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1.
Strains of Pseudocercosporella herpotrichoides collected in France on winter wheat give either fast-growing mycelial colonies with regular margins or slow-growing mycelial colonies with irregular margins. Most of the fastgrowing isolates were sensitive to triadimenol (EC50 below 2mg litre?1), but some of them were resistant to this inhibitor of sterol C-14 demethylation. In contrast, all the slow-growing strains were highly resistant to triadimenol (EC50 greater than 100 mg litre?1). This resistance was also expressed in inhibition of germ-tube elongation. Positive cross-resistance was observed between most of the inhibitors of sterol C-14 demethylation, with the exception of some imidazole derivatives (clotrimazole, prochloraz). All the fast-growing strains were tolerant to fenpropimorph and fenpropidin whereas the slow-growing ones were susceptible; the reverse was true with piperalin and tridemorph. All the field isolates were inhibited to the same extent by the inhibitors of squalene-epoxidase, nafifine and terbinafine. Two types of mutant resistant to triadimenol have been induced under laboratory conditions from sensitive fast-growing strains. The most common mutants were resistant to all the inhibitors of sterol C–14 demethylation and also in some conditions to fenpropimorph, tridemorph and the inhibitors of squalene-epoxidase. The other mutants were characterised by a reduced spectrum of cross-resistance between triadimenol and the other inhibitors of sterol biosynthesis. The field isolates and laboratory mutants resistant to triadimenol and propiconazole were also resistant to each of the four enantiomers of these two fungicides.  相似文献   

2.
After nitrosoguanidine- or UV-mutagenesis, three different benzimidazole-resistant phenotypes were isolated on media containing benomyl or a mixture of carbendazim and diethofencarb from wild-type strains of Botrytis cinerea Pers. ex Fr. and Ustilago maydis (D.C.) Corda. Mutants of B. cinerea with moderate (MBr) or low (LBr) resistance to benzimidazoles and high resistance to diethofencarb (Dr) were isolated from the fungicide-mixture-containing medium in low frequency (7–1 × 10?8). Only benzimidazole-resistant strains highly sensitive to diethofencarb (HBrDs) were identified on benomyl-containing medium at a frequency of 6.6 × 10?6. Fitness-determining characteristics such as sporulation, germination and germ-tube elongation, were found to be reduced significantly in the mutants of B. cinerea that were resistant to both benzimidazoles and diethofencarb. However, pathogenicity of a MBrDr mutant strain on cucumber seedlings was equal to that of the wild type and a carbendazim + diethofencarb mixture was found to control grey mould caused by the wild type, but was not effective when the plant cotyledons were infected by the mutant strain. Three benzimidazole-resistant phenotypes (HBrDs, HBrDr, MBrDr) were isolated easily in U. maydis from a benomyl-containing medium. In contrast with B. cinerea, only one-tenth of the benzimidazole-resistant strains were sensitive to diethofencarb. Genetic analysis of benzimidazole resistance in U. maydis showed that the three benzimidazole-resistant phenotypes were due to three allelic mutations in a single gene and one of them was responsible for the negative cross-resistance between benzimidazoles and diethofencarb.  相似文献   

3.
 Laboratory mutants of Cochliobolus heterostrophus resistant to iprodione were obtained after chemical mutageneses. All the mutants were able to grow on the medium amended with iprodione 100 μg/ml. They showed positive cross-resistance to procymidone and fludioxonil and were sensitive to high osmolarity. Crosses between the mutant and a wild-type strain revealed that the fungicide resistance and osmotic sensitivity traits were inherited by their offspring in a 1 : 1 mutant/wild type ratio, indicating that the mutant phenotypes in these strains were due to alteration at a single gene locus. Results from allelism tests indicated that three genes (Dic1, Dic2, Dic3) conferred the mutant phenotypes. Among them, Dic1 mutant strains were classified into three types on the basis of their phenotypes. The first type was moderately resistant to the fungicides and less sensitive to osmotic stress than the other Dic1 mutant strains. The second type showed moderate fungicide resistance, but growth was inhibited under lower osmotic stress (50 mM KCl). The other Dic1 mutant strains grew well on medium containing iprodione and fludioxonil even at a concentration of 100 μg/ml and were highly sensitive to osmotic stress. The Dic2 and Dic3 mutant strains had moderate resistance to the fungicides with low-level osmotic sensitivity. The Dic1 gene was epistatic to Dic2 and Dic3 for fungicide resistance and hypostatic to them for osmotic sensitivity. These results suggest that the osmoregulatory system is involved in fungicide resistance in laboratory mutants of C. heterostrophus. Received: March 14, 2002 / Accepted: August 13, 2002  相似文献   

