An Integrated Approach in the Control of Potato Root Eelworm

During the last decade, new control possibilities for the potato root eelworm have come to the fore, namely resistant potato varieties and soil disinfection. These have led to an integrated approach to the control of the potato root eelworm in the Netherlands. For this purpose, a number of potato rotations, aiming at the prevention or elimination of non-detectable populations of the potato root eelworm, are prescribed for non-infested fields. These regulations allow the farmer to grow potatoes more frequently on non-infested soils if he uses control measures (i.e. resistant potato varieties, soil disinfection). More stringent restrictions are in force for infested fields on which the growing of susceptible crops and propagation material is, of course, prohibited.     

Crop Rotation and Soil Pathogens — Trends in Germany

The need to cut costs has led to a simplification of crop rotation in several fields of plant cultivation. The results of Thormann, who has grown wheat continuously on parts of his farmland for 10 years, are discussed. Also, the preliminary results of our own experiments with increasing proportions of wheat and barley suggest that more wheat and barley may be cultivated in crop rotation than is allowed according to the conventional limits determined by the increase of foot rot diseases and cereal root eelworm. Even in successive crops of maize the problem of soil-borne pathogens can be tackled: the spread of blister smut is stopped by the control of the frit fly and by selection of tolerant varieties; root and stem rots of maize are overcome by the selection of appropriate varieties, too. On the contrary, the potato root eelworm is a serious pest in all sites of intensive potato production. Only an integrated control including the use of resistant varieties and the application of nematicides gives success. Much research work has to be done mainly to get more information on the biotical defence mechanisms of the soil.     

Een waarneming over het voorkomen van fysiologische rassen van het aardappel cystenaaltje,welke zich sterk kunnen vermeerderen in resistente nakomelingen vanSolanum tuberosum subsp.andigena

Ohne Zusammenfassung

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With a summary: A record of the existence of physiologic races of the potato root eelworm, which multiply vigorously in resistant progy, of Solanum tuberosum subsp. andigenum

     

Onderzoekingen over schimmels,die parasiteren op de cyste-inhoud van het aardappelcystenaaltje (Heterodera rostochiensis Wollenw.)

Ohne Zusammenfassung

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With a summary: Investigations on fungi, predacious on the cyst contents of the potato root eelworm (Heterodera rostochiensisWollenw.)

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Gedetacheerd door de Werkgroep Onderzoek Bestrijding Aardappelcystenaaltje T.N.O.; thans: Laboratorium voor Toegepaste Entomologie, Amsterdam.     

Distribution of Potato Cyst Eelworm in Scotland1

Although potato cyst eelworm has been known in Scotland for more than 60 years, infestations are fewer than might have been expected. In 22 years of soil testing, based on nominal 500 g samples and sampling units of up to 6 ha, 80% of the farms examined were found free from detectable infestation and 10%, i.e. half the infested farms, had one infestation only. Most populations were light; one third of all infested samples contained a single viable cyst and 80%, ten cysts or fewer. It is suggested that long rotations have kept eelworm populations in check over much of the country, but in some areas their effectiveness has been reduced by persistent groundkeepers. Surveys indicate that Heterodera pallida Stone is uncommon and so the progressive use of resistant varieties, which are proving popular with seed growers for their commercial qualities, coupled with the long rotations generally practised, may well tip the balance even more favourably towards increased control.     

Enkele waarnemingen over populatieschommelingen bij het havercystenaaltje,Heterodera avenae (= H. major) onder invloed van enige gewassen op zandgrond

Summary In the course of a survey of the occurrence of cereal root eelworm made in the province of Limburg in 1955, some observations were made on the population density of the nematodes before and after various crops, for although it was well known that non-host crops decreased the population, little information was available on the effect of different cereals and graminaceous crops on the eelworm numbers.In 54 fields of farms at IJsselstein (Limburg) the pre- and postcropping nematode population was estimated by examining samples of 200 ml of soil in March and November 1955. Each sample consisted of 60 rods well distributed over the field. The results are summarized in table 1. Oats is an efficient host plant, but rye, some grasses and leys decrease the eelworm population and these may therefore be considered to be suitable crops to precede oats on infested land. Some rotations are suggested which may be suitable for infested fields, and which may help to avoid damage to oats in Limburg province.     

