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1.
Under EC Council Directive 2007/33/EC member states of the European Union are recommended to take soil samples ranging from 100 mL to >1500 mL to monitor populations of potato cyst nematodes [PCN] ( Globodera spp.) in targeted fields. This study examines the effects of varying sample size on sample processing and cyst extraction using two widely used laboratory methods. Cyst recovery was stable using the Fenwick can from 100 mL up to the physical limits of the can. Recovery was significantly lower for low density 50 mL samples; however, this was partly due to a statistical artefact since higher numbers of cysts were lost from successively larger samples with constant cyst numbers (i.e. decreasing densities). The Schuiling centrifuge had functional limits of <100 mL and >500 mL. Outside this range, cyst recovery from low density samples was significantly reduced. Cyst recovery from samples of varying size, but with equal numbers of cysts was only constant above 100 mL. However, samples ranging from 200–500 mL were optimal for the Schuiling centrifuge. Cyst extraction efficiency was similar using both methods for samples ranging from 150 mL to 1500 mL, where larger samples were divided into <500 mL portions. However, processing times (i.e. cyst extraction and microscopic examination) and water consumption increased significantly with increasing sample size and were significantly higher when using the Fenwick can.  相似文献   

2.
An evaluation of the efficacy of the Schuiling centrifuge and traditional Fenwick can methods of extracting Globodera cysts from infested field soils confirmed the accuracy of the Schuiling centrifuge extraction method. Experience has shown that samples with a high organic matter content may reduce extraction efficiency. Improvements in the mechanical and electrical construction of the present Schuiling apparatus are needed, but once they have been made the choice of extraction method in large-scale statutory and advisory programmes need only depend on considerations such as convenience of use and cost-effectiveness.  相似文献   

3.
ABSTRACT The dynamics of Heterodera glycines spatial patterns were studied under different tillage systems in two naturally infested soybean fields in Iowa from 1994 to 1997. At each location, there were four different tillage treatments (conventional tillage, reduced tillage, ridge tillage, and no tillage). Soil samples were taken from 98 contiguous quadrats (5.2 m(2)) per plot in the fall of 1994, before any tillage was performed, and in the spring of the following 3 years shortly after planting. Cysts were extracted from soil samples by elutriation and counted, and eggs were extracted from cysts and enumerated. Spatial patterns of H. glycines populations were characterized by geostatistical analysis and variance-to-mean (VM) ratios. Semivariance values were calculated for cyst and egg densities and semivariograms were constructed. In general, there was greater spatial dependence among cyst populations than egg populations. In one field with a strongly aggregated initial H. glycines population, tillage practices resulted in changes in spatial patterns of H. glycines populations, characterized by spherical-model semivariogram parameters (sill, nugget effect, and range of spatial dependence). These parameters indicated increasing aggregation over time in no tillage and ridge tillage treatments, but decreasing aggregation in reduced and conventional tillage treatments. There was an increase of 350% in sill values (maximum semivariance) for cyst populations after 3 years of no tillage, but in the conventional tillage treatment, sill values remained unchanged or decreased over time as tillage was implemented. Semivariograms for cyst and egg population densities revealed strong anisotropy (directional spatial dependence) along soybean rows, coincident with the direction of tillage practices. VM ratios for cyst counts increased each year in the no tillage and ridge tillage treatments, but decreased for 2 years in reduced tillage and conventional tillage treatments. Final VM ratios for cyst and egg counts were highest in the no tillage treatment. In a second field, with low initial aggregation of H. glycines populations, there was little measurable change in semivariogram parameters after 3 years of no tillage, but in the conventional tillage treatment, populations became less aggregated, as the range, sill, and the proportion of the sill explained by spatial dependence decreased for cyst population densities. Our results indicated that in soybean fields with initially aggregated populations of H. glycines, no tillage and ridge tillage systems promoted aggregation of the nematode population, whereas conventional and reduced tillage systems resulted in a less aggregated spatial pattern.  相似文献   

