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1.
Changes in the incidence and onset of potato late-blight epidemics in Finland were investigated and compared with possible changes in climate, presence of soil-borne inoculum, and aggressiveness of Phytophthora infestans populations. Datasets were constructed from leaf blight assessments in cultivar trials or fungicide tests carried out at eight experimental sites during the periods 1933–1962 and 1983–2002. Additional data were obtained from late-blight monitoring projects carried out from 1991 to 2002. From 1998 to 2002, the risk of blight outbreak was 17-fold higher compared with the periods 1933–62 and 1983–1997. Simultaneously, the outbreaks of the epidemics began 2–4 weeks earlier. The changes observed were associated with a climate more conducive to blight in the late 1990s. Lack of rotation also advanced blight epidemics by an average of 9 days in 1998–2002, but it did not have this effect in 1992–1997, suggesting that soil borne inoculum may not have been a significant threat to potato until the late 1990s. The aggressiveness of the P. infestans isolates seemed to have only minor effect on the onset of the epidemics after 1991, as the apparent infection rate remained unchanged despite weather conditions more favourable to late blight in the late 1990s. As a consequence of the more frequent and earlier epidemics, the sales of fungicides used against late blight in Finland increased 4-fold from the 1980s to 2002.  相似文献   

2.
青海马铃薯晚疫病菌线粒体DNA单倍型鉴定及分析   总被引:1,自引:0,他引:1  
 为查明青海地区晚疫病菌单倍型分布情况,本研究对青海不同地区采自2006~2007年的70个晚疫病菌材料的线粒体单倍型进行了分析,结果表明:94.3%的菌株为Ⅱa型,5.7%的菌株为Ⅱb型,其中Ⅱb型均分离自番茄。这说明青海地区马铃薯晚疫病菌群体类型比较单一,主要为Ⅱa型,线粒体单倍型不存在多态性。  相似文献   

3.
 马铃薯晚疫病的病原是致病疫霉菌(Phytophthora infestans),该病原菌在侵染马铃薯过程中分泌大量RxLR型效应子,但目前绝大多数RxLR效应子的功能和作用机制尚不明确。本研究成功克隆了致病疫霉菌的一个RxLR效应子PITG_16427.2,在本氏烟中瞬时表达PITG_16427.2,发现该效应子能够抑制6种激发子(INF1、PsojNIP、BAX、SIF2、Avh238、Avh241)激发的植物免疫反应。进一步研究发现,效应子PITG_16427.2在晚疫病菌侵染马铃薯早期上调表达。在15个致病疫霉菌株和3个同属菌株中克隆该基因,克隆到氨基酸序列一致性超过93%的同源基因,这些同源基因均能在本氏烟中抑制INF1和Avh241引起的HR,揭示了该效应子在病原卵菌中序列和功能的高度保守性。在本氏烟和马铃薯感病品种Désirée中瞬时表达PITG_16427.2,发现该效应子能够显著促进晚疫病菌的侵染。通过qRT-PCR方法检测发现,乙烯信号的相关基因ERF1显著上调,而水杨酸信号相关基因PR1b显著下调,表明PITG_16427.2在晚疫病菌侵染过程中可抑制寄主的SA信号途径,促进晚疫病菌侵染。因此,RxLR型效应子PITG_16427.2是致病疫霉菌中一个重要的侵染致病因子。  相似文献   

4.
 将4.0%五倍子水悬浮液喷施田间马铃薯品种Bintje的叶片,于不同处理时间后,剪下叶片带回室内人工接种致病疫霉孢子囊悬浮液,保湿培养后调查各处理的发病情况。结果表明,喷施五倍子水悬浮液后48h内未经历降雨的处理,病情指数仅为7.41,与清水对照相比,防效为92.59%;喷施后96h接种的处理,由于在田间经历了降雨,完全丧失了防效,病情指数达100。室内毒力测定结果显示,0.4%五倍子水悬浮液喷施96h后,对致病疫霉游动孢子释放的抑制率仍在80%以上,在室外避雨不避光条件下五倍子水悬浮液96h内抑菌效果无显著降低,表明日光的影响作用较小。在室内盆栽条件下,通过喷淋水滴模拟田间降雨对药液的冲刷作用。结果表明,冲刷作用可导致五倍子水悬浮液对马铃薯晚疫病的防效显著降低。进一步说明,降雨是导致五倍子水悬浮液对马铃薯晚疫病田间防治效果降低的主要气象因素。  相似文献   

5.
近年来马铃薯晚疫病的重新暴发再次引起世界各国极大关注,特别对马铃薯晚疫病菌的分子遗传学的研究,包括病菌基因组遗传、转录和物理图谱的构建,病菌致病的分子机制以及马铃薯-马铃薯晚疫病菌互作分子机制等。本文就近几十年来对马铃薯晚疫病菌在生物学和病理学,分子遗传学等研究方面作简要综述,并对其研究趋势进行了展望。  相似文献   

