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1.
L11A-Fukushima (L11A-F) derived from attenuated isolate LuA of Tomato mosaic virus (ToMV) has the highest ability to cross protect against virulent ToMV among LuA and its derivatives and is stably inherited. Growth, yield, fruit quality and symptom attenuation of inoculated tomato plants did not differ significantly between L11A-F and L11A. The infectivity of progeny viruses in tomato infected with LuA-F was less than 4% of that with virulent ToMV. From these results, L11A-F appears to possess the properties necessary for practical use. To manage L11A-F strictly, a PCR-based assay to detect trace contamination of virulent ToMV in L11A-F preparations was established. Received 10 June 2002/ Accepted in revised form 30 October 2002  相似文献   

2.
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3.
The L11Y strain of Tomato mosaic virus (ToMV) causes severe chlorosis on infected tobacco leaves. Sequencing analysis for the genome showed that L11Y contained multiple nucleotide changes and that some led to amino acid substitutions, when compared with that of the common L strain of ToMV. The chimeric virus, which has the CP of L11Y in the context of the L strain RNA genome, caused severe chlorosis on infected tobacco plants, suggesting that the CP of L11Y containing three amino acid changes (E33S, A86T and E97K) was the determinant of the chlorosis. Two of these amino acid changes (A86T and E97K) were associated with the induction of chlorosis when present together in the CP. Severe destruction and deformation of chloroplasts and the formation of discrete dark-staining materials adjacent to chloroplasts were observed with electron microscopy in L11Y-infected plants. Fewer virus particles accumulated in the cytoplasm of L11Y-infected plant cells. The level of accumulation of CP subgenomic RNA and CP in the infected protoplasts was similar between L and L11Y. Fewer virus particles accumulated in L11Y-infected protoplasts, and many of them were shorter-than-full-length. The nucleotide sequence data reported is available in DDBJ/EMBL/GenBank databases as accession AB355139.  相似文献   

4.
During a survey of virus diseases affecting pepper grown in plastic houses in Crete, during 1984–1986, tomato mosaic virus (ToMV) and tobacco mosaic virus (TMV) were detected. The most common virus was TMV, being present in samples of alle pepper cultivars carrying the L1 resistance gene, while ToMV was isolated only from susceptible pepper cultivars. According to responses ofCapsicum spp. the isolates from 640 samples checked were classified into three pathotypes: P0, P1.2 and P1.2.3. Results of this study show that P1.2 represents at present the major threat to the Cretan pepper industry.Samenvatting Bij een in de jaren 1984–1986 gehouden inventarisatie van virusziekten in paprika in plastic-foliekassen op Kreta werd zowel het tabaksmozaïekvirus (TMV) als het tomatemozaïekvirus (ToMV) aangetoond. TMV kwam zeer algemeen voor: het werd aangetroffen in alle monsters van de paprikarassen met het resistentiegen L1. ToMV werd alleen geïsoleerd uit planten van vatbare paprikarassen. Volgens de waargenomen symptomen die de isolaten van 640 monsters opCapsicum spp. vertoonden, konden de isolaten in drie pathotypen, nl. P1, P1,2 en P1,2,3, worden geklassificeerd. Uit het onderzoek is gebleken dat P1,2 de belangrijkste bedreiging vormt voor de teelt van paprika op Kreta.  相似文献   