The Plant Protection Service in the Netherlands

A survey is given of the history, the tasks and the organization of the Plant Protection Service in the Netherlands. Its activities encompass two major fields, concerning phytosanitary and phytopharmaceutical aspects. In the phytosanitary field, a distinction can be made between long-term and short-term phytosanitary policy, depending on whether one has to deal with existing and established pests or diseases, or with a suddenly arising plant health problem. Two examples are given as illustrations, viz. the approach followed in designing new regulations for controlling potato root eelworm, and the campaign against the recent outbreak of fireblight. A further outline is given on the activities of the Plant Protection Service in the pesticides field, on the responsibilities of the different Ministries concerned, and on the basic elements of pesticides legislation. The restrictions imposed on the use of persistent organochlorine insecticides and organomercury fungicides are summarized. Finally, it is emphasized that the problems of plant protection are becoming increasingly complex as a result of a developing antagonism between phytosanitary and phytopharmaceutical requirements, and of a potential antagonism between these two on the one hand and environmental demands on the other. This situation calls for an integrated approach in plant protection matters, and for an intensified international collaboration.     

The potential for the Rapid Screening of Potato Cultivars (Solanum tuberosum) for Resistance to Powdery Scab (Spongospora subterranea) using a Laboratory Bioassay

Powdery scab of potato, once established in a field, is difficult to control because of the longevity of the resting spores (cystosori) of the causal organism, Spongospora subterranea f.sp. subterranea. Host resistance is likely to be the most efficient in a long-term control strategy for preventing build-up of field inoculum and spread of the disease. Resistance screening of potato cultivars is mostly done in laborious field trials where disease development is likely to be unpredictable. A bioassay with potato tissue cultured plantlets and cystosori as inoculum is described and was tested for its potential to screen potato cultivars at an early stage for their relative susceptibility to powdery scab by comparing the lab results with field data. With cystosori inoculum of Swiss origin, the laboratory test showed clear differences between the potato cultivars in the severity of zoosporangial root infection which correlated better with ranked tuber infection data, compared to root galling. There are apparent differences in the relative trends in susceptibility between roots and tubers of five selected cultivars when using naturally infested soil instead of prepared cystosori as inoculum in the lab bioassay. Furthermore, differences in the severity of zoosporangial root infection of two selected cultivars were found when cystosori from different countries where used as inoculum. A possible host genotype × pathogen interaction is discussed. The bioassay has the potential to screen and select for resistant material at an early breeding stage thus making field trials not unnecessary but more economical. It will allow the use of a standard set of pathogen collections and facilitate testing for inoculum virulence in infested soils.     

保水剂施用方式对马铃薯产量和水分利用效率的影响

采用盆栽试验,比较深施、浅施、侧施、全施和不施(对照)等保水剂应用方法在充分供水和水分亏缺两种供水条件下,马铃薯(Solanum tuberosum L)生长、产量和水分利用效率(WUE)效应.结果表明,除浅施处理外其它方式施用保水剂处理都能促进马铃薯株高,水分胁迫下能促进马铃薯根系发育.在充分供水和水分胁迫下,深施保水剂使马铃薯产量较对照提高9.4%和16.6%,WUE提高12.82%和54.73%,侧施保水剂使马铃薯产量较对照提高39.4%和21.5%,WUE提高58.79%和59.46%;在水分胁迫下,全施保水剂使马铃薯产量和WUE较对照分别提高15.4%,56.76%.     

