
Plots of spring wheat cv. Baldus were inoculated at GS 13 with four Mycosphaerella graminicola isolates, two relatively susceptible and two relatively resistant to DMI fungicides. Changes in the ratio of relatively susceptible to resistant types following fungicide or water sprays were measured. Three fungicides were compared: flutriafol, which is very mobile within leaves, fluquinconazole, which is less so, and prochloraz, which is almost immobile. All are inhibitors of sterol demethylation. In 1996, fungicide-treated plots were sprayed once with half the recommended dose at GS 39–47. In 1997, three doses were used: one-quarter and one-eighth of the recommended dose and a dual application of two one-eighth recommended doses, a week apart. Isolates were classified using a discriminating dose assay and the ratio of relatively susceptible to relatively resistant isolates in each field plot before and after fungicide application calculated. In both years, the numbers of relatively susceptible and relatively resistant isolates were equal just before fungicide application. All fungicides caused significant selection towards resistance, but the strength of selection varied with fungicide, dose and position in the crop canopy. Fluquinconazole selected most strongly and gave the best control of disease. Interactions between fungicide and dose were not significant. Selection was equally strong all along leaves sprayed with prochloraz, but increased smoothly from base to tip of leaves sprayed with fluquinconazole or flutriafol. Averaged over fungicides, reducing the dose of a single fungicide application from one-quarter to one-eighth slightly reduced selection towards resistance on both leaf layers. The dual one-eighth dose caused twice the change of the single one-eighth dose on the flag leaf, but was similar to a single spray on leaf 2.  相似文献   

16.
Laurel wilt is caused by Raffaelea lauricola, a nutritional symbiont of an Asian ambrosia beetle, Xyleborus glabratus. American members of the Lauraceae plant family are most susceptible and 300 million trees have been killed by the disease in the southeastern USA since 2003. Recently, commercial production of an important crop in the laurel family, avocado (Persea americana), has been affected in southern Florida. We summarize studies in which diverse measures were tested for managing the disease. In all studies, trees were treated with potential laurel wilt control measures and subsequently inoculated with R. lauricola. On potted plants in greenhouse experiments, commercial nutritional products (Greenstim and Keyplex 350) and SAR products (Agri-Fos and Nutri-Phite), when applied as soil drenches or foliar sprays, had either no impact on, or increased laurel wilt symptom development compared to non-treated control treatments. Bark applications of Tilt (a propiconazole fungicide for which emergency registration had been obtained in 2010) in a surfactant (Pentrabark) enabled significant laurel wilt protection in greenhouse studies on small potted plants, but Pentrabark and other surfactants moved little propiconazole into the xylem of fruit-bearing trees in field studies. In efficacy studies in the field, Propiconazole Pro (an injectable formulation of propiconazole), Tilt, and two experimental formulations of another triazole fungicide, tebuconazole, decreased the development of laurel wilt compared to nontreated control trees when applied as undiluted injections into branches and scaffold limbs (microinjection), or injection of dilute fungicide into tree flare roots (macroinfusion). However, symptoms developed in all treated trees by 10–11 months after inoculation with R. lauricola, indicating that trees would need to be re-treated at least on an annual basis. Regardless of how fungicides were applied, insignificant levels of different active ingredients entered fruit. Although fungicide treatment of fruit-bearing avocado trees is not a concern for food safety and several triazole and DMI fungicides can protect avocado trees from laurel wilt, cost-effective measures with which the xylem could be loaded with and protected by these products remains a challenge. Management of laurel wilt in commercial avocado production areas is discussed.  相似文献   

17.
Sour rot, green mold and blue mold are postharvest diseases of citrus fruit. Benzimidazole and imidazole fungicides control molds, and guazatine controls sour rot, but strains ofPenicillium spp. resistant to these chemicals have been reported. Aqueous formulations of fenpropimorph, a morpholine fungicide, are very active in controlling fungi attacking postharvest citrus fruits. The fungicidal effect of the chemical in the coating wax was investigated in combined treatments with guazatine in dip or spray applications on various citrus fruit varieties. Fenpropimorph alone was as good as or a better curative and protective treatment than the current commercial treatments applied in packinghouses in Israel for decay control.  相似文献   