4.
A method for the extraction of oospores of Peronospora viciae from soil is described. Approximately 75% of the oospores added to silty clay loam and loamy sand soil samples were recovered. Percentage recovery was independent of oospore density. This extraction method did not affect viability as determined by the tetrazolium bromide test and a germination assay and may therefore be used to study survival of oospores. Numbers of oospores extracted from soil samples taken from seven fields naturally infested with oospores of P. viciae f.sp. pisi ranged from 2 to 21 oospores per g soil. Oospore density was not significantly correlated with disease incidence as determined by a bioassay.  相似文献   

5.
Production, survival and infectivity of oospores of Phytophthora infestans   总被引：1，自引：0，他引：1  
The formation of oospores of Phytophthora infestans was studied in tomato and potato crops and volunteer plants under field conditions, and in laboratory tests with leaf discs of potato cultivars differing in their level of race-nonspecific resistance. Oospores were readily detected in blight-affected tomato leaflets and fruits, and in leaflets of field crops and volunteer potato plants. Oospores extracted from blighted potato leaflets yielded 13 oospore-derived progeny. Oospores were also produced following inoculation of leaf discs of eight potato cultivars expressing different levels of race-nonspecific resistance with a mixture of sporangia of A1 and A2 isolates. The highest numbers of oospores were produced in cvs Bintje (susceptible) and Pimpernel (resistant), and the lowest in Nicola (intermediate resistance). The relationship between lesions per leaflet and oospore incidence, affected by varying A1 : A2 ratios, was explored using a simple mathematical model, and validated by comparing actual oospore production in leaflets with multiple lesions of the race-nonspecific-resistant potato clone Lan 22-21 with the predictions generated by the model. Survival of oospores was investigated after their incorporation in either a sandy or a light clay soil in buried clay pots exposed to the local weather conditions. Over 6 years these soils were regularly assessed for their infection potential using floating leaflets in a spore-baiting bioassay. Sandy and clay soils contaminated with oospores remained infectious for 48 and 34 months, respectively, when flooded. Infections of floating potato leaflets occurred within 84–92 h and ceased after 11 days. Soil samples remained infective if dried and re-flooded on two, but not more, occasions.  相似文献   

6.
为探究河南省主要禾谷类作物孢囊线虫的发生分布,明确孢囊线虫对不同作物的危害情况,于2017—2020年对河南省18个市50个县（区）的小麦、玉米和水稻作物的孢囊线虫种类和发生分布进行随机取样调查,采用形态学特征、分子生物学鉴定和rDNA-ITS序列进化树分析技术鉴定不同作物孢囊线虫的种类,并根据土壤中孢囊基数和单孢囊卵数明确不同作物孢囊线虫的发病严重度。结果显示,共采集土壤样品308份,其中224份样品检测到孢囊,孢囊检出率为72.7%。小麦孢囊线虫发生分布范围覆盖40个县（区）,其中15个县（区）为禾谷孢囊线虫Heterodera avenae侵染,23个县（区）为菲利普孢囊线虫H. filipjevi侵染,南阳市西峡县西坪镇和开封市尉氏县张市镇为禾谷孢囊线虫和菲利普孢囊线虫混合侵染发生区;玉米孢囊线虫H. zeae在濮阳市清丰县韩村镇、许昌市长葛市董村镇和禹州市范坡镇检测点首次被发现;旱稻孢囊线虫H. elachista在信阳市潢川县魏岗乡、来龙乡和新乡市获嘉县亢村镇检测点首次被发现。孢囊线虫发病严重度数据表明,小麦田平均孢囊含量高达17.3个/100 mL;玉米田平均孢囊量为11.0个/100 mL;水稻田平均孢囊量为4.4个/100 mL。表明河南省孢囊线虫高发地块主要集中在豫北、豫东和豫中平原区。  相似文献   

