The effect of DD and dazomet treatments on nematode populations at various depths in the soil and on the transmission of soil-borne tobacco rattle virus to gladiolus

The relation between log dosage of DD injected at 15 cm depth or of dazomet applied to the soil surface (all in November 1971) and probit mortality ofRotylenchus and trichodorids in the top 20 cm of a field on sandy soil was found to be linear. Dosage increase efficiencies of both chemicals against both nematode species were medium to high. Superficial application of dazomet was very effective against the nematodes that would have survived if only a low dosage of DD had been injected at 15 cm depth. Injection of 40 ml or 80 ml DD per m² at 15 cm depth killed all nematodes between 20 cm and 60 cm deep. Gladiolus planted in the spring of 1972 grew better, flowered earlier and produced more weight of corms on treated than on untreated plots. The poor growth on the untreated plots cannot be ascribed to direct damage by nematodes or to the effect of TRV transmitted to the plants by the viruliferous trichodorids occurring in these plots in high densities. Symptoms of TRV infection in plants grown in 1973 from the corms harvested in the 1972 experimental field showed that only DD treatments had reduced the rate of TRV transmission considerably. However, even the highest dosages of DD had only reduced it from 26% (on untreated plots) to about 8%. Most probably, this residual TRV infection was due to transmission by trichodorids that had survived in soil layers below 60 cm depth. Therefore, soil treatment with nematicides, cannot prevent TRV transmission to gladiolus sufficiently where viruliferous trichodorids occur at great depths, as is the case in many sandy soils having a low water table.     

The transmission of rattle virus byTrichodorus pachydermus

Samenvatting De nematode-soortTrichodorus pachydermus Seinhorst kan ratelvirus overbrengen naar gezonde White Burley tabaksplanten. Eén aaltje, geïsoleerd uit met ratelvirus besmette grond, is zelfs in staat een tabaksplant met het virus te infecteren.Evenals ratelvirus komt deze nematode-soort vooral voor in lichtere grondsoorten. In kleigrond worden beide zelden aangetroffen. Het is mogelijk, dat de verspreiding van het virus beperkt is tot gebieden waarT. pachydermus voorkomt. Dit moet nog nader worden onderzocht.     

Behavior of pyriftalid in soil and its phytotoxic activity on Echinochloa oryzoides seedlings emerging from various soil depths

The phytotoxic activity of pyriftalid ([RS]‐7‐[4,6‐dimethoxypyrimidin‐2‐ylthio]‐3‐methyl‐2‐benzofuran‐1[3H]‐one) on barnyard grass (Echinochloa oryzoides) seedlings emerging from various depths in the soil was investigated in relation to its behavior in the soil. The growth of the barnyard grass seedlings in the soil mixed with pyriftalid was inhibited, depending on the concentration of the herbicide in the soil water but not on the amount in the total soil. A topmost pyriftalid‐treated layer was formed by applying the herbicide to the soil surface under water‐leakage conditions. The concentration of pyriftalid in the soil water and the amount that was adsorbed on the soil solid decreased with time, but the decrease was more marked in the pyriftalid concentration in the soil water than in the amount that was adsorbed on the soil solid. The emergence time of barnyard grass in the soil was faster in the seeds that were located in the shallower soil layer, compared to the deeper soil layer. The growth inhibition of the barnyard grass seedlings emerging from the shallower soil layer was greater than that of the barnyard grass seedlings emerging from the deeper soil layer after the soil surface application of pyriftalid. It is suggested that the emergence timing from the different soil depths is an important factor affecting the herbicidal activity of pyriftalid when it is applied to the soil surface under paddy field conditions.     

Winter-type california tobacco rattle virus in its relation to the infected cell

Particles of California tobacco rattle virus (CTRV) were observed in thin sections of vascular elements of leaves showing oak leaf symptoms. At no time during this study were particles observed in mesophyl cells of these leaves. A peculiar chloroplast breakdown is described.     

Acquisition and subsequent transmission of tobacco rattle virus isolates by Paratrichodorus and Trichodorus nematode species

Isolates of the PRN serotype of tobacco rattle virus (TRV) were transmitted with different efficiencies by the nematode vectorParatrichodorus pachydermus. Virus isolates which belonged to other serotypes were not acquired and/or transmitted by this vector, nor were PRN serotype isolates which had been obtained from naturally infected potato plants and maintained by mechanical transmission in the glasshouse for several years. PRN serotype TRV isolates from the Netherlands or from Scotland were equally well transmitted by initially virus-freeP. pachydermus populations from either country. Allowing a naturally viruliferous nematode population access for 3 weeks to uninfected or TRV-infected roots resulted in an increased proportion of the trichodorid population transmitting TRV.     

