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1.
Fifty-seven isolates of Phytophthora infestans from blighted potato foliage were collected in 1995 in southern Germany and analysed for mating type and sensitivity to metalaxyl. Fifty-six of them were characterised as A1 and one as A2 mating types. Resistance to metalaxyl was observed frequently: 53 isolates were resistant, three were partially sensitive, and one was sensitive. In a subsequent field study in 1999, 84 isolates collected from blighted potato and tomato foliage were analysed for mating type. Seventy-two were characterised as A1 and twelve as A2 mating types. The response of 76 isolates to metalaxyl and to propamocarb was tested. The majority (42) of the 76 isolates was classified as resistant to metalaxyl; 31 were partially sensitive and only three isolates were sensitive. The results with propamocarb were less discrete; 10 isolates were classified as resistant and three were clearly sensitive. AFLP fingerprinting was used to examine the genetic structure of the southern German P. infestans population collected in 1999 and indicated that the tested population can be sub-divided into a tomato group, a potato group and a mixed group containing isolates collected from both crops. The presence of Ia and IIa mitochondrial DNA haplotypes indicates that the German P. infestans isolates belong to the new pathogen population that has also been reported in neighbouring regions of Europe. The present study indicates that at the beginning of the season only a few genotypes were present, and the population became genetically more variable at the end of the growing season.  相似文献   

2.
Single-oospore progeny from matings between field isolates of Phytophthora infestans either highly resistant or sensitive to metalaxyl were analysed for fungicide sensitivity in vitro, mating type and, in some cases, allozyme variation at the locus for glucosephosphate isomerase ( GPI-1. ) In each cross the majority of first-generation (F1) progeny showed intermediate sensitivity to metalaxyl. Frequency distributions were skewed towards sensitivity and a few progeny were either wholly sensitive or resistant phenotypes. Allozyme analysis of F1 progeny from a cross between parents of Dutch and Mexican origin showed that c. 10% were selfs of both parents and of parental phenotype for metalaxyl sensitivity. The selfs of the A2 but not the Al parent segregated for mating type. Two backcross generations to the metalaxyl-resistant Dutch parent gave unexpected phenotypic frequency distributions and aberrant ratios for genotypes at the GPI-I locus.
Progeny of another backcross between an F1 isolate of intermediate sensitivity and its sensitive Egyptian parent gave a 1:1 ratio for sensitive: intermediate phenotypes. F2 progeny from a related sibmating between intermediate phenotypes segregated in a ratio close to 1:2:1 for sensitive: intermediate: resistant phenotypes. Segregation was also observed among sexual progeny of an intermediate self-fertile isolate from the backcross generation but not among progeny of a resistant self-fertile phenotype. Mating type segregated in both cases.
These data are consistent with resistance to metalaxyl in P. infestans being governed by a single nuclear locus exhibiting incomplete dominance. This hypothesis is discussed in relation to the incidence of resistance to metalaxyl in natural populations of P. infestans.  相似文献   

3.
烟草黑胫病菌抗甲霜灵突变体的诱导及其适合度研究   总被引：1，自引：0，他引：1  
室内离体条件下采用药剂诱导法,获得了11个烟草黑胫病菌抗甲霜灵突变体;检测了所有抗药突变体的抗药稳定性及抗性水平;比较了3个低抗和1个高抗突变体的适合度。结果表明:在2~20 μg/mL范围内,抗药突变体的发生频率随甲霜灵诱导浓度的增加而提高;所有抗药突变体的抗药性都能稳定遗传;11个抗药突变体中,10个为低抗突变体(抗性水平3.55~13.9倍,平均8.60倍),1个为高抗突变体(抗性水平510倍);低抗菌株20M-001、10M-003、10M-006和高抗菌株10M-004的适合度指数分别为0.56、0.38、0.38和0.87;抗药突变体的适合度指数与抗性水平不相关。  相似文献   

