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1.
X. Cui  J. Shao  X. Lu  Q. Meng  X. Liu 《Plant pathology》2014,63(6):1365-1373
A total of 1511 isolates of Phytophthora capsici were collected from farms with no history of exposure to the carboxylic acid amide (CAA) fungicides in 32 provinces in China during 2006 to 2013. All 1511 isolates were assayed for mating type and 403 were assayed for sensitivity to dimethomorph (DMM) and metalaxyl. The DMM EC50 values ranged from 0·126 to 0·339 μg mL?1. Both A1 and A2 mating types were detected on the same farms in four provinces and with a 1:1 ratio. Most isolates were sensitive to metalaxyl but a few exhibited intermediate resistance or resistance to metalaxyl. The segregation of DMM resistance and sensitivity among 337 progeny obtained from hybridization or self‐crossing in vitro indicated that the resistance of P. capsici to DMM is controlled by two dominant genes. Eighteen progeny that were derived from hybridization differed in DMM sensitivity and in fitness. Some progeny were as fit as parental isolates. Given the distribution of mating types and therefore the potential for sexual reproduction, the control of resistance by two dominant genes, and the fitness of hybrid progeny, the risk of P. capsici populations developing DMM resistance in China is substantial.  相似文献   

2.
Baseline sensitivity to flumorph, a carboxylic acid amide (CAA) fungicide used to control some oomycetes, was examined using 83 Phytophthora capsici isolates, resulting in a unimodal distribution of effective concentration for 50% inhibition of mycelial growth ranging from 0·716 to 1·363, with a mean of 1·033 ± 0·129 μg mL?1. To assess the potential risk of developing flumorph resistance, 13 flumorph‐resistant mutants of P. capsici were obtained using ultraviolet irradiation. Most of these mutants and their progeny had high levels of fitness, including mycelial growth, sporulation and virulence. The resistance to flumorph changed slightly, either increasing or decreasing, after 10 transfers on agar media. Cross‐resistance was found between flumorph and other CAA fungicides (dimethomorph and iprovalicarb), but not between flumorph and non‐CAA fungicides (cymoxanil, metalaxyl, azoxystrobin and cyazofamid). To investigate the genetics of the flumorph resistance, 619 progeny were obtained by self‐crossing and sexual hybridization. Segregation of sensitivity to fungicide was measured as a ratio of sensitive (S) to resistant (R) isolates. Segregation of the progeny, from self‐crossed isolate PCAS1 (flumorph resistant), was 1:15 in the first generation; and 0:1 or 1:15 in the second generation. In sexual hybridization, segregation of progeny was 0:1 and 1:7 for R × R hybridization; and 1:3 for R × S hybridization. Therefore, the resistance of P. capsici against flumorph was controlled by two dominant genes.  相似文献   

3.
Phytophthora capsici, Phytophthora cryptogea and Phytophthora nicotianae were isolated from tomato plants with symptoms of crown and root rot in plastic‐house crops in Sicilia and Calabria (southern Italy). The species were identified primarily on the basis of morphological and cultural characteristics. The identification was confirmed using molecular methods, polyacrylamide gel electrophoresis (PAGE) of mycelial proteins and polymorphism of DNA sequences amplified by polymerase chain reaction using random primers (RAPD‐PCR). P. capsici caused significant losses in tomato crops that had succeeded capsicum crops. P. cryptogea was found to be the most frequent species causing basal stem rot of tomato, a disease of increasing importance in commercial tomato crops in plastic houses in Sicilia. P. nicotianae was common in plastic houses where poor drainage resulted in standing water.  相似文献   