4.
The baseline sensitivity of Botrytis cinerea to propamidine and assessment of the risk of propamidine resistance in vitro are presented in this article. The baseline sensitivities of 41 wild-type strains were distributed as a unimodal curve with EC50 values of mycelial growth ranging from 0.182 to 1.460 μg ml−1, with a mean of 0.79 ± 0.27 μg ml−1. A total of 10 resistant mutants, obtained from one parental strain, were induced by UV irradiation and selected for resistance to propamidine with an average frequency of 1.98 × 10−9 and 0.025 respectively. These mutants were divided into three classes of resistant phenotypes with low (LR), moderate (MR) and high (HR) levels of resistance, determined by the EC50 values of 5.0–15.0 μg ml−1, 15.1–75.0 μg ml−1 and more than 75.0 μg ml−1 respectively. Neither positive cross-resistance nor negative cross-resistance was detected between propamidine and the fungicides, benzimidazole carbendazim, anilino-pyrimidine pyrimethanil, dicarboximide iprodione or procymidone. All 10 propamidine-resistant mutants showed reduced mycelial growth in vitro, sporulation, spore germination and pathogenicity when compared with the parental strain. These studies demonstrated that propamidine possesses a low risk of resistance developing. However, as B. cinerea is a high-risk pathogen, appropriate precautions against resistance development should be taken.  相似文献   

5.
The molecular basis of resistance to benzimidazole fungicides with laboratory and field mutant isolates of Botrytis cinerea was investigated. After chemical mutagenesis with N-methyl-N-nitrosogouanidine (NMNG) two different benzimidazole-resistant phenotypes were isolated on media containing carbendazim or a mixture of carbendazim and diethofencarb. The mutant isolates from the fungicide-mixture-containing medium were moderately resistant to carbendazim with wild-type tolerance to diethofencarb while mutant isolates from carbendazim-containing medium were highly resistant to carbendazim but sensitive to diethofencarb. The studied field isolates were highly resistant to benzimidazoles and sensitive to diethofencarb. Study of fitness characteristics of benzimidazole highly-resistant isolates showed that the resistance mutation(s) had no apparent effect on fitness-determining parameters. Contrary to this, the moderately benzimidazole-resistant strains, with no increased diethofencarb sensitivity, had a significant reduction in certain ecological fitness-determining characteristics. Analysis of the sequence of the β-tubulin gene revealed two amino acid replacements in the highly benzimidazole-resistant mutants compared to that of the wild-type parent strain. One was the glutamic acid (GAG) to alanine (GCG) change at position 198 (E198A), identified in both laboratory and field highly benzimidazole-resistant isolates, a mutation previously implicated in benzimidazole resistance. The second was a novel benzimidazole resistance mutation of glutamic acid (GAG) to glycine (GGG) substitution at the same position 198 (E198G), identified in a highly benzimidazole-resistant laboratory mutant strain. Molecular analysis of the moderately benzimidazole-resistant strains revealed no mutations at the β-tubulin gene. A novel diagnostic PCR-RFLP assay utilising a BsaI restriction site present in the benzimidazole-sensitive (E198) but absent in both resistant genotypes (E198G and E198A) was developed for the detection of both amino acid replacements at the β-tubulin gene.  相似文献   