4.
六省市致病疫霉交配型及其对几种杀菌剂的敏感性   总被引：14，自引：1，他引：14  
测定了2000-2002年采自四川、重庆、吉林、黑龙江、福建、北京六省(市)致病疫霉菌株的交配型及其对几种杀菌剂的敏感性。结果显示,来自六省市的74个菌株中73株为典型的A1交配型,1株采自四川的菌株为可自育的A1交配型,未发现A2交配型。测定的37株代表菌中,对甲霜灵表现敏感、中抗、高抗的分别占27.0％、27.0％和46.0％。吉林、福建、黑龙江及重庆都存在高抗菌株。研究中还发现甲霜灵可促进部分抗性菌株的菌丝生长。随机抽取15个对甲霜灵表现敏感、中抗和高抗的菌株,测定其对几种杀菌剂的敏感性,结果全部对腈嘧菌酯和烯酰吗啉表现敏感;其中2株对丙酰胺表现敏感,11株表现中抗,2株表现高抗。结果也显示:烯酰吗啉和腈嘧菌酯与甲霜灵之间不存在交互抗性,具有应用潜力。  相似文献   

5.
马铃薯晚疫病菌对甲霜灵抗性机制的初步研究   总被引：7，自引：0，他引：7  
 选取对甲霜灵敏感、中抗和高抗的马铃薯晚疫病菌(Phytophthora infestans)菌株各2株,采用电导率法和同位素掺入法,研究了甲霜灵对马铃薯晚疫病菌不同抗药性水平菌株细胞膜通透性和RNA聚合酶活性的影响,借助液相色谱分析方法检测了不同抗药性水平菌株对甲霜灵的降解作用。结果表明:甲霜灵对马铃薯晚疫病菌不同抗药性水平菌株的细胞膜通透性没有明显影响;随着甲霜灵浓度提高,敏感菌株的RNA聚合酶活性受到显著抑制,10μg/mL甲霜灵对敏感菌株RNA聚合酶活性的抑制率达到40%以上,而10和100μg/mL甲霜灵对高抗菌株的RNA聚合酶活性只表现轻微的抑制作用,抑制作用分别小于8%和21%,甲霜灵对中抗菌株RNA聚合酶活性的抑制作用介于对敏感菌株和高抗菌株的抑制作用之间。抗性菌株对甲霜灵有一定的降解作用,培养30d后高抗菌株HL105和SC1的降解率分别达到13.46%和16.14%。  相似文献   

6.
 2003~2005年,从云南省德宏州新兴冬作马铃薯主产区采集的马铃薯晚疫病病样中分离纯化到86株致病疫霉菌,对其代表性菌株的表型特征进行了较系统的研究。交配型实验结果表明:所测定的62个菌株都属于A1交配型,未发现A2交配型或自育型菌株。毒性基因鉴定、监测及生理小种组成分析显示:德宏州存在所有已知可鉴定的毒性基因,而且生理小种组成非常复杂;所测定的66个菌株可区分出36个生理小种,其中,出现频率最高的小种为1,2,3,4,5,6,7,8,9,10,11,占被测菌株的18.18%,在主产区潞西县和盈江县均有分布。对60个菌株的甲霜灵抗性测定结果表明:56.67%的菌株表现为敏感,25.00%的菌株中抗,18.33%的菌株对甲霜灵有抗性。本文对此实验研究结果作了初步的分析和讨论。  相似文献   

7.
In Mie Prefecture in Japan, rice blast isolates resistant to melanin biosynthesis inhibitors targeting scytalone dehydratase (SDH) were first observed in 2005. To analyze the distribution of the resistant isolates, 527 isolates were collected from wide areas in this prefecture during 2006 and 2007. Almost half of the isolates collected (233 of 527 isolates) carried a point mutation in the SDH gene conferring the resistant phenotype. To compare population structures of resistant and sensitive isolates, we analyzed the isolates with repetitive-element-based PCR DNA fingerprinting using a single primer complementary to a sequence in the terminal inverted repeat of transposable element Pot2. A majority of the resistant isolates were classified into a single DNA fingerprint haplotype, Mie1. Despite its prevalence in the resistant isolates, Mie1 was not found in the sensitive isolates. Furthermore, in a dendrogram constructed from the DNA fingerprint data, Mie1 and six other haplotypes formed a cluster composed of resistant isolates alone. These results suggest that the resistant isolates that belonged to the Mie1 haplotype had migrated from regions outside Mie Prefecture and selectively propagated in a short period in this prefecture.  相似文献   

