Journal of nematology最新文献

Pinewood nematodes threaten forest health and continue to interfere with international trade because they can be spread around the globe via nematode-infested wood. International Standards for Phytosanitary Measure (ISPM-15) requires that all pine wood be treated at 56°C for 30 min to ensure that all pests and pathogens are killed within sawn wood, whereas fumigation with methyl bromide is the currently approved practice and widely used in treating whole logs. A method of treatment that uses less energy and time or does not rely on environmentally damaging gases is urgently needed. Because vacuum with steam has shown promise in treating several different commodities, the purpose of this study was to use it to eradicate pinewood nematodes in whole logs. Three protocols were applied: 1) 48°C for 15 min., 2) 56°C for 30 min., and 3) 60°C for 60 min. The third protocol reduced the population to statistically zero; however, some samples contained at least 1 survivor. Unfortunately, these surviving nematodes increased in number one month after treatment, and one year later, they continued to reproduce in the wood. Therefore, this protocol needs to be further refined to remove pinewood nematodes completely. Explanation of the survival of individual nematodes within whole logs remains a matter for conjecture: 1) certain portions of the wood were somehow insulated from the heat and did not achieve the lethal temperature, and 2) survival stages may be able to survive temperatures that are deadly to the normal life stages.

Based on molecular markers, mating experiments, morphological observations and ecological data, two Pristionchus species (Nematoda: Diplogastridae) new to science are described. Both were collected from different Scarabaeoid beetles in South Korea, have a gonochoristic mode of reproduction and fall into a sub-clade of the pacificus clade. Pristionchus coreanus n. sp. does not show a eurystomatous morph under laboratory conditions and might therefore be suitable for the study of gain and loss of polymorphism. Pristionchus hangukensis n. sp. is phylogenetically close to Chinese and Japanese species and helps to separate an Asian clade from an American clade.

Mesodorylaimus pini n. sp., a new species isolated from the bark and cambium layer of a dead black pine tree is characterized herein using integrative taxonomy, considering both morphological and molecular phylogenetic analyses of the 18S- and 28S-rRNA genes. Mesodorylaimus pini n. sp. is characterized by having a medium-sized body 1.50-1.89 mm long; lip region angular and offset by a depression; a relatively long odontostyle (17.0-19.0 μm); vulval opening a transverse slit, positioned slightly posteriorly; pars refringens vaginae with two elongated drop-shaped to spindle-shaped sclerotizations; an intestine-prerectum junction with a long anteriorly directed conical or tongue-like projection; a relatively long female tail (115-187 μm); spicules 48.0-57.0 μm long; and regularly spaced 7-8 ventromedian supplements. It is closest to M. subtilis, especially in having similar body length and number of ventromedian supplements but can be differentiated from M. subtilis by the longer odontostyle, tongue-like projection, and longer spicules. The phylogenies based on the 18S- and 28S-rRNA sequences showed a well-supported sister relation of M. pini n. sp. with M. subtilis, M. japonicus, M. bastiani, M. pseudobastiani, Calcaridorylaimus castaneae, C. heynsi, and other member species of the group.

Pristionchus pacificus is a free-living nematode that shares many features with Caenorhabditis elegans, such as its short generation time and hermaphroditism, but also exhibits novel traits, i.e., a mouth-form dimorphism that enables predation. The availability of various genetic tools and genomic resources make it a powerful model organism for comparative studies. Here, we present an updated genome of the P. pacificus strain PS1843 (Washington) that is most widely used for genetic analysis. Assembly of PacBio reads together with reference-guided scaffolding resulted in a chromosome-scale genome spanning 171Mb for the PS1843 strain. Whole genome alignments between the P. pacificus PS1843 genome and the genome of the P. pacificus reference strain PS312 (California) revealed megabase-sized regions on chromosomes III, IV, and X that explain the majority of genome size difference between both strains. The improved PS1843 genome will be useful for future forward genetic studies and evolutionary genomic comparisons at the intra-species level.

The hop cyst nematode, Heterodera humuli, is the most common plant-parasitic nematode associated with hop worldwide. This study reports the draft genome of H. humuli generated on the PacBio Sequel IIe System with the ultra-low DNA input HiFi sequencing method, and the corresponding genome annotation. This genome resource will help further studies on H. humuli and other cyst nematodes.

