The Japanese Nematological Society
Nematological Research (Japanese Journal of Nematology)
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Phylogenetic analyses of the lotus root parasitic nematodes Hirschmanniella diversa and H. imamuri based on the 18S ribosomal RNA (rRNA) gene and 5.8S rRNA gene/internal transcribed spacer region
Kuroda K., Kurashita H., Takagi M., Narihiro T., Hatamoto M., Yamaguchi T.
Nematological Research (Japanese Journal of Nematology), 2021, цитирований: 2, doi.org, Abstract
In this study, phylogenetic analysis was performed based on nearly full-length sequences of the 18S ribosomal RNA (rRNA) gene and 5.8S rRNA gene/internal transcribed spacer (ITS) region of the plant-parasitic nematodes Hirschmanniella diversa and H. imamuri and other related taxa. The analysis placed H. diversa and H. imamuri in Clade I with 3 known species, namely, H. santarosae, H. pomponiensis and H. gracilis. Among the hosts of these nematodes, families Poaceae and Typhaceae were consistent among H. diversa and the 2 species in Clade I. Phylogenetic analysis based on the 5.8S rRNA gene/ITS region suggests that Hirschmanniella spp. in all clades can parasitize family Poaceae. Interestingly, although H. imamuri and H. oryzae are both rice (Oryza sativa) root-parasitic nematodes, they were placed in Clade I and Clade III, respectively, indicating that they have different evolutionary histories.
Mermithid nematodes isolated from the shield bug Parastrachia japonensis
Iryu T., Tanaka R., Yoshiga T.
Nematological Research (Japanese Journal of Nematology), 2020, цитирований: 5, doi.org, Abstract
Mermithid nematodes are parasites of a wide range of invertebrates but information on their life history associated with their hosts is limited. Here we investigated mermithids isolated from the shield bug Parastrachia japonensis, a univoltine and sedentary insect, to understand their life cycles and the effect of parasitism on their host. Mermithids were detected from 5 out of 6 sampling locations with infection ratios of 0% to 16.1%. Most cases were monoparasitism but hyperparasitism was also observed. Mermithids emerged from the host late in the final host nymphal stage and the host immediately died after the mermithid emerged. No mermithid was detected from adults in the present survey. There was no correlation between weights of hosts and mermithids. In addition, there was no difference in the weights between the nematode-infected and non-infected hosts, and apparent morphological and behavioral changes were not observed in the nematodeinfected nymphs, suggesting that nematode parasitism does not affect the host before the nematodes emerge. Phylogenetic analysis revealed that two species of mermithids parasitize P. japonensis.
Sugarcane yield loss in the ratoon crop carried over from the plant crop damaged by plant-parasitic nematode in a heavy clay field in Okinawa, Japan
Kawanobe M., Miyamaru N., Yoshida K., Kawanaka T., Fujita T., Toyota K.
Nematological Research (Japanese Journal of Nematology), 2019, цитирований: 7, doi.org, Abstract
Many field experiments have revealed sugarcane yield loss due to plant-parasitic nematodes, especially in sandy soil, but limited in clay soil. We previously reported a 15% sugarcane yield reduction in the plant crop in a heavy clay soil due to lesion nematodes suppressing the number of sugarcane tillers in the early growth stage (Kawanobe et al., 2016). Yet, it is unknown whether such early growth inhibition in plant canes will affect the ratoon crop yield in clay soil. The objective of this study was to examine the carry-over effect of yield decline from the plant crop to the ratoon crop in a field with high clay content (> 80%), in which early growth inhibition, possibly due to lesion nematodes, was observed in a plant crop of sugarcane. Though the Pratylenchus population density remained unchanged among treatments (fosthiazate-treated, 3 kg and 7.5 kg/ha at spring planting, and non-treated control), after 5 months (July) from the spring planting until the harvest of the ratoon crop, our study showed a 20–25% higher yield of the ratoon crop in the fosthiazate-treated crop than in the non-treated control. The result in the plant crop carried over to the ratoon crop, and implied that the healthier root growth of the plant canes achieved by a one-time nematicide application would carry-over to the ratoon crop. The result also suggested that the number of tillers and cane length observed at 5 months (July) in the ratoon crop might adequately reflect nematode damage and offer a good explanation for the level of the ratoon crop yield.
