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Summary Plant-parasitic nematodes (PPN) are an economically important group of crop pests and are oviparous animals; all nutrients required to develop and ensure the survival of their unhatched progeny need to be deposited within the egg, including proteins. The most abundant protein deposited is vitellin, formed of a precursor protein vitellogenin, which has roles in transporting lipids, providing amino acids and influencing post-embryonic development. The genes encoding vitellogenin have been well studied in Caenorhabditis elegans, but little is known about vitellogenin in PPN. Using the vitellogenin gene sequences from C. elegans, homologous sequences in the genomes of some economically important cyst and root-knot nematodes were identified and hypothetical vitellogenin genes were predicted. Protein domains were then determined. Sequences were aligned using MUSCLE and then used to construct phylogenetic trees using the maximum likelihood method. With the availability of genomic data and use of online local alignment tools, the vitellogenin encoding genes from C. elegans could be aligned to PPN genomes. All predicted genes contained the same protein domains as C. elegans; Vitellogenin_N, vitellogenin open beta-sheet and von Willebrand factor domain type D. The constructed phylogenetic tree clustered the species into four groups: root-knot nematodes, two cyst nematode groups and Caenorhabditis species. By determining the hypothetical vitellogenin genes in PPN and inferring their relationships, this could form a potential basis to understand further the role of vitellogenin in cyst and root-knot nematodes.

Summary Hirschmanniella diversa and H. imamuri parasitise the lotus, Nelumbo nucifera. Hirschmanniella spp. are the most important pests of lotus cultivation in Japan, but the distribution and species dominancy are not fully understood. In this study, we aimed to collect Hirschmanniella spp. individuals from lotus roots in the major lotus cultivation areas in Japan and identify them morphologically and molecularly using the 18S, D2-D3 regions of rRNA and mitochondrial cytochrome c oxidase subunit I (mtCOI). Hirschmanniella oryzae, commonly known to cause damage on rice in Japan, was also obtained and analysed for inter- and intraspecies sequence variations. All individuals of the genus Hirschmanniella extracted from lotus roots in 16 fields in ten prefectures were identified as H. diversa morphologically and molecularly. This result revealed that H. diversa is a dominant Hirschmanniella species parasitising lotus in Japan. Meanwhile, intraspecific sequence variations in H. diversa were relatively higher in the mtCOI (1-21 bases, ≦5.3%) than in the 18S rRNA and D2-D3 of 28S rRNA (0.0-0.3% and 0.0-0.4%, respectively) and in those of H. oryzae. Based on the mtCOI sequences, five haplotypes were identified and each haplotype was distributed in relatively close regions or regions in which the same lotus cultivars were grown, although further studies are required to verify this assertion. The morphological and genetic variations were higher in H. diversa than in H. oryzae (no intraspecific sequence variation in mtCOI), suggesting that H. diversa was not a recent invasive species.

Summary Our previous study using pots reported that short-term growth of mung bean (Vigna radiata) may be useful to decrease the density of the soybean cyst nematode (SCN), Heterodera glycines, in soil. The objective of this study was to determine whether short-term growth of mung bean and its incorporation by ploughing decreased SCN density in infested fields. Firstly, we did pot experiments to evaluate the optimum temperature and moisture for hatching in soil. SCN hatching was stimulated at 25 and 30°C and not at 20°C; however, it was stimulated at alternating temperature conditions between 20 and 25°C. Soil moisture levels with pF 2.76 or less were required to stimulate SCN hatch in soil. Field experiments were done in Saitama, Kanagawa and Nara Prefectures, Japan. SCN density was reduced by nearly half even in control plots, in which mung bean was not cultivated and ploughed, in Saitama and Nara Prefectures. However, SCN density was reduced by nearly 80% or more in the three Prefectures, except for one plot in Kanagawa, and the soil temperature and moisture conditions were kept at around 20-30°C and at −2. Overall, the present study revealed that short-term field cultivation of mung bean and ploughing was a profitable method to decrease SCN density in infested fields and thereby to increase yield of green soybean.

Summary Rice is an important agricultural crop in Vietnam. Nematodes are diverse in soil agroecosystems. However, little is known about their seasonal variation in extremely intensive rice cultivation in tropical regions. The objectives of this study were to investigate the seasonal variation and spatial distribution of the nematode community, and to assess its relationship with the soil chemical property and rice yield. Soils (0-10 cm and 10-20 cm deep) were collected at harvest in spring-summer (S-S), summer-autumn (S-A), and winter-spring (W-S) cultivation in 2017 and 2018. Plant-parasitic nematodes were the largest group and accounted for 47-80 and 79-92% of total nematode abundance in the topsoil and subsoil, respectively. Hirschmanniella was the most dominant taxon whose abundance in topsoil varied from 275-739 in W-S to 1010-1270 indiv. (100 g soil)−1 in the S-S season. Nematode assemblages differed between topsoil and subsoil, and those of topsoil had clear seasonal distribution patterns. Bacterivore nematodes were the predominant group of free-living nematodes, with increasing relative abundance in the topsoil of S-S (average 23.2% of total free-living nematodes) < S-A (average 41.9%) < W-S (average 57.3%). Furthermore, soil in the W-S season had the highest microbial activity in 2018. Soil pH, EC and abundance of Hirschmanniella spp. were significantly negatively related with rice yield. The present results suggest that the presence of Hirschmanniella spp. in soil may be involved in a reduction of rice yield in the triple rice system.