Six distinct COI mitochondrial Haplotype Groups (HG) are morphologically, ecologically, and genetically characterized from the aquatic nematode family Tobrilidae. Collection locations included the extreme habitats of the Alkaline Lakes in the western Nebraska Sandhills and the contaminated stream, Johnson Creek, bordering the AltEn 2021 catastrophic pesticide release near the village of Mead in eastern Nebraska. Maximum likelihood and genetic distance metrics supported the genetic integrity of the haplotype groups. Discriminant function analysis of COI haplotype group datasets of combined morphological characters and soil chemistry attributes for both male and female Tobrilidae were classified correctly in all but one case. Scanning electron microscopy revealed new details about amphid apertures, male supplements, and spicules. Partial 18S gene phylogeny suggests that the genus Semitobrilus may not be a member of the subfamily Neotobrilinae, and three specimens in the 226 tobrilid dataset provide evidence of incongruence between COI and 18S derived phylogenies. Given the strong signal provided by the environmental chemistry data, tobrilid mitochondrial haplotypes may well have value as environmental indicators.

Sweetpotato is an important crop whose roots are consumed by people worldwide. Meloidogyne enterolobii stands out as a highly deleterious variant among the species of root-knot nematode that causes significant damage in sweetpotato. In the present study, the activity of four nematicides against M. enterolobii was assessed both in vitro and in growth cabinet experiments. After 48 hours of exposure, fluopyram and cyclobutrifluram had a greater negative effect on the motility of M. enterolobii second-stage juveniles (J2s) compared to fluensulfone and hymexazol, with respective median effective concentration (EC₅₀) values of 0.204, 0.423, 22.335 and 216.622 mg L^-1. When M. enterolobii eggs were incubated for 72 hours at the highest concentration of each nematicides, the inhibitory hatching effect of cyclobutrifluram (2.5 mg L^-1), fluopyram (1.25 mg L^-1) and fluensulfone (80 mg L^-1) surpassed 85%, whereas hymexazol (640 mg L^-1) was only 67%. Similar results were observed in growth cabinet experiments as well. The disease index (DI) and gall index (GI) were significantly decreased by all four nematicides compared to the control. However, the application of hymexazol did not yield a statistically significant difference in the egg masses index compared to the control, a finding which may be attributed to its potentially limited penetrability through the eggshell barrier. Overall, this study has demonstrated that all four nematicides effectively suppress M. enterolobii in sweetpotato, and this is the first report on the nematicidal activity of cyclobutrifluram and hymexazol against M. enterolobii.

Turfgrass is a crop used extensively in athletic fields and golf courses in Maryland. A soil sample collected in July 2023 from an athletic field in Baltimore County, Maryland, part of a turfgrass nematode survey, contained Belonolaimus longicaudatus. In the southeastern United States, B. longicaudatus is an economically important pathogen of warm season turfgrass. The density was four individuals/100 cm³ of soil, and no visual symptoms were observed in the bermudagrass field. Morphological features and morphometrics of males and females were consistent with B. longicaudatus and placed the Maryland population in a subclade that was geographically represented by populations from north and west Florida, Texas, and South Carolina. Sequencing of the internal transcribed spacer region ITS1 and ITS2 and 28S large ribosomal subunit D2-23 expansion region confirmed the species' identity. Phylogenetic trees and parsimony network analysis placed the Maryland isolate in a large grouping of B. longicaudatus populations including those from Alabama, Delaware, Florida, Indiana, Mississippi, South Carolina, and Texas. To our knowledge, this is the first report of B. longicaudatus in Maryland.

Mexico is the 8^th largest producer of tomatoes. Meloidogyne enterolobii is reported in Sinaloa, affecting tomato cultivars with genetic resistance to Meloidogyne spp. We aimed to evaluate field applications of fluopyram, fluensulfone, and fluazaindolizine treatments for managing M. enterolobii on tomatoes. Experiments were set on raised beds in a shade house. Nematicides were applied via drip irrigation. Under fluopyram treatment, M. enterolobii did not reduce the number of extra-large-size fruits. The number of large-size fruits with fluopyram and fluazaindolizine plus fluopyram treatments was also unaffected by M. enterolobii. Yield from the treatments fluopyram, fluazaindolizine plus fluopyram, and fluensulfone plus fluopyram was similar to the control treatment without M. enterolobii. Finally, fluazaindolizine plus fluopyram, fluopyram, and fluensulfone plus fluopyram treatments showed the highest reduction of root galling. We conclude that the fluopyram was more effective as an individual treatment. Pre-plant applications of fluensulfone and fluazaindolizine reduced the damage to the plant and the loss of yield; however, the complementary application of fluorinated nematicides improved the management of M. enterolobii in the tomato crop.