Journal of nematology最新文献

The infective juveniles (IJs) of entomopathogenic nematode (EPN) Heterorhabditis bacteriophora find and infect their host insects in heterogeneous soil ecosystems by sensing a universal host cue (CO₂) or insect/plant-derived odorants, which bind to various sensory receptors, including G protein-coupled receptors (GPCRs). Nematode chemosensory GPCRs (NemChRs) bind to a diverse set of ligands, including odor molecules. However, there is a lack of information on the NemChRs in EPNs. Here we identified 21 GPCRs in the H. bacteriophora genome sequence in a triphasic manner, combining various transmembrane detectors and GPCR predictors based on different algorithms, and considering inherent properties of GPCRs. The pipeline was validated by reciprocal BLAST, InterProscan, GPCR-CA, and NCBI CDD search. Functional classification of predicted GPCRs using Pfam revealed the presence of four NemChRs. Additionally, GPCRs were classified into various families based on the reciprocal BLAST approach into a frizzled type, a secretin type, and 19 rhodopsin types of GPCRs. Gi/o is the most abundant kind of G-protein, having a coupling specificity to all the fetched GPCRs. As the 21 GPCRs identified are expected to play a crucial role in the host-seeking behavior, these might be targeted to develop novel insect-pest management strategies by tweaking EPN IJ behavior, or to design novel anthelminthic drugs. Our new and stringent GPCR detection pipeline may also be used to identify GPCRs from the genome sequence of other organisms.

Barley root-knot nematode, Meloidogyne naasi Franklin, 1965, is one of the most important pest nematodes infecting monocots (Franklin, 1965). Two-inch core soil samples collected from a golf course in Ada County, Idaho were submitted for identification in November of 2019. A high number of Meloidogyne sp. juveniles were recovered from both soil samples using sieving and decantation followed by the sugar centrifugal flotation method. They were examined by light microscopy, morphometric measurements, and multiple molecular markers, including the ribosomal 28S D2-D3 and intergenic spacer 2 (IGS-2) regions, mitochondrial markers cytochrome oxidase I (COI) and the interval from COII to 16S, and the protein-coding gene Hsp90. Morphometrics as well as BlastN comparisons with other root-knot nematode sequences from GenBank were consistent with identification as M. naasi. Phylogenetic trees inferred from 28S, IGS-2, COI, or Hsp90 alignments each separated the Idaho population into a strongly supported clade with other populations of M. naasi, while the COII-16S interval could not resolve M. naasi from M. minor. This report represents the first morphological and molecular characterization of Meloidogyne naasi from turfgrass in Idaho.

Plant-parasitic nematodes conduct a series of sophisticated behaviors to complete their life cycles. Among these, locomotion behaviors, including finding the host and migrating to the feeding site, directly affect the success of parasitism. Thus, disrupting locomotion behaviors has the potential to control these parasites. γ-Aminobutyric acid (GABA) is the prominent inhibitory neurotransmitter in nematodes. GABA-immunoreactive neurons are mostly found in motor neurons, where they regulate behaviors in the model nematode C. elegans. However, the GABA system in most stylet-bearing nematodes has received little attention. Using immunohistochemistry, we found variation in the pattern of GABA-immunoreactivity among two major plant-parasites and a fungal feeder. Some of these GABA-immunoreactive neurons lack clear homologs to C. elegans. Pharmaceutical assays showed that applying GABA, its agonist, and its antagonist, can disrupt the locomotion behaviors of these nematodes, although sensitivity to a given compound varied between species. Our data suggest that the GABA system is a potential target for the control of plant-parasitic nematodes.

Nematode samplings in various areas and crops of Greece were carried out and the recovered nematode species were characterized using morphological and molecular data. Seven species of plant-parasitic nematodes were recovered, three of which are reported for the first time in Greece, including Hemicycliophora poranga, Helicotylenchus dihystera and Tylenchorhynchus zeae. Four other recovered species had already been reported in Greece, including Bitylenchus hispaniensis, Helicotylenchus microlobus, Nanidorus minor and Scutellonema brachyurus. D2-D3 segments of 28S rRNA gene for all of these nematode species are provided.

Pigeons are a cosmopolitan group of birds with abundant and large populations associated with human activities. This study focused on determining parasitic infections within domestic pigeons (Columba livia domestica). Forty-eight pigeons were examined for infections, of which 29.16% were infected with a nematode parasite, identified as Hadjelia truncata (Habronematidae), under the koilin layer of their gizzards. The population of nematodes in infected gizzards did not exceed 20 adult worms. DNA from the gizzard worms was extracted and subjected to PCR using primers that amplify the partial 18S rDNA and cytochrome C oxidase subunit I (COX I) regions. Identification of this parasite based on microscopic study revealed the presence of trilobed lips with cephalic papillae and amphidial pores, as well as other characteristic features. In males, spicules were unequal with the presence of six pedunculated pairs of caudal papillae (4 pre- and 2 post-anal) and a tail surrounded with caudal ala. In females, the vulva was a rounded aperture located in front of the posterior end of the esophagus and uteri, which was filled with numerous embryonated eggs. DNA Sequences from partial 18S rDNA were homologous to sequences obtained from H. truncata in GenBank with a high percentage of identity. DNA sequences from mitochondrial gene COX I, however, were unique, and they were the first sequenced for H. truncata, since no sequences for this taxon were previously available in GenBank. Histopathological examination revealed enlargement of infected gizzards in comparison to non-infected ones, with the presence of necrosis and interstitial infiltration in the koilin layer. Concentrations of heavy metals (Fe, Cu, Zn, Cd, Cr, and Co) were measured using inductivity-coupled plasma in tissues (liver, muscles, and gizzards) from infected and non-infected pigeons as well as their parasites. Results showed different affinities of metals to tissues. Recovered parasites can minimize element concentration from their pigeon tissues. In Saudi Arabia, this study was considered the first report identifying pigeon nematodes and evaluating of the effects of their pathogenicity on the animals' welfare, as well as their application as a useful tool for monitoring environmental pollution.

