A Model for Infestation Foci of Potato Cyst Nematodes Globodera rostochiensis and G. pallida

ABSTRACT Infestation foci of potato cyst nematodes (Globodera rostochiensis and G. pallida) in the provinces of Zeeland, Friesland, Groningen, and Drente of the Netherlands were sampled to validate a model describing infestation foci based on data from Flevoland. Eighty-two fields were presampled to locate infestation foci using a coarse sampling grid (8 x 3 m). Parts of 37 fields containing one or more foci were sampled intensively by extracting at least 1.5 kg of soil per square meter (1.33 x 0.75 m). Forty foci were analyzed for spatial distribution characteristics of cysts using multiple regression with generalized linear models and classical linear models. The results showed that the data from all investigated cropping areas fit well to an exponential model with two parameters, the length and width gradient parameters. Significant differences in these parameter values between cropping areas could not be demonstrated. As both parameters follow a normal distribution, the probability of any combination can be described by a bivariate normal distribution. Gradient parameters were correlated, but significant correlations between these parameters and certain variables such as the nematode species involved, the time interval between sampling and the last potato crop, soil type, cropping frequency, and cyst density in the focus center could not be demonstrated.     

Development and Evaluation of Sampling Methods for Fields with Infestation Foci of Potato Cyst Nematodes (Globodera rostochiensis and G. pallida)

ABSTRACT A computer program, SAMPLE, was developed to evaluate existing and create new sampling methods for the detection of infestation foci of the potato cyst nematode (Globodera rostochiensis and G. pallida). By combining a model for the medium-scale distribution of cysts that provides the expected population densities at each position within the focus and a model for the small-scale distribution within square meters, sampling procedures can be simulated. The importance of the parameters of the two distribution models-the length and width gradient for the medium-scale distribution and the aggregation factor k of the negative binomial distribution for the small-scale distribution-was investigated by sensitivity analysis. Parameter k proved to be less important when calculating the average detection probability of a focus than were the length and width gradient parameters. Several existing versions of the statutory sampling method used in the Netherlands were tested for their performance on a standard infestation focus with a central population density of 50 cysts per kg of soil, which is small enough to use resistant potato cultivars as a control measure without noticeable yield reductions in a 1:3 year cropping frequency with potato. These methods did not perform with the desired average detection probability, set at 90%; therefore, SAMPLE was used to develop several new sampling methods for focus detection. SAMPLE is a tool to develop sampling methods on demand for every possible combination of characteristics required for use by seed and ware potato growers (recommendations for optimum control measures leading to maximum returns and integrated pest management) and by governments (legislation, quarantine, and export protection).     

A note on the chemical composition, intake and digestion of Striga hermonthica herbage by sheep

Striga hermonthica causes serious crop yield losses in West Africa. Hand pulling, an effective method for the reduction of light infestations, might be encouraged if farmers could use this weed as livestock feed. This study evaluated the chemical composition and the voluntary intake and digestion of S. hermonthica herbage by sheep. Crude protein (g kg⁻¹ dry matter (d.m.)) was 184 in the whole plant, 230 in the leaf and 87 in the stem. Ash content varied from 183 to 253 g kg d.m.⁻¹. The concentration of neutral and acid detergent fibre and lignin in whole pot-grown plants was 364, 278 and 127 g kg d.m.⁻¹ respectively. The digestibility of dry and organic (o.m.) matter was 493 and 657 g kg⁻¹, respectively, and intake of digestible o.m. was 27.1 g kg W^−0.75. The relatively high N and P levels in S. hermonthica warrant further evaluation in terms of its potential use as a source of protein or for compost. Its use as a feed appears to be limited by the high ash content and possibly by anti-nutritional effects on animals. These effects should be further investigated before recommending its use for this purpose.     

Effect of sample size on cyst recovery by flotation methods: Recommendations for sample processing during EU monitoring of potato cyst nematodes (Globodera spp.)