8.
The sensitivity of 127 Phytophthora infestans isolates to flumorph was determined in 2003 and 2004. The isolates originated from two geographical regions and showed similar levels of sensitivity in both years. Baseline sensitivities were distributed as a unimodal curve with EC50 values for growth of mycelia ranging from 0·1016 to 0·3228  µ g mL−1, with a mean of 0·1813 (± 0·0405) µ g mL−1. There was no cross-resistance between flumorph and metalaxyl. Laboratory studies were conducted to evaluate the risk of P. infestans developing resistance to flumorph. Mutants resistant to metalaxyl or flumorph were obtained by treating mycelium of wild-type isolates with ultraviolet radiation. Metalaxyl-resistant mutants were obtained with a high frequency and exhibited resistance factor values (EC50 resistant/EC50 sensitive phenotypes) of more than 100, while flumorph-resistant mutants were obtained at much lower frequencies and had very small resistance factors (1·5–3·2). There was cross-resistance between flumorph and dimethomorph, but not with azoxystrobin or cymoxanil. Most flumorph-resistant mutants showed decreases in hyphal growth in vitro and in sporulation both in vitro and on detached leaf tissues. These studies suggested that the risk of resistance developing was much lower for flumorph than metalaxyl. However, as P. infestans is a high-risk pathogen, appropriate precautions against resistance development should be taken.  相似文献   

9.
A total of 80 single–lesion isolates of Phytophthora infestans were collected from tomatoes and potatoes in several locations in Chiang Mai and Tak provinces in 2000–2002. These isolates were analyzed for mating type, metalaxyl sensitivity, mitochondrial DNA (mtDNA) haplotype RFLP pattern as determined by probe RG57, and for microsatellite markers. All isolates were A1 mating type. Isolates from tomato were usually sensitive to metalaxyl, but isolates from potato were usually resistant to metalaxyl. With one exception, all tomato isolates were related to the US-1 clonal lineage. With two exceptions, all potato isolates were related to two European lineages. In these two provinces, the populations of P. infestans on tomatoes are clearly different from those on potatoes.  相似文献   

10.
云南辣椒疫病的分子诊断及其病原菌群体特征研究   总被引：1，自引：1，他引：0  
 对2005~2007年分离自云南省辣椒疫病的病原菌进行分子生物学鉴定,并对病原菌的群体特征进行研究。PCR特异性扩增表明,引起云南辣椒疫病的病原菌是辣椒疫霉。交配型测定显示,234个云南辣椒疫霉菌株由A1、A2和A1A2(自育型)3种交配型组成,以A2和A1A2交配型为主。其中,A2占45.3%,A1A2占43.2%,A1仅占11.5%。大部分产区3种交配型共存,在田间进行有性生殖的可能性很大。甲霜灵敏感性测定的200个菌株中,甲霜灵敏感菌株是主要菌系,占测定菌株的95.5%,中抗和抗性菌株比例较低,分别为2.0%和2.5%。抗药性菌株的出现与甲霜灵的选择压力有关。云南辣椒疫霉群体组成较为复杂,A1A2交配型可能在云南辣椒疫霉的有性生殖中起到了重要的作用,成为影响群体结构的一个重要途径。  相似文献   

