草莓灰霉病菌对嘧菌酯的抗性检测及抗性菌株的生物学特性研究

由灰葡萄孢(Botrytis cinerea Pers.)引起的草莓灰霉病是严重危害草莓的病害之一。为了解草莓灰霉病菌对杀菌剂嘧菌酯的抗性情况,本研究针对2012年从国内10省市采集和分离的134株草莓灰霉病菌菌株,利用特异性引物BcAR-F/BcAR-R扩增其cytb基因的部分序列,进行了嘧菌酯抗性的分子检测;对检测出的抗性菌株在嘧菌酯浓度分别为22.4、112和224μg·mL~(-1)的含药培养基上进行抗性验证;此外,还比较了抗性菌株与敏感菌株主要生物学性状的差异。结果表明,有54个菌株对嘧菌酯表现抗性,均属于中等抗性水平,占检测总数的40.3%,分布于北京市、湖北、江苏、河北、辽宁和四川各省;对15个抗性菌株cytb基因的序列分析表明,其第143位发生突变,由甘氨酸变为丙氨酸;对随机选取的4株抗性菌株和2株敏感菌株的适合度测定结果发现,抗性菌株和敏感菌株在最适生长温度、菌落生长速度、孢子萌发率方面没有表现出规律性差异,但抗性菌株的产孢量和致病力均显著低于敏感菌株。     

Genetic control of the resistance of Erysiphe graminis f.sp. hordei to five triazole fungicides

The genetics of resistance to ergosterol demethylation inhibitor (DMI) fungicides of the triazole (conazole) group was examined in a cross between two isolates of the barley powdery mildew fungus, Erysiphe graminis (=  Blumeria graminis ) f.sp. hordei . One isolate, E1, was previously identified as being resistant to the triazole fungicide triadimenol, while the other, HL3/5, was sensitive. The 56 progeny tested were classified into two distinct groups, either being resistant to triadimenol, like E1, or sensitive, like HL3/5. The segregation ratio was not significantly different from 1:1, consistent with responses to triadimenol being controlled by a single gene. In further tests with cyproconazole, epoxiconazole, propiconazole and tebuconazole, all the progeny classified as resistant to triadimenol were also more resistant to each of these other triazole fungicides than were any of the triadimenol-sensitive progeny. This is consistent with the triadimenol resistance allele also conferring cross-resistance to the other triazoles. The ratio between the responses of the resistant and sensitive progeny (the resistance factor, RF) was greatest for triadimenol, followed by tebuconazole, propiconazole, epoxiconazole and cyproconazole, in that order. The RF for triadimenol was much greater when the fungicide was applied as a seed treatment than when it was sprayed. Five isolates, covering the five levels of responses to triadimenol identified previously in the UK population of E. graminis f.sp. hordei , were used as standards; a triadimenol-sensitive isolate and one with the lowest level of resistance were sensitive to all four of the other fungicides, while three isolates with higher levels of triadimenol-resistance were also more resistant to the other chemicals.     

Discontinuance of tebuconazole in the field restores sensitivity of Monilinia fructicola in stone fruit orchards

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.     

Adaptation to fungicides in Monilinia fructicola isolates with different fungicide resistance phenotypes

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.     

The occurrence of thiabendazole-resistant isolates of Polyscytalum pustulans and Helminthosporium solani on seed potato tubers in relation to fungicide treatment and storage

Tubers infected with thiabendazole-sensitive isolates of Polyscytalum pustulans and Helminthosporium solani were treated annually for 4 years with benomyl, thiabendazole or a formulated mixture of thiabendazole and imazalil, and grown at three farms in Scotland. The proportion of thiabendazole-resistant isolates of H. solani increased, and isolates producing black colonies became more common with successive annual applications of thiabendazole or benomyl. Silver scurf was not reduced after three annual applications. When these fungicides were applied once to untreated seed the incidence of resistant isolates of H. solani was much less in 1988 than in 1991 when tubers had been grown on farms for 3 years from untreated seed.
The proportion of resistant isolates of P. pustulans increased with the number of successive applications of thiabendazole or benomyl but at differing rates on each farm. At one farm, skin spot was not reduced by three annual applications of these fungicides whereas at the other farms it was reduced by 90–100% by four annual applications.
A smaller proportion of resistant isolates of P. pustulans and H. solani was obtained after applying the mixture of thiabendazole and imazalil than after benomyl or thiabendazole alone. Their occurrence was not related to the number of fungicide applications. The mixture also reduced both diseases by more than 75% over the 4 years.
At one farm where resistant isolates of H. solani were present, tubers were infected when stored on trays but not when stored in bags.     

