Journal of nematology最新文献

Plant-parasitic nematodes (PPNs) establish intimate interactions with their host plants, leading to significant economic losses worldwide. The molecular mechanisms underlying parasitism are complex, requiring tight regulation of numerous genes. MicroRNAs (miRNAs), small non-coding RNAs, regulate gene expression at the post-transcriptional level by binding to target messenger RNAs. However, the diversity and functional roles of miRNAs in PPNs are only beginning to be uncovered. This review summarizes the current knowledge on the nature, biogenesis, functions, and trafficking of miRNAs in PPNs. Beyond advancing our understanding of gene regulation throughout the nematode life cycle and during parasitism, miRNA characterization holds significant promise for novel control strategies. Emerging evidence suggests that miRNAs may function across kingdoms, modulating gene expression in host plants during parasitic interactions. We highlight compelling examples from other pathosystems and discuss preliminary findings on miRNA-mediated communication between PPNs and their hosts. Finally, we provide an overview of the main computational tools and databases available for identifying and predicting miRNAs and their targets, aimed at supporting researchers interested in this emerging field.

The soilborne pathogens Phytophthora rubi and Pratylenchus penetrans threaten commercial red raspberry production in the U.S. Pacific Northwest (Washington and Oregon). Due to these soilborne pathogens, the lifespan of raspberry fields has declined from over 10 years to 5-7 years. Management primarily revolves around pre-plant soil fumigation; however, regulations have made fumigation more difficult and expensive. Understanding the spatial distribution of soilborne pathogens may provide new insights into implementing targeted disease management. Therefore, this study assessed the distribution of disease severity, P. rubi, and P. penetrans in four raspberry fields in Oregon and Washington. Geostatistical analyses and spatial autoregressive modeling were performed to elucidate the interactions between soil physical characteristics and densities of P. rubi and P. penetrans, as well as disease severity, in infested fields. In general, disease severity and the pathogens were spatially clumped in the fields. Soil texture and field elevation did not consistently influence P. rubi and P. penetrans distributions in the field. Disease severity was mostly driven by P. rubi root infestation, and no significant interactions were found between P. rubi and P. penetrans in roots. This study aimed to provide a greater understanding of the ecology and epidemiology of soilborne pathogens in commercial red raspberry fields to enable the development of a targeted integrated pest management strategy.

During a survey on the members of the family Neotylenchidae in northern Iran, a population of Deladenus was recovered, which, based on the morphology and molecular characters, identified as a new species. Deladenus hyrcanus sp. n., was isolated from dead wood of Acer velutinum in Balaband forests, Mazandaran Province. Morphologically, the new species is characterized by the moderate body length of the mycetophagous females (718-806 μm) with c = 10.2-12.6, c' = 3.5-4.4 and V = 86-87, stylet length 7.5-10 μm with three small knobs inclined backward, the lateral field with 7-8 incisures, position of excretory pore at level of hemizonid or slightly posterior to it, lacking a post-uterine sac, elongate-conoid tail (58-72 μm), with rounded to pointed terminus and males not observed. According to similarities in general morphology, D. hyrcanus sp. n., resembles D. gilanica and D. zyzyphus; however, the new species is distinguished from them in body length, lateral field incisures, and tail length. It was furthermore compared with D. aridus, D. bonabensis and D. brevis, by similarities in the position of the excretory pore and hemizonid, posterior to the nerve ring, lack of a median chamber, and a conoid tail narrowing to a rounded to pointed terminus. Molecular phylogenetic analysis based on D2-D3 expansion domain of 28S rDNA placed the new species close to D. gilanica in a clade with 1.00 posterior probability. The measurements, line illustration, and LM photographs are provided for the new species.

Chrysodeixis includens (Lepidoptera: Noctuidae) is a significant soybean pest in the southern United States. As it has developed resistance to many commonly used insecticides, alternative control measures are necessary. Entomopathogenic nematodes (EPNs) may be one such alternative. Our previous study found that a surfactant Southern Ag Surfactant (SAg Surfactant), significantly increased the mortality caused by Steinernema carpocapsae on the first instars of Helicoverpa zea in corn plants. In this study, SAg Surfactant and two more adjuvants - dish soap and vegetable oil - were tested for efficacy of S. carpocapsae on C. includens larvae under laboratory and greenhouse conditions. The three adjuvant treatments tested were 0.125% dish soap (Soap), dish soap combined with 0.25% vegetable oil (Soap & Oil), and 0.066% SAg Surfactant. In laboratory conditions, insect mortality caused by S. carpocapsae 72 hr after application was significantly higher with the Soap & Oil treatment than with the no-adjuvant treatment at 1 and 4 hr of exposure, as well as with the Soap treatment at 4 hr of exposure. No significant difference was observed among the EPN with and without adjuvant treatments when the exposure times were extended to 8 and 24 hr. However, compared to the no-adjuvant treatment, insect mortality 24 hr after application was significantly higher for all EPN adjuvant treatments at 8 hr of exposure and for the Soap & Oil treatment at 4 and 24 hr of exposure. These results suggest that these adjuvants shortened the time needed for EPNs to kill C. includens larvae. In the first trial, under greenhouse conditions, insect mortality 72 hr after application was not affected by the adjuvant treatments. In the second trial, all the adjuvant treatments increased insect mortality. However, in the third trial, only the Soap & Oil treatment caused higher mortality compared to the no-adjuvant treatment. Additionally, the Soap & Oil treatment yielded the highest number of viable EPNs in most of the three trials, although this result was statistically significant only at one sampling point. Overall, our results showed that the adjuvants could enhance the efficacy of S. carpocapsae on C. includens larvae.

A new cryptic species of the genus Parasitorhabditis isolated from the bark of a dead pine tree was characterized using morphological features, morphometrics, and DNA barcodes. Parasitorhabditis paraterebrana n. sp. is characterized by its stoma 20-24 μm in depth; tips of prorhabdions not bent inwards; metarhabdions with two subventral, and two subdorsal teeth; corpus longer than postcorpus; hemizonid 15.0-26.5 μm posterior to excretory pore; vulva-anus distance 21.5-31.5 μm, ca equal to or slightly less than vulval body diameter; rectum distinctly longer than anal body diameter; female tail cupola-shaped, conoid posteriorly, with an extended spike; male with slender spicules, nearly straight to minimally curved towards a nearly acute to a bluntly rounded tip; and bursa with 10 pairs of bursal rays, with a 2 + 3 + 2 + 3 typical pattern. It differs from the morphologically similar P. terebrana by the non-bent tips of prorhabdions, the corpus being longer than postcorpus, the bursal rays' pattern, and a more cupola-shaped tail in female and DNA barcodes. The DNA phylogenies using the 18S rRNA, 28S rRNA and COI gene markers showed well-supported sister relations of Parasitorhabditis paraterebrana n. sp. with P. terebrana and P. obtusa.

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.