Journal of nematology最新文献

Viviparity is a very rare reproductive mode in nematodes, having been documented in only six species. Five of these species have been isolated among the dung beetles Onthophagus, suggesting that studying the environments associated with dung beetles may help shed light on why viviparity evolved in these particular species. Onthophagus atripennis is often closely associated with the viviparous nematode Tokorhabditis atripennis, as well as some other oviparous nematodes. Hence, the system involving T. atripennis and dung beetles could provide valuable insights into the adaptive significance of viviparity in nematodes. To explore this idea, it is essential to first gain a better understanding of the natural habitats of T. atripennis, which remain poorly understood. Therefore, we investigated the nematode communities associated with O. atripennis and identified potential habitats for T. atripennis in environments used by dung beetles. Nematodes associated with O. atripennis and those inhabiting its rearing cases were isolated from samples. Two Tokorhabditis species were isolated from the rearing cases of O. atripennis, suggesting that they inhabit environments used by O. atripennis. Regarding other oviparous nematodes, some appeared to have relatively strong associations with dung beetles, but more detailed studies are needed to confirm their specific habitats. Although further investigations are necessary, the fact that nematodes, including viviparous species, were isolated from environments used by dung beetles provides important information about the potential competitors or predators of T. atripennis in such environments.

Aeonium, or tree houseleek (Aeonium arboreum), is a bushy, perennial succulent and a popular ornamental plant in regions such as California, New Zealand, Australia, Sicily, Gibraltar, and Chile. It features rosettes of soft, waxy leaves at the tips of sparsely branched or occasionally single, bare stems. It is drought-tolerant and has a variety of colors and forms, making it a popular ornamental plant. In July 2024, a diseased Aeonium plant was submitted by a home gardener from Los Angeles County, California, to the Department of Nematology at the University of California, Riverside (UCR), for diagnosis. Root galls were observed on the plant, and further examination revealed high numbers of root-knot nematodes (Meloidogyne sp.). Molecular species identification was conducted using ribosomal DNA, mitochondrial haplotyping, and species-specific primer techniques, including the TRNAH/MHR106 and MORF/MTHIS primer sets, along with Meloidogyne incognita-specific primers (MIF/MIR). Amplification and sequencing of the marker genes identified the root-knot nematode infecting Aeonium as M. incognita. To our knowledge, this study presents the first report of M. incognita infecting Aeonium worldwide.

Fluensulfone is the active ingredient of the non-fumigant nematicide Nimitz. It is much less harmful to the environment and has much improved worker safety compared to broad-spectrum fumigant nematicides. The product is registered for use in a variety of crops, including fruiting vegetables, and is applied to soil 7-14 days before seeding or planting. Although labeled for soil application, earlier research suggested that fluensulfone has systemic nematicidal activity when applied as a leaf spray application but also may cause some phytotoxic effects in some crops when applied as a leaf spray. In replicated greenhouse pot experiments, the nematicidal activity and phytotoxicity of fluensulfone applied as a soil drench was compared to a leaf spray application in tomato, eggplant, melon, and three pepper cultivars. A leaf spray application with fluensulfone significantly reduced Meloidogyne incognita infestation of the roots but was highly phytotoxic to melon and eggplant. Tomato and particularly peppers were less sensitive to fluensulfone leaf sprays. In further experiments we showed that the active ingredient is exuded or leaks out of the roots into the rhizosphere as spraying tomato or pepper plants with fluensulfone resulted in a high mortality of M. incognita second-stage juveniles in a water suspension surrounding the roots. This effect was observed within 12-24 hr after the spray application.