11.
ABSTRACT Stability of phenotypes of isolates of Botrytis cinerea that were sensitive or resistant to benzimidazole and dicarboximide fungicides was examined in the absence of fungicides in laboratory and growth room experiments. Twelve greenhouse isolates of B. cinerea were subcultured on potato dextrose agar (PDA) for 20 generations and on geranium seedlings for 15 generations. Three isolates of each of the following four phenotypes were used: sensitive to the fungicides thiophanate-methy1 (a benzimidazole) and vinclozolin (a dicarboximide) (S(T)S(V)), resistant to both fungicides (R(T)R(V)), resistant to thiophanate-methy1 and sensitive to vinclozolin (R(T)S(V)), and sensitive to thiophanate-methy1 and resistant to vinclozolin (S(T)R(V)). In three trials on PDA, 36 populations were subcultured; 8 populations changed phenotypes by the end of 20 generations, as determined by conidium germination on fungicide-amended medium. Five of the eight initially were S(T)R(V); the resulting phenotypes were S(T)S(V), R(T)S(V), and R(T)R(V). Populations from eight other isolates exhibited temporary changes in phenotype during intermediate generations on PDA but reverted to initial phenotypes by the twentieth generation; five of these populations changed to phenotype R(T)R(V). In two geranium seedling trials, each of the 12 greenhouse isolates was inoculated onto a set of three seedlings for each generation, and diseased tissue that developed was used to initiate the next generation. Therefore, a total of 72 populations of B. cinerea were subcultured in the two trials; 5 of these populations changed phenotype at the end of 15 generations. Three of the five initially were S(T)R(V); these changed to phenotypes S(T)S(V) or R(T)R(V). In each of the two trials on geranium seedlings, a population subcultured from one S(T)S(V) isolate changed phenotype one to phenotype R(T)R(V) and one to phenotype R(T)S(V). In all trials, no population resistant to thiophanate-methy1 changed to a thiophanate-methy1-sensitive phenotype, and no population changed to phenotype S(T)R(V). Random amplified polymorphic DNA (RAPD) fingerprints were generated with the 12 initial isolates and 49 isolates subcultured on PDA or geranium seedlings. Cluster analyses of RAPD markers showed that subcultured isolates exhibiting the same phenotype clustered together and that subcultured isolates derived from a common greenhouse isolate but with different phenotypes were in different clusters. Some populations that did not change phenotype exhibited considerable differences in RAPD marker patterns. The results of this study indicate that, in the absence of fungicides, sensitive populations of B. cinerea can develop resistance to thiophanate-methy1 and vinclozolin, and this resistance can be maintained in populations through multiple generations. Populations resistant only to vinclozolin (S(T)R(V)) exhibited a high frequency of phenotype change, and populations resistant to both fungicides (R(T)R(V)) were stable.  相似文献   

12.
棉铃疫病菌对甲霜灵的抗药性风险研究   总被引：8，自引：3，他引：8  
在实验室条件下,对分离自安徽省芜湖、无为、宣城、望江、肥东、寿县、滁州等7个地区的棉铃疫病菌(Phytophthora boehmeriae Sawada)对甲霜灵的抗药性进行了测定。结果显示,甲霜灵对各供试菌株的EC50分布为0.008 3～0.079 1μg／mL,平均为0.026 1 μg／mL,远小于1 μg／mL,且供试菌株在含甲霜灵质量浓度为1μg／mL的LBA平板上菌丝生长几乎完全被抑制,表明各供试菌株对甲霜灵十分敏感,但其敏感程度地区间存在较大差异。通过室内药剂直接诱变,获得抗甲霜灵菌株,经抗性测定结果表明,抗性菌株的抗性水平较其敏感亲本菌株高13 000倍以上,提示安徽省棉铃疫病菌对甲霜灵具有潜在的抗药性风险。  相似文献   

13.
Four lines (designated MR0, MR1, MR2, and M8) from 13 accessions of Beta vulgaris subsp. maritima were selected on the basis of phenotypes produced after foliar rub-inoculation with Beet necrotic yellow vein virus (BNYVV). The susceptible phenotype developed bright yellow local lesions, whereas the resistant phenotype had symptoms ranging from no visible lesions to necrotic lesions at the inoculation site. MR1 and MR2 lines had a resistant phenotype depending on the isolate and the MR0 line was susceptible to all isolates of BNYVV tested. The M8 line was highly susceptible; the virus spread systemically and caused severe stunting. These plant lines will be useful for distinguishing BNYVV isolates having different pathogenicities, especially those controlled by RNA3 and/or RNA5.  相似文献   