Population densities of the pine wood nematode, Bursaphelenchus xylophilus, in dead pine trees caused by pine wilt disease in cool areas of Japan
Mamiya Y., Kobayashi K., Hoshizaki K., Yoshida A., Ohta K.
Nematological Research (Japanese Journal of Nematology), 2018, цитирований: 1, doi.org, Abstract
Pine wilt disease caused by the pine wood nematode, Bursaphelenchus xylophilus, (PWN), is the most devastating disease of pine trees (Pinus densiflora and P. thunbergii) in Japan. The disease has spread to the northern part of Japan, where the cool climate (annual mean temperature < 12℃) delays disease development. The current study, which was conducted in northern Japan, demonstrated PWN population dynamics in dead pine trees infected with PWN in the previous year and died in early spring through early summer. PWN numbers in dead trees were lower in the cold climate than previously reported in warm climates. PWNs were widely distributed throughout each dead tree and had a contagious distribution. Oviposition scars of the PWN vector, Monochamus alternatus, were not detected on the dead trees killed in spring to early summer because the time of disease development and tree death did not coincide with the time of insect oviposition.
Limited distribution of Caenorhabditis japonica in Japan
Yoshiga T.
Nematological Research (Japanese Journal of Nematology), 2018, цитирований: 2, doi.org, Abstract
Caenorhabditis japonica forms a species-specific and female host-biased phoretic association with the shield bug Parastrachia japonensis. To determine the distribution of C. japonica, nematodes from P. japonensis were surveyed in islands ranging from Kyushu to Okinawa of Japan. C. japonica was isolated from all 6 sampled populations of P. japonensis from Kyushu, Amami Oshima, and Tokunoshima Islands, but not from those from Okinawa Island. The limited distribution of C. japonica in these islands is suggestive of the origin of C. japonica and its limited phoretic association with P. japonensis in this region.
The composition of hindgut microbiota of Periplaneta japonica in the presence of thelastomatid parasitic nematodes
Vicente C.S., Ozawa S., Hasegawa K.
Nematological Research (Japanese Journal of Nematology), 2018, цитирований: 2, doi.org, Abstract
Thelastomatid nematodes (Nematoda: Oxyurida: Thelastomatoidea) are obligatory parasites that occur naturally in the hindgut of arthropods. Their origin and impact in the host is still unknown. Previous studies showed that the presence of thelastomatid nematodes in the gut of cockroaches (Periplaneta fuliginosa and P. americana) could influence the composition of their hindgut microflora. Through a metagenomic approach (16S rRNA V3-V4 sequencing), we have characterized the hindgut microbiome of P. japonica in the presence of thelastomatid nematodes (L1986, natural parasitic nematode Protrellus sp. present as a natural infection condition; and L1987, non-native parasitic nematode Leidynema appendiculatum present as an artificial infection condition). The hindgut microbiome of P. japonica in both conditions were mainly composed of Bacteroidetes, Firmicutes and Proteobacteria. Moreover, the natural and artificial infection by thelastomatid nematodes lead to shifts in the relative abundance of these main resident flora as seen in P. americana. The OTUs percentage of Bacteroidetes and Proteobacteria were higher in P. japonica infected with Protrellus sp. (L1986) than in P. japonica infected by L. appendiculatum (L1987), while OTUs from Firmicutes phylum was higher in L1987 than in L1986. This study fosters a detailed investigation in the role played by these animal parasites in their host insect.
Case study on a modified method to quantify the density of some soil-borne plant-parasitic nematodes in a simpler and less expensive way
Cheng Z., Shirai S., Toyota K., Ritz K.