The biological characteristics of dicarboximide-resistant isolates of Monilinia fructicola from New Zealand stone-fruit orchards

Dicarboximide-resistant isolates of Monilinia fructicola were detected in New Zealand stone fruit orchards in 1985. The EC₅₀ values of resistant isolates ranged from 3 to 217 mg a.i./l iprodione, compared with 0-3 to 0-7 mg a.i./l for sensitive isolates. The degree of dicarboximide resistance was maintained over nine generations in fruit tissues in most isolates, but in four isolates there was a significant decline. Three resistant and two sensitive isolates were selected for further study on agar and host tissues. Resistant isolates caused disease, grew and sporulated as well as sensitive isolates on flowers not amended with dicarboximide fungicides, but some were less fit on fruit. The pathogenicity and spore production of a resistant strain on flowers was reduced significantly by dicarboximide applied prior to pathogen inoculation. Fitness of isolates on flowers and on fruit was poorly correlated. Resistant isolates were significantly less competitive than sensitive isolates when mixed inocula were applied to flowers and fruit. The relative performance on flowers and fruit was not a reliable indicator of competitive ability.     

Persistence and fitness of carbendazim- and dicarboximide-resistant isolates of Monilinia fructicola (Wint.) Honey in flowers, shoots and fruit of stone fruit

Flowers on detached peach shoots and ripe fruit were inoculated under controlled conditions in order to estimate the competitive ability of Monilinia fructicola isolates sensitive and resistant to carbendazim and dicarboximide fungicides. Isolates varied considerably, but there was no consistent relationship between carbendazim resistance and competitive ability; there was, however, evidence of reduced competitive ability in the single dicarboximide-resistant and the dual dicarboximide/high carbendazim-resistant isolate examined. The ability to produce conidia on twig cankers inoculated in late spring 1989 was retained under field conditions by all sensitive and resistant isolates for at least 1 year. Dicarboximide-resistant isolates produced fewer conidia than the carbendazim-resistant and sensitive isolates on cankers. The production of conidia on mummified fruit inoculated in February 1990 decreased in the field during the winter and the following spring, but some conidia were produced by all isolates. Measures of pathogenicity, virulence and fitness for all isolates were similar to the original values after survival for 1 year. The evidence presented in this paper supports field observations that carbendazim-resistant isolates are likely to persist permanently in the M. fructicola population, whereas dicarboximide-resistant isolates are more likely to decline unless fungicide selection pressure is maintained.     

The effect of dose and mobility on the strength of selection for DMI fungicide resistance in inoculated field experiments

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.     

番茄灰霉病菌对嘧霉胺的抗药性

2001年从辽宁省不同地区的保护地中采集番茄灰霉病果或病叶，经单孢分离共获得番茄灰霉病菌70株。采用菌丝生长速率法测定了其对嘧霉胺的敏感性。结果表明，番茄灰霉病菌已对嘧霉胺产生中等水平抗药性，抗性频率为20．0％。经室内药剂诱导获得了高抗菌株，抗性倍数最高达35．7倍。嘧霉胺与多菌灵及嘧霉胺与速克灵间不存在交互抗药性。野生抗性菌株具有较好的遗传稳定性，连续转接9次后抗药性无明显下降。不同菌株的菌丝生长速度、鲜重和渗透敏感性存在显著差异，但该差异与灰霉病菌对嘧霉胺的敏感性无相关性。抗性菌株与敏感菌株具有同样的致病能力。     

Carbendazim resistance in the eyespot pathogen Pseudocercosporella herpotrichoides

Mycelial isolates (115) of Pseudocercosporella herpotrichoides were obtained from five field sites in England. Carbendazim-resistant isolates were detected by their mycelial growth on agar containing 1 μg/ml carbendazim. Resistant isolates were found at two of the five sites examined and one of these had never been treated with benzimidazole fungicides. Amongst the carbendazim- resistant isolates there was a predominance of isolates with pale mycelium, an irregular colony margin and a relatively slow growth rate; however, this association was not absolute. Large differences in the effects of carbendazim on mycelial growth of sensitive and resistant isolates were demonstrated; growth of sensitive isolates was completely inhibited at 0.5 μg /ml carbendazim whilst five of the six resistant isolates examined grew on agar containing 1000 μg/ml fungicide. The carbendazim-resistant isolates were cross-resistant to benomyl, thiophanate-methyl and to a Icsser degree thiabendazole, but not to prochloraz. Conidia of carbendazim-resistant isolates were as resistant. Carbendazim-resistant isolates were just as pathogenic to wheat as sensitive isolates. The implications of these results and other reports of benzimidazole resistance in P. herpotrichoides are discussed in relation to disease control.     