4.
A. Rojas  W. W. Kirk 《Plant pathology》2016,65(6):1022-1033
Severe potato and tomato late blight epidemics in Michigan since 2008 prompted characterization of Phytophthora infestans isolates from the region. From eight counties in Michigan, 124 isolates were collected from infected potato and tomato plants from 2008 to 2010 and characterized using ‘classical’ markers and microsatellites. The classical markers included mating type, Gpi allozyme, mitochondrial DNA haplotype, sensitivity to metalaxyl‐M and tuber pathogenicity. All isolates from 2008 to 2010 were A2 mating type and Ia mtDNA haplotype (124 isolates), 105 isolates had Gpi profile 100/122, 17 isolates had the profile 100/100/111 and the remaining two isolates had 100/111/122. Sensitivity to metalaxyl‐M, expressed as EC50 for mycelial growth in vitro, ranged from <0·1 to 91 μg mL?1, where 95 and 96% of isolates were classified as either sensitive or intermediate in 2008–2009 and 2010 respectively. The metalaxyl‐M sensitivity and dominant Gpi profile were typical of clonal lineage US‐22, first isolated in 2008 in North America from tomato plants. Tuber pathogenicity, characterized as severity of tuber late blight, was also variable among isolates; however, isolates were less aggressive than previous genotypes present in Michigan, such as US‐8. Microsatellites (simple sequence repeats; SSRs) revealed a shift in the population, characterized by two clusters differentiated over time. These results suggested displacement of the US‐8 genotype by US‐22 from 2008 to 2010 in Michigan. Continuous tracking of changes within P. infestans populations provides evidence of genetic shifts due to migration, prompting modification of management strategies based on the phenotypic characteristics of causal genotypes.  相似文献   

5.
The antibiotic nucleoside tubercidin produced by Streptomyces viola-ceoniger was evaluated for in-vivo efficacy and in-vitro activity against Phytophthora capsici, Magnaporthe grisea and Colletotrichum gloeosporioides. Tubercidin was more effective against P. capsici and M. grisea than against C. gloeosporioides in inhibiting mycelial growth. The bioassay on TLC plates was the most sensitive method and allowed the evaluation of antifungal activity of tubercidin even at a low concentration of 0.1 μgml?1. As compared to the systemic fungicide metalaxyl, tubercidin was similar or somewhat higher in inhibition of mycelial growth of P. capsici. When applied to pepper stems, tubercidin was equally as effective as metalaxyl in the control of phytophthora blight in pepper plants, irrespective of application time and concentration. The treatment with 1000 μg ml?1 tubercidin induced phytotoxicity in pepper plants. No control efficacy of phytophtora blight was observed in pepper plants supplied with a soil drench of tubercidin. Treatment with tubercidin at 500 μg ml?1 completely protected pepper plants at first branch stage from phytophthora blight until four days after application. The control efficacy of tubercidin drastically declined seven days after application.  相似文献   

6.
抗氟吡菌胺辣椒疫霉菌株的诱导及其生物学特性的研究   总被引：2，自引：0，他引：2  
 采用菌丝生长速率法, 测定了采自泰安、平谷、杭州和昆明4个地区的42株辣椒疫霉病菌对氟吡菌胺的敏感性, 结果表明, 其EC50值在0.618 ~0.927 μg·mL-1之间, 平均EC50 =(0.743±0.067 7) μg·mL-1。 42个菌株对氟吡菌胺的敏感性分布呈单峰曲线, 未出现抗性的病原菌亚群体, 可将其单峰曲线作为辣椒疫霉对氟吡菌胺的敏感性基线。采用药剂驯化和紫外照射对辣椒疫霉敏感菌株TA进行诱变处理, 获得了2株辣椒疫霉抗氟吡菌胺菌株;利用菌落直径法测定抗氟吡菌胺菌株的遗传稳定性、菌丝生长速率及对其它杀菌剂的交互抗性;通过活体叶盘法测定抗氟吡菌胺菌株和敏感菌株的致病力及产孢子囊能力, 分析抗性和敏感菌株之间生物学特性差异。结果表明, 敏感菌株TA经过氟吡菌胺 48代连续汰选, 其抗性达58.0倍, 获得中抗菌株TA-R;紫外照射获得了抗性达260.6倍的高抗菌株TA-UV, 且其抗性均能稳定遗传;TA-R和TA-UV对甲霜灵、霜脲氰表现出正交互抗性, 对烯酰吗啉、百菌清、代森锰锌和丙森锌无交互抗性;抗氟吡菌胺菌株TA-R、TA-UV与敏感菌株在活体叶盘上的致病力、离体产孢能力均差异不显著(P＜0.05), 但其菌丝生长速率、菌丝干重均低于敏感菌株。  相似文献   