7.
Soils were collected from a potato-growing area in Serres, Northern Greece, where the nematicide ethoprophos was reported to have lost its effectiveness against cyst nematodes following 30 years of regular use. Incubation studies with ethoprophos and two bioassays using root-knot nematodes demonstrated that, in this heavily treated soil, the nematicide was degraded rapidly and nematicidal activity persisted only up to 14 days. In soil from an adjacent field with no known history of nematicide use during the preceding 14 years, ethoprophos was degraded more slowly and retained its nematicidal activity for more than 35 days. Ethoprophos efficacy was extended when the soil that had been treated in the field was autoclaved, although the effect was only transitory. The addition of ‘pre-conditioned’ soil from the previously treated field to samples of soil from the previously untreated field resulted in a significant acceleration of ethoprophos degradation compared with that observed in unamended soil from the previously untreated field. © 1999 Society of Chemical Industry  相似文献   

8.
为了解河南省小麦主产区菲利普孢囊线虫与禾谷孢囊线虫的发生情况,作者分别于2014年和2015年5月通过随机采样调查方法,从商丘、漯河、许昌、新乡、鹤壁、安阳、濮阳、焦作等八地区19个县市采集到61份小麦孢囊线虫(CCN)的根围土壤样品,分析了样品的孢囊密度,发现采自商丘、新乡、鹤壁、安阳和濮阳地区的样品孢囊密度普遍较高,CCN发生比较严重;利用双重PCR技术对样品的CCN种类进行了快速检测鉴定,检测出禾谷孢囊线虫单一侵染的样品有33份;菲利普孢囊线虫单一侵染的样品有9份,与禾谷孢囊线虫复合侵染的样品有19份。菲利普孢囊线虫主要采自商丘、漯河、许昌、新乡、焦作等五个地区,其中商丘地区发生比较普遍。该研究可为河南省小麦的品种布局和孢囊线虫的综合防治提供指导。  相似文献   

9.
 在山东省5个植烟县/市采集烟草线虫土壤样本24份,其中10份土样中分离到孢囊线虫的孢囊,对之进行系统的形态学观测。孢囊阴门锥突出,双半膜孔,下桥和泡囊发达,阴门裂长（44.1±3.5） μm,阴门窗长（50.4±4.8） μm、宽（36.6±4.1） μm,下桥长（83.8±4.7） μm、宽（11.0±0.9） μm。利用大豆孢囊线虫特异性引物对分离到的孢囊线虫群体进行了分子鉴定。形态学和分子鉴定结果表明,山东省寄生烟草的孢囊线虫为大豆孢囊线虫Heterodera glycines Ichinohe,1952。对这10个孢囊线虫群体rDNA-ITS区进行了PCR扩增产物用7种限制性内切酶进行酶切和测序比对。发现,所有孢囊线虫群体均能扩增出一条大约1 000 bp大小的片段;用Alu Ⅰ、Bsh 1236 Ⅰ、Hae Ⅲ、Hha Ⅰ 、Mva Ⅰ 、Rsa Ⅰ酶切后,产生的酶切表型均相同;用Ava I酶切后,产生了2种酶切表型。所测孢囊线虫群体与GenBank收录的大豆孢囊线虫序列相似度高达99%以上。  相似文献   

10.
为探索一种准确测定土壤根结线虫种群数量的方法,采用NaOCl消解附着在土壤病残体上的根结线虫卵囊与线虫常规离心技术相结合的方法,测试了不同NaOCl浓度、离心时间对根结线虫回收效率的影响,筛选出最佳测定条件,并与浅盘法、离心法、Byrd法等线虫常规分离方法进行了比较。结果表明,在9个NaOCl处理浓度中,1.0%~2.5%NaOCl处理对土壤根结线虫的回收效率显著高于3.0%NaOCl处理,达到71.6%~99.4%。在1.0%、1.5%、2.0%和2.5%NaOCl处理30 s后,分别离心2~5、2~3、2~3 min和2 min对根结线虫的回收效率明显高于其它时间处理,在每50 m L土壤平均接种976粒线虫卵的人工病土中,上述处理分离线虫数量分别达到804.3~930.0、810.7~838.7、843.7~867.0和820.7。本研究的改良方法对自然病土中根结线虫的分离数量分别是浅盘法、离心法和Byrd法的29.3、13.4和2.1倍,显著提高了土壤中根结线虫的分离效率,可准确测定土壤根结线虫种群的数量。  相似文献   