玉米和马铃薯根系分泌物对马铃薯生长的影响

通过溶液培养法获取供体玉米和马铃薯根系分泌物,用来浇灌盆栽受体马铃薯“会-2号”,设单株马铃薯浇玉米根系分泌物（P+M-RE）、单株马铃薯浇马铃薯根系分泌物（P+P-RE）和单株马铃薯浇自来水（CK）3个处理,研究玉米、马铃薯根系分泌物对盆栽马铃薯生长的影响。结果表明：（1）盛花期和成熟期,P+M-RE处理的块茎生物量比P+P-RE增加了42.4%和28.5%,比CK增加了28.8%和8.2%,P+P-R比CK减少了23.7%和28.4%,差异分别为显著和极显著;（2）分枝期、盛花期和成熟期与CK相比,P+M-RE处理地上和地下部分生物量分别提高了8.3%~12.7%和7.5%~45.6%,P+P-RE处理分别降低了1.7%~12.9%和5.5%~20.9%;两处理的茎叶比均比CK低,根冠比在盛花期和成熟期比CK提高了64.1%、42.5%和56.8%、40.0%;(3)观测期内,P+M-RE处理叶片、茎秆、根系和块茎的化感敏感指数RI>0,表现为促进作用,敏感程度为根系>叶>块茎>茎秆;P+P-RE处理根系RI<0,叶片、块茎在分枝期和盛花期RI>0,成熟期为RI<0,整体表现为抑制作用;（4）盛花期马铃薯干物质转移率(DMME)及贡献率（DMCR）P+M-RE处理比CK分别提高了45.6%和48.0%,P+P-RE处理比CK分别提高了30.7%和43.9%。由此说明,玉米根系分泌物对马铃薯地上茎叶和地下根系及块茎生长具有净促进作用,有利于块茎的膨大,而马铃薯根系分泌物对自身地上和地下生长则具有抑制作用,影响了块茎膨大,这为揭示玉米||马铃薯体系增产机制提供了一定的理论依据。     

The influence of cyst nematodes and drought on potato growth

In two experiments in the Wageningen Rhizolab with potato cv. Mentor planted in soils with or without potato cyst nematodes (Globodera pallida, W) the number of roots per cm² was observed two weekly by video camera, in horizontally placed minirhizotrons at depths varying from 5 to 100 cm. In both experiments initial root growth was more rapid in the top soil of the uninfected soil. In the first experiment under optimal water supply, root formation continued longer in the top 30 cm of infested soil leading to twice as many roots at the end of the growing season as in uninfested soil. In the subsoil from 30 to 100 cm, however, root formation was strongly reduced by cyst nematodes leading to an uneven distribution of roots throughout the profile. In the second experiment potato cyst nematodes only increased rooting in the top soil with reduced irrigation. Potato cyst nematodes did not affect the water use efficiency of the crop whereas reduced irrigation increased water use efficiency by about 22%. Without potato cyst nematodes the soil profile was depleted of mineral nitrogen until a depth of 1 m whereas with high initial population densities no nitrogen was taken up in the subsoil between 30 and 100 cm. The spational heterogenity of roots and nitrogen in the soil is an important mechanism of damage. This finding may lead to improved cultural practices and breeding for tolerance.     

Biocontrol of powdery scab of potato by seed tuber application of an antagonistic fungus, <Emphasis Type="Italic">Aspergillus versicolor</Emphasis>, isolated from potato roots

An environmentally friendly measure to control potato powdery scab caused by a protozoan pathogen Spongospora subterranea f.sp. subterranea (Sss) was developed by focusing on antagonistic microorganisms that were considered compatible with potato root. Five hundred and eight soil fungi, isolated from potato root cultivated in soil suspensions from four potato fields in Hokkaido, were screened for suppressiveness of root infection by Sss in a hydroponic culture system and for powdery scab severity in greenhouse and field experiments. Antagonistic isolate Im6-50, identified as Aspergillus versicolor, was selected as a potent biological control agent. In a 3-year field test, A. versicolor Im6-50 suppressed powdery scab with a protection value of 54–70 (100?=?complete protection) when applied directly on seed tubers compared with a protection value of 77–93 by the synthetic fungicide fluazinam. A. versicolor Im6-50 was detected from the surface of daughter tubers and from the soil in which the inoculated seed tubers were cultivated by PCR using species-specific primers. The establishment of A. versicolor Im6-50 on the stolon of inoculated potato plants and in the rhizosphere is considered to contribute to the mechanism for disease suppression.     