Saltwater intrusion is a potential risk damaging crop diversity and productivity due to degraded soil physicochemical properties. However, little is known about how salinity affects the structure and function of soil nematodes community in intensive rice cultivated area. This study aimed (1) to assess the impacts of saltwater intrusion on the nematode community in alluvial and acid sulfate soils; and (2) to evaluate its relation with soil conditions. Saltwater intrusion reduced the abundance of both free-living nematodes (FLN) and plant-parasitic nematodes (dominated by Hirschmanniella) in soils. FLN community was different among sites with different physicochemical properties. The omnivorous genera Aporcelaimellus and Thornenema were only found in non-salt-affected alluvial soil, whilst Mesodorylaimus was dominant in salt-affected acid sulfate soil, suggesting that this genus might be tolerant to higher EC and soluble Na+, K+, Ca2+. The bacterivorous nematodes (dominant taxa Chronogaster, Rhabdolaimus) were dominant in both non-salt affected and salt-affected alluvial soils, which accounted for 48% and 40%, respectively, whilst it accounted for 21% in salt-affected acid sulfate soil. The abundance of fungivorous nematodes (Aphelenchoides, Ditylenchus, Filenchus) were greater in salt-affected alluvial soil in contrast to the other treatments, suggesting that these might be tolerant to salinity and low pH. Saltwater intrusion reduced biological diversity (Margalef, Shannon-Wiener, and Hill’s indices), maturity index (∑MI, MI25), and clearly affected functional guilds of nematode community, especially c-p 5 group was reduced in both salt-affected soils. This study suggests that saltwater intrusion showed a potential risk in the degradation of soil properties, as indicated by the altered nematode community, trophic structure, functional guilds and their ecological indices in paddy fields.

Avoidance of intensive rice cultivation (IRC) and soil amendments are potential practices to enhance soil properties. There is only limited information on the effects of reduced IRC and its mixture with compost or silicate fertilizer (Si) on the soil nematode community in salt–affected soils. This study aimed to assess the shifts of soil nematode community by reducing a rice crop from triple rice system (RRR) to a double rice system and mixed with compost or Si in paddy fields in acid sulfate soil (ASS) and alluvial soil (AL) in the Mekong Delta, Vietnam. Field experiments were designed with four treatments in four replicates, including RRR and a proposed system of double–rice followed by a fallow (FRR) and with 3 Mg ha–1 crop−1 compost or 100 kg ha–1 crop−1 Si. Soils were collected at harvest after the 2 year experiment, reflecting the fifth and third consecutive rice crop in RRR and FRR system, respectively. Results showed that reduced IRC gave a significant reduction in abundance of plant–parasitic nematodes (PPN), dominated by Hirschmanniella and increased abundance bacterivorous nematodes when mixed to compost and silicate fertilizer in ASS. In addition, reduced IRC increased nematode biodiversity Hill’s indices and reduced herbivorous footprint in ASS. Proposed system having compost or Si had strongly increased in bacterivorous and omnivorous footprints. Particularly, reduced IRC mixture with Si increased abundance of Rhabdolaimus, Mesodorylaimus and Aquatides, metabolic footprints (structure footprint, bacterivorous, omnivorous and predator) and diversity Hill’s N1 index in ASS. Our results highlighted that reduced IRC was a beneficial practice for decreasing abundance of PPN in salt-affected soils and increasing abundance of FLN in ASS. IRC mixture with compost or Si had potential in structuring the nematode communities with increasing biodiversity, trophic structure, and metabolic footprints.

This chapter focuses on some of the principal techniques for analysing nematode behaviour and physiology, such as attraction/repulsion plate assays, pluronic gel assays, movement assays, electrophysiology, stylet activity, water content changes, oxygen consumption assays, collection of female sex pheromone, virgin females and males and viability tests, among others.