Regeneration of yarrow (Achillea millefolium L.) rhizome fragments of different length from various depths in the soil

The regenerative response of the rhizomes of Achillea millefolium L. to fragmentation and burial was studied in field experiments on three different soils. The percentage of buds producing shoots (estimated from surviving rhizome fragments) from 4 cm (1·6 nodes), 8 cm (3·8 nodes) and 16 cm (6·7 nodes) rhizome fragments was 63, 44 and 32 respectively averaged over all soils and depths of 5, 10 and 15 cm. The depth at which 50% of the fragments failed to produce an emerged shoot (LD₅₀ depth) was 9·3, 12·4 and 17·9 cm for 4-, 8- and 16-cm fragments respectively averaged over all soils. No fragments survived on the soil surface. The time of emergence of the first shoots was delayed and the rate of emergence and ultimate shoot population reduced with increasing depth of burial. Dry-matter production by aerial shoots and new rhizomes decreased linearly with depth of burial of the rhizome fragments. Soil type had no effect on the regeneration of the fragments. The significance of the results for the control of A. millefolium is discussed.     

Molecular diagnostics of some trichodorid nematodes and associated Tobacco rattle virus

Several Paratrichodorus and Trichodorus (trichodorid) nematode species are natural vectors of Tobacco rattle virus (TRV) and cause economically important diseases, especially in potato and ornamental bulbous crops. Identification of trichodorid species based on morphological characters is laborious, time-consuming, and requires the services of highly trained personnel. Molecular diagnostics for trichodorid nematodes, using the ribosomal DNA repeat unit, were successfully developed to distinguish two Paratrichodorus and two Trichodorus species. The complete sequences of the 18S genes and the ITS-1 regions for these species were obtained and species-specific primers successfully designed for them. An RT-PCR assay was developed utilizing isolate-specific primers that amplify serologically distinguishable strains of TRV in individual trichodorid nematodes. The primers were based on the highly conserved RNA-1 segment of the bipartite genome and also on different parts of the RNA-2 segment of the virus genome.     

缓释与普通尿素分层配施对土壤氮素和玉米生长的影响

通过2 a大田随机区组试验,探究缓释与普通尿素分层配施对土壤氮素含量、玉米根叶衰老及产量的影响机理。试验设置不施氮肥(CK)、普通尿素1次施肥PU1 (5～10 cm土层)、普通尿素传统2次施肥PU2 (5～10 cm土层,60%种肥+40%追肥)、普通尿素1次分层施肥PU3 (5～10 cm土层20%N+15～20 cm土层30%N+25～30 cm土层50%N)、不同土层深度缓释与普通尿素配施PCU1～PCU4 [均为5～10 cm土层20%N(普通尿素)+15～20 cm土层30%N(配施)+25～30 cm土层50%N(配施),其中PCU1～PCU4的15～20 cm和25～30 cm土层PCU∶PU分别为3∶7、3∶7,5∶5、5∶5和3∶7、5∶5,5∶5、3∶7]共8个处理。结果表明,与PU1、PU2、PU3相比,缓释与普通尿素分层配施处理在玉米生育后期(吐丝期和灌浆期)土壤中NO~-_3-N含量提高了4.21%～133.44%,NH~+_4-N含量提高了17.09%～72.95%;叶片SOD、POD、CAT、可溶性蛋白分别提高了9.22%～26.75%、7.72%～23.35%、7.66%～22.96%、11.67%～32.98%,MDA降低了2.34%～37.53%;根系SOD、POD、CAT、可溶性蛋白分别提高了7.93%～22.75%、19.09%～42.13%、9.71%～60.98%、12.42%～103.57%,MDA降低了3.01%～31.6%。缓释与普通尿素分层配施玉米产量在2017年和2018年比其它处理分别提高2.32%～26.16%和1.32%～22.36%,经济效益增加1.67%～31.84%和0.33%～27.49%,各处理中PCU4处理产量最高,2017年和2018年分别为13 899.08 kg·hm~(-2)和12 439.35 kg·hm~(-2),经济效益分别为17 022.25元·hm~(-2)和14 832.65元·hm~(-2)。综合来看PCU4处理是最佳的缓释尿素施用方式。     

Stimulation of germination of sclerotia of Sclerotium cepivorum at different depths in soil by artificial onion oil

