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1.
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   

2.
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   

3.
In Calabria (southern Italy), control of crown and root rot of capsicum caused by Phytophthora capsici has relied primarily on soil drenches of metalaxyl. However, severe outbreaks occur every year in glasshouse crops, in which the practice of using plastic mulch and furrow irrigation favours the disease. Single‐hypha isolates of P. capsici collected in Calabria in 1992/1998 were tested in vitro for their level of sensitivity to metalaxyl. Isolates of other species of Phytophthora were used as reference. Fungicide sensitivity was determined by plating mycelial plugs onto potato dextrose agar amended with metalaxyl, at final concentrations ranging from 0.1 to 1000μg mL?1 a.s. Inhibition of radial growth (%) was determined when colonies on unamended medium had covered approximately two‐thirds of the plate. The ED50 values for inhibition of mycelial growth of P. capsici isolates ranged from 1.41 to44.6μg mL?1 a.s. More than 80% of the P. capsici isolates from commercial plastic‐house crops in Calabria showed a moderate level of resistance as they were inhibited less than 60% at 5 μg mL?1 but more than 60% at 100μg mL?1  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.
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   

6.
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   

7.
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   

8.
Late blight, caused by Phytophthora infestans, has emerged as the most destructive disease of potato and tomato in South India since 2008. One hundred and fifty‐seven isolates of Phytophthora infestans, 63 from potato and 94 from tomato, were collected from major potato and tomato production areas of South India between 2010 and 2012. Their phenotypic and genotypic characteristics were determined and compared with reference isolates. Isolates were characterized based on mating type, in vitro metalaxyl sensitivity, mitochondrial DNA haplotype, RG57 DNA fingerprinting patterns, SSR markers and aggressiveness on potato and tomato, in order to monitor population changes in P. infestans. All isolates were A2 mating type, metalaxyl resistant, mtDNA haplotype Ia and had RG57 and SSR fingerprints almost identical to the 13_A2 clonal lineage reported in Europe. Variation at the D13 and SSR4 loci allowed discrimination of minor variants, designated as 13_A2_3, 13_A2_3b, 13_A2_3c and 13_A2_1. A comparison of the lesion diameters caused by 157 isolates on detached leaflets of three potato and tomato cultivars showed all isolates to be equally aggressive, confirming that the same clonal population is infecting both hosts. This study demonstrates that the 13_A2 lineage was responsible for severe late blight outbreaks on potato and tomato in South India and has replaced the prior population represented by the US‐1 and other genotypes. Revised management strategies will be required to combat this destructive 13_A2 clonal lineage and monitoring of the population across other potato‐ and tomato‐growing regions of India is warranted.  相似文献   

9.
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   

10.
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   

11.
Control of the potato late blight pathogen Phytophthora infestans relies heavily on chemicals. The fungicide metalaxyl‐M (Mefenoxam) has played an important role in controlling the disease, but insensitivity to the fungicide in certain isolates is now of major concern. A genetic basis for resistance to metalaxyl suggests the possibility for linking resistance phenotypes to specific population genetic markers, but in order to do this, the population genetic structure and mode of reproduction in a population must first be well described. The dynamics of metalaxyl‐M resistance in the Danish population of P. infestans was characterized over the course of the 2013 growing season, as was the population genetic structure, using simple sequence repeat (SSR) genotypes and single nucleotide polymorphism (SNP)‐based mitochondrial haplotyping of over 80 isolates. Both mating types A1 and A2 were present in most fields, but tests for recombination showed that clonal reproduction dominates in Danish populations. Genotype was not linked to haplotype and no differentiation was observed at the haplotype level, but rather between fields. Resistance phenotypes were linked to specific SSR alleles, demonstrating the potential for a more precise SNP‐based marker system for predicting resistance to metalaxyl‐M.  相似文献   

12.
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   

13.
Limited knowledge is available on Phytophthora infestans populations in Sub‐Saharan Africa (SSA). Therefore, and in response to recent severe late blight epidemics, P. infestans isolates from potato, tomato and Petunia × hybrida from eight SSA countries were characterized. Isolates were characterized with ‘old’ markers, including mating type (176 isolates), mitochondrial DNA haplotype (mtDNA) (281 isolates), glucose‐6‐phosphate isomerase (Gpi) (70 isolates), restriction fragment length polymorphism analysis with probe RG‐57 (49 isolates), and by metalaxyl sensitivity (64 isolates). Most isolates belonged to the US‐1 genotype or its variants (US‐1.10 and US‐1.11). The exceptions were genotype KE‐1 isolates (A1 mating type, mtDNA haplotype Ia, Gpi 90/100 and unique RG‐57 genotype), identified in two fields in Kenya, which are related to genotypes previously identified in Rwanda (RW‐1 and RW‐2), Ecuador and Europe. Metalaxyl‐resistant P. infestans isolates from potato were present in all the countries except Malawi, whereas all the isolates from tomato were sensitive. Genotyping of 176 isolates with seven simple sequence repeat (SSR) markers, including locus D13 that was difficult to score, revealed 79 multilocus genotypes (MLGs) in SSA. When this locus was excluded, 35 MLGs were identified. Genetic differentiation estimates between regional populations from SAA were significant when locus D13 was either excluded (P = 0·05) or included (P = 0·007), but population differentiation was only low to moderate (FST = 0·044 and 0·053, respectively).  相似文献   