6.
BACKGROUND: Fenhexamid, a sterol biosynthesis inhibitor effective against Botrytis, inhibits the 3‐ketoreductase (Erg27) involved in C‐4 demethylation. Several fenhexamid‐resistant phenotypes have been detected in Botrytis cinerea populations from French vineyards. The field isolates with the highest resistance levels display amino acid changes in Erg27 (F412S, F412I or F412V). RESULTS: Fenhexamid‐resistant mutants were generated by site‐directed mutagenesis of the erg27 gene in a sensitive recipient strain to overcome the impact of different genetic backgrounds. The wild‐type erg27 allele was replaced by the three mutated alleles (erg27F412S/I/V) by homologous recombination. These isogenic strains were shown to be fenhexamid‐resistant and were used to quantify the impact of F412 mutations on fungal fitness. Several parameters, including radial growth, the production of sclerotia and conidia, freezing resistance and aggressiveness, were quantified in laboratory conditions. Analysis of variance demonstrated significant differences between the mutant and parental strains for some characters. In particular, the mutants grew more slowly than the wild‐type strain and displayed variations in the production of sclerotia and conidia with temperature and susceptibility to freezing. CONCLUSIONS: The results highlight a moderate but significant impact of F412 mutations on the survival capacity of B. cinerea strains displaying high levels of resistance to fenhexamid in laboratory conditions, potentially limiting their dispersal and persistence, particularly in terms of overwintering, in field conditions. Copyright © 2011 Society of Chemical Industry  相似文献   

7.
Resistances of 33- and 27-fold to the pyrethroids fenvalerate and deltamethrin, respectively, have been induced in larvae of the Egyptian cotton leafworm Spodoptera littoralis (Boisd.) by selection of two subcolonies of a field population in the laboratory. Selected strains showed relatively high levels of resistance (11- to 36-fold) to all the tested pyrethroids, moderate levels of cross-resistance (3- to 13-fold) to DDT and the carbamate aminocarb, and a slight increase in tolerance levels to endrin and lindane. The pyrethroid-resistant strains, by contrast, manifested no cross-resistance to the organophosphorus compounds that were tested. Moreover, a negative crossresistance was observed in the pyrethroid-resistant strains to dicrotophos, methamidophos and the carbamate methomyl.  相似文献   

8.
为明确琥珀酸脱氢酶抑制剂类新型吡啶酰胺杀菌剂氟唑菌酰羟胺在中国小麦赤霉病防治中的应用潜力,分别采用菌丝生长速率法和孢子萌发法,测定了氟唑菌酰羟胺对湖北省6个地区106株禾谷镰孢菌的室内毒力、田间防效及其与多菌灵和氰烯菌酯的交互抗性。结果显示:氟唑菌酰羟胺对106株禾谷镰孢菌菌丝生长的EC50值为 (0.018 0 ± 0.209 0) mg/L,平均值为 (0.072 8 ± 0.025 9) mg/L;对分生孢子萌发的EC50值为 (0.052 7 ± 0.473 2) mg/L,平均值为 (0.176 0± 0.059 6) mg/mL;且其EC50值频率分布均呈单峰曲线,因此可分别将菌丝生长和孢子萌发的平均EC50值作为禾谷镰孢菌对氟唑菌酰羟胺的敏感性基线。初步的交互抗性测定结果表明,抗多菌灵或氰烯菌酯的菌株对氟唑菌酰羟胺均未表现出抗性。田间试验显示,氟唑菌酰羟胺有效剂量200 g/hm2处理的防效 (超过90.0%) 显著高于对照药剂氰烯菌酯600 g/hm2的防效 (78.0%),与空白对照相比增产效果在127%~135%之间。经氟唑菌酰羟胺处理后,小麦籽粒中由禾谷镰孢菌产生的毒素脱氧雪腐镰刀菌烯醇 (DON) 的含量比空白对照降低了55.09%。研究表明,氟唑菌酰羟胺对禾谷镰孢菌呈现出较高的室内活性且田间防效优越,同时还能降低小麦籽粒中DON毒素的含量及提高小麦产量,因此可作为生产中防治小麦赤霉病的替代或后备药剂,同时也可考虑用作为禾谷镰孢菌对多菌灵抗性治理的替代药剂。  相似文献   