5.
Baseline sensitivity of Sclerotinia sclerotiorum, causal agent of stem rot of rapeseed, to a dicarboximide fungicide iprodione was determined using 50 isolates (historic population) collected in 2001 from the rapeseed fields without a previous history of dicarboximide usage. The 50% effective concentration (EC50) values to iprodione of these wild-type isolates ranged from 0.163 to 0.734 μg/ml with a mean of 0.428 μg/ml. In 2007 and 2008, 111 isolates (current population) were collected from rapeseed fields with 4–5 years of iprodione application. The EC50 values of these 111 isolates ranged from 0.117 to 0.634 μg/ml. The historic and current populations were not significantly (P > 0.05) different in sensitivity to iprodione. The EC50 values of these 161 isolates to a carboxamide fungicide boscalid ranged from 0.002 to 0.391 μg/ml with a mean of 0.042 μg/ml. In the laboratory, three iprodione-resistant (IR) isolates HA17-IR, SZ31-IR, and SZ45-IR were induced from wild-type isolates HA17, SZ31, and SZ45, respectively. The EC50 values of the IR isolates were 200-fold higher than those of the original wild-type parents. The IR isolates showed an increase in osmotic sensitivity. The IR isolate HA17-IR lost its ability to produce sclerotia, and showed a significantly lower virulence on rapeseed leaves than its parent isolate HA17. In contrast, the IR isolate SZ31-IR had a significantly higher virulence than its wild-type parent SZ31. PCR assays showed that the partial two-component histidine kinase (os-1) gene, which is the putative target gene of iprodione, was deleted in the low virulent IR isolate HA17-IR. DNA sequence analysis showed that each of the other two IR isolates SZ31-IR and SZ45-IR had two point mutations in their partial os-1 genes. These results indicate that the mutations in os-1 gene may be associated with dicarboximide sensitivity, sclerotial development, and virulence in S. sclerotiorum.  相似文献   

6.
In Cryphonectria parasitica, the causal agent of chestnut blight, hypovirulence is commonly associated with the presence of cytoplasmically transmissible, double-stranded RNA (dsRNA). Recently, hypovirulent isolates of C. parasitica that do not have detectable levels of dsRNA have been obtained from healing cankers on chestnut trees. In these isolates, most of the respiratory activity is cyanide-resistant and salicylhydroxamate-sensitive, indicating that the mitochondrial alternative oxidase was induced. In contrast, the respiration of virulent isolates from the same trees and most of the dsRNA-containing hypovirulent isolates from a variety of geographical locations was cyanide sensitive. In all of these isolates, the alternative oxidase could be induced by growing them in the presence of chloramphenicol, an inhibitor of mitochondrial protein synthesis. The attenuated virulence and altered respiratory phenotypes could be transferred from the dsRNA-free hypovirulent isolates to virulent strains through hyphal anastomosis. Some of the dsRNA-free hypovirulent isolates grew more slowly than virulent strains. These results indicate that, in Cryphonectria, cytoplasmically transmitted hypovirulence may have more than one cause, and that mitochondrial mutations sometimes may be involved in the generation of this phenotype.  相似文献   

7.
Dark brown, necrotic pods with extensive water-soaked lesions caused by plant pathogenic bacteria were found on okra plants in different fields in Malaysia in 2010. PCR amplification of the pectate lyase (pel) gene and amplification of the 16S–23S rRNA (ITS) with G1 and L1 primers produced 434-, 535- and 570-bp fragments, respectively. From the similarity between the results of biochemical tests and their equivalency with standard bacteriological sources, PCR-based pel gene, and RFLP analysis of the ITS-PCR products, all isolates were identified as Pectobacterium carotovorum. This is the first report of P. carotovorum in okra from Malaysia.  相似文献   

8.
Four Cucumber mosaic virus (CMV) (CMV-HM 1–4) and nine Tomato mosaic virus (ToMV) (ToMV AH 1–9) isolates detected in tomato samples collected from different governorates in Egypt during 2014, were here characterized. According to the coat protein gene sequence and to the complete nucleotide sequence of total genomic RNA1, RNA2 and RNA3 of CMV-HM3 the new Egyptian isolates are related to members of the CMV subgroup IB. The nine ToMV Egyptian isolates were characterized by sequence analysis of the coat protein and the movement protein genes. All isolates were grouped within the same branch and showed high relatedness to all considered isolates (98–99%). Complete nucleotide sequence of total genomic RNA of ToMV AH4 isolate was obtained and its comparison showed a closer degree of relatedness to isolate 99–1 from the USA (99%). To our knowledge, this is the first report of CMV isolates from subgroup IB in Egypt and the first full length sequencing of an ToMV Egyptian isolate.  相似文献   

