Journal of nematology最新文献

The genera Chambersiella and Geraldius (Nematoda) are nearly morphologically identical, differing primarily in female ovary number: Chambersiella was described as monodelphic, while Geraldius was diagnosed as didelphic. This note reevaluates the validity of that distinction, incorporating original descriptions and a previously overlooked archival note from N. A. Cobb. Field observations failed to recover monodelphic specimens, even in type localities. We propose synonymizing Geraldius with Chambersiella, supported by Cobb's archived observations and consistent morphological evidence.

Criconemoides iraqicus n. sp. recovered from the rhizospheric soil of pomegranate in Misan province, Iraq, is described based on morphological and molecular data. The new species is characterized by its lip region comprised of two annuli, true submedian lobes absent, pseudolips present, body annuli smooth and with few anastomoses (R = 76-79), stylet 64.6-75.3 μm long, with anchor-shaped basal knobs, excretory pore at one to three annuli posterior to the pharynx base, vulva closed, vulval lips not projecting above body contour, and tail conical with one to three terminal lobes. Based on the number of body annuli, stylet length, smooth annuli, and shape of postvulval body region, C. iraqicus n. sp. is closely similar to C. amorphus, C. ananasi, C. geraerti, C. informis, C. neoinformis, and C. tenuiannulatus. The phylogenetic relationships of the new species with representatives of the family Criconematidae were reconstructed and discussed using partial sequences of the small subunit, D2-D3 expansion segments of the large subunit, and internal transcribed spacer regions of ribosomal DNA (SSU, LSU D2-D3, and ITS rDNA) based on Bayesian inference (BI). In phylogenetic trees, sequences of the new species formed clades with corresponding sequences of C. geraerti, C. informis, Discocriconemella parasinensis, and D. sinensis with different levels of relatedness.

The alfalfa cyst nematode (Heterodera medicaginis) is an invasive and pathogenic species parasitizing the agriculturally important forage crop alfalfa (Medicago sativa L.). To date, no genome assembly of H. medicaginis has been reported in the literature. In this study, for the first time, we assembled a draft genome of this species. This research is important as it provides genomic insights into a damaging pest recently discovered in the United States that affects the third most valuable crop in the country.

Beech leaf disease (BLD), caused by the anguinid nematode Litylenchus crenatae mccannii (Lcm), has recently emerged as a severe threat to beech trees (Fagus spp.) in eastern North America. In response, the scientific community has accelerated research on this invasive plant-parasitic nematode (PPN). Advances in BLD pathophysiology can be useful for developing management strategies. However, characteristics of both the pest and host trees make BLD uniquely challenging to manage, leaving arborists, nursery managers, and plant health care specialists with limited treatment options. The first treatment demonstrated to directly affect Lcm and suppress BLD was a late-summer foliar application program using fluopyram. These three sequential field trials explore several variables that must be determined when developing a novel management program: site appropriateness, product dosage, and the timing of foliar applications. The results support the efficacy of fluopyram-based programs in suppressing BLD but emphasize the importance of site conditions, noting that dense beech forests are unlikely to benefit from this treatment. The results also show that significantly reduced product doses can yield excellent control. Finally, the findings suggest that initiating the foliar application program earlier in the summer could be equally or more effective than beginning in late summer. This information will guide the implementation of novel management programs tailored to address the growing threat of BLD.

Although soil biota mediates many key processes that deliver multiple environmental benefits, interactions between soil biota are not well characterized. In an ecological context, studies to date on the associations between nematodes and bacteria have mostly focused on either intracellular bacteria or bacteria that have a potential role in crop pathogenesis by endoparasitic nematode species, that is, those species that have a component of their life cycle within the plant host. Moreover, evolutionary studies have utilized the model nematode species, Caenorhabditis elegans, for studies on survival, behavior, and fecundity. In this study, we characterize the bacterial communities associated with an ectoparasitic nematode species, Trichodorus primitivus, whose complete life cycle is external to the plant host. Compared to the soil from which the nematodes were extracted, the diversity of bacterial communities associated with T. primitivus was reduced. By contrast, the nematode-associated bacterial community was significantly enriched with Janthinobacterium, a known antagonist of soilborne pathogens. This study advances knowledge on the interactions between bacteria and ectoparasitic nematodes, which could help inform the future development of novel strategies for nematode control.

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.