7.
Laboratory studies were conducted to evaluate the risk of developing field resistance to zoxamide, a new Oomycete fungicide which acts on microtubules. Zoxamide, metalaxyl and dimethomorph were compared with respect to the ease with which fungicide‐resistant mutants could be isolated and their level of resistance. Attempts to generate mutants of Phytophthora capsici and P infestans with resistance to zoxamide by mycelial adaptation on fungicide‐amended medium were unsuccessful. Similarly, changes in sensitivity to zoxamide were small (resistance factors ≤2.2) in mutants of P capsici isolated by chemical mutagenesis of zoospore cysts. In parallel experiments with metalaxyl, highly resistant mutants were obtained using both adaptation (P capsici or P infestans) and chemical mutagenesis (P capsici). For dimethomorph, chemical mutagenesis (P capsici) yielded moderately resistant mutants (maximum resistance factor = 20.9), and adaptation (P capsici or P infestans) did not induce resistance. It is proposed that failure to isolate mutants resistant to zoxamide results from the diploid nature of Oomycete fungi and the likelihood that target‐site mutations would produce a recessive phenotype. Our studies suggest that the risk of a highly resistant pathogen population developing rapidly in the field is much lower for zoxamide than for metalaxyl. However, as with any site‐specific fungicide, appropriate precautions against resistance development should be taken. © 2001 Society of Chemical Industry  相似文献   

8.
Mefenoxam is one of the most commonly used fungicides for managing diseases caused by Phytophthora spp. on ornamentals. The objectives of this study were to determine whether Phytophthora nicotianae, a destructive pathogen of numerous herbaceous annual and perennial plant species in nurseries, has developed resistance to mefenoxam, and to evaluate the fitness of mefenoxam‐resistant isolates. Ninety‐five isolates of P. nicotianae were screened for sensitivity to mefenoxam on 20% clarified V8 agar at 100 a.i. µg mL?1. Twenty‐five isolates were highly resistant to this compound with EC50 values ranging from 235·2 to 466·3 µg mL?1 and four were intermediately resistant with EC50 values ranging from 1·6 to 2·9 µg mL?1. Sixty‐six isolates were sensitive with EC50 values less than 0·04 µg mL?1. Nine resistant and seven sensitive isolates were tested for mefenoxam sensitivity on Pelargonium × hortorum cv. White Orbit. Mefenoxam provided good protection of pelargonium seedlings from colonization by sensitive isolates, but not by any resistant isolates. Four resistant and four sensitive isolates were compared for fitness components and their relative competitive ability on Lupinus Russell Hybrids in the absence of mefenoxam. Resistant isolates outcompeted sensitive ones within 3 to 6 sporulation cycles on lupin seedlings, regardless of their initial proportions in mixed zoospore inoculum. Resistant isolates exhibited greater infection rate and higher sporulation ability than sensitive ones when they were applied separately onto lupins. These results suggest that fungicide resistance may pose a serious challenge to the continued effectiveness of mefenoxam as a control option for nursery growers.  相似文献   

9.
A total of 618 isolates of corynespora leaf spot fungus (Corynespora cassiicola) collected from 24 commercial cucumber greenhouses in 12 cities in Ibaraki Prefecture, Japan, were tested for their sensitivity to boscalid. Boscalid‐resistant isolates were detected in 17 out of 19 greenhouses with a history of use of this fungicide and detection frequencies of the resistant isolates exceeded 47% in nine greenhouses. Frequencies of very highly resistant (VHR) isolates with 50% effective concentration (EC50) values of boscalid exceeding 30 μg mL?1 were higher than those of moderately resistant (MR) isolates with EC50 ranging from 2·0 to 5·9 μg mL?1 in 11 greenhouses. Additionally, highly resistant (HR) isolates with EC50 from 8·9 to 10·7 μg mL?1 were first detected. Furthermore, molecular characterization of genes encoding succinate dehydrogenase (SDH) subunits (SdhA, SdhB, SdhC and SdhD) was carried out to elucidate the amino acid substitution responsible for the resistance to boscalid. All 23 VHR isolates had the same mutation from CAC to TAC in the SdhB gene leading to the substitution of histidine with tyrosine at amino acid position 278 (B‐H278Y). At the same position, the substitution to arginine conferred by a mutation to CGC (B‐H278R) was detected in all four HR isolates. Some MR isolates showed a substitution from serine to proline at position 73 in SdhC (C‐S73P), from serine to proline or from glycine to valine at position 89 (D‐S89P) and 109 (D‐G109V), respectively, in SdhD. There was no common mutation in SDH genes of all MR isolates.  相似文献   