Root exudates of potato onion are involved in the suppression of clubroot in a Chinese cabbage-potato onion-Chinese cabbage crop rotation

Clubroot, caused by Plasmodiophora brassicae, has emerged as a serious disease threatening cruciferous crop production throughout the world. Crop rotation with non-host species is commonly practised to avoid clubroot, but it is not known whether rotation crops can control clubroot when the resting spores of P. brassicae remain unaffected. Pot experiments were performed to investigate the response of clubroot in Chinese cabbage to crop rotation with potato onion. The results showed that Chinese cabbage rotated with potato onion exhibited less clubroot disease than Chinese cabbage monoculture. Compared with residues from potato onion, the addition of root exudates from potato onion significantly decreased the disease incidence and index of clubroot (p ≤ 0.05). Potato onion root exudates decreased the number of secondary plasmodia of P. brassicae and the expression of the PRO1 gene of P. brassicae. These results suggest that root exudates from potato onion may play an important role in suppressing clubroot in a Chinese cabbage-potato onion-Chinese cabbage rotation system.     

Root infection of potato by Spongospora subterranea: knowledge review and evidence for decreased plant productivity

Information is reviewed on root infection of potato by the plasmodiophorid Spongospora subterranea f. sp. subterranea. This pathogen has long been recognized as the cause of root galls (hyperplasia) and the economically important disease powdery scab on tubers (modified stolons). The significance for plant productivity of the zoosporangium stages of the pathogen in potato roots has only recently begun to be documented. Two experiments are described that assessed effects of S. subterranea root infection on potato plant root function and productivity. A greenhouse experiment measured root function and plant parameters for eight potato cultivars with markedly different susceptibilities to tuber powdery scab. Water uptake and plant growth were reduced by S. subterranea inoculation in all eight cultivars. The magnitudes of these negative effects, and intensities of root hyperplasia, differed among the cultivars, but were not related to respective susceptibilities to tuber powdery scab. A field trial assessed root function and plant productivity for a cultivar (Iwa) that is very susceptible to Spongospora tuber and root diseases. Soil water content beneath uninoculated plants was consistently less than for inoculated plants, indicating that inoculation reduced water uptake (root function). Inoculation reduced shoot and root dry weights, and reduced weight of tubers per plant by 42%. Spongospora subterranea causes three diseases of potato: root membrane dysfunction, root hyperplasia and tuber powdery scab. The root diseases caused by the pathogen are likely to be important both for powdery scab management and for deleterious effects on potato crop yields.     

马铃薯根系分泌物组分对不同种植模式的响应

作物根系分泌物与作物连作障碍密切相关,为寻求减小作物连作障碍的途径,在轮作(大豆-马铃薯)、固定间作(马铃薯/大豆)和马铃薯连作3种种植模式下,分离鉴定了马铃薯根系分泌物的主要组分。结果表明:与轮作处理相比,固定间作和连作处理马铃薯根系分泌物种类分别增加了13.79%和17.24%,烷烃类物质的相对含量分别增加了52.17%和52.60%,酸类物质的相对含量分别增加了65.41%和14.79%。连作处理马铃薯根系分泌物中鉴定出乙胺、N-乙基吗啉和邻苯二甲酸二丁酯的相对含量分别为1.46%、2.87%和5%,而在轮作和间作处理中均未检测到。与轮作处理相比,间作和连作处理N,N-二乙基乙酰胺相对含量分别高出123.29%和47.95%,棕榈酸相对含量分别高出23.18%和40.0%,硬脂酸相对含量分别高出27.36%和39.80%。说明大豆-马铃薯轮作可有效降低马铃薯根系分泌物组分的种类和含量。因此,生产实践中,可通过大豆-马铃薯轮作克服因某一种马铃薯化感物质累积而造成的毒害作用。     

引起青海省马铃薯根腐类病害的镰刀菌种类鉴定

<正>马铃薯是继水稻、小麦和玉米之后的第四大粮食作物~([1]),也是我国青海省主要的经济作物。马铃薯干腐病是镰刀菌根腐类病害中最重要的一种病害,其窖藏期发病率最高可达60%~([2]),根腐类病害已成为限制青海省马铃薯产业发展的重要因素。本文通过形态学、EF-1α基因序列分析的分子生物学鉴定及致病性测定,明确了引起青海省马铃薯根腐类     

Control of soil rot of sweet potato by the incorporation of the fresh aerial tissue of Geranium carolinianum L. into the soil