The influence of depth of inoculum on white rot and plant growth, and the response of sclerotia ofSclerotium cepivorum Berk. to artificial onion oil, at various depths in soil, was investigated.Field tests showed that effects of depth of inoculum were apparent 12 weeks after sowing and by week 14, sclerotia buried at 0–2, 10–12 and 18–20 cm reduced onion growth by 75, 56 and 37% in comparison with controls. The results indicate the importance of correct placement of treatments, such as onion oil, in soil to achieve maximum levels of disease control. In vitro tests in closed containers at 15°C showed that between 50–70% of sclerotia ofS. cepivorum germinated on soil treated with artificial onion oil. Production of secondary sclerotia was restricted to 0.5% of those which germinated. Application of oil at 10 cm depths in columns of soil caused germination of 60–70% of sclerotia at 3, 6, 14 and 17 cm over 4 weeks at 15°C. Germination at the soil surface was reduced. In field plots onion oil and one of its components, diallyl disulphide, reduced recovery of introduced sclerotia by 70%.Samenvatting Het effect van de diepte in grond waarop het inoculum vanSclerotium cepivorum berk. zich bevindt op het optreden van witrot in ui en op de ontwikkeling van de uieplant werd onderzocht. Ook werd de uitwerking van in grond geïnjecteerde uienolie op de op verschillende diepten in grond geplaatste sclerotiën bestudeerd.In veldexperimenten werd na 12 weken een duidelijk effect van de diepte van het inoculum op de ontwikkeling van de planten waarneembaar. Na 14 weken bleken sclerotiën die op 0–2, 10–12 en 18–20 cm diepte in grond waren geplaatst de groei van de uieplanten met respectievelijk 75, 56 en 37% te hebben verminderd ten opzichte van de controleplanten. Deze resultaten wijzen er op, dat voor een zo goed mogelijke bestrijding van witrot, de diepte in grond waar middelen zoals uienolie moeten worden toegediend, van grote betekenis kan zijn.Bij in vitro toetsen in gesloten Conway-schalen bij 15°C kiemde 50–70% van de sclerotiën vanS. cepivorum op het oppervlak van grond die behandeld was met synthetische uienolie. De vorming van secundaire sclerotiën beperkte zich tot 0,5% van het aantal gekiemde sclerotiën. Toediening van uienolie op 10cm diepte in grondkolommen veroorzaakte de kieming van 60–70% van de sclerotiën op 3, 6, 14 en 17 cm diepte over een periode van 4 weken bij 15°C. Bij het grondoppervlak was de kieming lager. In veldexperimenten werd na behandeling van grond met uienolie en met een bestanddeel daarvan, diallyl-disulfide, het aantal in grond geïntroduceerde sclerotiën dat kon vorden teruggevonden, met 70% gereduceerd.The senior author was a visiting scientist of the Plant Research Institute, Melbourne, Australia who received a scholarship administered by the International Agricultural Center (IAC) from the Netherlands Ministry of Agriculture.     

Viruses of the tobacco rattle virus group in Northern Italy: Their vectors and serological relationships

Four species ofTrichodorus have been found in northern Italy, viz.Trichodorus viruliferus, T. teres, T. nanus and an undescribed species. In seven cases tobacco rattle virus (TRV) was isolated from soil samples by means of bait seedlings and in three of these cases the vector was found to beT. viruliferus. The seven virus isolates reacted with an antiserum against a Dutch TRV isolate and were divided into two groups according to their reaction with this serum. One isolate from each group was subjected to a more detailed examination. Of these, one was found to be closely related to a Dutch isolate from gladiolus with notched leaf symptoms, while the other showed a distinct relationship to the pea early-browning virus found in Britain. One of the isolates proved to be more closely related to the Dutch TRV than is the Dutch gladiolus isolate.     

Tobacco rattle virus serotypes and associated nematode vector species of Trichodoridae in the bulb-growing areas in the Netherlands

Soil samples from the coastal bulb-growing areas in the provinces of North- and South-Holland and the North-East Polder in the Netherlands were examined for trichodorid nematodes and tobacco rattle virus (TRV) serotypes. At least one of a total of eight species of Trichodoridae, of whichParatrichodorus pachydermus was most prevalent, was found in 93% of the samples from the provinces of North- and South-Holland and TRV, including four serotypes, was obtained from 49% of these samples. In the North-East Polder one of three species of trichodorids, of whichP. teres occurred most frequently, was present in 72% of the samples, and TRV of one serotype was obtained from 28% of these samples. The TRV isolates recovered from these samples reacted serologically with one of four antisera to strains of TRV. Virus transmitted byP. pachydermus reacted to the PRN-, byTrichodorus viruliferus to the RQ-, byP. teres to the N5- and byT. similis, to the TS-antiserum, respectively.     