Anguina tritici is the first plant-parasitic nematode described in literature, dating back to the year 1743. It is responsible for causing earcockle (seed gall) and tundu diseases in wheat and rye. Notably, this nematode has been observed to survive in an anhydrobiotic state for up to 32 years within wheat seed galls. These exceptional characteristics have inspired the sequencing of the A. tritici genome. In this study, we present the initial draft genome of A. tritici, obtained using the Illumina MiSeq platform with coverage of 60-fold. The genome is estimated to have a size of 164 Mb and comprises 39,965 protein-coding genes, exhibiting a GC content of 39.1%. The availability of this genome data will serve as a foundation for future functional biological investigations, particularly for genes whose functions remain unknown to this day.

A new root-knot nematode (RKN) species, Meloidogyne karsseni n. sp., associated with sweet pepper from Mexico, and a population of M. paranaensis from Guatemala, are described using data from morphological, biochemical (isozyme enzymes), molecular, and phylogenetic analyses. Meloidogyne karsseni n. sp. can be morphologically diagnosed using the combined features of the second-stage juveniles, viz. body length (345 to 422 μm), a conical rounded head region, a post-labial annule lacking transverse striation, a thin stylet 11 to 12 μm long, rounded to oval and backwardly sloping knobs, dorsal gland orifice (DGO) at 5.2 to 6.0 μm from the knobs, a hemizonid just above the secretory-excretory (SE) pore, a tapering tail with finely rounded terminus and one or two very weak constrictions at hyaline tail tip; the female characters viz. oval-to-rounded perineal pattern with coarse striation on lateral sides around the anus, low dorsal arch with finer striations, and distinctly visible lateral lines; and the male characteristics viz. a rounded and continuous head, a post-labial annule without transverse striations, a robust stylet 20 to 24 μm long, rounded-to-oval and slightly backwardly sloping knobs, and a DGO at 2.4 to 2.9 μm from the knobs. In all the studied males of M. paranaensis, a characteristic sclerotization around the duct of SE-pore was also observed for the first time. Sequences of 18S, D2-D3 of 28S, and ITS of rDNA, and cox1 of mtDNA were generated for the two species, and in the phylogenetic trees based on these genes, both species appeared in the tropical RKN species complex clade.

Rotylenchulus reniformis (reniform nematode, RN) is among the most important nematodes affecting cotton. Cultural practices, such as rotation and soil amendment, are established methods for managing RN. Management may be enhanced if crop residue has biofumigant properties against RN. The objective was to evaluate the efficacy of winter crop amendments for managing RN in the greenhouse. Reniform nematode-infested soil was amended with dry or fresh organic matter (OM, 2% w/w) from winter crops - canola, carinata, hairy vetch, oat, or no crop. Cotton was subsequently grown in this soil. Independent of the crop, dry OM amendments were more effective than no amendment at managing RN, while fresh OM amendments were not. Soil and root RN abundances and reproduction factors were generally lower in Trials 1 and 3 for dry OM than fresh OM amendments or control without OM. In Trial 2, none of the OM treatments reduced RN parameters compared with no OM control. In general, when compared to plants without RN or OM, RN did not produce significant changes in growth parameters but did affect physiology (Soil Plant Analysis Development, or SPAD, values). In conclusion, dry OM amendments can help manage RN, crop growth does not always relate to RN abundances, and SPAD values could help indicate RN presence.

Sixteen Meloidogyne isolates from tomato fields in California grown with resistant cultivars were multiplied on resistant tomato in a greenhouse. Of these resistance-breaking isolates, one was identified as M. javanica, and all others as M. incognita. The reproduction of the M. javanica isolate and four M. incognita isolates on six resistant tomato cultivars and on susceptible and resistant cultivars of pepper, sweetpotato, green bean, cotton, and cowpea was evaluated and compared to an avirulent M. incognita population in greenhouse pot trials. On resistant tomato cultivars, there were minor but significant differences between the resistance-breaking Meloidogyne isolates and between the different tomato cultivars. Of the other resistant crop cultivars, pepper was resistant to all isolates and green bean to all M. incognita isolates, while cotton and cowpea allowed reproduction of one of the resistance-breaking M. incognita isolates. The resistant sweetpotato cv. Bonita behaved like resistant tomato, allowing reproduction of all five resistance-breaking isolates but not of the avirulent M. incognita. Our results showed that variability exists among resistance-breaking Meloidogyne isolates, and that isolates overcoming resistance in tomato may also be virulent on resistant sweetpotato.

Plant parasitic nematodes are significant contributors to yield loss worldwide, causing devastating losses to every crop species, in every climate. Mitigating these losses requires swift and informed management strategies, centered on identification and quantification of field populations. Current plant parasitic nematode identification methods rely heavily on manual analyses of microscope images by a highly trained nematologist. This mode is not only expensive and time consuming, but often excludes the possibility of widely sharing and disseminating results to inform regional trends and potential emergent issues. This work presents a new public dataset containing annotated images of plant parasitic nematodes from heterologous soil extractions. This dataset serves to propagate new automated methodologies or speedier plant parasitic nematode identification using multiple deep learning object detection models and offers a path towards widely shared tools, results, and meta-analyses.