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.     

Occurrence of Globodera pallida in Hungary

Golden potato cyst nematode, Globodera rostochiensis , has been known to occur in Hungarian potato fields for more than 20 years. The Hungarian NPPO has been carrying out a country-wide Globodera monitoring programme since 1995 and has inspected 16 000 samples. Until 2000, all records were of G. rostochiensis . However, in 2001, three localities in Pest county were found to be infested with Globodera pallida . This was the first official record of G. pallida in Hungary. The two species have been found together in five fields. Unmixed populations of G. pallida have not been found. Identification was based on morphometric data, as well as on biochemical methods (ELISA technique).     

Comparison of sulfonylurea herbicide residue detection in soil by bioassay, enzyme-linked immunosorbent assay and hplc

The ability of bioassay, enzyme-linked immunosorbent assay (ELISA) and high-performance liquid chromatography (hplc) methods to detect sulfonylurea herbicides in soil was evaluated as part of a project studying the leaching and persistence of these herbicides in the alkaline soils of south-eastern Australia. Soil samples with known concentrations between 0.1 and 10 μg a.i. kg⁻¹ chlorsulfuron, metsulfuron-methyl or triasulfuron were prepared by an independent laboratory and supplied in coded bags to separate laboratories for testing. The accuracy of the results was analysed, and the merits of each method are discussed. Bioassay was suitable for measuring biologically active residues from 0.1 to 1.0 μg a.i. kg⁻¹. ELISA accurately measured residues in the range of 0.1–10 μg a.i. kg⁻¹, making it the most widely adaptable assay tested. It will be useful for measuring residues in sodic subsoils where bioassay plants grow poorly. There was good reproducibility between the bioassay and ELISA. The hplc technique used in this study was not as accurate as bioassay or ELISA at quantifying residues of 3.0–10 μg a.i. kg⁻¹ and could not detect residues at or below 1.0 μg a.i. kg⁻¹.     

PM 7/40(2): Globodera rostochiensis and Globodera pallida

Specific scope

This standard describes a diagnostic protocol for Globodera rostochiensis and Globodera pallida ¹ 1 Use of brand names of chemicals or equipment in these EPPO Standards implies no approval of them to the exclusion of others that may also be suitable.
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Specific approval and amendment

This Standard was developed under the EU DIAGPRO Project (SMT 4‐CT98‐2252) by partnership of contractor laboratories and intercomparison laboratories in European countries. Approved as an EPPO Standard in 2003–09. Revision approved in 2009–09.

     

Seed-potato production of cultivars resistant to Globodera rostochiensis in Poland1

Changes in the production of Polish seed potatoes of cultivars that are resistant to potato cyst nematodes have been followed. Over the period from 1972 to 1998, 35 cultivars resistant to Globodera rostochiensis (pathotype RO₁) were introduced. Among them, one (Drop) was also resistant to Globodera pallida (PA₃) and a number had multiple resistance to diseases and nematodes. Planting of seed potatoes of these resistant cultivars concerned only 0.4% of the total potato area. Against a background of much reduced seed-potato production, the area planted with resistant cultivars fell by 47% over the years 1989/1997). However, the share of resistant cultivars in the total seed-potato area increased from 16% in 1989 to 47% in 1997, the most important cultivars being Lawina, Orlik, Ibis and Irga. In 1992/1993, resistant cultivars occupied only 6–8% of the total potato area.     