Strawberries are primarily cultivated in the Central Region of Costa Rica due to the favorable growing conditions there. However, several factors can affect the final yield and quality of strawberries, including the presence of plant-parasitic nematodes (PPN). Unfortunately, no surveys have been conducted in the country to identify the PPN affecting production. This study aimed to identify morphologically PPN genera associated with strawberry in the Central Region of Costa Rica, and to identify the Meloidogyne and Pratylenchus species using molecular techniques. A nematode survey was performed between 2018 and 2021 across four provinces: Cartago, Alajuela, Heredia, and San José. The most frequent nematodes found in both root samples (n = 55) and soil samples (n = 53) were Meloidogyne (Frequency of occurrence, FO = 78% in root and 62% in soil) and Pratylenchus (FO = 56% and 43%, respectively) (p < 0.05). Molecular techniques with species-specific primers, such as PCR-RFLP and PCR, allowed for the identification of 13 Meloidogyne populations, all confirmed to be M. hapla. DNA sequencing of the partial mitochondrial COI gene and PCR with species-specific primers found 11 Pratylenchus populations, with 10 identified as P. penetrans and one as P. hippeastri. Further studies should focus on pathogenicity assays with a diversity of strawberry cultivars to assess damage potential and develop strategies for integrated management of PPN in strawberry production.

Soybean cyst nematode (SCN; Heterodera glycines) is a major pathogen of soybean (Glycine max) in North America. Although nematodeprotectant seed treatments can complement SCN-resistant soybean varieties in managing this pathogen, their efficacy across different SCN virulence phenotypes remains unclear. This study evaluated whether SCN phenotype influences seed treatment performance and assessed treatment effects on SCN reproduction under controlled conditions. Seeds of the SCN-resistant variety P37A27X (PI 88788) were treated with a base fungicide and insecticide, or the base combined with Aveo EZ (Bacillus amyloliquefaciens); Bio ST (heat-killed Burkholderia rinojensis); Clariva PN (Pasteuria nishizawae); ILEVO (fluopyram); Saltro (pydiflumetofen); or Trunemco (cis-jasmone and B. amyloliquefaciens). Untreated resistant and susceptible seeds served as controls. One non-virulent (HG type 0) and two virulent (HG types 2.5.7 and 1.2.5.7) phenotypes were tested, and treatments were evaluated 30 days after planting. Base-and-ILEVO treatment reduced the population of SCN females by 29% to 72% across phenotypes, and also reduced root mass by 28%, indicating early phytotoxic effects.

The new nematode species Hoplolaimus tuberosus n. sp., isolated from potato rhizosphere in Budwale sub-county, Mbale district, Eastern Uganda, is characterized based on light and scanning electron microscopy alongside four molecular markers. Females of H. tuberosus n. sp. are moderately large (1.2-1.6 mm) and exhibit distinctive morphological features, including an offset lip region with 4-5 lip annuli, a basal lip annule divided into 10-12 irregular blocks, a robust stylet (45-50 μm), a variable lateral field, characterized by one incisure (zigzag longitudinal line formed by anastomoses) anteriorly and posteriorly, and 2-3 irregular, incomplete striae at mid-body, a secretory-excretory pore positioned anterior to the hemizonid, 6 gland nuclei, and a hemispherical to bluntly rounded tail with 8-10 annuli. Males are slightly smaller at 1.0-1.3 mm, have a basal lip annule divided into 2-4 blocks and relatively long spicules (46-58 μm). Phylogenetic analyses of COI mtDNA, ITS-rRNA, 18S-rRNA and D2D3 of 28S-rRNA demonstrated a close relation of the new species with morphologically similar species (Hoplolaimus columbus, Hoplolaimus indicus, Hoplolaimus seinhorsti, Hoplolaimus dubius and Hoplolaimus pararobustus) yet H. tuberosus n. sp. had in all analyses a distinct phylogenetic position. The population density of 50-75 H. tuberosus n. sp. per 100 ml of soil, combined with the polyphagous nature of related Hoplolaimus species, suggests that this new species could pose a significant pest threat to potato crops, warranting further pathogenicity studies.