In a previous study, we found that a 70% aqueous ethanol extract of the fresh aerial tissue of Geranium carolinianum L. showed antimicrobial activity against the pathogen causing soil rot of sweet potato. As the appropriate time for cultivation of sweet potato and the growing period of G. carolinianum do not overlap in Okinawa Prefecture, Japan, the fresh aerial tissue is available in order to control soil rot of sweet potato. Thus, we examined the control effect of fresh aerial tissue against soil rot of sweet potato. The various trials (a single repetition of 20 m²) were performed in fields that had undergone 8 years of continuous cropping of sweet potato at Okinawa Prefectural Agricultural Experiment Station, Horticultural branch. After harvest, when the disease severity was evaluated by determining the necrotic area of the storage root, the incorporation of fresh aerial tissue (5000 kg 1000 m^-2) into the soil was considered to be highly effective, with a protective value of 75.4. This result shows that G. carolinianum could be used as a biological agent for the control of soil rot of sweet potato.     

马铃薯枯萎病生防芽胞杆菌筛选及生防效果研究

马铃薯枯萎病是马铃薯主要土传真菌病害之一,已成为限制我国马铃薯产业健康发展的重要因素之一。菌株ZF128是本实验室从马铃薯根际土壤分离筛选得到的一株对马铃薯枯萎病菌具有显著抑制效果的生防细菌。经生理生化、BIOLOG GENIII和系统发育树分析,鉴定菌株ZF128为贝莱斯芽胞杆菌Bacillus velezensis。抑菌谱测定结果显示,ZF128对5种病原真菌和5种病原细菌都具有显著拮抗效果。光学显微观察发现,菌株ZF128处理的病原菌菌丝生长受到抑制并出现膨胀变粗现象。发酵试验表明,菌株ZF128在甘露醇培养基中发酵上清液对马铃薯枯萎病菌的抑制效果最好。盆栽试验结果证明,接种菌株ZF128后马铃薯发病明显减轻,防效为82.46%。此外,定殖和促生试验表明,菌株ZF128能在马铃薯根际和根部有效定殖30d以上,处理组马铃薯株高、根长、地上部和地下部鲜重及叶绿素含量等指标均显著高于对照组。综上,菌株ZF128生防性状优良,是一株具有潜在应用价值的芽胞杆菌。     

分蘖洋葱与番茄伴生根系分泌物对根结线虫的影响

为明确根系分泌物在番茄伴生分蘖洋葱Allium cepa var. agrogarum Don.体系中减轻番茄根结线虫病的作用,本研究以番茄Lycopersicon esculentum和分蘖洋葱为试材,通过双室试验及外源添加根系分泌物等方法,研究了根系分泌物对根结线虫死亡率、卵孵化率的影响以及根系分泌物对线虫的吸引率。结果表明,番茄单作-分蘖洋葱伴生番茄双室系统中,分蘖洋葱伴生处理的土壤中线虫数量比番茄单作处理减少68.0%(P<0.05);番茄单作-分蘖洋葱单作的双室系统中,分蘖洋葱单作处理的土壤中线虫数量比番茄单作处理减少69.0%(P<0.05)。外源添加单作分蘖洋葱根系分泌物、伴生分蘖洋葱根系分泌物以及伴生体系中番茄和分蘖洋葱的根系分泌物初期,线虫死亡率能够显著提高34.5%~39.0%,卵孵化降低22.0%~53.2%,对线虫的吸引率降低10.9%~37.0%。研究结果为揭示伴生分蘖洋葱根系分泌物在减轻番茄根结线虫病中的作用奠定了基础。     

Ditylenchus radicicola (Greeff, 1872) Filipjev, 1936, een wortelaaltje in het Nederlandse grasland

Summary Ditylenchus radicicola (Greeff, 1872)Filipjev 1936, has been found since 1950 in 75% of the Netherlands' old meadows as a generally distributed parasite on grass roots. Additional data on the morphology of the eelworm are given. Eleven grass varieties were found to be attacked under natural conditions; 7 of them are new host plants. Damage in our meadows was not observed. However this eelworm is considered a noxious parasite of cereals abroad and in view of the economic importance of grassland in our country further information would be desirable.