Long-term intensive rice monoculture, triple rice cultivation (rice crops are cultivated three times per year) in the Mekong Delta, Vietnam, causes a reduction in topsoil quality. Rotating rice with an upland crop in a tropical paddy field may improve the soil physicochemical properties but effects on the soil nematode community are unknown. This study was conducted in a triple rice field to evaluate the responses of the nematode community to a crop rotation (the first rice in a year was replaced with sesame and soybean, and the second and third crops were rice) and to organic amendment. The experiment was based on a split-plot design with two factors that were crops (main factor, n = 3) and compost amendment (sub-factor, n = 3). The crops were rice, soybean, and sesame and the sub-factors were cow manure plus rice straw compost, sugarcane compost, and no amendment. Soil samples were taken at harvest of the first crops in topsoil (0–10 cm) and subsoil (10–20 cm) in 2017 and 2018. In 2018, the abundance of free-living nematodes (FLN), which were dominated by bacterivores and fungivores, was greater in upland crops, while that of plant-parasitic nematodes (PPN) was greater in paddy rice. In particular, the density of the most predominant PPN genus, Hirschmanniella, was lower in upland crops than in paddy rice. Cultivation of sesame also reduced the number of the second predominant PPN genus, Bitylenchus, resulted in an increase in the ratio of the free-living to plant-parasitic nematodes. The diversity evenness index (J), Shannon-Wiener (H′) and Hill's indices increased in upland crops compared to those in rice fields in 2018. Crop rotation with sesame or soybean in a paddy field enhanced abundance and biodiversity of FLN and suppressed PPN and thus can be proposed for agricultural sustainability.

In Japan, Hirschmanniella diversa is an important pest in lotus cultivation in paddy fields and only lime nitrogen is registered for its control. Therefore, additional nematicides are required to control the nematode. The objective of this study was to screen for an effective nematicide. Fourth-stage juveniles and adults of H. diversa sampled from a lotus field were tested in in vitro solution experiments against 37 pesticides that are registered for the pest control of crops in Japan. Carbamate-based benfuracarb, organophosphate-based fenthion, nereistoxin-based cartap hydrochloride and cyanamide showed nematicidal effects against H. diversa. Benfuracarb at 1 &mu, g/mL showed a nematostatic effect on H. diversa in an agar plate assay. Further, H. diversa treated with benfuracarb did not resume activity 7 days post nematicide treatment when transferred to distilled water. Benfuracarb was tested in micro-field experiments, in which H. diversa density and lotus tuber damage levels were monitored. Results showed that benfuracarb reduced H. diversa densities in the roots during the cultivation period in 2012 and consistently reduced damage levels during a five year study period. Thus, benfuracarb is recommended as an effective nematicide to be used for H. diversa control in lotus cultivation.

Two commercially available seaweed products, derived from Ascophyllum nodosum (An) and Ecklonia maxima (Em), were evaluated for their potential as control agents for the root-knot nematodes, Meloidogyne chitwoodi and Meloidogyne hapla. The effects of both products on hatching, host location and penetration by second-stage juveniles (J2) were examined. Continuous exposure of M. chitwoodi egg masses to 50 and 100 % An significantly reduced the final percentage hatch, but this result could not be confirmed. In a bioassay with pluronic gel, more J2 of M. chitwoodi and M. hapla were found within the 0.5-cm vicinity of a tomato root tip after 24- and 6-h pre-exposures to Em, respectively. On agar plates, J2 of M. chitwoodi pre-exposed to An or Em showed less attraction to tomato root diffusate compared with distilled water (DW). Moreover, J2 pre-exposed to An lost the ability to differentiate repellent and attractant solutions on agar plates, unlike J2 pre-exposed to Em or DW. A 24-h pre-exposure to An reduced the infectivity of M. chitwoodi and M. hapla, whereas pre-exposure to Em enhanced the infectivity of M. chitwoodi. In a glasshouse pot experiment, treatments with Em reduced M. hapla multiplication on tomato. For M. chitwoodi, no effect on the number of nematodes per gram root was seen. The root biomass significantly reduced for untreated plants infested with M. chitwoodi compared to Em- and An-treated plants. The results indicate that these seaweed products adversely affect hatching and sensory perception in in vitro assays, but assumptions about in vivo effects may be unwise as dilutions of the products when applied as soil drenches may compromise activity.

The aim of this review was to undertake a survey of researchers working with plant-parasitic nematodes in order to determine a ‘top 10’ list of these pathogens based on scientific and economic importance. Any such list will not be definitive as economic importance will vary depending on the region of the world in which a researcher is based. However, care was taken to include researchers from as many parts of the world as possible when carrying out the survey. The top 10 list emerging from the survey is composed of: (1) root-knot nematodes (Meloidogyne spp.); (2) cyst nematodes (Heterodera and Globodera spp.); (3) root lesion nematodes (Pratylenchus spp.); (4) the burrowing nematode Radopholus similis; (5) Ditylenchus dipsaci; (6) the pine wilt nematode Bursaphelenchus xylophilus; (7) the reniform nematode Rotylenchulus reniformis; (8) Xiphinema index (the only virus vector nematode to make the list); (9) Nacobbus aberrans; and (10) Aphelenchoides besseyi. The biology of each nematode (or nematode group) is reviewed briefly.