10.
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   

11.
The aim of the present study was to investigate the effects of the phytotoxin fusaric acid (FA) on the biocontrol traits of two biocontrol strains Paenibacillus polymyxa WR‐2 and SQR‐21. The results showed that the growth of both WR‐2 and SQR‐21 decreased with increasing FA concentration, and at 70 and 80 μg mL?1 FA, respectively, the strains were unable to grow. The biocontrol traits of both strains were negatively affected by FA concentration higher than 2·5 μg mL?1. However, at 2·5 μg mL?1 FA, biofilm formation and root colonization were not affected and there was even a positive effect on the production of spores and hydrolytic enzymes (protease and β‐l,3‐glucanase). The production of fusaricidin‐type antifungal compounds was increased with an increase in FA concentration up to 50 and 60 μg mL?1 for WR‐2 and SQR‐21, respectively. The production of antifungal volatile organic compounds by WR‐2 and SQR‐21 was increased only at 2·5 μg mL?1 FA. The effect of FA on the overall metabolic activity of WR‐2 and SQR‐21 was also determined. This study will help to understand the response of P. polymyxa strains to FA and will help to improve their biocontrol efficiency.  相似文献   

12.
为了明确福建省辣椒疫霉菌群体遗传结构的表型特征,对分离自福建省15个市(县)的300株辣椒疫霉菌的交配型、甲霜灵敏感性及生理小种进行了测定。结果显示,288株为A2交配型,12株为A1交配型,出现频率分别为96%和4%,以A2占优势,在各采集点均有分布。263株对甲霜灵表现敏感,28株为中间型,9株为抗性,分别占总体的87.67%、9.33%和3.00%,甲霜灵敏感菌株为主要菌系。根据菌株对辣椒疫霉菌生理小种鉴别寄主的致病性测定结果,可将辣椒疫霉菌划分为3个生理小种,其中168株为小种3,126株为小种2,6株为小种1,分别占56%、42%和2%,小种3为福建辣椒疫霉菌优势小种。  相似文献   

13.
The isolation frequency of Microsphaeropsis sp. in spring in association with necrotic lesions on leaves in Tasmanian pyrethrum (Tanacetum cinerariifolium) fields has increased substantially since first identification in 2001. Examination of morphological features and sequencing of the internal transcribed spacer region (ITS) resulted in the identification of a new species, herein described as Microsphaeropsis tanaceti sp. nov. The pathogenicity of three M. tanaceti isolates to two pyrethrum cultivars was confirmed by inoculating glasshouse‐grown plants in three experiments. No significant differences in the susceptibility of the two cultivars to infection by M. tanaceti were found. Symptoms were tan‐coloured spots which coalesced around the margins of the leaves. Therefore, the name ‘tan spot’ is proposed for this new disease of pyrethrum. The sensitivity of seven M. tanaceti isolates to difenoconazole and azoxystrobin, commonly used fungicides for the management of foliar diseases in spring, was assessed under in vitro conditions. Sensitivity testing for difenoconazole was conducted using a mycelial growth assay on potato dextrose agar, whilst testing for sensitivity to azoxystrobin used a conidial germination assay on water agar. Microsphaeropsis tanaceti was found to be more sensitive to azoxystrobin than difenoconazole, with complete inhibition of conidial germination at concentrations above 0·625 µg a.i. mL?1. By comparison, concentrations of 50 µg a.i. difenoconazole mL?1 or greater were required for significant inhibition of mycelial growth. It therefore appears likely that there is currently some control of tan spot as a result of the use of azoxystrobin and to a lesser extent, difenoconazole, for the control of other diseases.  相似文献   