11.
ABSTRACT The ability of Dactylella oviparasitica and Fusarium oxysporum to suppress Heterodera schachtii numbers was examined in field microplots. Fungi were individually added to fumigated field soil that was seeded with sugar beet. Four weeks later, soils were infested with H. schachtii second-stage juveniles (J2). At two harvests, 11 weeks and 19 weeks (1,469 and 2,547 degree days (base 8 degrees C), respectively) after nematode-infestation, H. schachtii cyst and egg numbers were assessed. At both time points, D. oviparasitica reduced H. schachtii population densities to those in the naturally suppressive soil, even when additional H. schachtii J2 were added to the microplots after the first harvest. Although F. oxy-sporum did not alter H. schachtii population densities after 11 weeks, significant reductions were detected after 19 weeks. The sustainability of the H. schachtii suppressiveness created by single applications of the fungi at the beginning of the microplot trials was further examined in a greenhouse study. Soil collected at the completion of the microplot trials was potted and seeded with sugar beet. Four weeks later, each pot was infested with H. schachtii J2. Approximately 16 weeks (1,389 degree days) after seeding, the D. oviparasitica-amended soil produced greater fresh root weights and considerably smaller nematode population densities than the nonamended control.  相似文献   

12.
Beet cyst nematode-resistant cultivars, which were introduced recently, originated from the homozygous inbred line B883. This translocation product was unstable and the transmission of resistance when crossed with a susceptible cultivar did not exceed 94%. Tests with the resistant cultivars in climate cabinets showed a wide variety of resistance against Heterodera schachtii and beet necrotic yellow vein virus (BNYVV), expressed as average numbers of infective units per plant and percentages of resistant plants. In a series of field trials at different levels of infection of H. schachtii, their multiplication rates on all resistant cultivars depended on the initial density, which was caused by the presence of small numbers of susceptible plants. Since tolerance to wilting was also incorporated in B883, reasonable yields were obtained in the presence of H. schachtii. However, at increasing initial densities of H. schachtii, yields decreased considerably, since penetrating juveniles cause a hypersensitivity reaction in resistant plants. Based upon the results of three series of field trials, it was concluded that resistant cultivars should preferably be applied at population densities between 500 and 2000 eggs and juveniles of H. schachtii per 100ml of soil. Cultivars with double resistance against H. schachtii and BNYVV behaved like those with H. schachtii resistance in soils infected with beet cyst nematodes, but not with BNYVV. In soils with a combined infection of H. schachtii and BNYVV double resistant cultivars were far superior to single resistant ones, since damage caused by BNYVV was far more serious than damage caused by H. schachtii. No substantial interaction between soil pathogens nor types of resistance could be detected.  相似文献   

13.
An HPLC method has been developed to determine adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP) in eggs and juveniles ofHeterodera schachtii in cysts extracted from soils. ATP levels in eggs and juveniles were highly correlated with the numbers of hatched juveniles in root diffusate (r=+0.92) in series of soil samples originating from field trials testing different doses of fumigant nematicides. The measured ATP concentrations in the cysts explained 59% of the sugar-yield reduction on these fields, which was similar to the value based on the hatching test. After fumigation, carried out in a laboratory experiment, ATP and the adenylate energy charge, (AEC=ATP + 0.5 * ADP)/(ATP + ADP + AMP), decreased greatly within a few days. In a series of greenhouse trials in whichH. schachtii had been parasitized severely byVerticillium clamydosporium and other antagonists, there were significant correlations between the numbers of hatched juveniles and the ATP content of the cysts (r=+0.85), and between the percentages of hatched juveniles and the AEC (r=+0.75). The HPLC method is faster than conventional methods and can be used to establish the viability ofH. schachtii field populations affected by soil fumigation or egg pathogens.  相似文献   