Effects of sanitation processes on survival of Synchytrium endobioticum and Globodera rostochiensis

The two quarantine pests Synchytrium endobioticum, the causal agent of potato wart disease and Globodera rostochiensis, the yellow potato cyst nematode are currently present in Germany. Winter sporangia of Synchytrium endobioticum and cysts of Globodera rostochiensis can be spread with waste from potato processing industries, if infected tubers are processed. The German Biowaste Ordinance prescribes sanitation of organic waste before it can be used on arable land as fertilizer or filling material. Sanitation parameters prescribed by the German Biowaste Ordinance include composting for 7 days at 65°C or 14 days at 55°C or pasteurisation for 60 min at 70°C. The effect of composting and pasteurisation processes on winter sporangia of Synchytrium endobioticum and cysts of Globodera rostochiensis was tested with varying time-temperature relations. Cysts of Globodera rostochiensis were killed by composting for 7 days at 50–55°C and by pasteurisation for 30 min at 70°C. In contrast, viable winter sporangia of Synchytrium endobioticum could be extracted from sample material after composting for 70 days at 30–45°C, composting for 21 days at 50–55°C and after composting for 12 days at 60–65°C. Likewise viable winter sporangia could be extracted after pasteurisation for 90 min at 70°C and heating in a water bath at 80°C and in a dry oven at 90°C for 8 h. The parameters prescribed in the German Biowaste Ordinance are sufficient to kill cysts of Globodera rostochiensis but not sufficient to kill winter sporangia of Synchytrium endobioticum in organic waste.     

Influence of light-enhanced glycoalkaloids on resistance of potato tubers to Fusarium sulphureum and Fusarium solani var. coeruleum

Increases in resistance to Fusarium sulphureum and Fusartium solani var. coeruleum were determined in seed tubers of cultivars Desiree, Pentland Hawk and Kerr's Pink with light-enhanced glycoalkaloids. Glycoalkaloid concentration in the tubers ranged from 78.0 to 885.9 mg kg⁻¹ fresh weight. Exposure of tubers to light prior to inoculation decreased fungal invasion, the greater reductions generally reflecting longer light exposure periods. In most cases, no direct relationship between resistance and glycoalkaloid concentrations was recorded for F . sulphureum. Surface infection indices and reduced depth of rot caused by F. solani var. coeruleum were closely correlated with tuber glycoalkaloid content. No significant effects on spore length and width were recorded. Exposure to light of seed tubers that are not destined for human or animal consumption could provide a pretreatment to reduce fungal invasion by F. sulphureum and F. solani var. coeruleum .     

PM 7/40 (4) Globodera rostochiensis and Globodera pallida

Specific scope

This Standard describes a diagnostic protocol for Globodera rostochiensis and Globodera pallida. 1 Terms used are those in the EPPO Pictorial Glossary of Morphological Terms in Nematology. 2 This Standard should be used in conjunction with PM 7/76 Use of EPPO diagnostic protocols.

Specific approval and amendment

Approved as an EPPO Standard in 2003‐09. Revisions approved in 2009‐09, 2012‐09 and 2017‐02.     

实时荧光PCR检测马铃薯白线虫技术研究

马铃薯胞囊线虫是马铃薯上最重要的有害生物之一,也是我国特别关注的重要植物检疫性线虫.针对马铃薯白线虫ITS序列,我们设计了引物和TaqMan探针,使用15种马铃薯胞囊线虫群体和4种其它胞囊线虫样品进行验证,可高度灵敏地检测单个马铃薯白线虫的胞囊或幼虫,最高检测灵敏度达到10fs;同时开展了混合样品和未知样品的检测,证明了引物的专化性和TaqMan探针特异性.该检测方法可自动化检测马铃薯白线虫并进行定量,适合进行标准化的常规检测.     

Field performance of potato cultivars resistant and partially resistant to Globodera pallida1

Results of field trials of cultivars resistant or partially resistant to Globodera pallida are reported. The effects of the varying resistance levels on the nematode populations were examined. The initial population levels had an important effect on the Pf/Pi ratio. The ranking of the cultivars using the field Pf/Pi values consistently agreed with the resistance ranking obtained using the closed canister method of assessment. Many of the partially resistant cultivars effectively limited the level of increase of the final cyst-nematode population, if not decreasing the levels from their initial values. It is argued that such partial resistance can contribute positively to the control of potato cyst nematodes within the context of a crop rotation.     