9.
BACKGROUND: QoI fungicides, inhibitors of mitochondrial respiration, are considered to be at high risk of resistance development. In several phytopathogenic fungi, resistance is caused by mutations (most frequently G143A) in the mitochondrial cytochrome b (cytb) gene. The genetic and molecular basis of QoI resistance were investigated in laboratory and field mutants of Botryotinia fuckeliana (de Bary) Whetz. exhibiting in vitro reduced sensitivity to trifloxystrobin. RESULTS: B. fuckeliana mutants highly resistant to trifloxystrobin were obtained in the laboratory by spontaneous mutations in wild‐type strains, or from naturally infected plants on a medium amended with 1–3 mg L?1 trifloxystrobin and 2 mM salicylhydroxamic acid, an inhibitor of alternative oxidase. No point mutations were detected, either in the complete nucleotide sequences of the cytb gene or in those of the aox and Rieske protein genes of laboratory mutants, whereas all field mutants carried the G143A mutation in the mitochondrial cytb gene. QoI resistance was always maternally inherited in ascospore progeny of sexual crosses of field mutants with sensitive reference strains. CONCLUSIONS: The G143A mutation in cytb gene is confirmed to be responsible for field resistance to QoIs in B. fuckeliana. Maternal inheritance of resistance to QoIs in progeny of sexual crosses confirmed that it is caused by extranuclear genetic determinants. In laboratory mutants the heteroplasmic state of mutated mitochondria could likely hamper the G143A detection, otherwise other gene(s) underlying different mechanisms of resistance could be involved. Copyright © 2012 Society of Chemical Industry  相似文献   

10.
Sensitivity profiles of Botrytis cinerea field isolates to zoxamide and the molecular basis of the resistance mechanism involved in cross-resistance relationships between benzamides, benzimidazoles and N-phenylcarbamates were investigated. B. cinerea isolates collected from southern, central and northern Greece were characterized based on their sensitivity to zoxamide, the benzimidazole carbendazim and the N-phenylcarbamate diethofencarb. Isolates exhibiting baseline sensitivity to carbendazim and zoxamide but no sensitivity to diethofencarb were considered wild type (S phenotype) and accounted for 44% of the total strains sampled. Thirty-three percent of the isolates had increased sensitivity (HS phenotype) to zoxamide and diethofencarb and were highly resistant to carbendazim compared to S isolates. Eight percent of the sample was highly resistant (HR phenotype) to all anti-tubulin agents studied. The rest of the isolates were moderately resistant to zoxamide (MR phenotype) and equally sensitive to benzimidazoles and N-phenylcarbamates compared to isolates of the S phenotype. Fungitoxicity tests with botrycides belonging to other chemical classes revealed no cross-resistance relationships between zoxamide and the phenylpyrrole fludioxonil, the dicarboximide iprodione, the hydroxyanilide fenhexamid, the anilinopyrimidine cyprodinil, the carboxamide boscalid and the strobilurin-type fungicide pyraclostrobin. Study of fitness characteristics did not show any significant difference between zoxamide resistant and sensitive isolates with respect to the parameters tested. PCR-RFLP analysis of a part of the β-tubulin gene sequence detected mutations in position 198 for both HS and HR zoxamide-sensitivity phenotypes. DNA sequence analysis of the B. cinerea β-tubulin gene revealed two previously described benzimidazole-resistance-conferring mutations. The first one was the glutamic acid (GAG) to alanine (GCG) change at position 198 (E198A), which was identified in all HS isolates. The second mutation (E198K) was a GAG-to-AAG substitution resulting in the replacement of glutamic acid with lysine present in all B. cinerea isolates highly resistant to all three anti-tubulin classes of fungicides. A number of mutations in other positions of the β-tubulin gene were detected in the moderately zoxamide-resistance phenotype.  相似文献   

11.