Development of resistance to thiabendazole in Helminthosporium solani (silver scurf) as a result of potato seed tuber treatment

Applying thiabendazole to potato seed tubers affected with silver scurf caused by Helminthosporium solani sensitive to thiabendazole decreased the severity of disease on progeny tubers at harvest, but about 50% of the isolates from these were resistant to the fungicide. The disease was not decreased when samples of the progeny tubers were treated with thiabendazole and planted in the following year, and the incidence of resistant isolates increased. Resistant isolates continued to be present when tubers were planted in the next 2 years without fungicide treatment. Treatment with a mixture of thiabendazole and imazalil also decreased the disease and fewer isolates were resistant than when treated with thiabendazole alone, although the proportion increased after treatment with the mixture in the following year. When seed tubers were infected with thiabendazole-resistant H. solani , silver scurf on progeny tubers was not affected by thiabendazole applied to the seed tubers but was decreased by the mixture of thiabendazole and imazalil. Imazalil was equally effective against H. solani sensitive or resistant to thiabendazole.
Some isolates of H. solani had grey aerial mycelium and of 516 of these isolates obtained in 4 years 29% were resistant to the fungicide. Other isolates produced small, black colonies and their frequency increased with thiabendazole treatment of seed tubers. Of 244 of these isolates, 62% were resistant.     

Resistance to thiabendazole in isolates of Helminthosporium solani, the cause of silver scurf disease of potatoes

Isolates of Helminthosporium solani were obtained from potato tubers and cultured on agar containing thiabendazole. Some grew on agar containing 100 mg/l and these were classified as resistant, whereas sensitive isolates produced no mycelial growth on agar containing 5 mg/l. Isolates were also found that were intermediate in their sensitivity to the fungicide. All isolates from Scottish virus tested stem cutting stocks (VTSC) on two farms were resistant whereas those from another farm were sensitive to the fungicide. The proportion of resistant isolates from eight English once-grown seed stocks ranged from 0 to 96%. There has been no previous report of fungicide resistance in H. solani and the possible reasons for these results and their implications are discussed.     

Multiple resistance of Botrytis cinerea from kiwifruit to SDHIs,QoIs and fungicides of other chemical groups

BACKGROUND: Botrytis cinerea Pers.: Fr. is a high‐risk pathogen for fungicide resistance development that has caused resistance problems on many crops throughout the world. This study investigated the fungicide sensitivity profile of isolates from kiwifruits originating from three Greek locations with different fungicide use histories. Sensitivity was measured by in vitro fungitoxicity tests on artificial nutrient media. RESULTS: Seventy‐six single‐spore isolates were tested for sensitivity to the SDHI fungicide boscalid, the QoI pyraclostrobin, the anilinopyrimidine cyprodinil, the hydroxyanilide fenhexamid, the phenylpyrrole fludioxonil, the dicarboxamide iprodione and the benzimidazole carbendazim. All isolates from Thessaloniki showed resistance to both boscalid and pyraclostrobin, while in the other two locations the fungal population was sensitive to these two fungicides. Sensitive isolates showed EC₅₀ values to boscalid and pyraclostrobin ranging from 0.9 to 5.2 and from 0.04 to 0.14 mg L^?1 respectively, while the resistant isolates showed EC₅₀ values higher than 50 mg L^?1 for boscalid and from 16 to > 50 mg L^?1 for pyraclostrobin. All QoI‐resistant isolates carried the G143A mutation in cytb. Sensitivity determinations to the remaining fungicides revealed in total eight resistance phenotypes. No isolates were resistant to the fungicides fenhexamid and fludioxonil. CONCLUSION: This is the first report of B. cinerea field isolates with resistance to both boscalid and pyraclostrobin, and it strongly suggests that there may be a major problem in controlling this important pathogen on kiwifruit. Copyright © 2010 Society of Chemical Industry     

Alternative oxidase reduces the sensitivity of Mycosphaerella graminicola to QOI fungicides

Forty-six (1.5%) of nearly 3000 isolates of Mycosphaerella graminicola assayed in vitro were resistant to the QOI fungicide azoxystrobin, but on sub-culturing only ten remained resistant. Cross-resistance extended to other QOIs, but varied between different isolates. In planta the resistant isolates were not well controlled, especially at lower azoxystrobin dose rates. Propyl gallate, an inhibitor of alternative oxidase, potentiated the activity of azoxystrobin in vitro so that resistance was no longer observed. The growth of resistant strains in the presence of azoxystrobin led to alternative oxidase activation. This increased flexibility in respiration allows resistant strains to survive in the presence of a QOI fungicide. Under these conditions, selection for target-site mutations can occur. Using QOIs preventatively reduces the risk of resistance since the alternative oxidase cannot by itself generate all the energy needed for germination and early infection.     