18.
依据鉴别浓度检测了中国不同地理来源的114株草坪草币斑病菌对甲基硫菌灵的敏感性,并采用菌丝生长速率法测定了供试菌株对异菌脲和丙环唑的敏感性。结果显示:对甲基硫菌灵敏感的菌株共98株,占总数的85.96%,抗性菌株16株,占总数的14.04%;在8个有甲基硫菌灵施药历史的采样点中,5个点检测到了抗性菌株。异菌脲和丙环唑对草坪草币斑病菌的EC50值分别在0.012 1~1.264 4和0.000 4~0.100 4 μg/mL之间,平均EC50值分别为（0.525 6 ± 0.207 7）和（0.015 2 ± 0.020 1）μg/mL,最大EC50值和最小EC50值分别相差104.7和251.0倍。敏感性频率分布结果显示,币斑病菌对异菌脲和丙环唑已出现敏感性下降的亚群体。与从未施过相关药剂地区的币斑病菌群体相比,分离自8个有施药历史地块的菌株群体对异菌脲的敏感性均显著降低,4个有施药历史地块的群体对丙环唑的敏感性显著降低。相关性分析显示,对丙环唑最不敏感的10株币斑病菌对异菌脲的敏感性均呈现下降趋势,且两者间存在一定的正相关关系（ρ = 0.755 4,P < 0.000 1）,推测这部分菌株可能存在多药抗药性。本研究结果可为杀菌剂的合理使用及币斑病的有效防治提供理论支持。  相似文献   

19.
Field occurrence of vinclozolin resistance in Monilinia fructicola   总被引：1，自引：1，他引：0  
Strains of Monilinia fructicola resistant to vinclozolin were isolated from fruit affected by brown rot from an orchard where the fungicide had been used over four seasons. Resistant isolates were pathogenic to peach fruit, and resistance of one isolate was confirmed following dipping of inoculated fruit in fungicide suspensions. In culture, one of four resistant isolates was identical in colony morphology and sporulation to sensitive isolates from different geographic areas. The other resistant isolates produced dark mycelium on PDA and were slower growing. Vinclozolin-resistant isolates were resistant in vitro to two other dicarboximide fungicides, iprodione and procymidone.  相似文献   

20.
Fungicides are the preferred rice blast (Pyricularia oryzae) control option by farmers. However, no fungicides are yet registered for this purpose in Australia. Hence, it is important to test the baseline sensitivity of P. oryzae isolates collected from blast-affected regions across northern Australia, which have not yet been exposed to the fungicides, as part of a resistance management strategy. Further, it is also important to investigate and compare effect of application timing of fungicides on conidial development, including germination and germ tube growth, and penetration on susceptible rice. The EC50 of a collection of fungicide-sensitive blast isolates were within the range of 0.02–2.02 and 0.06–1.91 mg L?1 for azoxystrobin and propiconazole, respectively. Azoxystrobin was shown to have greater inhibitory effect on conidial germination than propiconazole. In addition, for pre-inoculation application, only germ tubes in the presence of external nutrients continued to grow from 24 to 48 hpi. On susceptible seedlings, both fungicides completely controlled blast disease when applied the same day as inoculation. However, for pre- or post-inoculation application of fungicide, the extent of disease control was reduced, with azoxystrobin more efficacious than propiconazole. A stimulatory effect of both fungicides at low dose was observed on certain P. oryzae isolates. This is the first study to assess the baseline sensitivity of the P. oryzae population in Australia and the first to report a stimulatory effect of low azoxystrobin concentration on growth of P. oryzae. The study highlights, for the first time, the critical role of external nutrients in promoting germ tube growth under fungicide stress conditions. Lastly, it demonstrates the high degree of efficacy of the fungicides and their potential for future rice blast management in Australia.  相似文献   

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