Sensitivity and inherent resistance risk of Alternaria solani to fludioxonil, cross-resistance profiles and the potential implications of resistance mutations on fitness parameters were investigated. Fludioxonil was highly effective against a wild type A. solani field strain both in vitro (EC50?=?0.05 μg/mL) and in preventive applications on artificially inoculated tomato fruit. Mutants with low [Resistance factor (Rf): 15 based on EC50], medium (Rf: 150–300) and high (Rf: > 1000) levels of phenylpyrrole resistance were isolated from the wild type strain at high frequencies following mutagenesis with UV irradiation and selection on fludioxonil containing medium. Resistant isolates retained their resistance levels even after 9 subcultures on fungicide-free growth medium while they could express their resistant phenotypes in planta. Investigation of cross-resistance relationships showed that fludioxonil resistance mutations also reduce the sensitivity of mutant strains to the aromatic hydrocarbon fungicide quintozene as well as the dicarboximides iprodione and vinclozolin. No cross-resistance was observed between fludioxonil and fungicides with different modes of action such as the sterol biosynthesis inhibitors (DMIs) imazalil and flusilazole and the carboxamide boscalid. All fludioxonil resistant isolates were more sensitive to the anilinopyrimidine pyrimethanil, while only two isolates were less sensitive to the QoI pyraclostrobin compared to the wild-type strain. Study of fitness determining parameters showed that resistance mutation(s) had no adverse effects on mycelial growth, conidial germination and sensitivity to osmotic stress while they had a pleiotropic effect on virulence and conidia production in resistant mutants. Results of the present study indicate that fludioxonil is a highly effective fungicide against A. solani, while the risk of resistance development to this fungicide is considered to be medium making fludioxonil an ideal alternative to high risk fungicides such as boscalid and pyraclostrobin whose performance against early blight has already been compromised by resistance development.

  相似文献   

12.
Six reddish brown polyxin-resistant mutants of Cochliobolus heterostrophus were isolated after ethyl methanesul-phonate and N-nitroquinoline oxide mutageneses followed by selection on polyoxin. All the mutants were highly resistant to polyoxin (MIC > 1600 μg/ml). When mutants were crossed with the wild-type strain, all crosses had a 1 : 1 ratio of mutant (reddish brown pigmentation and polyoxin resistance) : wild type (non-reddish brown pigmentation and polyoxin sensitivity), indicating that the phenotypes in these strains were due to alteration at a single gene locus in each strain. Allelism tests revealed the existence of two loci, Pol2 and Pol5. The results of the crossing and mutation-rate studies suggest that the each gene was pleiotropic for the reddish brown color and polyoxin resistance. Received 19 September 2001/ Accepted in revised form 25 December 2001  相似文献   

13.
In light of growing environmental concerns, surveys of fungicide resistance are needed to ensure efficient control of fungi and avoid unnecessary treatments. Investigations of fungicide resistance in Fusicoccum amygdali are scarce despite the economic impacts of this pathogen in peach and almond orchards. Thiophanate-methyl has been registered for more than 20 years to control F. amygdali but no resistance has been reported to date. This propesticide is metabolized by fungi into carbendazim, a β-tubulin inhibitor. Sensitivity to carbendazim of nine populations of F. amygdali from French orchards was assessed using germination bioassays. Also, resistance levels of 63 strains isolated from four populations were evaluated using mycelial growth assays. The underlying mechanism of resistance was investigated by sequencing the β-tubulin gene, the molecular target of thiophanate-methyl, in a set of isolates with different levels of sensitivity to carbendazim. Cross-resistance to thiophanate-methyl and to another β-tubulin inhibitor, diethofencarb, was also assessed in carbendazim-sensitive and -resistant strains. Isolates highly resistant to carbendazim were found in one of the nine orchards studied. Sequencing showed that resistant phenotypes carry a mutation in the β-tubulin gene leading to E198K substitution. Positive cross-resistance to thiophanate-methyl was confirmed and no negative cross-resistance to diethofencarb was identified in the phenotyped isolates, which were all resistant to this active substance. To our knowledge, this is the first report of resistance to thiophanate-methyl in F. amygdali. The high level of resistance of isolates sampled in one population is of concern, although the limited geographical scope of resistance suggests its recent emergence.  相似文献   