6.
为明确福建省部分马铃薯产区晚疫病菌群体结构,2017年-2019年在龙海市、福安市、霞浦县共分离获得96株马铃薯晚疫病菌。采用对峙培养法、鉴别寄主法和PCR-RFLP法对这些菌株的交配型、生理小种及线粒体DNA (mtDNA)单倍型进行分析。交配型测定结果显示,除了福建省福安市有5株(5.21%)为A1交配型外,其余91株(94.79%)均为自育型,未发现A2交配型及A1A2型菌株。从96个菌株中检测出16个生理小种类型,龙海市和福安市的优势生理小种均是可克服11个显性抗病单基因的1.2.3.4.5.6.7.8.9.10.11,霞浦县的优势生理小种为1.2.3.4.5.6.7.8.10。供试菌株均至少含有6个毒性基因。mtDNA单倍型共检测出3种类型,其中55个菌株(龙海市22株、福安市8株、霞浦县25株)为Ⅰa型,占57.29%,32个菌株(龙海市2株、福安市25株、霞浦县5株)为Ⅱa型,占33.33%,9个菌株(福安市7株、霞浦县2株)为Ⅱb型,占9.37%。研究结果表明,福建省马铃薯晚疫病菌群体遗传多样性日趋复杂。  相似文献   

7.
Nitric oxide (NO) is a bioactive molecule involved in many physiological processes. Among its biological function, NO has been proved to be cytotoxic against microorganisms in cells of the immune response, thus preventing infection. We have specifically studied the effect of a NO donor, sodium nitroprusside (SNP), on the chlorophyll content in potato leaves infected with the pathogenic fungus Phytophthora infestans (Pi). Fifteen days after infection, chlorophyll content strongly decayed in water-treated potato leaf sections. SNP was able to partially revert that loss in a dose-dependent manner, being the effective SNP concentrations between 10 µM and 100 µM. NaNO2 and NaNO3, the SNP-derived residual products, were unable to prevent the chlorophyll loss. Treatments with SNP did not affect the survival of Pi and the fungus was able to grow in a V8-agar medium containing 100 µM SNP. Both the amount and the extent of germination of Pi sporangia resulted similar in the absence and in the presence of SNP. Respiratory inhibitors of the cyanide-sensitive and cyanide-resistant pathways, 2,4-dinitrophenol and salicylhydroxamic acid respectively, did not change the chlorophyll levels in infected potato leaves, suggesting that NO effect should not be on mitochondrial respiration. These results indicate that NO could be a protective molecule, either preserving the chloroplast membrane of infected leaf sections against the toxicity of reactive oxygen species or being directly involved in any step of the chlorophyll metabolic pathway.(both authors contributed equally to this work)  相似文献   

8.
9.
Late blight, caused by Phytophthora infestans , is the most severe disease of potato worldwide. Controlling late blight epidemics is difficult, and resistance of host cultivars is either not effective enough, or too easily overcome by the pathogen to be used alone. In field trials conducted for 3 years under natural epidemics, late blight severity was significantly lower in a susceptible cultivar growing in rows alternating with partially resistant cultivars (mixtures) than in unmixed plots of the susceptible cultivar alone. Partially resistant cultivars behaved similarly in unmixed and mixed plots. Mixtures of cultivars reduced disease progress rates and sometimes delayed disease onset over unmixed plots, but did so significantly only for the slowest epidemic. This suggests that reduction of area under the disease progress curve (AUDPC) in mixtures resulted from the cumulative action of minor effects. Disease distribution was focal in all plots at all dates, as shown by Morisita's index values significantly exceeding 1. Significant yield increases for the susceptible cultivar, and occasionally for the partially resistant ones, were observed in mixed-cultivar plots compared with single-cultivar plots. These results show that cultivar mixtures can significantly reduce natural, polycyclic epidemics in broadleaved plants attacked by pathogens causing rapidly expanding lesions.  相似文献   

10.
A blight disease on fruits and foliage of wild and cultivated Solanum spp. was found to be associated with a new species of Phytophthora. The proposed novel species is named Phytophthora andina Adler & Flier, sp. nov. based on morphological characteristics, pathogenicity assays, mitochondrial DNA haplotyping, AFLP fingerprinting and nuclear and mitochondrial DNA sequence analyses. Isolates of P. andina (n = 48) from the Andean highland tropics of Ecuador were collected from 1995 to 2006. Phytophothora andina is closely related to P. infestans and has semipapillate, ellipsoidal sporangia borne on sympodially branched sporangiophores. It is heterothallic and produces amphigynous antheridia. The species consists of several clonal lineages, including the EC‐2 and EC‐3 RFLP lineages, which were described previously as P. infestans. Approximately 75% of isolates react as compatibility type A2 when paired with an A1 compatibility type isolate of P. infestans. However, when A2 isolates from the Anarrhichomenum section of Solanum were paired in all combinations, viable oospores were obtained in several crosses, suggesting that there is a unique compatibility interaction in P. andina that is complementary to that described in P. infestans. Nuclear and mitochondrial sequence analysis supported the species designation of P. andina. This newly identified heterothallic pathogen shares a common ancestor with P. infestans and may have arisen from hybridization events with sister taxa in the Andes.  相似文献   