Stability and fitness of pyraclostrobin- and boscalid-resistant phenotypes in field isolates of Botrytis cinerea from apple

Phenotype stability, fitness, and competitive ability of pyraclostrobin- and boscalid-resistant isolates of Botrytis cinerea from apple were investigated. Stability of resistance was determined after consecutive transfers on potato dextrose agar (PDA) or being cycled on apple fruit. In vitro fitness components mycelial growth, osmotic sensitivity, conidial germination, and sporulation were evaluated on agar media. Pathogenicity, virulence and sporulation on apple fruit were evaluated at both 20 and 0°C. Competition between fungicide-resistant and -sensitive isolates on apple fruit also was evaluated. Resistance to the two fungicides was retained at levels similar to that of the initial generation after 20 and 10 transfers on PDA and five and three disease cycles on apple fruit at 20 and 0°C, respectively. Great variability in individual fitness components tested was observed among isolates within the same phenotype groups either sensitive or resistant to the fungicides but, when compared as phenotype groups, there were no significant differences in the mean values of these fitness components between resistant and sensitive phenotypes except that the phenotype resistant only to boscalid produced fewer conidia in vitro than sensitive isolates. Resistant isolates were as pathogenic and virulent on apple fruit as sensitive isolates. There was no significant correlation between the values of individual fitness components tested and the level of resistance to pyraclostrobin or boscalid, except that virulence at 20°C positively correlated with the level of resistance to the two fungicides. The final frequency of pyraclostrobin-resistant individuals in the populations was significantly decreased compared with the initial generation and no boscalid-resistant individuals were detected after four disease cycles on apple fruit inoculated with a pair mixture of a dual-sensitive isolate and one isolate each of the three phenotypes resistant to pyraclostrobin, boscalid, or both. The results suggest that resistance of B. cinerea to pyraclostrobin and boscalid was stable in the absence of the fungicides and that resistance to the two fungicides did not significantly impair individual fitness components tested. However, both pyraclostrobin- and boscalid-resistant isolates exhibited competitive disadvantage over the dual-sensitive isolate on apple fruit.     

Nested PCR‐RFLP is a high‐speed method to detect fungicide‐resistant Botrytis cinerea at an early growth stage of grapes

BACKGROUND: Grey mould caused by the fungus Botrytis cinerea Pers. ex Fr. is one of the major diseases in grapes. The use of fungicides is a simple strategy to protect grapes against B. cinerea disease. However, phenotypes exhibiting resistance to fungicides have been detected in B. cinerea populations. The variation of fungicide‐resistant B. cinerea isolates renders B. cinerea disease control difficult in grapevine fields. RESULTS: The authors have developed a nested polymerase chain reaction–restriction fragment length polymorphism (PCR‐RFLP) method to detect fungicide‐resistant B. cinerea isolates at an early growth stage of grapes in grapevine fields. The nested PCR‐RFLP method was carried out to detect benzimidazole‐, phenylcarbamate‐ and/or dicarboximide‐resistant B. cinerea isolates from grape berries and leaves at Eichorn–Lorenz growth stage 25 to 29. This method successfully detected fungicide‐resistant B. cinerea isolates at an early growth stage of grapes. In addition, only 8 h was required from tissue sampling to phenotyping of fungicide resistance of the isolates. CONCLUSION: It is proposed that the early diagnosis of fungicide‐resistant B. cinerea isolates would contribute to further improvement of integrated pest management against B. cinerea in grapevine fields, and that the nested PCR‐RFLP method is a high‐speed, sensitive and reliable tool for this purpose. Copyright © 2008 Society of Chemical Industry     

Phenotypic and genotypic diversity in Phytophthora infestans on potato in Great Britain, 1995–98