14.
为了明确我国不同地区马铃薯晚疫病菌对甲霜灵和精甲霜灵的抗性状况,2007-2009年从河北、黑龙江、吉林、辽宁和内蒙古马铃薯主产区采集马铃薯晚疫病菌,采用菌丝生长速率法和叶盘漂浮法测定其对甲霜灵的敏感性,采用叶盘漂浮法测定其对精甲霜灵的敏感性.结果表明:以菌丝生长速率法检测的380株晚疫病菌中和以叶盘漂浮法检测的222株晚疫病菌中对甲霜灵的抗性菌株分别占80％和73.5％;菌丝生长速率法检测结果显示,河北省对甲霜灵的抗性菌株所占频率从2007年的100％降为2008年的66.4％,2009年又回升至74.2％,而吉林和黑龙江两省对甲霜灵的抗性菌株分布频率呈上升趋势.叶盘漂浮法检测的95个菌株中对精甲霜灵的抗性菌株占54.5％,其中河北省40个菌株对精甲霜灵的中间型菌株占优势(62.5％),抗性菌株仅占34.9％,而其他4省55个菌株对精甲霜灵的抗性菌株占优势(69.1％).受检测的北方五省(区)马铃薯晚疫病菌群体中对甲霜灵和精甲霜灵的抗性菌株已占优势,马铃薯晚疫病菌已普遍对甲霜灵及精甲霜灵产生抗性.在对甲霜灵和精甲霜灵普遍产生抗性的地区,应优先选用与甲霜灵、精甲霜灵作用机理不同的药剂防治马铃薯晚疫病.  相似文献   

15.
The characteristics of populations of Phytophthora infestans from organic farms, small conventional farms and large conventional farms were determined from isolates collected in northern Estonia in 2004 and 2005. For the population as a whole 41% were A2; all virulence factors to the 11 R genes from Solanum demissum were found; and more than 70% had high or intermediate resistance to metalaxyl. Isolates from organic farms tended to have more complex pathotypes than isolates from either large or small conventional farms, but there was a higher proportion of metalaxyl resistant isolates from large conventional farms than from small conventional farms or from organic farms.  相似文献   

16.
In Poland in 2002 and 2005 two different isolates of Pepino mosaic virus signed PepMV-SW and PepMV-PK were obtained. Both isolates were compared on the basis of their symptomatology on a series of plant species. In addition, the isolates were characterized by the nucleotide sequence analysis of the triple gene block, coat protein and a part of the polymerase genes. The studies showed that the Polish isolates differ from each other and belong to two strains. PepMV-SW was highly similar to European isolates, showing extensive sequence identity, ca. 99%. Pairwise comparisons of PepMV-PK with other PepMV isolates from the GenBank database showed that the highest nucleotide sequence identity was with two isolates: Ch2 from Chile and US2 from the USA.  相似文献   

17.
The effectiveness of Quinone outside Inhibitor (QoI) fungicides against grape downy mildew in European vineyards has significantly decreased in the last decade. One nucleotide polymorphism, G143A in the cytochrome b gene of Plasmopara viticola, is involved in resistance to QoIs. Previous genetic examination on the mitochondrial genomes showed four major haplotypes (IR, IS, IIR, IIS) coexisting in European vineyards. A resistant allele (G143A) was present in IR and IIR haplotypes. The purpose of the present study was to estimate the diversity of the different mitochondrial haplotypes and their distribution in QoI-resistant populations before evaluating the potential cost of the resistant mutation G143A in P. viticola population. From 2000 to 2004, the frequencies of resistant isolates ranged from 0% to 23.25% with an average of 4.64 % among the populations examined. To evaluate the fitness of sensitive and resistant isolates, a comparison of different biological parameters including latent period, spore production and infection frequency was performed, enabling a fitness index (FI) to be determined. Resistant isolates exhibited greater infection frequency than sensitive isolates, whereas no significant difference was found in sporulation ability and latent period between sensitive and resistant isolates. To further investigate competitiveness among isolates, an assay including two resistant isolates in different proportion with a sensitive isolate was conducted on eight asexual growing cycles in the absence of a QoI fungicide. The competitiveness of resistant isolates varied according to their fitness parameters, suggesting that there is no noticeable cost of QoI resistance in controlled conditions in Plasmopara viticola.  相似文献   