Nematological Research (Japanese Journal of Nematology), 2018, цитирований: 2, doi.org, Abstract
Quantification of plant-parasitic nematodes (PPN) in soil with real-time PCR is a useful diagnosis to estimate damage to crops. However, previously reported methods involve high consumable and labor costs. The objectives of this study were to combine previously reported methods for soil pretreatment, DNA extraction and real-time PCR to quantify the density of soil-borne PPN in a simpler and less expensive way and to confirm the usefulness of a new simple method. Soils infested with either Heterodera glycines (soybean cyst nematode), Ditylenchus destructor (potato rot nematode) or Meloidogyne incognita (root-knot nematode) were ball-milled. DNA was then extracted with phosphate buffer and purified with a commercially available column. Real-time PCR was conducted to quantify the target nematodes. The cycle threshold (Ct) values obtained by the new method showed highly significant correlations with those by the conventional method for all three species (R2 > 0.75). Significant correlations (R2 > 0.987) were also obtained between the Ct values and the numbers of nematodes inoculated into soils. The DNA extraction from 6 samples by the new simple method required only 1 hr and about $4.8 of consumables, while that by the conventional method required 3 hr and about $12 of consumables. These results demonstrate that the method consisting of ballmilling and simple DNA extraction enables rapid and less expensive quantification of nematodes in soils.
Southern root-knot nematode race SP6 is divided into two races
Tabuchi H., Kuranouchi T., Kobayashi A., Monden Y., Kishimoto K., Tahara M., Okada Y., Iwahori H.
Nematological Research (Japanese Journal of Nematology), 2017, цитирований: 6, doi.org, Abstract
The southern root-knot nematode (SRKN) includes at least nine races, SP1 to SP9, which were identified based on their different responses to five differential sweetpotato cultivars, ' Norin-1', ' Norin-2', 'Tanegashimamurasaki-7', 'Elegant Summer', and 'J-Red'. In this study, we propose a modified method for SRKN race identification in which the threshold of response is 10 egg masses instead of the two-egg-mass threshold used in the original method, when a sweetpotato plant was inoculated with 500 second-stage juveniles. According to this method, two isolates of SP6, Okiishi-12 and Ishigaki-2, showed the same response to each of these five cultivars. We found, however, that three sweetpotato cultivars, 'Murasakimasari', 'Suzukogane', and 'Chienoha', were resistant to the Okiishi-12 isolate and susceptible to the Ishigaki-2 isolate. These results indicated that the Okiishi-12 and Ishigaki-2 isolates were distinct and that SP6 included at least two races. We suggest that the Okiishi-12 and Ishigaki-2 isolates should be distinguished by sub-numbers and designated SP6-1 and SP6-2, respectively. Five isolates of SP6 collected from a sweetpotato field in Chiba prefecture were examined, and all of them were identified as SP6-1.
Nematode fauna of paddy field flooded all year round
Okada H., Niwa S., Hiroki M.
Nematological Research (Japanese Journal of Nematology), 2016, цитирований: 2, doi.org, Abstract
The rice paddy fields in Asia are being recognized as biodiversity hotspots. We have reported the seasonal dynamics of nematode communities in a conventional type of paddy field (CPF) in Japan, which is flooded only in spring and summer. The CPF nematode fauna included the typical taxa of bacterial feeders (BAC) and algal feeders (ALG) that inhabit the sediment of freshwater ponds or lakes, as well as fungal feeder + facultative root feeder (FFR) and obligatory root feeders (ORF). Here, we report on the nematode fauna of paddy fields flooded all year round (PFF), which were developed to imitate" yatsu" paddy fields located at the bottom of a valley. We examined the fauna at soil depths of 0–50 mm in May, August, and November, 2008. One half or more of the total nematode abundance was concentrated into the 0–15 mm layer. This concentration was enhanced after the physical disturbances of puddling and rice transplanting in June. Nevertheless, the compositions of feeding groups and nematode taxa were stable across the study seasons, and generally identical across soil layers. PFF fauna comprised typical sediment taxa with two dominant BAC, Paraphanolaimus (Aphanolaimidae) and Paraplectonema (Leptolaimidae) (60–90% of total density), whereas the FFR and ORF taxa were scarce. Not surprisingly, the PFF fauna was quite different from those in the adjacent terrestrial habitat (ATH), which was composed mainly of FFR and ORF taxa. PFF fauna, however, also had some taxa in common with ATH; e.g., BAC of Monhysteridae, Aphanolaimus, and Chronogaster. Patches of wet peat moss in ATH might be important for the occurrence of these taxa.
