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Nematology
Brill Academic Publishers
Nematology

Brill Academic Publishers

1388-5545

Nematology/Journal NematologySCIISTP
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    Development and characterisation of SSR markers in the potato rot nematode Ditylenchus destructor

    Jukui MaJingwei ChenChengling Zhang
    11页
    查看更多>>摘要：The potato rot nematode, Ditylenchus destructor, causes serious disease limiting the production of many crops. This disease usually decreases sweet potato yield by 20-50%, and in heavily infested fields the crop may be completely lost. Although the nematode has economic importance in China, its transmission route and genetic diversity are unknown. In this study, a collection of 1761 contigs of the D. destructor genome was mined for simple sequence repeat (SSR) markers, which resulted in the identification of 9745 SSRs. A total of 150 pairs of SSR primers were further developed and used for validation of the amplification rate and assessment of the polymorphism. Nine SSR markers were finally identified and analysed using 96 individual specimens of D.destructor sampled from four provinces in China. These loci were found to be moderately polymorphic with 2-8 alleles per locus. The observed and expected heterozygosity across the four populations ranged from 0.000 to 0.833 and from 0.000 to 0.666, respectively. This is the first report of the development and characterisation of genomic SSR markers in D. destructor. Our study demonstrated the obvious gene differentiation among different populations of D. destructor in China. This suggests that D. destructor in China may have been introduced from multiple origins. Much more work is needed on this species to identify patterns of spread, and the microsatellite loci we develop here should be useful in many regions for modelling range expansion, studying the evolution of resistance, and increasing the effectiveness of pest management strategies.
      原文链接:
    • NSTL

    Influence of entomopathogenic nematodes, symbiotic bacteria and ascarosides on the dispersal behaviour of Meloidogyneincognita

    Li CaoZhihua HuangKang Dai
    11页
    查看更多>>摘要：Dispersal is an important behaviour for nematodes. Entomopathogenic nematodes (EPN) are able to regulate plant-parasitic nematodes in the field. However, the mechanism for the interactions between two types of nematodes is not clearly known. The effects of 12 synthesised ascarosides, three EPN species (Steinernema carpocapsae All, Heterorhabditis bacteriophora H06 and H. indica LN2), and 15 symbiotic bacterial isolates from EPN on the dispersal of Meloidogyne incognita were investigated. The resultsrevealed that M. incognita juveniles were repelled, to various degrees, by most of the tested ascarosides (especially ascr#9), three species of EPN, and by bacterial isolates (especially TT01 from H. bacteriophora TT01 and H06 from H. bacteriophora H06),compared with the controls. Ascr#9 was abundant in M. incognita juvenile-conditioned supernatant. This provides useful cues for elucidating the interaction mechanism between two nematode groups and establishing alternative techniques for the safe and effective control of root-knot nematodes.
      原文链接:
    • NSTL

    Parasitic variability of Meloidogyne hapla relative to soil groups and soil health conditions

    Isaac LarteyAlexandra KravchenkoGregory Bonito
    10页
    查看更多>>摘要：Parasitic variability (PV) of Meloidogyne hapla populations exists in broad production landscapes. How PV relates to soil health as described by the soil food web (SFW) is unknown. In an experiment replicated three times, nine M. hapla populations from muck and mineral soils with degraded and disturbed SFW conditions from three regions were used to test a hypothesis that PV varies by SFW conditions. The populations were inoculated at 2000 and 4000 eggs in 300 cm3 soil per pot. While the populations’reproductive potential varied by the SFW condition, soil group, region and/or their interactions, they clustered into high (Population 13), medium (Population 8), and low (all populations from muck and one from mineral soil) PV. Populations 8 and 13 arefrom degraded mineral soils and the low PV populations are from disturbed and degraded soils, indicating that the conditions where PV exists are variable within or across soil groups. Consequently, the hypothesis is not supported.
      原文链接:
    • NSTL

    Morphometric changes of the pine wood nematode, Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle, under different environmental conditions

    Pengfei WEIYongxia LiXuan Wang
    9页
    查看更多>>摘要：The pathogen of pine wilt disease, Bursaphelenchus xylophilus, has caused serious damage to forest ecology and the forestry economy. As an invasive species, the reproduction ability of B. xylophilus is a significant factor that influences its pathogenicity. There are few reports on the morphometric changes to B. xylophilus in different environments. This paper describes our study of the effects of fungal species, B. xylophilus population density, and nutrition on the growth and development of B. xylophilus and the comparative fitness of different-sized eggs in this species. The results showed that B. xylophilus could feed on different fungal species, but there were differences in the sizes of adult females and eggs and the number of offspring. Adultfemale size, egg size and number of offspring of B. xylophilus decreased as the population densities increased or mycelium weight decreased. The results also showed that larger eggs had a fitness advantage over smaller eggs under the experimental treatment conditions.
      原文链接:
    • NSTL