Currently available nematode identification techniques rely on visual microscopic examination of their morphology and limited molecular assays. These methods generally serve their purpose of enumerating nematode genera and informing management recommendations. However, when identifying variations in pathogenicity or virulence within nematode populations and species - which is crucial for specific plant-parasitic nematode management recommendations - these methods are insufficient. Here, we demonstrate that nucleotide sequence information for tens of thousands of monoclonal antibodies (mAbs) can be generated for identification purposes using a single-cell RNA-seq of mature B cells obtained from mice immunized with nematode antigens. We also provide proof of concept by synthesizing two of these mAbs in vitro and demonstrate specificity using ELISA. Since mAbs can bind to a variety of molecules, their potential use may surpass discrimination among pathotype groups and shed light on what contributes to pathogenicity or virulence of nematodes that produce, or are associated with, these antigenic molecules.

Hirschmanniella maritima n. sp. was recovered from the roots of Potamogeton perfoliatus L. plants collected in several locations along the Baltic coast (from the Puck Bay to the Vistula Lagoon) in Poland. H. maritima n. sp. is characterized by a long (L = 1787 μm-3085 μm) body; anteriorly rounded or slightly flattened lip region with four to six lip annuli; medium stylet (19.5 μm-24.5 μm) with large, oval knobs directed approximately laterally; excretory pore located posterior to pharyngo-intestinal junction; intestine partially overlapping rectum; medium-sized spicules (34.0 μm-43.2 μm); gubernaculum slightly arcuate, narrow with hook-shaped distal part; elongate-conoid tail (c' = 4.7-8.1); and tail end irregular in size and shape, without annulations, but with a pointed terminus up to an axial mucro-like projection. Inside the roots of P. perfoliatus, the nematodes were found in intercellular spaces surrounded by degraded cortex cells. Morphological and 28S rDNA-based phylogenetic molecular analyses showed H. maritima n. sp.'s similarity to H. santarosae and H. pomponiensis, with a strong sister relationship between these three species and the clade encompassing H. diversa and H. halophila. The mtCOI-based phylogenetic analysis confirmed a close relationship between H. maritima n. sp. and H. diversa.

Sting nematode (Belonolaimus longicaudatus) acutely damages many vegetables in the Southeast U.S. Brassicas are known to suppress some plant-parasitic nematodes (PPNs), but the relationship of many brassicas with sting nematode has not been studied. This information would help growers in making decisions about using brassicas in rotation with vegetables in the region. Therefore, the objective of this study was to assess the host suitability of arugula (Eruca sativa 'Nemat'), caliente mustard (Brassica juncea 'Rojo') and carinata (Brassica carinata 'NJUET 400') brassicas for sting nematode as compared to crops with known host status for sting nematode: a poor host, sunn hemp (Crotalaria juncea 'Crescent Sunn') and a good host, sorghum-sudangrass (Sorghum x drummondii 'Defiance'). Repeated greenhouse experiments were conducted in 2024 with each treatment replicated 6 times. All brassicas - arugula, caliente mustard, and carinata - had higher final sting nematode abundances than sunn hemp and greater or similar abundances to sorghum-sudangrass. This, along with the reproductive factor > 1, indicated that the brassicas tested are good hosts for sting nematode and may not be suitable options for rotation where this nematode is present. However, field research is needed to verify this result and evaluate the impacts of these brassicas on subsequent cash crops.

The plant-parasitic nematode Meloidogyne incognita causes significant financial losses in agriculture due to its wide range of host plants. Microbe-based biological control is increasingly being recognized as a viable and environmentally sustainable alternative to synthetic chemical nematicides. With this in mind, the present study evaluated the potential of microorganisms found in the larval food of stingless bees for the biological control of M. incognita. Screening of these microorganisms revealed the presence of a bacterium with nematicidal activity against M. incognita. Pot tests with soybean plants demonstrated that the bacterium Mq-MCK-07 reduced the population of M. incognita, while in vitro tests confirmed its nematicidal effect on second-stage juveniles (J2) as well as its inhibitory effect on egg hatching. DNA sequencing identified the bacterium as Enterococcus faecalis strain mandacaium, and revealed potential genes of interest for the control of multiple pathogens. This study provides a theoretical foundation for E. faecalis strain mandacaium as a promising eco-friendly nematicide.