Detection of tobacco rattle virus by ELISA and test plants in main sprouts of tulip bulbs during storage at different temperatures

The detectability of tobacco rattle virus (TRV) in the main sprouts of primarily and secondarily infected tulip bulbs of cv. Apeldoorn stored at different temperatures from the lifting in July up to February is described. Detection by ELISA was not affected by the size of the main sprout, nor by the size of the bulbs. The rates of TRV-infected bulbs found by ELISA were highest during storage at 13, 9 or 5°C continuously, and when temperatures were lowered from 20 or 17°C to 5°C in October. The percentages detected via test plants, but undetectable by ELISA were also lowest at these temperatures. The unfavourable effect of continuous storage at 20, 17, or 2°C as expressed in low ELISA absorbances not significantly different from the mean value of healthy bulbs, was largely overcome during long storage by the change of temperature down to 5°C from 20 and 17°C or upwards from 2°C. The reverse from 5°C upwards to 17 and 20°C affected the detectability by ELISA unfavourably. The rate of detection via test plants in the main sprout and in the small sprouts from different positions in bulbs was only possible at low percentages.The effect of some factors, like different temperatures during storage, detectability of different TRV serotypes, interference of irregular occurrence of TRV in the removed scale and basal-plate tissue with the main sprout, and variable recurrence of TRV in progeny bulbs, is discussed in view of its impact on routine testing of bulbs during storage.     

Detection of tobacco rattle virus in nematodes by reverse transcription and polymerase chain reaction

An assay, based on amplification of cDNA synthesized from genomic viral RNA, has been developed to detect tobacco rattle virus in infected plant material and viruliferous nematodes. A range of different TRV strains could be detected using the procedure developed. The presence of one to three viruliferous nematodes in a nematode suspension was sufficient for the detection of TRV. The minimum amount of purified virus detectable in the assay was 15 fg, indicating an increased sensitivity of the PCR-based assay as compared to serological detection methods, like ELISA. A dot-blot hybridization procedure was developed for the detection of the PCR products, making agarose gel electrophoresis dispensable.     

Separation of long and short particles of tobacco rattle virus with polyethylene glycol

Two methods to separate long and short particles of tobacco rattle virus with polyethylene glycol 6,000 (PEG) are described. The first is based on specific precipitation, the second on specific solubilization of particles with different lengths at different PEG concentrations. The results of the separations are comparable to, or better than those obtained by sucrose-gradient centrifuging. The advantage of the methods using PEG is that no expensive equipment is required.Samenvatting Twee methoden om lange en korte deeltjes van het tabaksratelvirus met behulp van polyethyleenglycol 6000 (PEG) te scheiden worden beschreven. De ene is gebaseerd op specifieke precipitatie, de andere op specifieke oplosbaarheid van deeltjes met verschillende lengten bij verschillende PEG-concentraties. De resultaten van de scheidingen zijn even goed als of beter dan die van scheidingen verkregen door centrifugeringen op een suikergradiënt. Het voordeel van de PEG-methoden is gelegen in het feit dat er geen kostbare apparatuur voor nodig is.     

Notched leaf inGladiolus spp., caused by viruses of the tobacco rattle virus group