14.
The new powdery mildew fungicide quinoxyfen belongs to the novel quinoline class of chemistry. Although its biochemical mode of action is unknown, quinoxyfen does not act in the same way as other cereal fungicides. It is a systemic protectant which inhibits the early stages of mildew infection on a wide range of crops, and provides season-long protection from a single early-season spray applied around GS 31. The base-line sensitivity profile of quinoxyfen was defined for barley powdery mildew (Erysiphe graminis f.sp. hordei) from over 340 field isolates collected from different parts of the UK from 1991 onwards. Sensitivities ranged from <0·0001→0·16 mg litre-1 with a mean of 0·003 mg litre-1. Current work is extending the base-line sensitivity studies to wheat powdery mildew (E. graminis f.sp. tritici), and includes isolates from European trials, but so far this new data set has shown no differences from barley powdery mildew. Quinoxyfen-resistant mutants were generated in the laboratory, and some similar resistant strains were obtained from treated field crops. These laboratory and field strains were always defective, in some way, for sporulation and, curiously, all required the presence of quinoxyfen for survival in culture. Attempts to generate resistant mutants that sporulated normally were unsuccessful. These studies suggested that the resistance risk for quinoxyfen is low. The recommended anti-resistance strategy accompanying introduction of quinoxyfen avoids seed treatments and late-season applications. Instead, a single early (GS 31) treatment using either pre-formulated mixtures or alternating with a fungicide with different mode of action is recommended. This strategy will be supported by continued monitoring of wheat and barley powdery mildew. ©1997 SCI  相似文献   

15.
The ring-substituted N-phenylanilines, N-(3-chlorophenyl)aniline (MC-1) and N-(3,5-dichlorophenyl)aniline (MC-2) were tested for their antifungal activity against Botrytis cinerea Pers. ex Fr. and Venturia nashicola Tanaka et Yamamoto. In both fungi, increased sensitivity to MC-1 and MC-2 was clearly observed in ‘highly carbendazim-resistant, diethofencarb-sensitive’ (HR, S) phenotypes. Sensitivity was low in ‘carbendazim-sensitive, diethofencarb-resistant’ (S, R) and ‘intermediately carbendazim-resistant, diethofencarb-resistant’ (IR, R) strains. On cucumber cotyledons, other strains of B. cinerea, possessing the phenotype ‘highly carbendazim-resistant, diethofencarb-resistant’ (HR, R) were not controlled by either MC-1 or MC-2. Response to MC-2 was also examined using random ascospore progenies from V. nashicola crosses. In these progenies, high-level carbendazim resistance and MC-2 sensitivity always segregated together. Sensitivity to MC-2 is controlled by a single gene which is either identical to or very closely linked to one conferring high-level resistance to carbendazim.  相似文献   

16.
Nitrate non-utilising (Nit) mutants of six field strains and three single-ascospore strains of Botryotinia fuckeliana were selected by plating mycelial plugs onto a nitrate-containing minimal medium amended with chlorate. Mutants were characterised by growth responses on minimal medium amended with various sole nitrogen sources. For each parental strain two mutants were produced: nit1, defective in nitrate reductase apoenzyme; and NitM, defective in the molybdenum cofactor pathway. Complementation on nitrate minimal medium was observed between nit1 and NitM mutants from the same parent in all instances. However, complementation was not observed between any such combinations when the mutants were derived from different parents. It is concluded that a vegetative incompatibility system operates in B. fuckeliana resulting in multiple vegetative compatibility groups. One of the single-ascospore strains was derived from a cross between two of the field strains, indicating that new compatibility groups can be generated during sexual reproduction. Mycelial interaction zones were formed between all parental strains when they were paired on NaCl-amended medium, indicating congruence between mycelial incompatibility and vegetative incompatibility.  相似文献   

17.
The type virus of the family Hypoviridae, Cryphonectria hypovirus 1 strain EP713 (CHV1-EP713), infects Cryphonectria parasitica, the filamentous causal fungus of chestnut blight, and reduces its virulence. This pathosystem serves as a model to study fungus-mycovirus interactions. We previously developed a genetic screening protocol for host factors associated with symptom induction by CHV1-EP713 and its mutants. In the procedure the standard field fungal isolate EP155 was transformed by cDNA from a mild hypovirus mutant Cys(72), launching virus infection, and mutagenized by random plasmid insertion with pHygR conferring hygromycin resistance. We now report an extension of the study to characterize different mutant strains, with different phenotypes than their parental strain TCys(72)-1. TCys(72)-1 is moderately reduced in pigmentation and sporulation compared to the uninfected wild-type strain EP155. Mutants sfb1, sfb2 and k202 were characterized biologically and molecularly in comparison to the previously isolated mutant (namA) and the parental strain. These mutants harbored one (sfb1) or more copies (sfb2 and k202) of the mutagenic plasmid, pHygR. The three mutants had similar biological attributes; that is, vegetative growth rate, conidiation and virulence (assay on apples) was reduced on potato dextrose agar media, relative to the parental strain and pigmentation was the same or slightly increased. Interestingly, viral dsRNA accumulation levels were apparently unaltered in these mutants. The screening method was efficient for mining fungal mutants with unusual hypovirus symptoms. Further, characterization of the mutants provides interesting insights into symptom induction by the hypovirus.  相似文献   