9.
An inoculation method using Lupinus luteus was developed for estimating virulence of isolates of the white root rot fungus, Rosellinia necatrix Prillieux. Fungal cultures grown on pieces of mulberry twigs were placed in contact with the hypocotyl of 3-week-old seedlings growing in pots of soil. Disease development was uniform and reproducible in repeated experiments. Of 24 isolates with double-stranded RNA, eight were weakly virulent. This method is useful throughout the year for estimating virulence of many isolates of the fungus and for screening for hypovirulent isolates. Received 2 March 2001/ Accepted in revised form 25 May 2001  相似文献   

10.
Downy mildew resistance was previously identified from screening a Brassica oleracea collection against two standard UK isolates of Hyaloperonospora parasitica. Sources of resistance were chosen from this material and developed further in this study by generating doubled haploid (DH) and inbred lines. Seedlings from the new lines were tested for resistance to a larger collection of H. parasitica isolates collected in 2001–2002 and 2007–2008 from the main broccoli and cauliflower production regions of the UK. Three lines (derived from borecole or summer cabbage) were broadly resistant to the pathogen isolates. Three of the remaining lines exhibited strong isolate‐specific resistance; several examples of weak or basal level of resistance to some isolates were observed. A new H. parasitica variant collected in 2008 was virulent in the broadly resistant lines, but was avirulent in a line with narrow specificity of resistance. The F2 and BC1 seedlings derived from outcrossing each of the three broadly resistant lines to susceptible broccoli and cauliflower lines segregated in a manner indicating that the resistance was controlled by a single dominant gene. No susceptibility was observed amongst F2 seedlings derived from intercrossing the three resistant lines, indicating that they all share the same or closely linked broad‐spectrum resistance gene(s). DH lines were produced from F1 plants, and resistant plants were further backcrossed to produce broccoli and cauliflower‐like lines that could be useful pre‐breeding material. A combination of resistance from lines with broad and narrow specificity is recommended for controlling downy mildew in UK brassica production.  相似文献   

11.
为了解新疆番茄上病毒病的发生情况,利用一步法RT-PCR技术检测了南北疆番茄上南方番茄病毒(Southern tomato virus,STV)、黄瓜花叶病毒(Cucumber mosaic virus,CMV)、番茄花叶病毒(Tomato mosaic virus,ToMV)以及马铃薯Y病毒(Potato virus Y,PVY)的感染情况,并利用分段克隆的方法进行全基因组测序,通过RT-PCR方法检测健康植株与携带病毒植株杂交育种的F1代植株带毒率以分析STV的种子传播特性。结果显示,新疆番茄上CMV、STV、ToMV和PVY在北疆的检出率分别为52%、37%、27%和14%;在南疆的检出率分别为79%、60%、69%和0;且以STV、CMV及ToMV的复合侵染为主。从我国加工番茄上首次获得了长3 437 nt的STV SHZ-1核苷酸序列,序列比对分析发现其与已报道STV只有1~9个核苷酸的变异,且序列变异与地域无相关性。分析杂交F1代加工番茄植株上STV的传播特性,发现其除可由种子传播外,也可通过花粉传播。表明STV是侵染新疆番茄的主要病毒之一,且该病毒可通过种子或杂交育种途径进行传播。  相似文献   

12.
BACKGROUND: Isolates of Didymella bryoniae (Auersw.) Rehm, causal agent of gummy stem blight on cucurbits, developed insensitivity to azoxystrobin in the eastern United States 2 years after first commercial use in 1998. Baseline sensitivity of this fungus to azoxystrobin has never been reported. The objectives were to compare baseline sensitivities of D. bryoniae from South Carolina and other locations to sensitivities of isolates exposed to azoxystrobin for one or more seasons, and to compare sensitivity in vitro and in vivo. RESULTS: Sixty‐one isolates of D. bryoniae collected before 1998 were sensitive. Median EC50 was 0.055 mg L?1 azoxystrobin (range 0.005 to 0.81). Forty isolates collected after exposure during 1998 also were sensitive. Fifty‐three of 64 isolates collected in South and North Carolina between 2000 and 2006 were insensitive to 10 mg L?1 azoxystrobin. Sensitive and insensitive isolates were distinguished by disease severity on Cucumis melo L. seedlings treated with azoxystrobin (20 or 200 mg L?1). CONCLUSIONS: An azoxystrobin baseline sensitivity distribution was established in vitro for isolates of D. bryoniae never exposed to strobilurins. Baseline values were comparable with those of other ascomycetes. Insensitive isolates were found in fields with a history of strobilurin applications. An in vivo method distinguished sensitive and insensitive isolates. Copyright © 2009 Society of Chemical Industry  相似文献   