18.
A total of 108 isolates of cucurbit powdery mildew (CPM) fungi, 78Golovinomyces cichoracearum (Gc) and 30Podosphaera xanthii (Px), originating from nine Czech regions and 22 districts of the Czech Republic were collected in the years 2001–2004. These isolates were screened for tolerance and/or resistance to the three frequently used fungicides (fenarimol, dinocap, benomyl). Fungicide sensitivity was determined by a modified leaf-disc bioassay with five concentrations. Fungicide efficacy differed significantly: fenarimol was the most effective and all isolates of both CPM were controlled by the recommended concentration (36μg a.i. ml−1). Some isolates expressed resistance (profuse sporulation) or tolerance (limited sporulation) to lower concentrations (9.6 and 18μg a.i. ml−1). Specific temporal variation in tolerance/resistance was observed, with some isolates ofGc from 2002 evincing tolerant or resistant reactions to these low fenarimol concentrations, but isolates with similar reactions were not detected during the years 2003–2004. Dinocap showed decreasing efficacy during all 3 years. A shift to more tolerant reactions in the CPM populations was detected forGc in 2001–2002, and forPx in 2001 and 2004. Benomyl was found to be ineffective, because the majority of screened isolates (88%Gc and 97%Px) belonged to the highly resistant strains, with resistant reaction on the recommended concentration (250μg a.i. ml−1) and tolerance or resistance on higher concentrations (500 and 1000μg a.i. ml−1). Sensitivity differed between the CPM species. Whereas practically allPx isolates (except one from 2003) were resistant, 12% ofGc isolates from the years 2001–2003 showed sensitive and/or tolerant reactions. In 2004, only benomyl-resistantGc strains were detected. Variation in tolerance/resistance was detected to all screened fungicides during the course of this study at some repeatedly sampled locations. http://www.phytoparasitica.org posting June 12, 2008.  相似文献   

19.
Plasmopara halstedii isolates showing an atypical reaction to metalaxyl were collected in France, in 1995 and 1996, and tested in the laboratory for their level of sensitivity to this fungicide. Primary and secondary infections caused by one of these isolates were not controlled by the metalaxyl concentration registered for seed treatment. The EC50 of this isolate was 12 800 mg a.i. kg-1 compared with 22 mg a.i. kg-1 for sensitive isolate, indicating a 582-fold decrease in sensitivity to the compound. There was no reduction in the agressiveness of the resistant isolate. Using other anti-oomycete fungicides, it appeared that propamocarb, contact fungicides (fluazinam, folpet, mancozeb) and the mixed formulations dimethomorph + mancozeb, cymoxanil + mancozeb and ofurace + folpet were effective against primary infections made with metalaxyl resistant and sensitive isolates, but not against secondary infections. Metalaxyl mixed with fluazinam, folpet or mancozeb was more effective against primary infections with the resistant isolate than metalaxyl alone. The EC50 of five other isolates ranged from 5 800 to 32 900 mg a.i. kg-1, indicating a variability in metalaxyl sensitivity of resistant sunflower downy mildew isolates. This is the first report of physiological resistance to metalaxyl in Plasmopara halstedii.  相似文献   

20.
Isolates of Phytophthora erythroseptica , causal agent of pink rot of potato, were obtained from diseased tubers collected in Prince Edward Island (PEI), Canada. In an in vitro assay of field and single-zoospore isolates, all isolates of the pathogen from PEI were sensitive to metalaxyl (EC50 < 0·5  µ g mL−1), unlike moderately or highly resistant reference isolates obtained from Maine, USA. Allozyme-banding patterns at the glucose-6-phosphate isomerase ( Gpi ) locus were identical (91/91) for all isolates of P. erythroseptica examined from PEI and Maine, but could be used to distinguish isolates of P. erythroseptica from local isolates of Phytophthora infestans . Inoculation of potato tubers from plants treated with foliar applications of metalaxyl in the field indicated that compounds inhibitory to metalaxyl-sensitive isolates of P. erythroseptica were present in the periderm, even after 4 months' storage. By contrast, moderately or highly resistant isolates of the pathogen caused significantly ( P  ≤ 0·05) more disease than sensitive isolates in tubers from plants treated with metalaxyl. The effectiveness of metalaxyl in controlling pink rot in a particular region will depend on resistance levels of local populations of P. erythroseptica . Preventing the development and spread of resistant strains of P. erythroseptica will be critical in maintaining metalaxyl as an effective chemical for control of this pathogen.  相似文献   

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