    Insect-parasitic phases in the development of the mycetophagous wood nematode, Bursaphelenchus trypophloei, in its vector, an aspen bark beetle Trypophloeus asperatus

    Marek TOMALAK
    14页
    查看更多>>摘要：Bursaphelenchus trypophloei is a common wood nematode associated with the poplar bark beetle, Tiypophloeus asperatus, in European aspen, Populus tremula. The nematode develops and reproduces in larval galleries of T. asperatus and is transmitted to new breeding trees by adult beetles during their flight and oviposition. Its dispersal third-stage juveniles (DJm) are unique because of their exceptionally early penetration into the haemocoel of the second- or third-larval stage of the future vector/hostand long-term (up to 10 months) occupation of this environment. Detailed morphological/anatomical, and bionomic study revealed that while living in the vector’s haemocoel the nematode dispersal/dauer juveniles pass through a series of intermittent changes with three distinct developmental phases. The sequence of these phases corresponded to the process of diapause observed in many plant and animal parasites. Throughout the period of living in the haemocoel, the nematodes remained at their dispersal juvenile stage (DJm) but clearly increased in size and changed their morphometries and shape of such anatomical/morphological characters as the metacorpus and tail terminus. Moreover, the juveniles apparently ingested the food from the vector’s haemolymph. Specifically, in the insect haemocoel, the body of dispersal/parasitic juveniles became less transparent with most organs being obscured by an increasing amount of refractive nutrient storage granules. After penetration into the insect the process of diapause was irreversible, irrespective of the availability of food (i.e., Leptographium spp. fungus). The nematodes could resume their further development only after the natural emergence from the vector beetle to its new galleries or a few days earlier,when mature third phase DJ (DJm.3) juveniles were dissected from the beetle and transferred to a fresh fungal culture. The data indicate that B. trypophloei is exclusively mycetophagous when free-living in the larval galleries of its insect vector, T. asperatus, and parasitic in the haemocoel of this insect.
      原文链接:
    • NSTL

    Evaluation of cover crops for reducing Heterodera glycines populations in microplot experiments

    Kamal NEUPANEGuiping YanAddison PLAISANCE
    13页
    查看更多>>摘要：Soybean cyst nematode (SCN; Heterodera glycines) is a major yield-reducing pathogen of soybean worldwide. Microplot experiments were conducted to evaluate ten cover crops for their effects on two SCN populations (SCN 103 and SCN2W) collected from North Dakota, USA, soybean fields in 2019 and 2020. Experiments were conducted in a randomised complete block design using naturally infested field soil. A susceptible soybean ‘Barnes’ and non-planted natural soil (fallow) were used as controls. Plants were grown in outdoor conditions for 75 days before soil samples were collected. SCN eggs and juveniles were extracted from the soil samples to determine final population, population reduction and suppression. Soybean had significantly greater final population densities than all the cover crops and fallow. All cover crops and fallow reduced the initial densities of both SCN populations. All the cover crops, except chickling vetch ‘Pulse’, had lower final population densities than fallow and suppressed the SCN populations throughout the experiments. Sunnhemp (cultivar not stated; CNS), oilseed radish ‘Concorde’ and ‘Control’, and daikon radish ‘Eco-Till’ significantly reduced the SCN103 population compared to fallow. Sunnhemp, alfalfa ‘Bullseye’,and daikon radish had significant population reductions of SCN2W than fallow. Sunnhemp was found to have the greatest reductions in SCN populations ranging from 55 to 86% compared to the initial densities. This study demonstrated cover crop species/cultivars with the ability to reduce SCN populations in outdoor conditions, and the findings indicate that they could be utilised in infested fields to manage SCN.
      原文链接:
    • NSTL

    Taxonomic revision of the free-living marine nematode genus Deontostoma (Enoplida: Leptosomatidae) and inclusion of a new species from the Southern Ocean

    Daisuke ShimadaNaoto JlMI
    17页
    查看更多>>摘要：A new species of free-living marine nematode, Deontostoma quadridentatum sp. nov., is described from a deep-sea sediment sample collected off the South Orkney Islands, the Southern Ocean, during a cruise (KH-19-6-Leg 4) conducted on the R/V Hakuho-Maru. Deontostoma quadridentatum sp. nov. differs from its congeners by the possession of: i) a cephalic capsule with a smooth posterior edge and without intralobar lacunae; ii) interlobar fenestrae with two posterior incisions; iii) four odontia on each mandible; iv) three onchia; v) spicules with velum and lateral process; vi) gubemacula with a hollow triangular crus, vii) one ventromedian supplement; viii) two precloacal subventral rows consisting of 8-10 setae and 12-20 papillae; and ix) by the lack ofocelli. Partial 18S rRNA and cytochrome c oxidase subunit I gene sequences were determined for D. quadridentatum sp. nov., and the diagnosis of Deontostoma and the dichotomous keys to the subfamilies of Leptosomatidae, genera of Deontostomatinae, and species of Deontostoma were revised. Two known species, Triceratonema montredonense comb. nov. and Triceratonema papillosum comb, nov., were transferred from Deontostoma. Our molecular phylogenetic analysis did not clarify the position of Deontostoma quadridentatum sp. nov., but we placed this species into Deontostoma based on morphological observations. We also tried to find a relationship between distribution and morphological characteristic because it seems that there are two phylogenetic lineages thatexist in Deontostoma based on the distribution of all species. However, no such relationships could be found from our literature survey.
      原文链接:
    • NSTL