14.
Pristine® (pyraclostrobin + boscalid) is a fungicide registered for the control of alternaria late blight in pistachio. A total of 95 isolates of Alternaria alternata collected from orchards with and without a prior history of Pristine® sprays were tested for their sensitivity towards pyraclostrobin, boscalid and Pristine® in conidial germination assays. The EC50 values for 35 isolates from orchards without Pristine® sprays ranged from 0·09 to 3·14 µg mL?1 and < 0·01 to 2·04 µg mL?1 for boscalid and Pristine®, respectively. For pyraclostrobin, 27 isolates had EC50 < 0·01 µg mL?1 and six had low resistance (mean EC50 value = 4·71 µg mL?1). Only one isolate was resistant to all three fungicides tested, with EC50 > 100 µg mL?1. Among 59 isolates from the orchard with a history of Pristine® sprays, 56 were resistant to pyraclostrobin; only two were sensitive (EC50 < 0·01 µg mL?1) and one was weakly resistant (EC50 = 10 µg mL?1). For the majority of these isolates EC50 values ranged from 0·06 to 4·22 µg mL?1 for boscalid and from 0·22 to 7·74 µg mL?1 for Pristine®. However, seven isolates resistant to pyraclostrobin were also highly resistant to boscalid and Pristine® and remained pathogenic on pistachio treated with Pristine®. Whereas strobilurin resistance is a common occurrence in Alternaria of pistachio, this is the first report of resistance to boscalid in field isolates of phytopathogenic fungi. No cross resistance between pyraclostrobin and boscalid was detected, suggesting that Pristine® resistance appears as a case of multiple resistance.  相似文献   

15.
Since 2007, serious damage to tomato from leaf mould caused by Passalora fulva has frequently been observed in commercial greenhouses in Gifu Prefecture, Japan. One of the factors relating to this damage was suspected to be a decrease in azoxystrobin sensitivity of the pathogen. Biological and molecular studies were conducted to characterize fungicide resistance. In in vitro sensitivity tests using mycelial homogenate placed on fungicide‐amended medium, the minimum inhibitory concentrations (MIC) of azoxystrobin for mycelial growth of the isolates divided into two ranges, 0.031–0.5 mg L?1 and 8–32 mg L?1. Isolates with MICs within the two ranges were considered as sensitive and resistant, respectively, to azoxystrobin because, in in vivo tests, the percentage protection conferred by this fungicide (100 mg a.i. L?1) against these isolates was 89.7–100% and 4.5–31.1%, respectively. Resistant isolates had a replacement of phenylalanine with leucine at codon 129 (F129L) in cytochrome b. Forty‐five percent of the 271 isolates collected from 63 tomato greenhouses from 2007 to 2008 were resistant to azoxystrobin. In many greenhouses where the isolation frequency of resistant isolates was 80% or more, azoxystrobin had been used twice per crop for approximately 6 years. In 2012, 27% of the 405 isolates collected were resistant to azoxystrobin, and there was a marked difference in the frequency of occurrence of resistant isolates in the field populations between the three locations sampled. The occurrence of azoxystrobin‐resistant P. fulva isolates (F129L mutants) inflicted considerable damage on greenhouse tomatoes.  相似文献   

16.
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   

17.
The glycolipid antibiotic rhamnolipid B isolated from Pseudomonas aeruginosa strain B5 was evaluated for in vitro antifungal activity and in vivo control against phytophthora blight and anthracnose under glasshouse conditions. Rhamnolipid B showed antifungal activity against Cercospora kikuchii, Cladosporium cucumerinum, Colletotrichum orbiculare, Cylindrocarpon destructans, Magnaporthe grisea and Phytophthora capsici. Microscopic observation revealed that the high level of antifungal activity (10 µg ml −1) against P capsici was mainly due to a lytic effect on zoospores. Zoospore lysis began in the presence of 10 µg ml −1 of rhamnolipid B and most of the zoospores were collapsed at 25 µg ml −1. Rhamnolipid B showed inhibitory activity against the germination of zoospores and hyphal growth of P capsici at concentrations of 50 µg ml −1. Spore germination of the anthracnose plant pathogen C orbiculare was also inhibited in the presence of 50 µg ml −1 of rhamnolipid B, although hyphal growth was not affected at this concentration. In the glasshouse, the efficacy of rhamnolipid B against phytophthora blight was similar to that of metalaxyl on pepper plants when treated just before inoculation with P capsici. Treatment with either at 500 µg ml −1 completely protected pepper plants from phytophthora blight. Rhamnolipid B also suppressed the development of C orbiculare infection on leaves of cucumber plants. © 2000 Society of Chemical Industry  相似文献   