Axenic liquid static culture of entomopathogenic nematode Steinernema carpocapsae supplemented with nematode-infected insect cadaver
Fuchi M., Ono M., Kondo E., Yoshiga T.
Nematological Research (Japanese Journal of Nematology), 2016, цитирований: 5, doi.org, Abstract
To establish an easy axenic culture method for Steinernema carpocapsae and to understand the nutrition provided for nematode growth and propagation produced in the insect cadaver, we tested several supplementations to axenic liquid cultures. S. carpocapsae grew but reproduced poorly on the liquid static axenic culture developed for bacterial-feeding nematodes; however, supplementation by S. carpocapsae-infected insect cadavers sterilized by autoclaving largely improved nematode growth and propagation. These results suggest supplementation of the cadaver is a useful method to improve axenic culture and the autoclaved nematode-infected insect contains important heat-stable nutritional factors for the growth and reproduction of S. carpocapsae.
Continuous effects of winter flooding on soil fauna, as revealed by community structure of soil nematodes in a paddy field in northern Japan
Takemoto S., Akita K., Katayanagi N., Urata E., Ito T., Saito M., Okada H.
Nematological Research (Japanese Journal of Nematology), 2016, цитирований: 1, doi.org, Abstract
Beneficial effects of winter flooding in rice paddies have been proved for birds and other above-ground wildlife. However, there have been few studies that accounted for soil organisms. In this study the effects of winter flooding together with an organic amendment on soil fauna as represented by nematodes were examined. Soil samples were taken from experimental rice paddies in northern Japan with one of three treatments, i.e., winter flooding with organic farming (WFO), no winter flooding with organic farming (NFO), and no winter flooding with conventional farming (CVN, only chemical fertilizers and chemicals applied). During this study period of over one year and a half, nematodes were extracted and counted to estimate their density. Then to evaluate nematode diversity, a polymerase chain reaction-denaturing gradient gel electrophoresis analysis of the nematode 18S rRNA gene was conducted， which found 34 operational taxonomic units with Tobrilus spp. and Hirschmanniella sp. as the three most dominant taxa. Statistical analysis showed the following trends: 1) nematode density in the 0–5 cm soil layer was WFO > NFO > CNV, and 2) nematode diversity, H′, in the 5–10 cm layer was WFO < CNV < NFO. The results of our nematode and soil physico-chemical analyses suggest, 1) winter flooding and organic farming could increase nematode density at least in the upper soil layer with increased fertility, and 2) on the contrary, winter flooding could be harmful to maintain nematode diversity in the deeper part of soil, probably due to an increased soil reduction level.
Host suitability of a common oat cultivar Sniper for five plant-parasitic nematode species
Tateishi Y., Uesugi K., Iwahori H.
Nematological Research (Japanese Journal of Nematology), 2016, цитирований: 3, doi.org, Abstract
A newly bred, common oat cultivar Sniper, which has originated from Tachiibuki, a known fall forage cultivar that suppresses root-knot nematodes damage to succeeding crop of sweet potatoes, was tested to examine its susceptibility to five major nematode species which were distributed in upland of Kyushu, Japan.Sniper showed poor host suitability to the four Meloidogyne species in a pot experiment.Meanwhile, its host suitability for Pratylenchus coffeae was similar to that exhibited by other common oat cultivars examined in this study.Nematol.Res. 46(1), 21-24(2016).