14.
Residues of linuron and simazine were measured by both bioassay and gas-chromatographic methods in soil from field plots that had been treated either 20 weeks (both compounds). 41/2 years (linuron) or 51/2 years (simazine) previously. There were no significant differences between the results obtained with the two methods; therefore the relationship between extractable herbicide and that available to plants was independent of the age of the residue. Hence‘bound’residues, if they existed in these plots, had no phytocidal significance.  相似文献   

15.
BACKGROUND: Metsulfuron‐methyl is a low‐application‐rate sulfonylurea herbicide that is widely used to control broad‐leaved weeds in wheat. Owing to its persistent nature, its residues may be present at phytotoxic levels for the next crop in rotation. Therefore, a comparative evaluation of HPLC and bioassay techniques was made for the analysis of this herbicide in wheat field soil. RESULTS: Metsulfuron‐methyl was applied to wheat crop at different rates (4, 8 and 12 AI ha?1) at 28 days after sowing as a post‐emergence application, and the soil was analysed for metsulfuron‐methyl residues by HPLC and lentil seed bioassay techniques. The bioassay was found to be the more sensitive technique. At the recommended rate of application, 4 g AI ha?1, the bioassay technique could detect the residue up to 30 days in surface soil, while, with HPLC, residues were not detectable on the 15th day. The half‐lives of metsulfuron‐methyl by HPLC and bioassay were calculated as 6.3–7.8 and 17.5 days respectively. Under field conditions, residues of metsulfuron‐methyl were also detected in subsurface soil by the bioassay technique at trace levels, but were not detected by the solvent extraction/HPLC method. CONCLUSION: Lentil seed bioassay is a more sensitive technique than HPLC. Traces of residues detected in subsurface soil indicated the mobility of metsulfuron‐methyl into lower layers. Copyright © 2009 Society of Chemical Industry  相似文献   

16.
Increased crop yield of nematode resistant sugar beet varieties compared to non-resistant varieties is dependent upon density of the sugar beet nematode, Heterodera schachtii, being below a certain threshold level. Therefore there is a requirement for an inexpensive quantitative laboratory test for H. schachtii. Currently the standard method to determine nematode densities relies on extraction of cysts from soil samples and their subsequent enumeration which is time-consuming. The method described in this article involves the extraction of nematodes obtained by a technique inducing the hatching of juveniles. Hatching of larvae is induced by incubation of the soil sample with “Acetox” followed by a Baermann funnel extraction. Instead of a visual estimation of nematode densities using a microscope, H. schachtii larvae are identified by a molecular diagnostic. The aim of this study is to distinguish between the three threshold infestation levels by comparing the intensities of PCR products derived from samples containing known numbers of target H. schachtii.  相似文献   

17.
The sensitivity of a bioassay in detecting soil inoculum of Colletotrichum coccodes and Helminthosporium solani was examined using potato minitubers and microplants. Tests were conducted on soils which were collected from fields in which the interval after a previous potato crop differed, and which were also artificially infested with conidia or microsclerotia. For C. coccodes , determining plant infection based on the occurrence of infected roots after 9–12 weeks was a sensitive method for detecting and quantifying the amount of inoculum in soil. Infestations of less than 0·4 microsclerotia per g soil were detected in artificially infested soils. A semiselective medium, developed for isolating C. gloeosporioides from pepper, detected soil infestations by C. coccodes as low as nine conidia or one microsclerotium per g soil in artificially infested soil. For H. solani , infection on minitubers was a sensitive measure, with soil inoculum of fewer than 10 conidia per g soil being detected. Soil infestation could be quantified by assessing the percentage surface area of minitubers covered by sporulating lesions, which was strongly related to the amount of soil infestation. The results of these bioassay tests were compared with published results for real-time quantitative PCR assays on the same soils. The two methods were in good agreement in artificially infested soils, but the bioassay appeared to be more sensitive with naturally infested soils.  相似文献   