{null=The potato cyst nematode, Globodera rostochiensis, is a quarantine organism. Environmentally benign control measures for this economically important pest are needed. Green manures, in particular plants from the Brassicaceae, suppress some plant-parasitic nematodes and have potential as control agents. This study examined if growing and incorporating cover crops from the Brassicaceae family influenced hatching of G. rostochiensis. The effect of root diffusates and plant extracts, as well as soil incorporation of plant material from three commonly used species of green manures, was studied in in vitro bioassays and pot tests. The results showed that brassica diffusates and plant extracts were not nematicidal. In addition, although they did not cause hatch by themselves, pretreatment with these solutions enhanced subsequent hatch in host root diffusates. The results are discussed in the context of the hatching response of G. rostochiensis and the likely influence on field usage of these green manures., en= The potato cyst nematode, Globodera rostochiensis, is a quarantine organism. Environmentally benign control measures for this economically important pest are needed. Green manures, in particular plants from the Brassicaceae, suppress some plant-parasitic nematodes and have potential as control agents. This study examined if growing and incorporating cover crops from the Brassicaceae family influenced hatching of G. rostochiensis. The effect of root diffusates and plant extracts, as well as soil incorporation of plant material from three commonly used species of green manures, was studied in in vitro bioassays and pot tests. The results showed that brassica diffusates and plant extracts were not nematicidal. In addition, although they did not cause hatch by themselves, pretreatment with these solutions enhanced subsequent hatch in host root diffusates. The results are discussed in the context of the hatching response of G. rostochiensis and the likely influence on field usage of these green manures. }

The root-knot nematodes, Meloidogyne chitwoodi and M. fallax, cause severe damage to economically important crops and, in 1998, both species were listed as quarantine pests in Europe. Comparative studies were made on the effects of root diffusates and host age on the in vitro hatching of M. chitwoodi and M. fallax. There is a marked contrast in the hatching response of the two species. Hatching of second-stage juveniles (J2) of M. chitwoodi produced on young plants did not require host root diffusate stimulus, whereas at the end of the plant growing season, egg masses contained a percentage of unhatched J2 that require host root diffusate to cause hatch. This form of obligate quiescence at the end of the host growing season was not found in M. fallax. This species hatched well in water and did not require hatch stimulation from root diffusate, irrespective of the age of the plant on which the egg masses were produced. The number of eggs per egg mass for M. fallax collected on senescing plants was significantly greater than the number of eggs per egg mass for M. chitwoodi. The number of eggs per egg mass of M. chitwoodi decreased with plant age. The results are discussed in the context of the differing survival strategies of the two species.

Abstract Analysis of the contraction and relaxation of pharyngeal musculature derives from measurements of electrical currents, termed electropharyngeograms (EPG). EPG were recorded from adults of six species of free-living nematodes, Anatonchus amiciae, Aporcelaimus superbus, Plectus parietinus, Mesorhabditis cranganorensis, Seleborca complexa and Panagrellus redivivus, during exposure to artificial pond water (APW) and to 0.1 mg ml-1 of the neurotransmitter serotonin for 5, 10 and 15 min. A marked difference was observed in the pharyngeal muscle activity of species with grinders in a three-part pharynx compared with that in species with cylindroid or two-part pharynx without grinders. The EPG results from the non-grinder predator A. amiciae showed no electrical activity in response to either APW or serotonin. There was no electrical activity from the non-grinder predator Aporcelaimus superbus in APW and only occasional electrical activity when it was exposed to serotonin; no stylet activity was observed in this species in any treatment combination. The four grinder species, P. parietinus, M. cranganorensis, S. complexa and P.redivivus, gave consistent EPG results in APW, irrespective of the period of exposure. The time intervals between two consecutive pharyngeal pumps were between 1.0 and 1.5 s for M. cranganorensis, S. complexa and P. redivivus but pharyngeal activity of P. parietinus was much slower with intervals of 4.8-4.9 s between two pumps. The effect of serotonin on these four species was inconsistent. Only P.redivivus showed EPG responses that demonstrated an enhanced rate of pharyngeal pumping; the rate of pumping of this species also increased with increase in exposure period to serotonin.

Abstract The total lipid (TL) content and the fatty acid composition of the different lipid classes in infective juveniles of Steinernema feltiae and Heterorhabditis megidis isolates from Greece (GR) and from the United Kingdom (UK) were compared, and the changes during storage were determined. Steinernema feltiae GR had a greater amount of TL than S. feltiae UK, which was reflected in a greater neutral lipid (NL) content. The phospholipid and free fatty acid fractions of the two Steinernema populations were similar. The two Heterorhabditis populations did not differ in their lipid content. In both S. feltiae populations, NL decreased by ca 60% during the first 4 weeks but remained more or less stable during the next 16 weeks. In the two Heterorhabditis populations, NL decreased by ca 70% during the first 4 weeks and continued to decrease, with 3-5% remaining after 12 weeks. The fatty acid profiles and the percentages of saturation of NL and phospholipid fractions in each population were similar before and after storage.