A field experiment with nematicide treatment revealed potential sugarcane yield loss caused by plant-parasitic nematodes in Okinawa, Japan
Kawanobe M., Miyamaru N., Yoshida K., Kawanaka T., Toyota K.
Nematological Research (Japanese Journal of Nematology), 2016, цитирований: 5, doi.org, Abstract
Sugarcane yield in Japan has continuously decreased by 17% over the past 20 years. The objective of this study was to quantify the sugarcane yield loss caused by plant-parasitic nematodes (PPN) under field conditions in Japan. We set up 15 plots in a sugarcane field in Kitadaito, Okinawa, and assigned them to nematicide-treated (fosthiazate, 3 kg (×0.7) and 7.5 kg (×1.7) per ha) and non-treated control plots in 5 replicates. Initially, the numbers of lesion nematodes (Pratylenchus zeae) did not differ significantly among the three treatments, but were significantly lower in ×1.7 fosthiazate than in the control after 3 and 5 months. Sugarcane yield in 12 months was significantly higher by ca. 15% in both the ×0.7 and ×1.7 nematicidal treatment (55 t/ha) plots than in the control (48 t/ha) plots. The results implied that the lesion nematode may suppress the number of tillers in the early stage, resulting in yield reduction.
Reproduction of Meloidogyne incognita on eggplant rootstock cultivars and effect of eggplant rootstock cultivation on nematode population density
Uehara T., Sakurai M., Oonaka K., Tateishi Y., Mizukubo T., Nakaho K.
Nematological Research (Japanese Journal of Nematology), 2016, цитирований: 6, doi.org, Abstract
The southern root-knot nematode Meloidogyne incognita is an important pathogen of solanaceous plants worldwide. To assess resistance and suppressiveness to the nematode of the Japanese cultivars of eggplant rootstocks, we conducted greenhouse experiments. Numbers of nematode egg masses were significantly lower on Solanum torvum rootstock cultivars, Tonashimu, Torero, and Torvum vigor, than the cultivars of the other Solanum species after 45 days of cultivation. Next, we examined the effect of Tonashimu on the population density of the nematode in soil. After 116 days of cultivation, the second-stage juvenile density of the nematode in soil was reduced, and was significantly lower in pots of Tonashimu, than in those of Solanum melongena cultivars. These results suggest that the Japanese rootstock cultivars of S. torvum are resistant to the nematode, and could suppress nematode density in soil.
Detection of Meloidogyne species from wild herbaceous plants in non-crop fields in northwest Kyushu, Japan
Ishibashi Y., Yoshiga T.
Nematological Research (Japanese Journal of Nematology), 2016, цитирований: 2, doi.org, Abstract
Root-knot nematodes (Meloidogyne spp.) were surveyed from suitable wild herbaceous plant hosts in non-crop fields at an elevation of less than 200 m of northwest Kyushu by pulling out and observing the root systems for galls. Nematodes were detected in 10 out of 49 surveyed sites (20%): M. hapla in nine sites and M. incognita in one site. Nematodes were identified by perineal patterns of adult females or size of amplicon of partial mitochondrial DNA. Our survey suggests that M. hapla is the predominant species in non-crop fields in northwest Kyushu.
Characterizations of community and trophic structures of soil nematodes in a coastal Japanese black pine forest
Kitagami Y., Torii M., Matsuda Y.