警惕检疫性有害生物马铃薯孢囊线虫(Globodera rostochiensis和G. pallida)入侵我国

马铃薯孢囊线虫包括马铃薯金线虫Globodera rostochiensis和马铃薯白线虫G. pallida, 是马铃薯生产上危害最为严重的植物寄生线虫, 一般造成30%的产量损失, 在热带发病严重地区, 产量损失高达80%~90%, 甚至绝收?由于其危害严重性, 包括我国在内的100多个国家将其列为重要检疫性有害生物?我国目前尚无马铃薯金线虫和白线虫的发生报道, 但随着贸易全球化, 马铃薯孢囊线虫传入我国的风险日趋增高?本文主要对马铃薯孢囊线虫的发生分布?危害症状?经济损失?生物学特性?传入我国的潜在风险和预防控制措施进行综述, 旨在为防止马铃薯孢囊线虫入侵我国提供参考?     

Morphological and molecular characterization of Globodera populations from Oregon and Idaho

An unusual population of cyst nematode was found in soils collected from a Powell Butte, OR field with a cropping history including potato, wheat, other crops, and significant weed presence. These nematodes could not be placed with certainty into any known species and exhibited some unique morphological features in some specimens. Compared with Globodera pallida, the cyst body length was slightly longer and the second-stage juvenile stylet length was slightly shorter. In some individuals, the J2 stylet knob height was greater and the tail annules were more prominent than in G. pallida, and the tail abruptly narrowed, with a slight constriction near the posterior third of the hyaline terminus. Compared with G. rostochiensis, the hyaline tail terminus had a larger number of refractive bodies, and cysts of this population had a smaller Granek's ratio and fewer cuticular ridges between the anus and vulva. In some individuals, the tail termini of second-stage juveniles were more bluntly pointed, and the stylet knobs were more anteriorly directed with greater height. Unlike G. tabacum, the cyst wall often lacked a network-like pattern and, in some individuals, the juvenile tail terminus distinctly narrowed after a constriction. Molecularly, the population was distinct from G. pallida, G. rostochiensis, and G. tabacum. Multiplex polymerase chain reaction of the internal transcribed spacer (ITS) rDNA region gave results similar to G. tabacum; however, ITS restriction fragment length polymorphism patterns were observed to have individual bands in common with G. rostochiensis and G. pallida. Phylogenetic analysis based on ITS1 and -2 rDNA sequences showed greatest similarity to populations from Argentina and Chile; together, they form a moderately supported clade, distinct from G. rostochiensis, G. tabacum, G. "mexicana," European type G. pallida, and several G. pallida populations from South America.     

Influence of straw management, nitrogen fertilization and dosage rates on the dissipation of five sulfonylureas in soil

The dissipation behaviour of metsulfuron-methyl, tribenuron-methyl, thifensulfuron-methyl, triasulfuron and amidosulfuron were studied in soil following post-emergence spring applications to cereal crops. Incorporation or removal of straw and different fertilizer applications had no influence on the disappearance time (DT₅₀) of the herbicides. However, in laboratory trials dissipation of metsulfuron-methyl, triasulfuron and amidosulfuron at higher application rates was accelerated after incorporation of straw into the soil. The addition of straw decreases soil pH thereby causing faster hydrolysis of the compounds. Addition of nitrogen fertilizer increased the half-lives (t_1/2) of the herbicides. Combination of both straw and N fertilizer, however, had no effect. Neither straw nor N influenced the degradation of tribenuron-methyl and thifensulfuron-methyl.
The DT₅₀ of all herbicides investigated varied from 6 to 17 days in the field trials. Except for amidosulfuron, herbicides could not be detected 38–68 days after application. In the laboratory, t_1/2 values were higher than those in the field at 75 days (amidosulfuron), 63 days (metsulfuron-methyl), 35 days (triasulfuron) and 13 days (tribenuron-methyl). Only the t_1/2 of thifensulfuron-methyl was at 29 h faster under laboratory conditions. T_1/2 values of all herbicides were influenced by their initial concentration. The t_1/2 values of amidosulfuron and tribenuron-methyl at 1 mg a.i. kg⁻¹ soil were 2–2.5 times higher than at the recommended field application rate of 42 μg a.i. kg⁻¹ soil.     