DiTera® (Valent BioSciences Corp.), a novel biological nematicide obtained from fermentation with a hyphomycete fungus, adversely affected activity and movement through sand columns of second stage juveniles (J2) of Globodera rostochiensis. Electrophysiological tests demonstrated that exposure to 1% DiTera® prevented sensory perception of potato root diffusate. Electropharyngeograms of stylet protractor muscle activity showed that prior exposure of fourth stage juveniles of Ditylenchus dipsaci and J2 of G. rostochiensis to 1% DiTera® significantly reduced stylet thrusting when nematodes were transferred to artificial tap water or 10 mM serotonin, respectively. The modes of action and the control potential of this biological nematicide are discussed.

Use of the electrophysiological technique to examine the sensory perception of live, intact nematodes has provided detailed analysis of responses to known concentrations of test chemicals. The use of larger nematodes, such as the animal-parasite Syngamus trachea, enabled direct extracellular recordings from individual sensilla; with smaller nematodes, the recording electrode was inserted close to the cephalic region. Extracellular recordings from the cephalic region of second-stage juveniles and males of the potato cyst nematodes, Globodera rostochiensis and Globodera pallida, were obtained after exposure to a variety of semiochemicals, including sex pheromones and certain putative phagostimulatory compounds. The responses of adult females of the animal-parasitic nematode, Brugia pahangi, to some possible host cues, and the inhibition by ivermectin of the response to a known allelochemical were investigated. Exposure to acetylcholine was used to compare the concentration-dependent responses of second-stage juveniles of G. rostochiensis and adult females of B. pahangi and the insect-parasitic nematode Leidynema appendiculata. Use of a perfusion system enabled sequential exposure of individual nematodes to different test chemicals or to different concentrations of the same chemical. Incubating second-stage juveniles of G. rostochiensis for 24 h in a mAb showing specificity to amphidial secretions resulted in blocking of the normal response to host root diffusates. The potential of the electrophysiology technique for analysing perturbation of sensory perception is discussed.

Analysis of the contraction and relaxation of pharyngeal musculature derives from measurements of electrical currents, termed electropharyngeograms (EPG). EPG of stylet protractor muscle activity of second stage juveniles (J2) of Globodera rostochiensis, in response to 0.1, 1.0 and 10 mg ml-1 concentrations of the neurotransmitter serotonin, have now been obtained and correlated with stylet protrusion and retraction using video analysis. The antagonist, gramine (10 mg ml-1), incorporated with 10 mg ml-1 serotonin, almost completely eliminated stylet thrusting by J2. Stylet movement can be determined accurately over extended periods with EPG and this approach has potential for investigating factors involved in activation and perturbation of stylet protrusion.

Dopamine-like immunoreactivity was detected in various parts of the nervous system of adult males and females of the free-living nematode Panagrellus redivivus , including the nerve ring and some cephalic processes, the ventral nerve cord, and the tail region. Positive immunoreactivity for dopamine was not found in infective second stage juveniles (J2) of the root-knot nematode Meloidogyne incognita. This putative neurotransmitter was detected by HPLC in homogenates of both species, the dopamine content in P.redivivus being eight times greater than in M. incognita. No other catecholamine compounds were detected in these species by HPLC. The development of a more sensitive immunocytochemical assay for dopamine will be required to determine the location of dopamine in the nervous system of M. incognita J2.

Summary Glyphosate, applied early or later or twice to genetically modified glyphosate-tolerant sugar beet, gave excellent control of planted ‘volunteer’ potatoes growing within the crop compared to conventional herbicide programmes with or without clopyralid. In three out of four trials, this resulted in significant reductions in the numbers of eggs and cysts of potato cyst nematodes (Globodera rostochiensis and G. pallida) where infestations were moderate (23–89 eggs g−1 soil). In the fourth trial, which had very high initial populations (130 eggs −1 soil), none of the herbicide treatments had any significant effect on numbers of nematode eggs or cysts. This was probably due to competition for feeding sites, and the early death of the potatoes in all treatments caused by feeding damage by the nematodes and infection by blight, which prevented the nematodes from completing their life cycle. Glyphosate also significantly reduced the number and size of daughter tubers produced, thus helping to prevent a further volunteer problem in the next crop in the rotation. This was achieved by one or two applications of one chemical compared to 2–5 applications of cocktails of conventional herbicides.