A total of 2691 single-lesion isolates of Phytophthora infestans was established from samples of late-blight disease from 354 commercial and garden/allotment sites in Scotland, England and Wales over four growing seasons, 1995–98. The A2 mating type was rare (3·0% of isolates) and was detected at only 34 sites. In vitro tests of sensitivity to the phenylamide fungicide metalaxyl showed that 316 sites yielded isolates with some insensitivity (resistant and/or intermediate); these were more often commercial sites than garden/allotment sites. Over the four seasons, the frequency of isolates with intermediate fungicide sensitivity increased, while the frequency of resistant phenotypes decreased. Resistant isolates were always of A1 mating type. A subset of 1459 isolates from 326 sites was analysed for molecular diversity. Mitochondrial DNA (mtDNA) haplotype Ia predominated (91·0% of isolates); haplotype IIa was present at 54 sites and both haplotypes at 33 sites. The multilocus RFLP probe RG57 detected 30 fingerprints. Four fingerprints were particularly common (RF002, RF006, RF039 and RF040) and 10 were unique to a single site in a single year. The three commonest fingerprints (RF039 > RF002 > RF006) were of A1 mating type and the fourth (RF040) was A2. RF002 isolates were resistant to the phenylamide metalaxyl and were more common in Scotland than in England and Wales. Small sample sizes limited the usefulness of estimates of diversity. Although approximately half of all sites appeared to be colonized by RF039 genotypes, some sites (both commercial and garden/allotment) showed a higher diversity, having both common and unique genotypes. The genotypic diversity within isolates collected from commercial sites and those from garden/allotment sites were similar. The contributions of sexual reproduction and alternatives to sex to the generation of variation are discussed.     

Field Resistance to Strobilurin (Q(o)I) Fungicides in Pyricularia grisea Caused by Mutations in the Mitochondrial Cytochrome b Gene

ABSTRACT Gray leaf spot caused by Pyricularia grisea is a highly destructive disease of perennial ryegrass turf. Control of gray leaf spot is dependent on the use of preventative fungicide treatments. Strobilurin-based (Q(o)I) fungicides, which inhibit the cytochrome bc(1) respiratory complex, have proven to be very effective against gray leaf spot. However, in August 2000, disease was diagnosed in Q(o)I-treated perennial ryegrass turf on golf courses in Lexington, KY, Champaign, IL, and Bloomington, IL. To determine if resistance was due to a mutation in the fungicide target, the cytochrome b gene (CYTB) was amplified from baseline and resistant isolates. Nucleotide sequence analysis revealed an intronless coding region of 1,179 bp. Isolates that were resistant to Q(o)I fungicides possessed one of two different mutant alleles, each of which carried a single point mutation. The first mutant allele had a guanine-to-cytosine transition at nucleotide position +428, resulting in a replacement of glycine 143 by alanine (G143A). Mutant allele two exhibited a cytosine-to-adenine transversion at position +387, causing a phenylalanine-to-leucine change (F129L). Cleavable amplified polymorphic sequence analysis revealed that neither mutation was present in a collection of baseline isolates collected before Q(o)I fungicide use and indicated that suspected Q(o)I- resistant isolates found in 2001 in Indiana and Maryland possessed the F129L mutation. The Pyricularia grisea isolates possessing the G143A substitution were significantly more resistant to azoxystrobin and trifloxystrobin, in vitro, than those having F129L. DNA fingerprinting of resistant isolates revealed that the mutations occurred in just five genetic backgrounds, suggesting that field resistance to the Q(o)I fungicides in Pyricularia grisea is due to a small number of ancestral mutations.     

梨黑斑病菌抗药性检测及其对啶酰菌胺的敏感性基线

黑斑病是梨的主要病害之一,近年来不少地区反映多菌灵等传统常用杀菌剂对其防治效果已出现下降。作者从浙江、江苏和安徽3省分离了252株梨黑斑病菌Alternaria kikuchiana,采用菌丝生长速率法检测了其抗药性发生情况。结果发现:所检测的黑斑病菌群体(n=252)对苯并咪唑类杀菌剂多菌灵的抗性频率为57.1%,且全部为高水平抗性(HR);对二甲酰亚胺类杀菌剂异菌脲的抗性频率为46.8%,全部为低水平抗性(LR);对甾醇脱甲基抑制剂类杀菌剂苯醚甲环唑的抗性为低水平(LR)及中等水平(MR),抗性频率均为28.6%;表明梨黑斑病菌对常用杀菌剂已产生较为严重的抗性。供试252株梨黑斑病菌对琥珀酸脱氢酶抑制剂啶酰菌胺的EC50值分布在0.12~3.85μg/m L之间,平均EC50值为(1.21±0.12)μg/m L,且其分布呈近似正态的单峰曲线。研究表明,啶酰菌胺可作为潜在的梨黑斑病防治替代药剂,其平均EC50值(1.21±0.12)μg/m L可作为梨黑斑病菌对啶酰菌胺的敏感性基线。