Nematological Research (Japanese Journal of Nematology), 2016, цитирований: 9, doi.org, Abstract
The species diversity and abundance of soil nematodes can be an indicator reflecting environmental changes in a given soil ecosystem. As a rather simple type of forest ecosystem, coastal pine forests make a good model system for characterizing nematode communities. The purpose of this study was to determine the heterogeneity and community structure of soil nematodes in a coastal Japanese black pine (Pinus thunbergii) forest. We examined nematodes from sandy soils in the forest over one year and divided them into trophic groups based on morphological traits. The abundance of nematodes (per g dry soil) in all plots ranged from 0.4 ± 0.2 (mean ± SD) in February to 8.3 ± 4.4 (mean ± SD) in July. There was a significant interaction in the abundance of nematodes between the plots and months. Among 7,295 nematodes detected, the 18 taxa retrieved were dominated by the genera Aphelenchoides (24.3%), Ditylenchus (19.0%), and Acrobeloides (18.6%). The trophic structures of nematodes were continuously dominated by bacterivorous and fungivorous ones. These findings suggest that nematode distribution was spatially heterogeneous, their abundance varied with time, and the rather limited taxa of these trophic groups likely play important roles in the coastal soil ecosystem.
Pathogenicity of the axenic entomopathogenic nematode Steinernema carpocapsae against Galleria mellonella and Spodoptera litura larvae
Fuchi M., Ono M., Kondo E., Yoshiga T.
Nematological Research (Japanese Journal of Nematology), 2016, цитирований: 3, doi.org, Abstract
Pathogenicity of the entomopathogenic nematode Steinernema carpocapsae depends on its symbiotic bacterium Xenorhabdus nematophila. To understand the pathogenicity of the nematode itself, and its influence on insect tissues, we compared nematode invasion, insect mortality, nematode development in insects, and differences in the effects on the insect tissues between infection by axenic or monoxenic nematodes. Invasion of axenic infective juveniles (IJs) was lower than that of monoxenic IJs. Axenic as well as monoxenic nematodes killed both axenic and xenic Galleria mellonella and Spodoptera litura larvae, although it took a longer time for axenic nematodes to kill the insects, especially axenic ones. Axenic nematodes grew and reproduced in insects; however, their growth and reproduction were delayed as compared to that of monoxenic nematodes. Tissue destruction of axenic IJ-infected insect larvae was delayed as compared with monoxenic IJ-infected insect larvae, and suppression of insect hemolymph melanization was not observed in the axenic nematodes. These results suggest that S. carpocapsae is able to kill insects and partly degrade insect tissues in the absence of any bacteria; however, the pathogenicity of axenic nematodes is weaker than that of monoxenic nematodes.
A simple method for the detection and discrimination of Pratylenchus and Meloidogyne species in nematode communities
Kushida A., Kondo N.
Nematological Research (Japanese Journal of Nematology), 2015, цитирований: 2, doi.org, Abstract
We developed a very simple method for simultaneous detection and discrimination of the principal Pratylenchus and Meloidogyne species in nematode communities collected from Japanese fields. The method consists of a single polymerase chain reaction (PCR) and polyacrylamide gel electrophoresis (PAGE) process using group-specific primers (PNem-F and PNem-R1, 2) constructed from the rDNA-ITS region. DNA from the target species (nine Pratylenchus species and three Meloidogyne species) was amplified with sufficient specificity, and most PCR products could be clearly separated by PAGE using a commercial precast polyacrylamide gel. Although these primers also amplified the DNAs of cyst nematodes and Scutellonema brachyurum, as the sizes of these PCR products were larger than those of the target species, detection and discrimination of the target species bands was not hindered. Even when two or more target species coexisted in a community, these could easily be detected and distinguished, simultaneously and accurately. We confirmed that the combination of a group-specific primer with a community analysis technique was effective for nematode diagnosis. Thus, this method could be a useful tool for the diagnosis of Pratylenchus and Meloidogyne species in Japanese fields.
Protocol for root-knot nematode culture by a hydroponic system and nematode inoculation to Arabidopsis
Nishiyama H., Ngan B.T., Nakagami S., Ejima C., Ishida T., Sawa S.