Abstract Electrophysiological techniques were developed to obtain recordings of electrical activity from the anterior end of live, second stage juveniles (J2) of Globodera rostochiensis. Sequential exposure of individual J2 to test semiochemicals was also possible using a modified perfusion system. Concentration-dependent responses were obtained from J2 during exposure to 0.1, 1, 10 and 100 mM acetylcholine. The delay before any response was not concentration-dependent. The responses to 10 mM concentrations of several chemicals known to elicit a feeding response in insects were assessed. There was a significant increase in spike activity when J2 were exposed to D-tryptophan but glycine and citric acid elicited no responses. Exposure to D-glutamic acid resulted in a significant increase in spike activity but exposure to the L-isomer gave no response. This was confirmed by sequential exposure of J2 to the L- then to the D-isomer. Exposure to potato root diffusate elicited a response, whereas a non-host root diffusate from sugar beet and female secretory-excretory (S-E) product caused no change in activity. Die Analyse chemosensorischer Reaktionen von Juvenilen des zweiten Stadiums von Globodera rostochiensis mit elektrophysiologischen Techniken - Zur Gewinnung von Informationen über die elektrische Aktivität des Vorderendes von Juvenilen des zweiten Stadiums (J2) von Globodera rostochiensis wurden elektrophysiologische Untersuchungsmethoden entwickelt. Aufeinander folgende Behandlungen einzelner J2 zur Prüfung von Semiochemikalien wurden auch durch ein verändertes Perfusionssystem erreicht. Bei der Behandlung von J2 mit 0.1, 1, 10 und 100 mM Acetylcholin wurden konzentrationsabhängige Reaktionen erzielt. Die Verzögerung vor dem Sichtbarwerden einer Reaktion war dagegen nicht konzentrationsabhängig. Es wurden auch die Reaktionen auf 10 mM Konzentrationen mehrerer Substanzen geprüft, die bei Insekten eine Nahrungsaufnahme auslösen. Bei D-Tryptophan trat eine deutliche Erhöhung der Spitzenaktivität ein, bei Glycin und Zitronensäure erfolgte keine Reaktion. Eine Behandlung mit DGlutaminsäure erhöhte die Spitzenaktivität deutlich, nicht jedoch das L-Isomer. Diese Beobachtung wurde bestätigt, wenn man die J2 erst dem L- und anschließend dem D-Isomer aussetzte. Die Behandlung mit Kartoffelwurzel-Ablaufwasser rief eine Reaktion hervor, nicht aber Wurzelextrakte des Nichtwirtes Zuckerrübe und Produkte des sekretorisch-exkretorischen Systems von Weibchen.

Abstract The root-knot nematode, Meloidogyne triticoryzae, produces three kinds of unhatched second stage juveniles (J2): i) those that hatch freely in water, ii) those that require stimulus from rice root diffusate (RRD), and iii) those that do not hatch even in the presence of RRD. The proportion of these three types varies with generation, with the final generation produced on senescing plants having a large proportion of unhatched J2 of the third type, which is likely to equate with diapause. Dilution of RRD reduced its hatching activity and there is no evidence of the presence of inhibitors in the diffusate. The hatching response of M. triticoryzae may be modified additionally by the growing conditions: submergence of infected plants may have delayed hatch, possibly by causing anoxybiosis in unhatched J2, and thereby delayed the appearance of the second and third generations of the nematodes. Le nématode Meloidogyne triticoryzae produit trois types de juvéniles de 2ème stade (J2) non encore éclos: i) ceux qui éclosent d’eux-même dans l’eau; ii) ceux qui requièrent le stimulus produit par le diffusat radiculaire de riz (RRD); enfin iii) ceux qui n’éclosent pas même en présence de RRD. La proportion de ces trois types varie avec la génération du nématode, la dernière génération, produite sur un hôte sénescent, contenant une grande proportion de J2 non éclos de type 3, ce fait représentant l’équivalent d’une diapause. La dilution du RRD diminue l’éclosion et aucune évidence d’inhibiteurs n’a été relevée dans le diffusat. Chez M. triticoryzae l’éclosion peut de plus être modifiée par les conditions de croissance de l’hôte; ainsi la submersion des plants infestés peut retarder l’éclosion, l’anoxybiose ainsi induite affectant vraisemblablement les J2 non éclos et retardant de ce fait l’apparition des deuxième et troisième générations du nématode.

