Journal of nematology最新文献

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.

This experiment investigates five small grain winter cover crops including multiple genotypes of barley (Hordeum vulgare L), oats (Avena sativa L.), rye (Secale cereale L.), triticale (x Triticosecale Wittmack), and wheat (Triticum aestivum L.) as a sustainable nematode management strategy for Meloidogyne incognita (root-knot nematode) and Rotylenchulus reniformis (reniform nematode) in cotton production in a Southeastern U.S. Greenhouse (2019), and field experiments (2019-2021) evaluated these crops for nematode host status, forage quality, and grain yield. Greenhouse experiments showed that all small grains had higher average M. incognita egg counts than a standard corn (Zea mays L.) variety. Overall, barley and wheat were suitable hosts (Rf>2), triticale and oat were moderate hosts (Rf=1-2), while three cultivars (Forerunner' and 'OG170039' triticale, "ORO 4372' oat) were poor hosts (Rf<1). In field trials, oat had the highest biomass and grain yield, followed by triticale, barley, rye, and wheat. Barley supported the highest population density of M. incognita. Oat, barley, and rye displayed similar population density of R. reniformis and were greater than triticale and wheat. Forage quality experiments showed oat with the highest biomass, wheat with the highest crude protein, and rye and triticale leading in fiber content. Oats had the greatest total digestible nutrients (TDN) and relative feed value (RFV), indicating superior digestibility. All small grains demonstrated high forage quality (RFV>100). Cover crop selection should be based on specific management and agronomic goals as nematode populations varied by cover crop but were low in all field trials. Further research on crop-specific responses and long-term effects on nematode populations and soil health is needed to optimize small grain winter cover crops in integrated pest management programs.

Entomopathogenic nematodes (EPNs) used as biocontrol agents are sensitive to ultraviolet (UV) light, high temperature, and desiccation. Thus, formulations have been developed to protect EPNs during application. However, the ability of these formulations to enhance storage capacity has not been investigated. This study analyzed storage capacity (survival and efficacy) of EPN species, Heterorhabditis bacteriophora (SGI 245), Steinernema tophus (ROOI 352) and Steinernema innovationi (SG I35) produced either in vivo or in vitro and formulated in 2% gel of either Barricade^® or potassium polyacrylate hydrogel (PPH). The formulations were stored at 10°C and survival of the infective juvenile nematodes (IJs) was evaluated at two-weeks intervals for eight weeks. The efficacy of formulated nematodes was evaluated using Tenebrio molitor. After two weeks, all control treatments had 0% IJ survival for all the three isolates, whereas the gel formulations exhibited 58-76% survival. The three isolates in both the Barricade^® gel and PPH formulations exhibited 37-69% IJ survival at six weeks, which declined to 0-13% after eight weeks. Both formulations of the three isolates were 60-90% effective at six weeks. The in vitro-produced IJs had a higher survival than the in vivo-produced IJs for S. innovationi and H. bacteriophora. However, the in vivo-produced IJs were more effective at killing T. molitor than the in vitro-produced EPNs for H. bacteriophora but not the Steinernema spp. In conclusion, Barricade^® and PPH gel formulations substantially increased survival of the three EPN species during storage.

A new species of the genus Geraldius isolated from the wood of a dead black pine tree is characterized using morphological data and molecular DNA barcodes. Geraldius jejuensis n. sp. is characterized by its lateral fields with two incisures; lip region conoid to rounded and continuous with body; hemizonid and excretory pore located posterior to nerve ring; excretory pore opening just at the beginning of hemizonid or within the contour of hemizonid; vulva a transverse slit in ventral view; opening in a depression, creating a circular profile in lateral view; rectum 1.4 to 1.7 times longer than anal body diameter; phasmids located 55.0 to 78.5 μm from anal opening; tail elongated, 146.0 to 177.0 μm long; gubernaculum 27.0 to 33.5 μm long, caudal papillae arrangement of seven pairs pre-cloacal, two adcloacal, and six post-cloacal; and three additional midventral papillae on anterior cloacal lip. The new species was compared with the three known species of the genus, including G. bakeri, G. galapagoensis and G. inserrai. The phylogenetic relationships among species were reconstructed using 18S-rRNA and 28S-rRNA gene sequences. Inferences from both genes corroborate the close morphological relationships between Geraldius and Diastolaimus.

Nematodes such as Caenorhabditis elegans and Pristionchus pacificus are powerful models for associating phenotypes to genotypes. However, exploring the evolution of identified genetic loci requires a robust phylogenomic framework. Here, we present an updated genome of the nematode Parapristionchus giblindavisi which is the only known member of the sister group of Pristionchus. Reassembly of previously generated long read sequencing data combined with new Hi-C data resulted in a near chromosome-scale genome assembly spanning 302.5Mb. The Hi-C contact map, karyotyping data and comparative genomic analysis support an organization of the P. giblindavisi genome into six chromosomes, whereby all autosomes correspond to individual Nigon elements and the sex chromosome represents a fusion of Nigon elements D and X. The further improved P. giblindavisi genome will be useful as an outgroup for dating and polarizing lineage-specific genomic signatures.

[This corrects the article DOI: 10.2478/jofnem-2023-0033.].