18.
Seventy three isolates of Pythium aphanidermatum obtained from cucumber from four different regions of Oman and 16 isolates of muskmelon from the Batinah region in Oman were characterized for aggressiveness, sensitivity to metalaxyl and genetic diversity using AFLP fingerprinting. Twenty isolates of P. aphanidermatum from diverse hosts from different countries were also included in the study. Most isolates from Oman were found to be aggressive on cucumber seedlings and all were highly sensitive to metalaxyl (EC50 < 0·80 µg mL?1). Isolates from cucumber and muskmelon were as aggressive as each other on both hosts (P > 0·05), which implies a lack of host specialization in P. aphanidermatum on these two hosts in Oman. AFLP analysis of all isolates using four primer–pair combinations resolved 152 bands, of which 61 (~40%) were polymorphic. Isolates of P. aphanidermatum from Oman and other countries exhibited high genetic similarity (mean = 94·1%) and produced 59 different AFLP profiles. Analysis of molecular variance indicated that most AFLP variation among populations of P. aphanidermatum in Oman was associated with geographical regions (FST = 0·118; P < 0·0001), not hosts (FST = –0·004; P = 0·4323). These data were supported by the high rate of recovery (24%) of identical phenotypes between cucumber and muskmelon fields in the same region as compared to the low recovery (10%) across regions in Oman, which suggests more frequent movement of Pythium inoculum among muskmelon and cucumber fields in the same region compared to movement across geographically separated regions. However, recovering clones among regions and different countries may imply circulation of Pythium inoculum via common sources in Oman and also intercontinental spread of isolates.  相似文献   

19.
2006-2008年在黑龙江省和吉林省共分离获得61株马铃薯晚疫病菌,测定了这些菌株对交配型、氟啶胺和甲霜灵的敏感性。交配型测定结果显示所有菌株都显示A1交配型。甲霜灵测定结果显示10个菌株(16.4%)显示为敏感性,11个菌株(18.0%)显示为中抗,40个菌株(65.6%)显示为抗性。这说明吉林省和黑龙江省发生的晚疫病菌已对甲霜灵产生抗性。氟啶胺敏感性测定结果表明,不同地区、不同年份分离的马铃薯晚疫病菌对氟啶胺的敏感性无显著差异, 其敏感性呈连续的单峰曲线分布, EC50在0.203 3~0.783 7 μg/mL之间, 最不敏感菌株是最敏感菌株的3.85倍, 平均值为(0.4781±0.0163)μg/mL, 未出现敏感性下降的抗药性群体, 因此可作为马铃薯晚疫病菌对氟啶胺的敏感性基线;83.6%的供试菌株对甲霜灵的敏感性下降, 甲霜灵与氟啶胺之间不存在交互抗药性。测定氟啶胺对马铃薯晚疫病的盆栽防治试验结果表明,氟啶胺可湿性粉剂、氟啶胺悬浮剂和烯酰吗啉能很好地控制晚疫病,防治效果分别为85.71%、87.00%、82.19%,而甲霜灵的为23.92%。  相似文献   

20.
Stems of pepper seedlings were inoculated with zoospores of Phytophthora capsici 18 h after a soil-drench with metalaxyl solution (5 μg ml?1) or water. Infected stem tissues were examined by electron microscopy 24 h after inoculation. Compared with untreated controls, in which the fungal cells were generally normal in shape and ultrastructure, the most conspicuous effects of metalaxyl treatment on the fungal ultrastructure in the stem tissue were an abnormal shrinking of the fungal cell, a separation of the plasma membrane from the hyphal wall, a peculiar invagination and breakdown of the plasma membrane, the presence of vesicles in the invaginated spaces and within the damaged fungal cells, and an indistinct structure of cell organelles. In metalaxyl-treated stems, an electron-dense material was apposed in those sites of the host cell wall in most intimate contact with the fungal cell wall, indicating that the deposition of these substances from the host cell walls may function as a plant defence reaction to the fungus, whereas in untreated controls, the dark-stained host cytoplasm did not aggregate around the sites of fungal contact. The haustorium was encased by the extra-haustorial matrix in treated stems. These results suggest that metalaxyl treatment not only changes the fine structure of P. capsici, but may also induce the plant defence reaction.  相似文献   

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