Abstract Entomopathogenic nematodes were incubated in a balanced salt solution based on soil water analysis, supplemented with different concentrations of sodium chloride. Two nematode isolates from Malaysia, Steinernema sp. SSL85 (isolate 25) and Heterorhabditis indicus (isolate 11), showed an initial loss of water during the first 6 h of incubation in hyper-osmotic media (200 and 1000 mOsmKg-1) followed by a complete recovery of their water content during the next 18-48 h. A third Malaysian isolate, Steinernema sp. (M1), showed a more limited ability to regulate its water content. Studies on a wild type H. megidis (UK 211) and one desiccation tolerant mutant indicate that the ability for hypo-osmotic regulation does not necessarily involve permeability differences in the cuticle. Régulation hypo-osmotique chez les nématodes entomopathogènes: Steinernema spp. et Heterorhabditis spp. - Des nématodes entomopathogènes ont été mis en incubation dans une solution saline, équilibrée en fonction d'une analyse de l'eau contenue dans le sol, et additionnée de chlorure de sodium en concentration variable. Deux isolats de nématodes provenant de Malaisie, Steinernema sp. SSL 85 (isolat 25) et Heterorhabditis indicus (isolat 11), ont montré une perte initiale d'eau au cours des 6 premières heures d'incubation dans un milieu hyperosmotique (200 et 1000 mOsmKg-1), perte suivie par un rétablissement complet du contenu hydrique au cours des 18 à 48 h suivantes. Un troisième isolat malaisien, Steinernema sp. (M1) a montré une capacité plus limitée à réguler son contenu hydrique. Des études ayant concerné un type sauvage d' H. megidis (UK 211) et un mutant tolérant vis-à-vis de la dessication ont montré que la capacité d'une régulation hypo-osmotique n'infère pas une différence dans la perméabilité de la cuticule.

The infectivity of populations of the entomopathogenic nematodes Steinernema feltiae and Heterorhabditis megidis from Greece (GR) and the UK was compared using Galleria mellonella larvae as hosts. Dose-response tests showed that the two Steinernema populations did not differ in their establishment rates but they were more infective than H. megidis UK 211. The temperature range for infectivity was greater than that for development. However, the optimal temperature for infection and development for all populations was 23°C. Infectivity of Steinernema populations was not affected by storage for 12 weeks. However, 12 week-old H. megidis UK 211 infective juveniles (IJ) were less infective than fresh IJ. H. megidis GR showed very low establishment rates at all the doses and temperatures tested, before and after storage. The results are discussed in relation to the nematodes' climatic origin and lipid content. Pouvoir infestant de populations des nématodes entomopathogènes Steinernema feltiae et Heterorhabditis megidis suivant la température, l'âge et le contenu lipidique - Le pouvoir infestant de populations des nématodes entomopathogènes Steinernema feltiae et Heterorhabditis megidis provenant de Grèce et du Royaume Uni a été comparée, utilisant comme hôte Galleria mellonella. Les tests de dose/réaction ont montré que les taux d'établissement des deux populations ne diffèrent pas mais que leur pouvoir infestant était plus élevée que celle de H. megidis UK211. La plage des températures permettant l'infestation était plus étendue que celle relative au développement. Cependant, les températures optimales pour l'infestation et pour le développement étaient l'une et l'autre de 23°C pour toutes les populations. L'infestivité des populations de Steinernema n'a pas été affectée par un stockage de 12 semaines. Les juvéniles infestants de H. megidis UK211 âgés de 12 semaines montraient toutefois une infestivité plus faible que celle d'individus frais. Les specimens de H. megidis provenant de Grèce présentaient - que ce soit avant ou après le stockage - des taux d'établissement très faibles pour toutes les doses et les températures testées. Ces résultats sont discutés en relation avec l'origine climatique et le contenu lipidique des nématodes.

Upon immersion in water, anhydrobiotic nematodes display a period of apparent inactivity, the lag phase, before they commence spontaneous movement. Following a period of desiccation of the fourth stage juveniles of the plant-parasitic nematode Ditylenchus dipsaci, electrical activity during rehydration was recorded using glass microelectrodes inserted into individual nematodes. The pattern observed was a period of no electrical activity, followed by low amplitude electrical events and then also high amplitude events. Movement of the nematode was associated with the high amplitude events, whose recordings formed trains of spikes that coincided with the activity of the nematode. The lag phase represents a period during which the physiological functions of the nerves and muscles are restored. This may involve the restoration of ionic gradients between the inside and the outside of the cells, which is reflected in an increase in spike amplitude in those nematodes where a sustained period of high amplitude activity was recorded. Activité électrophysiologique durant la sortie d'anhydrobiose chez le quatrième stade juvénile de Ditylenchus dipsaci - Immergés dans l'eau, les nématodes anhydrobiotiques passent par une période d'inactivité apparente - la phase de latence - avant que des mouvements spontanés ne débutent. Pendant la réhydratation qui suivait une période de dessication l'activité électrique de juvéniles de quatrième stade de Ditylenchus dipsaci a été enregistrée grâce à des microélectrodes de verre implantées dans le nématode. La courbe observée correspondait à une période sans activité électrique, suivie par des phénomènes électriques de faible amplitude, combinés ensuite à des phénomènes de forte amplitude. Les mouvements des nématodes étaient associés aux phénomènes de forte amplitude dont le tracé consiste en une suite de pics coïncidant avec l'activité du nématode. La phase de latence correspond à la période pendant laquelle les fonctions physiologiques nerveuses et musculaires sont restaurées. Cela peut englober la restauration des gradients ioniques à l'intérieur et à l'extérieur des cellules, phénomène reflété par une augmentation des pics chez ceux des nématodes où une période soutenue d'activité de forte amplitude a été notée.