13.
Field isolates of Alternaria solani, which causes early blight of potato in Idaho, USA were evaluated in vitro for their sensitivity towards the succinate dehydrogenase inhibitor (SDHI) fungicides boscalid, fluopyram and penthiopyrad. A total of 20 isolates were collected from foliar‐infected tissue in 2009, 26 in 2010 and 49 in 2011. Fungicide sensitivity was tested using the spiral‐gradient end point dilution method. The frequency of boscalid‐resistant isolates (>50% relative growth when using a spiral dilution gradient starting at 507 mg L?1) drastically increased over the duration of this study (15% in 2009, 62% in 2010 and 80% in 2011). Increasing resistance to fluopyram and penthiopyrad was observed. However, cross‐resistance was only observed between boscalid and penthiopyrad. The target site of this fungicide class is the succinate dehydrogenase (SDH) enzyme complex, which is vital for fungal respiration. Sequence analysis of the SDH complex revealed mutations in the subunits B and D that were correlated with the emergence of boscalid resistance in potato fields in Idaho. In particular, H277R and H133R were identified in SDH subunits B and D, respectively. The presence of restriction sites in the gene sequences allowed the development of a rapid PCR‐RFLP method to assess boscalid sensitivity in A. solani populations.  相似文献   

14.
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  相似文献   

15.
Twenty-eight Pyricularia isolates from two wild foxtails—green foxtail (Setaria viridis) and giant foxtail (S. faberii)—in Japan were taxonomically characterized by DNA analyses, mating tests, and pathogenicity assays. Although most of the isolates failed to produce perithecia in mating tests with Magnaporthe oryzae, a diagnostic polymerase chain reaction-restriction fragment length polymorphism phenotype of M. oryzae was detected in the beta-tubulin genomic region in all isolates. The pathogenicity assays revealed that host ranges of the isolates were similar to those of isolates from foxtail millet (S. italica), which were exclusively pathogenic on foxtail millet. In addition to the 28 isolates from wild foxtails, 22 Pyricularia isolates from 11 other grasses were analyzed by RFLP using single-copy sequences as probes. In a dendrogram constructed from the RFLP data, isolates that were previously identified as M. oryzae formed a single cluster. All the wild foxtail isolates formed a subcluster with foxtail millet isolates within the M. oryzae cluster. From these results, we conclude that Pyricularia isolates from the wild foxtails are closely related to isolates from foxtail millet and should be classified into the Setaria pathotype of M. oryzae.  相似文献   

16.
To investigate the role of environmental conditions on the selection of virulent Potato virus Y (PVY) isolates subject to pressure from the recessive resistance gene va in tobacco, a field survey was performed in Brazil where va‐derived genotypes have been recently introduced and now represent less than one‐third of cultivated tobacco genotypes. A serological analysis of 397 leaves collected from different Brazilian tobacco‐growing areas and mainly from plants with symptoms indicated that 52·4% of samples were infected by at least one of the viral species tested. PVY was present in 72·1% of infected samples. The probability of a plant being infected with PVY was reduced in va hosts. However, the biological characterization of PVY isolates on indicator hosts showed that 20 of the 29 tested isolates were able to overcome the alleles of the va gene. Moreover, the observed biological diversity of isolates was higher in susceptible tobacco genotypes than in va‐resistant ones. Comparison of these data with the PVY diversity in French tobacco fields shows that the use of va‐derived genotypes in two environments with contrasting climatic conditions, local hosts and cultural contexts, leads to a similar outcome: the prevalence of virulent isolates. These results strongly suggest an important role of the va gene in the modification of PVY populations.  相似文献   