应用TaqMan探针进行马铃薯金线虫实时荧光PCR检测技术研究

马铃薯孢囊线虫是全球性的植物检疫性线虫,亦是我国重点关注的有害生物。针对马铃薯金线虫ITS序列,设计了引物和TaqMan 探针,使用15个马铃薯孢囊线虫群体和4个其他孢囊线虫样品进行验证,可高度灵敏地检测单个马铃薯金线虫的孢囊或幼虫,并可进行定量;最高检测灵敏度达到10fg;同时开展了混合样品和未知样品的检测,证明了引物的专化性和TaqMan探针的特异性。该检测方法可自动化检测马铃薯金线虫并进行定量,适合进行标准化的常规检测。     

Foliar calcium concentration of potato and its relation to genotype lateness and tolerance of cyst nematodes

In field trials during three years respectively 18, 22 and 57 potato genotypes were grown on soils moderately or heavily infested with potato cyst nematodes (Globodera pallida) after soils were fumigated or not. Nematode infection increased leaf calcium contents but genotypes that were relatively tolerant of potato cyst nematodes (Globodera pallida) had lower leaf calcium concentrations on a particular sampling date. Tolerance of potato cyst nematodes was closely linked to genotype lateness and may be related to tolerance of drought. When using the method in plant breeding and screening for genotypes with tolerance, plants may be planted in infected or in uninfected soils, without influencing the outcome. The relationship between tolerance and calcium contents was clearest when sampling took place towards the end of the growing season when the variability was at it highest with a good distinction between newly formed leaves in late maturing genotypes and aged leaves in early maturing cultivars.     

Molecular characterization of a morphologically unusual potato cyst nematode*

During routine screening of soil samples for potato cyst nematodes, a morphologically variant cyst was detected. The internal transcribed spacer regions of the ribosomal DNA repeat unit from individual juveniles hatched from the cyst were amplified by PCR. The resulting products were digested with a range of restriction enzymes and their RFLP profiles compared with standard samples of Globodera rostochiensis and Globodera pallida . Most of the RFLP profiles yielded patterns similar to those of G. pallida although some restriction enzymes gave hybrid patterns showing elements of both G. rostochiensis and G. pallida . Clones of individual ITS regions from a single nematode from the variant cyst displayed either a G. pallida or G. rostochiensis pattern.     

Appropriateness of inexpensive, hand-held global positioning system units for creating weed maps in a pasture

This paper describes the practical use of a global positioning system receiver (hand-held GPS) as a means of measuring and describing pasture areas invaded by weeds. The accuracy of two GPS units, a hand-held GPS with an external antenna (GPS with an antenna) and the differential global positioning system receiver (DGPS), were examined in Morioka, northern Japan. In addition, an area of weed patches and a pasture, determined using the GPS with an antenna, were compared to the measurements made with a conventional tape and a weed map was created based on the coordinate data of latitude and longitude measurements. The accuracy of the GPS with an antenna was poor (8.3 m); however, the precision of the unit was reasonable in measuring area. An area estimation error by the GPS with an antenna was 7% when practically measuring weed patches of 141 m² and 1% in a paddock of 12 566 m². From these results, it appears that the GPS with an antenna might have an acceptable error in measuring areas for weed control in a pasture. A weed map produced from the coordinate data surveyed using the GPS with an antenna enables the state of weed growth and its domination in an area of pasture to be visually understood. Therefore, GPS technologies easily can be applied to quickly obtain information on weed infestation.