DiTera® (Valent Biosciences Corp.), a novel biological nematicide, did not stimulate hatch of Globodera rostochiensis or G. pallida, but exposing cysts to 1 and 10% DiTera® in distilled water for 5 weeks irreversibly prevented hatch when the cysts were transferred to the natural hatching stimulus potato root diffusate (PRD). Similarly, exposing cysts of both species for 5 weeks to 1 and 10% DiTera® dissolved in PRD resulted in a significant inhibition of hatch which was irreversible when cysts were transferred to PRD alone. Tests on free eggs indicated that, when mixed with PRD, DiTera® prevented eggshell permeability change, normally caused by PRD as an initial phase in the hatching process, in a majority of eggs. This indication that DiTera® interfered with the specific hatching mechanism of G. rostochiensis was reinforced by the lack of hatch inhibition of Meloidogyne incognita. The potential for DiTera® as a novel control agent to prevent hatch of G. rostochiensis or G. pallida in the field is discussed.Das neuartige biologische Nematizid DiTera® (Valent Biosciences Corp.) regte das Schlüpfen von Globodera rostochiensis und G. pallida nicht an. Wenn Zysten 5 Wochen lang in 1 und 10%igen Lösungen von DiTera® in destilliertem Wasser gehalten wurden, war das Schlüpfen auch nach Überführung in das natürliche Schlüpfmedium Kartoffelablaufwasser (PRD) irreversibel blockiert. In ähnlicher Weise trat eine signifikante Schlüpfhemmung auf, wenn die Zysten für 5 Wochen in 1 und 10%igen Lösungen von DiTera® in PDR waren. Diese Schlüpfhemmung war irreversibel, auch wenn die Zysten anschliessend in reines PRD gebracht wurden. Versuche mit freien Eiern zeigten, dass DiTera® in Mischung mit PRD den Wechsel in der Durchlässigkeit der Eischale verhindert, der normalerweise bei den meisten Eiern als Anfangsphase des Schlüpfvorganges durch PRD verursacht wird. Dieser Hinweis darauf, dass DiTera® den spezifischen Schlüpfmechanismus von G. rostochiensis stört, wurde dadurch bestätigt, dass das Schlüpfen von Meloidogyne incognita nicht gestört wurde. Die Verwendungdsmöglichkeiten von DiTera® als neuartiges Bekämpfungsmittel zur Verhinderung des Schlüpfens von G. rostochiesis oder G. pallida im Freiland werden diskutiert.

The D3 expansion region of the 28S gene and the ITS1-5.8S-ITS2 region of rDNA sequences from Globodera rostochiensis, G. pallida, G. tabacum tabacum, G. tabacum virginiae and G. tabacum solanacearum have been aligned and compared. There are no nucleotide differences in the D3 region sequences between G. rostochiensis and G. pallida. Sequence analysis and RFLPs of ITS-PCR products showed that several haplotypes are present in the genomes of G. rostochiensis and G. pallida populations. Restriction patterns of PCR products for eight enzymes for differentiation of these two species are given. Phylogenetic analysis of 41 ITS region sequences obtained from populations and species of the subfamily Punctoderinae revealed four distinct main clades within Globodera parasitising solanaceous plants: G. rostochiensis, G. tabacum, G. pallida and an undescribed Globodera sp. from South America. The utility of RFLP profiles and sequences of the rDNA are discussed for diagnostics and phylogeny of Globodera . Variabilité dans les séquences de l'ADN ribosomal et phylogénie des Globodera parasitant les Solanacées - La région d'expansion D3 du gène 28S et la région ITS1-5.8S-ITS2 des séquences d'ADNr de Globodera rostochiensis, G. pallida, G. tabacum tabacum, G. tabacum virginiae et G. tabacum solanacearum ont été alignées et comparées. Il n'y a pas de différence dans les nucléotides de la séquence de la région D3 entre G.rostochiensis et G.pallida. L'analyse séquentielle et les RFLP des produits du ITS-PCR montrent que plusieurs haplotypes sont présents dans les génomes des populations de G. rostochiensis et G. pallida. Les profils de restriction des produits du PCR de huit enzymes choisies pour la différenciation de ces deux espèces sont donnés. L'analyse phylogénique séquentielle de 41 regions ITS de populations et espèces appartenant à la sous-famille des Punctonerinae a révélé l'existence de quatre clades chez les Globodera parasitant les Solanacées: G. rostochiensis, G. tabacum, G. pallida et une espèce non décrite provenant d'Amérique du Sud. L'utilité pour le diagnostic et la phylogénie des Globodera des profils de RFLP et des séquences d'ADNr est discutée.