17.
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   

18.
Downy blight, caused by Peronophythora litchii, is an important disease of lychee (litchi) plants in China. The in vitro sensitivities of various asexual stages of P. litchii to the three carboxylic acid amide (CAA) fungicides dimethomorph, flumorph and pyrimorph were studied with four single‐sporangium isolates. None of the three fungicides affected zoospore discharge from sporangia, but they strongly inhibited mycelial growth (mean EC50 values of 0·075, 0·258 and 0·115 mg L?1, respectively); sporangial production (mean EC50 values of 0·085, 0·315 and 0·150 mg L?1, respectively); germination of cystospores (mean EC50 values of 0·140, 0·150 and 0·645 mg L?1, respectively); and germination of sporangia (mean EC50 values of 0·203, 0·5 and 0·743 mg L?1, respectively). As mycelial growth was the most sensitive stage to dimethomorph and pyrimorph, it was chosen to test baseline sensitivities to the three fungicides. In 2007, from 131 isolates collected in Fujian, Guangdong and Guangxi provinces, 127, 116 and 113 isolates were used to establish baseline sensitivity for dimethomorph, flumorph and pyrimorph respectively. Isolates from different provinces exhibited similar baseline sensitivity to the same fungicide. Baseline sensitivities to dimethomorph, flumorph and pyrimorph were distributed as unimodal curves, with mean EC50 values of 0·082 (± 0·01), 0·282 (± 0·047), and 0·115 (± 0·032) mg L?1, respectively. This information will serve as a baseline for tracking future changes in sensitivities of P. litchii populations to these three CAA fungicides.  相似文献   

19.
Previously, we cloned a putative osmosensing histidine kinase gene (BcOS1) and revealed that a single amino acid substitution, isoleucine to serine at codon 365, conferred dicarboximide resistance in field isolates of Botrytis cinerea. This point mutation (type I) occurred within the restriction enzyme TaqI site of the wild-type BcOS1 gene. Thus, a procedure was developed for detecting the type I mutation of the BcOS1 gene using a polymerase chain reaction (PCR) in combination with restriction fragment-length polymorphism (RFLP). Diagnosis by PCR-RFLP was conducted on the 105 isolates isolated from 26 fields in Japan. All dicarboximide-sensitive isolates (49 isolates) had the wild-type BcOS1 gene, and the 43 isolates with the type I mutation were resistant to dicarboximides without exception. These data indicate that dicarboximide-resistant isolates with type I mutation are widespread throughout Japan. However, other types of dicarboximide resistance were detected among isolates from Osaka; among the 24 resistant isolates from Osaka, 12 had the BcOS1 gene without the type I mutation. BcOS1 gene sequencing of these resistant isolates classified them into two groups, type II and type III. The type II isolates have three amino acid substitutions within BcOS1p (368Val to Phe, 369Gln to His, and 447Thr to Ser). The type III isolates have two amino acid substitutions within BcOS1p (369Gln to Pro and 373Asn to Ser). These amino acid changes are located on the amino acid repeat domain in BcOS1p. The three types of resistant isolates were all moderately resistant to dicarboximides without significant osmotic sensitivity, and their pathogenicity on cucumber leaves was also very similar to that of the wild-type isolate.  相似文献   

20.
Isolates of Pyrenochaeta lycopersici, the causal agent of corky root rot on tomato plants, were assessed for physiological and genetic characteristics using conventional and molecular techniques. All isolates were able to produce necrosis on tomato roots and classified into temperature group according to the optimal growth temperatures. Specific-PCR assays and DNA sequence analysis of the ribosomal DNA (rDNA) internal transcribed spacer region confirmed the existence of both types (Type 1 and Type 2) of the pathogen among the isolates tested. All isolates were identified as Type 2 except for isolate Pl-4, which was classified as Type 1. Restriction fragment length polymorphism (RFLP) analysis with six enzymes resulted in three distinct banding patterns among the isolates depending on the length and restriction profiles of the rDNA intergenic spacer region. Inter-simple sequence-repeat analysis revealed a high level of genetic diversity among the isolates in agreement with the data of RFLP analysis. These results indicated that there were three different intraspecific groups among Turkish isolates of P. lycopersici. The presented study is the first attempting to characterize Turkish isolates of P. lycopersici. The results obtained will be useful in screening of tomato seedlings for resistance to P. lycopersici.  相似文献   

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