Nematological Research (Japanese Journal of Nematology), 2015, цитирований: 14, doi.org, Abstract
Root-knot nematodes (Meloidogyne incognita) are one of the most economically damaging nematodes; thus it is important to know the molecular mechanisms involved in the phases of nematode infection.To use this nematode as a material for research, we must constantly prepare sufficient numbers of nematodes, preferably sterilized.Here we have developed alternative methods for culture, sterilization, and inoculation of root-knot nematodes that are especially suitable for the use of Arabidopsis thaliana Heynh as host plants.Nematol.Res. 45(1), 45-49(2015).
Development of real-time PCR primers specific to the garlic-damaging potato rot nematode Ditylenchus destructor to quantify its density in soil and outer skin of garlic
Cheng Z., Toyota K., Yamashita K.
Nematological Research (Japanese Journal of Nematology), 2015, цитирований: 6, doi.org, Abstract
The potato rot nematode Ditylenchus destructor is a major threat to garlic production in Aomori Prefecture, Japan. The objectives of this study were i) to design real-time PCR primers specific to D. destructor, and ii) to make calibration curves to evaluate the relationships between the number of D. destructor inoculated to soil or outer skin of garlic and the cycle threshold (Ct) values. Ditylenchus destructor strains were collected from 11 major growing regions in Aomori Prefecture and their ITS regions were sequenced. Strains from different regions showed the same sequence and, thus, real-time PCR primers specific to D. destructor were designed. The specific primers (Ddf and Ddr) matched 100% with 10 out of 11 D. destructor sequences from different countries as well as with the Aomori strains, while there are 7 and 16 bp mismatches in the closest species D. africanus and D. askenasyi, respectively. There were highly significant correlations (soil: y =－1.1221x + 35.225, R2 = 0.9973; outer skin of garlic: y =－1.145x + 35.295, R2 = 0.9883) between the log-transformed numbers of nematodes inoculated (x) and the respective Ct values (y). Based on this calibration curve, the densities of D. destructor in soils were estimated to be 43/10 g of soil in an infested field and 0/10 g of soil in a field without a history of garlic cultivation. These results demonstrated that the presently designed primers are useful to quantify the density of D. destructor in both soil and garlic.
Root-knot nematode species and the frequency of resistance-breaking nematodes in major green pepper production regions of Japan
Iwahori H., Uesugi K., Sugita W.
Nematological Research (Japanese Journal of Nematology), 2015, цитирований: 2, doi.org, Abstract
ピーマンの主要産地である宮崎県、鹿児島県、高知県、茨城県の線虫汚染ピーマン圃場50 カ所より土壌および被害根を採取し、これらよりネコブセンチュウの2 期幼虫および雌成虫を分離し、PCR-RFLP法によって各圃場10 ～ 25個体を1 頭ずつ同定した。その結果、同定された種は、1例を除きすべてサツマイモネコブセンチュウであった。また、上記の汚染圃場のうち31 圃場について、これらの線虫汚染土壌20 g を3 系統の線虫抵抗性トウガラシ（CM334、LS2341、PI322719）に接種したところ、6 圃場（19%）の汚染土壌において多数の根こぶおよび卵嚢が形成された。このことより、これらの圃場では抵抗性打破線虫が高い頻度で生息していると考えられた。
Distinguishing between inactivated and dead second stage juveniles of Meloidogyne incognita using the NaOH method
Harada Y., Yoshiga T.
Nematological Research (Japanese Journal of Nematology), 2015, цитирований: 14, doi.org, Abstract
The ability to distinguish inactivated nematodes from dead ones is sometimes difficult because of their immobile. We tested whether the NaOH method could be applied to distinguish second stage juveniles (J2s) of the root-knot nematode Meloidogyne incognita that were inactivated under different conditions. The J2s inactivated by abamectin, a GABA agonist, or under the hypoxic conditions caused by CO2, reacted to the addition of NaOH. On the other hand, the J2s inactivated by fosthiazate, an organophosphate that causes muscle contraction, and those by NaN3, which inhibits respiration, did not react well to the NaOH treatment. However, these J2s reacted to the NaOH treatment after subsequent removal of the chemicals. The J2s inactivated by low temperature showed no reaction to the NaOH treatment. The NaOH method was demonstrated to be applicable for naturally immobilized nematodes such as the entomopathogenic nematode Steinernema litorale and the plant parasite Aphelenchoides besseyi. These results suggest that the NaOH method is applicable to distinguish between inactivated and dead nematodes but caution is warranted with regard to treatment temperature and the modes of action of the chemicals that are used.