18.
A real-time PCR assay specific for Sclerotium cepivorum, the causal agent of white rot in onions, was developed for use with a new DNA extraction method capable of processing up to 1?kg of soil in weight. The assay was specific for S. cepivorum when tested against 24 isolates representative of 14 closely related species and other pathogens of onion. The assay was highly sensitive when used with soil DNA extracted using the new DNA extraction procedure. In three different field soils tested, a good relationship between cycle threshold (Ct) and number of sclerotia was observed (R2?=?0.89). Twenty-nine soil samples from onion and leek crops were obtained and the pathogen was detected in four samples. All four positive samples were associated with current or past outbreaks of white rot of onion. Additional assays were also used on the 29 field soil samples, Botrytis aclada and Rhizoctonia solani AG8 were also detected, in one soil sample each. Rhizoctonia solani AG2-1 was more widespread and was detected in eight different soil samples. The method is therefore suitable to quantify levels of S. cepivorum in soil samples, with the added advantage that the technique allows other soil pathogens of interest to be assayed from the same DNA sample. The bulk soil DNA extraction method described here has the potential to be used to detect soil-borne pests and pathogens for other crops in a wide range of soil types.  相似文献   

19.
A rapid glasshouse‐based bioassay method to screen large numbers of cotton plants for responses to Fusarium oxysporum f. sp. vasinfectum (Fov) was developed. Different Fov inoculum concentrations and methods of inoculation were assessed using resistant and susceptible cotton cultivars. Cotton seeds were planted directly into Fov‐inoculated soil. Studies of seed germination, seedling establishment, seedling mortality and fusarium wilt symptoms (i.e. stunting, foliar symptoms and vascular browning) were performed to optimize the bioassay parameters. Growing seedlings in Fov‐inoculated soils at 5 × 104 or 1 × 105 CFU g?1 soil, in individual seedling tubes with 12 h at 28–30°C and 12 h at 15–18°C, gave consistent results when assessing Fov disease responses 6 weeks after inoculation. When fusarium wilt resistance ranks (FWRRs) and vascular browning index (VBI) means of 18 Australian and other cotton cultivars from the Fov glasshouse bioassay were compared against their fusarium field performance ranks (F‐ranks), assessed on adult plants for cotton cultivar release, Pearson’s correlation was highly significant for both comparisons. The level of congruence between field and glasshouse data indicated that this protocol should be an effective tool for large‐scale screening for Fov‐resistance responses in diverse germplasm and breeding populations and for advancing genetic research to develop molecular markers for Fov resistance in cotton.  相似文献   

20.
采用乙腈提取、固相萃取净化和高效液相色谱法,分析测定了啶虫脒在露地和大棚2种种植条件下黄瓜和土壤中的残留及消解动态。结果表明:9%啶虫脒可湿性粉剂同时在露地和大棚中按有效成分30.375 g/hm2剂量(推荐高剂量的1.5倍)施药1次,啶虫脒在露地和大棚黄瓜及其土壤中的原始沉积量分别为0.20、0.13 mg/kg和0.29、0.14 mg/kg,露地黄瓜和土壤中的原始沉积量均分别低于大棚;相应地,啶虫脒在黄瓜和土壤中的半衰期分别为9.7、9.4 d(露地)和10.1、11.9 d(大棚)。9%啶虫脒可湿性粉剂同时在露地和大棚中按有效成分20.25 g/hm2和30.375 g/hm2的剂量施药1次和2次,在相同施药剂量、施药次数和采收间隔期情况下,除个别情况外,露地黄瓜中啶虫脒的最终残留量均低于大棚,分别为0.01~0.05 mg/kg(露地)和0.01~0.09 mg/kg(大棚)。  相似文献   

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