    Responses of infective juveniles of the soybean cyst nematode (Heterodera glycines) and the root-knot nematodes (Meloidogyne hapla, M. incognita) to amino acids

    Ye JiangMinghui HUANGChunjie Li
    14页
    查看更多>>摘要：Plant-parasitic nematode infective juveniles (J2) use phytochemical signals released into the rhizosphere to locate host roots. Amino acids are the second most abundant metabolites of root exudates, but it is unknown if they are associated with J2 chemotaxis. In this study, J2 chemotaxis and mortality of the soybean cyst nematode (Heterodera glycines) and root-knot nematodes (Meloidogyne incognita and M. hapla) were examined in response to 15 amino acids and the corresponding pH values for tested amino acid solutions were measured. Responses varied by amino acid and among the species. Significant attraction, determined by J2 count within amino acid solution dispensers after 24 h exposure, occurred with 19 out of 45 J2-amino acid combinations. Heterodera glycines, M. hapla and M. incognita were attracted to nine, three and seven amino acids, respectively. Strongest attractions were to acidic polar amino acids aspartate and glutamate (H. glycines, M. hapla) and basic polar arginine (M. hapla), as previously reported, acid and basic pH attracting nematodes, thereby indicating that pH might be one of the attraction factors for these amino acids. All three nematodes exhibited clustering behaviours, such as halo or balling formations, just outside aminoacid solution dispensers, with H. glycines, M. hapla and M. incognita responding to four, 12 and two amino acids, respectively. Six of 15 amino acid solutions, representing a range of pH values, caused increased mortality. Certain aspartate and glutamate affected both H. glycines and M. hapla; arginine, aspartate, cysteine, lysine, methionine affected M. incognita', and cysteine caused complete mortality in M. hapla. All the results suggest that amino acids affect nematode attraction and mortality.
      原文链接:
    • NSTL

    New taxonomic information of Cryphodera kalesari (Nematoda: Heteroderidae)

    Sorokhaibam Mexico SlNGHPhougeishangbam Rolish SlNGHMayanglambam Ojit Kumar SlNGH
    10页
    查看更多>>摘要：A population consisting of only second-stage juveniles of Cryphodera kalesari (Nematoda: Heteroderidae) was detected in the rhizosphere of bamboo in a forest in Mizoram state of India. New taxonomical information is provided for the juveniles, including the first light microscopy and scanning electron microscopy images. The juveniles are characterised by a body length of 0.3-0.4 mm, lateral field with three longitudinal incisures forming two areolated bands, a well-sclerotised and offset lip region with three lip annuli, a robust and strong stylet measuring 25-28 /im in length, anteriorly flat to slightly concave knobs, a secretory-excretory pore often at isthmus level, a conoid tail 47-52 jim long tapering to a narrow rounded terminus, a pore-likephasmid, and a distinct hyaline portion of the tail occupying roughly half of the tail length. The first molecular data of C. kalesari (sequences of 18S and D2-D3 of 28S rRNA genes and COI gene of mtDNA) were found to be almost identical to that of an unidentified Cryphodera sp. reported from Myanmar, Thailand and Vietnam, indicating that C. kalesari is widespread across south-east Asia.
      原文链接:
    • NSTL

    Ultrastructural detection of intracellular bacterial symbionts in the wood-inhabiting nematode Bursaphelenchus mucronatus (Nematoda: Aphelenchoididae)

    Vladimir V. YushinLyubov A. GLIZNUTSAAlexander Ryss
    11页
    查看更多>>摘要：Ultrastructural observations of the wood-inhabiting fungal- and plant-feeding nematode, Bursaphelenchus mucronatus, revealed intracellular bacteria in the male and female gonads. In males, bacteria were present inside the testis epithelial cells, spermatocytes, spermatids and immature spermatozoa. Spermatheca of females contained amoeboid pseudopod-bearing mature spermatozoa with bacteria closely associated with the sperm nucleus. Tissues of the females studied were free from bacteria. The gram-negative bacteria in their localisation, size, ultrastructure, and especially characteristic internal bundle of parallel filaments, were identified preliminary as related to the genus Cardinium (Bacteroidetes), which includes obligate endosymbionts of diversearthropods and is known to be associated with several species of plant-parasitic nematodes.
      原文链接:
    • NSTL