18.
恶苗病是水稻生产上较为严重的种传真菌病害,咪唑类广谱内吸性杀菌剂咪鲜胺是目前防治该病害的主要药剂。以对咪鲜胺抗性及敏感的田间水稻恶苗病菌为试材,研究了其适合度及对几种常用杀菌剂的交互抗性。结果显示:抗性菌株的抗药性可稳定遗传,其温度敏感性与敏感菌株无明显差异,部分抗性菌株在菌丝生长速率、产孢量、孢子萌发率和致病力方面显著高于田间敏感菌株;咪鲜胺与三唑类及2-氰基丙烯酸酯类杀菌剂之间均无交互抗性。研究表明,对咪鲜胺产生抗性的水稻恶苗病菌具有较强的适合度,在田间自然条件下有可能形成优势群体,因此需合理轮换使用不同作用机制的杀菌剂,以延缓其抗药性的发展。  相似文献   

19.
The baseline sensitivity ofFusarium graminearum Schwade [teleomorph =Gibberella zeae (Schweinitz) Petch] to the fungicide JS399-19 (development code no.) [2-cyano-3-amino-3-phenylacrylic acetate] and the assessment of risk to JS399-19 resistancein vitro are presented. The mean EC50 values for JS399-19 inhibiting mycelial growth of three populations of wild-typeF. graminearum isolates were 0.102±0.048, 0.113±0.035 and 0.110±0.036 μg ml−1, respectively. Through UV irradiation and selection for resistance to the fungicide, we obtained a total of 76 resistant mutants derived from five wild-type isolates ofF. graminearum with an average frequency of 1.71 × 10−7% and 3.5%, respectively. These mutants could be divided into three categories of resistant phenotypes with low (LR), moderate (MR) and high (HR) level of resistance, determined by the EC50 values of 1.5–15.0 μg ml−1, 15.1–75.0 μg ml−1 and more than 75.0 μg ml−1, respectively. There was no positive cross-resistance between JS399-19 and fungicides belonging to other chemical classes, such as benzimidazoles, ergosterol biosynthesis inhibitors and strobilurins, suggesting that JS399-19 presumably has a new biochemical mode of action. Although the resistant mutants appeared to have comparable pathogenicity to their wild-type parental isolates, they showed decreased mycelial growth on potato-sucrose-agar plates and decreased sporulation capacity in mung bean broth. Nevertheless, most of the resistant mutants possessed fitness levels comparable to their parents and had MR or HR levels of resistance. As these studies yielded a high frequency of laboratory resistance inF. graminearum, appropriate precautions against resistance development in natural populations should be taken into account. http://www.phytoparasitica.org posting August 7, 2008.  相似文献   

20.
A new series of compounds with high contra-selective activity against benomyl-resistant fungal strains was found among ring-substituted N-phenyl-anilines. Hydrophobic substitution in one of the benzene rings, together with the secondary amine character of the molecule, are important factors for high fungitoxicity. The sensitivities of benomyl-resistant isolates to some representatives of the N-phenylanilines equal or even surpass their sensitivity to diethofencarb or MDPC. The negative cross-resistance with benzimdazole fungicides is valid for strains of Botrytis cinerea, Venturia nashicola and Venturia inaequalis. The strains of B. cinerea with double insensitivity to benzimidazoles and phenyl-carbamates are insensitive also to N-phenylanilines. However, the similarly double-insensitive strain of V. nashicola was found to be just as sensitive to the N-phenylanilines tested as the strain resistant only to benzimidazoles. The latter result revealed an important bonus compared with diethofencarb. Preventive application of one of the most active representatives of the N-phenylanilines to young cucumber plants was effective against infection with benomyl-resistant isolates of B. cinerea. Moderate apical translocation after root-dipping was also observed.  相似文献   

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