14.
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   

15.
The evolution of fungicide resistance in the cereal pathogen Zymoseptoria tritici is a serious threat to the sustainability and profitability of wheat production in Europe. Application of azole fungicides has been shown to affect fitness of Z. tritici variants differentially, so it has been hypothesized that combinations of azoles could slow the evolution of resistance. This work assessed the effects of dose, mixtures and alternations of two azoles on selection for isolates with reduced sensitivity and on disease control. Naturally infected field trials were carried out at six sites across Ireland and the sensitivity of Z. tritici isolates monitored pre‐ and post‐treatment. Epoxiconazole and metconazole were applied as solo products, in alternation with each other, and as a pre‐formulated mixture. Full and half label doses were tested. Isolates were partially cross‐resistant to the two azoles, with a common azole resistance principal component accounting for 75% of the variation between isolates. Selection for isolates with reduced azole sensitivity was correlated with disease control. Decreased doses were related to decreases in sensitivity but the effect was barely significant (P = 0·1) and control was reduced. Single applications of an active ingredient (a.i.) caused smaller decreases in sensitivity than double applications. Shifts in sensitivity to the a.i. applied to a plot were greater than to the a.i. not applied, and the decrease in sensitivity was greater to the a.i. applied at the second timing. These results confirm the need to mix a.i.s with different modes of action.  相似文献   

16.
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   

17.
This study was conducted on potato late blight samples collected for monitoring early attacks in Finland from 1997 to 2000. Most of the 1726 Phytophthora infestans isolates were collected soon after the onset of the epidemics. Most of the isolates were tested for mating type as well as metalaxyl and propamocarb hydrochloride (HCl) sensitivity, while virulence on potato R-gene differentials and mitochondrial DNA (mtDNA) haplotype were determined for a subset of the isolates. In half of the fields from which more than one isolate was tested, both mating types were detected, indicating strong potential for sexual reproduction. The mating types coexisted more often in organic fields or gardens than in conventional fields. The proportion of A1 mating type decreased from approximately 80% (1997 and 1998) to 22% by the year 2000. Simultaneously, the proportion of isolates resistant to metalaxyl decreased from approximately 40% to 16%. Resistance to metalaxyl was confined to the IIa mtDNA haplotype and clearly associated with the A1 mating type, as resistance was 10 times more common among A1 isolates than among A2 isolates. Resistance to metalaxyl therefore probably derives from common descent from an isolate with the IIa haplotype. Most of the regional variation in metalaxyl sensitivity was also linked to mating type, as both metalaxyl resistance and the A1 mating type were most common in the north and south-west of Finland. In contrast to metalaxyl, only three propamocarb-HCl-insensitive isolates were found, but propamocarb-HCl sensitivity decreased significantly during the study.  相似文献   

18.
A collection of 96 Polish isolates of Phytophthora infestans sampled in the years 2006, 2008 and 2009 were analysed using phenotypic and genotypic markers. Mating type, virulence, resistance to metalaxyl, mitochondrial haplotype and polymorphism at 12 simple sequence repeat (SSR) loci were determined. The majority of isolates were of the A1 mating type, mitochondrial haplotype Ia and sensitive to metalaxyl. Virulence factors against potato R genes R1, R3, R4, R7, R10 and R11 were present in most isolates. Genotyping using SSR markers revealed high genetic diversity within the Polish P. infestans population. Amongst the 96 isolates 66 unique genotypes were identified, 49 of which were observed only in single isolates. Eight isolates of the genotype 13_A2 lineage that has been reported in other parts of Europe were also found in Poland. The implications of these results are discussed.  相似文献   

19.
The population of Phytophthora infestans on potato landraces in three provinces (Carchi, Chimborazo and Loja) of Ecuador was analysed. All isolates (n = 66) were of the A1 mating type. Simple sequence repeats (SSR) were used to assess the genetic diversity of the isolates. The P. infestans isolates from the potato landraces grouped in a single clade together with reference isolates belonging to the clonal lineage EC‐1. In the 66 SSR profiles obtained, 31 multilocus genotypes were identified. The 66 isolates constituted 49 different races according to the Solanum demissum differential set ( R1 to R11). The P. infestans population was complex and virulent on 4 to 11 R genes. Analysis showed that the subclonal variation in the Ecuadorian EC‐1 clone is increasing over time and is much larger than clonal variation in lineages in the Netherlands and Nicaragua, suggesting high mutation rates and little or no selection in Ecuador.  相似文献   

20.
In order to better understand the Phytophthora infestans population structure in South Korea, 172 isolates were collected between 2009 and 2016 from four major potato cultivation areas. Fungicide (metalaxyl and dimethomorph) response, mating type, and microsatellite (SSR) genetic fingerprints were analysed to characterize these isolates. Ten isolates collected in Gyeongnam Province, which specializes in protected winter cultivation in polytunnels, were A2 mating type. All other isolates were A1 mating type. Overall, 42% of the isolates were resistant to metalaxyl, and 43% were sensitive. All isolates were sensitive to dimethomorph. From the SSR fingerprints, 45 distinct genotypes were identified, which could be clustered into four clonal lineages: KR_1_A1, KR_2_A2, SIB-1, and US-11. KR_1_A1 was the predominant P. infestans genotype in South Korea. KR_2_A2 was only found in Gyeongnam Province; all isolates were A2 mating type and resistant to metalaxyl. SIB-1 was dominant until 2013 but its frequency has gradually decreased in more recent years. US-11 was first found in 2014, after which its frequency has increased to become codominant with KR_1_A1. The calculated standardized index of association (IA) suggests that the South Korean P. infestans population is undergoing clonal reproduction. When compared with populations of P. infestans from the Netherlands, it has less genetic diversity and the dominant Netherlands P. infestans genotype, EU_13_A2 (Blue_13), was not found in South Korea. Such monitoring of the pathogen population contributes to a more efficient integrated pest management-based control strategy for potato late blight control in South Korea.  相似文献   

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