11.
Many race-specific resistance genes to potato late blight are overcome in France, but the disease appears later on genotypes carrying the R2 gene. This study examined whether R2 could contribute to durable late-blight control in France, and analysed the conditions of its performance. Plants grown from tubers of different physiological ages showed no difference in R2 expression in field and climate-chamber experiments, demonstrating that the delay in epidemic onset provided by R2 was not the result of gene inactivation in old plants. Among isolates collected at one site, those virulent on R2 were classified into three AFLP profiles. AFLP-VII comprised exclusively isolates virulent to R2 , whereas AFLP-IV and AFLP-V included both virulent and avirulent isolates. No significant aggressiveness differences were observed between virulent and avirulent isolates from AFLP-V; however, isolates from AFLP-VII were significantly less aggressive than virulent isolates from AFLP-V. These results indicate that: (i) the delayed onset of epidemics on R2 cultivars is the result of the breakdown of R2 by virulent isolates; (ii) aggressiveness of isolates virulent to R2 depends primarily on the genetic background of the pathogen where the mutation to virulence occurs; and (iii) this mutation does not lead per se to lower pathogenic fitness. It is suggested that R2 is unlikely to make a lasting contribution to late-blight control in France, and that diversification strategies such as cultivar mixtures might not considerably increase its durability.  相似文献   

12.
The rate of late blight disease was analysed for individuals of a diploid Solanum phureja – Solanum tuberosum dihaploid hybrid population (PD), using three different assessment techniques, in the laboratory, screenhouse, and field. These hybrids expressed low disease rates in the field, comparable to resistance based on intact R genes. However, none of the parents of PD expressed any R genes and the pattern of segregation within the PD population was not indicative of R-gene inheritance. The foliage (or leaflet) area diseased had the largest broad-sense heritability of all criteria analysed, in all tests performed. In the field evaluations, the PD population showed intermediate levels of broad-sense heritability for foliage area diseased, relative to the much larger heritability detected for the group of controls possessing R genes. Resistance in the field of the PD hybrids had very little genotype-environment (G × E) interaction, indicating stability of its expression. All genotypes without R genes exhibited heritable, reduced rates of late blight disease in the field, but they were susceptible with low heritability in screenhouse and laboratory tests. This differential expression of disease indicates that the plants' indirect response to unknown environmental stress in the field may have been measured. The value of the PD hybrids for breeding of late blight resistant potato and the use of the disease rate data for detection of the underlying quantitative trait loci are discussed.  相似文献   

13.
Runoff formation is a complex meteorological-hydrological process impacted by many factors,especially in the inland river basin.Based on the data of daily mean air temperature,precipitation and runoff during the period of 1958-2007 in the Kaidu River watershed,this paper analyzed the changes in air temperature,precipitation and runoff and revealed the direct and indirect impacts of daily air temperature and precipitation on daily runoff by path analysis.The results showed that mean temperature time series of the annual,summer and autumn had a significant fluctuant increase during the last 50 years(P < 0.05).Only winter precipitation increased significantly(P < 0.05) with a rate of 1.337 mm/10a.The annual and winter runoff depthes in the last 50 years significantly increased with the rates of 7.11 mm/10a and 1.85 mm/10a,respectively.The driving function of both daily temperature and precipitation on daily runoff in annual and seasonal levels is significant in the Kaidu River watershed by correlation analysis.The result of path analysis showed that the positive effect of daily air temperature on daily runoff depth is much higher than that of daily precipitation in annual,spring,autumn and winter,however,the trend is opposite in summer.  相似文献   

14.
Y. Tian  J. Sun  H. Li  G. Wang  Y. Ma  D. Liu  J. Quan  W. Shan 《Plant pathology》2015,64(1):200-206
Late blight caused by Phytophthora infestans is the most serious disease of potato worldwide. To understand the P. infestans population structure in northern Shaanxi, an emerging potato production region in China, 125 single‐lesion isolates were randomly collected from farmers' fields in 2009 and characterized phenotypically and genotypically. A mating type assay showed that 94 isolates were A1 mating type. Virulence determination of selected isolates on a set of differential potato lines containing R1 to R11, respectively, showed the presence of two pathotypes, of which the pathotype lacking avirulence genes Avr3, Avr4 and Avr10 was dominant. Isolates lacking all avirulence factors Avr1 to Avr11 were detected but at lower frequency (13·6%). Analysis for mtDNA haplotype showed all 61 examined isolates were IIa. A total of seven multilocus genotypes were distinguished among 125 isolates, as determined with seven polymorphic microsatellite markers. The genotype SG‐1 was dominant in the population with a frequency of 75·2% and was present throughout the region. Analysis of the phenotypic and genotypic structures of P. infestans populations indicated strict clonal reproduction of the pathogen and suggested that sexual reproduction probably does not occur. Potential implications for disease management are discussed.  相似文献   

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