First record of the free-living marine nematode Deontostoma magnificum (Timm, 1951) Platonova, 1962 (Nematoda: Leptosomatidae) from Japan
Shimada D., Kakui K.
Nematological Research (Japanese Journal of Nematology), 2015, цитирований: 6, doi.org, Abstract
We describe and illustrate the free-living marine nematode Deontostoma magnificum (Timm, 1951) Platonova, 1962 (Nematoda: Leptosomatidae) as a new record of this genus from Japanese waters. Specimens examined agree well with the original and redescriptions of D. magnificum in the characters of the cephalic capsule, the buccal cavity armed with mandibles and teeth-like structures, the ocelli, and the male genital organs. We also provide partial DNA sequences of the mitochondrial cytochrome c oxidase subunit I (COI) and the nuclear 18S ribosomal RNA genes for DNA based identification.
Detection of the potato cyst nematode resistance gene Hero A in Japanese tomato cultivars by the PCR-RFLP method
Uehara T., Narabu T., Ito K., Masuta C.
Nematological Research (Japanese Journal of Nematology), 2015, цитирований: 1, doi.org, Abstract
We developed polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) markers for the potato cyst nematode (PCN) resistance gene Hero A in tomato. Using these PCR-RFLP markers, we evaluated the presence of Hero A in 22 tomato cultivars. All cultivars displayed complete concordance between their PCN phenotype and the genotype as determined by PCR-RFLP. We confirmed that PCN-resistant tomato cultivars in Japan contained the Hero A gene, whereas susceptible cultivars did not. PCN is a highly important quarantine pest, and the PCR-RFLP markers for Hero A provide a means of testing for resistance without the need to use live nematodes.
Quantification of lesion nematode (Pratylenchus zeae), stunt nematode (Tylenchorhynchus leviterminalis), spiral nematode (Helicotylenchus dihystera), and lance nematode (Hoplolaimus columbus), parasites of sugarcane in Kitadaito, Okinawa, Japan, using real-time PCR
Kawanobe M., Miyamaru N., Yoshida K., Kawanaka T., Toyota K.
Nematological Research (Japanese Journal of Nematology), 2015, цитирований: 15, doi.org, Abstract
The lesion nematode (Pratylenchus zeae), the stunt nematode (Tylenchorhynchus leviterminalis), the spiral nematode (Helicotylenchus dihystera), and the lance nematode (Hoplolaimus columbus) were major plant-parasitic nematode (PPN) species identified in the sugarcane fields on Kitadaito Island, Okinawa, Japan, for which real-time PCR primer sets were developed. Since the four PPN species ubiquitously inhabited Kitadaito, P. penetrans, which was confirmed to be absent in Kitadaito, was used as a benchmark to establish a soil calibration curve. Kitadaito soil samples were inoculated with juveniles and adults of P. penetrans at densities of 8, 32, 128, and 256/10 g fresh soil, and a soil calibration curve was obtained: y =-0.95x + 34.83 (y = Ct values, x = log2 (the number of P. penetrans ). The soil calibration curve was consistent with a calibration curve derived from serially diluted DNA samples of handpicked single P. penetrans (y =-1.01x + 34.73), after adjusting the DNA dilution rates to the densities in soil. The results suggested that calibration curves developed using serially diluted DNA samples (y =-1.13x + 37.00, y =-0.99x + 30.76, y =-1.06x + 35.52, and y =-1.00x + 28.96 for P. zeae, T. leviterminalis, H. dihystera, and H. columbus, respectively) may be appropriate to quantify target PPN in Kitadaito soil.
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