Symptoms of notched leaf in gladiolus are described in this paper. The disease can occur either in patches in the field (only on sandy or light sandy loam soils) or in plants scattered throughout a field planted with a certain stock (independent of soil type). Experiments showed that this disease is caused by tobacco rattle virus (TRV), which is transmitted byTrichodorus pachydermus Seinhorst andT. similis Seinhorst. Gladiolus corms planted in infested soil show a more or less serious reduction of growth and sometimes typical symptoms of notched leaf. In experiments these notched leaf symptoms could be reproduced in the first season only whenTrichodorus from infested soil was able to infect the young sprouts on top of the corms. If infection took place through the roots, the growth of the plants was not or only slightly retarded and the typical notched leaf symptoms appeared in the offspring in the following season. At least two serologically different strains of TRV could be isolated from affected gladiolus. These serotypes were not found to be typical for a certain location as in some cases both were isolated from the same infested field. In fields where potatoes showed stem-mottle and/or spraing, gladiolus was affected by notched leaf.Samenvatting Kartelblad in gladiolen kenmerkt zich door slecht uitgegroeide, misvormde planten, waarbij langs de randen en de nerven van de bladeren necrotische strepen en karakteristieke kartel- en zaagranden optreden (fig. 1). De planten komen meestal niet tot bloei. Alle overgangen tussen normale planten en die met de beschreven symptomen komen voor.In de knollen en kralen van de aangetaste planten zijn geen kenmerkende symptomen waar te nemen. In het gewas te velde kunnen deze aangetaste planten, in variërende percentages, verspreid tussen de gezonde planten van een partij voorkomen, terwijl aangrenzende partijen geheel gezond kunnen zijn. In deze gevallen, die op alle grondsoorten worden aangetroffen, is de partij één of meer seizoenen eerder geïnfecteerd. In andere gevallen worden planten als zojuist beschreven pleksgewijs in het gewas aangetroffen (fig. 2). Dergelijke aantastingen komen uitsluitend voor op de lichtere gronden en hierbij wordt eveneens een abnormale ontwikkeling van het wortelstelsel waargenomen (fig. 3).In proeven kon worden aangetoond dat de ziekte veroorzaakt wordt door virussen van de ratelvirusgroep (zie tabel 1 tot en met 6). In de grond aanwezige aaltjes van het geslachtTrichodorus (T. pachydermus Seinhorst,T. similis Seinhorst en mogelijk nog andere soorten) brachten het virus op de waardplant over (tabellen 2, 5 en 6).In het seizoen waarin infectie plaatsvond, ontstonden uitsluitend kenmerkende kartelblad-symptomen indien aaltjes, afkomstig van besmette grond, de mogelijkheid werd gegeven jonge, nauwelijks uitgegroeide spruiten aan te tasten (fig. 5, tabel 6). Infectie in de wortels veroorzaakt geen of slechts een geringe groeistoornis, maar in de nakomelingschap van deze planten komen in het volgende seizoen de typische symptomen van kartelblad voor (fig. 4, tabel 3, 5 en 6).Op een aantal gronden waar aardappelen waren geïnfecteerd door stengelbont of kringerigheid, werden gladiolen door kartelblad aangetast. In proeven waar gladiolen en aardappelen door TRV op dezelfde percelen waren geïnfecteerd, bleek een opmerkelijke overeenkomst in het verloop van kartelbladaantasting bij gladiolen en stengelbontaantasting bij aardappelen te bestaan (tabel 4).Bij het onderzoek van verschillende TRV-isolaties uit gladiolen met kartelblad-symptomen en uit andere waardplanten die afkomstig waren van met TRV enTrichodorus sp. besmette gronden, konden tenminste twee verschillende serotypen van het TRV worden aangetoond. Isolaties van het ene serotype bleken nauw verwant te zijn met een TRV-isolatie uit tabak White Burley, waartegen een antiserum is vervaardigd doorMaat (1963). Vertegenwoordigers van het andere serotype reageerden alle serologisch positief met een antiserum bereid tegen een TRV-isolatie uit gladiool. Beide serotypen bleken niet specifiek te zijn voor bepaalde plaatsen, daar beide verspreid door het land blijken voor te komen en in sommige gevallen uit eenzelfde perceel konden worden geïsoleerd. In een volgende publikatie zal hierop nader worden ingegaan.A preliminary report on this subject has been published in Nematologica 10 (1964):69–70.     

Evaluation of various methods for the detection of barley yellow dwarf virus by the tissue-blot immunoassay and its use for virus detection in cereals inoculated at different growth stages

Various modifications of the tissue-blot immunoassay (TBIA) for the detection of barley yellow dwarf virus (BYDV, luteovirus) were compared. Similar results were obtained by using three different labelled molecules; goat anti-rabbit antibodies conjugated to alkaline phosphatase, protein A conjugated with alkaline phosphatase and goat anti-rabbit antibodies conjugated with colloidal gold. Blocking the nitrocellulose membrane with polyvinyl alcohol for 1 min was effective and allowed the procedure to be shortened by one hour. TBIA was sensitive enough to detect BYDV in old dry tissue wich had been soaked in water for 1 h.BYDV was monitored by TBIA in wheat, oat and barley after inoculation at heading, flowering and grain filling growth stages. The later the inoculation date, the greater the chance of detecting the virus in stem bases rather than in the upper part of the stem. The later the inoculation the less virus moved, from the inoculated tiller to other tillers of the same plant.