Journal of nematology最新文献

California is the primary US producer of processing tomatoes. After decades-long excellent protection against the common tropical Meloidogyne spp. M. incognita, M. javanica, and M. arenaria (root-knot nematode: RKN) by Mi-resistant tomato cultivars, resistance-breaking RKN populations are spreading throughout the San Joaquin Valley. For some time, nematicidal crop management tools have diminished under CA State regulatory pressure. In recent years, new non-volatile compounds have been developed with novel modes of action. In this project with susceptible processing tomato grown on an M. incognita-infested site, the efficacy of three fluorinated nematicides was evaluated in 10 field trials from 2011 to 2021. Seven trials included fluensulfone, six included fluazaindolizine, and five included fluopyram. On average, tomato root-galling (0 - 10 scale) at harvest was reduced by 3.2, 2.3, and 2.5 by fluazaindolizine, fluensulfone, and fluopyram, respectively, compared to the untreated control. These reductions in root-galling corresponded with estimated yield gains of approximately 21%, 14%, and 15%, respectively, over the untreated control. The reproduction of RKN during the tomato crop was not affected by the nematicides. The tested compounds have a very low acute mammalian toxicity and are more target-specific than previous generations of nematicides. However, there is considerable concern about the persistence of synthetic per- and polyfluoroalkyl substances (PFAS) in the environment, including pharmaceuticals and pesticides containing fluorine with the C-F3 functional group.

A new species of the genus Paractinolaimus isolated from the bark of a dead red pine tree was characterized using morphometric data and molecular DNA barcodes. Paractinolaimus uljinensis n. sp. was characterized by its medium sized body 2.50 to 2.98 mm long; lip region truncate, angular and offset by a depression; odontostyle 23.5 to 27.0 μm long; basal shield of pharynx present; vulval opening wide and longitudinal, positioned slightly anteriorly (V = 42.5-47.7); several advulval papillae; female tail long and filiform (324.0-435.0 μm long, c' = 10.1-14.2); a clearly visible copulatory hump; spicules 60.0 to 70.5 μm long; 12 to 15 (mostly 12-14) large contiguous ventromedian supplements, and male tail conoid to broadly rounded. The new species was morphologically compared with P. intermedius, P. sahandi, P. decraemerae, P. acutus, P. macrolaimus, and P. tuberculatus. The phylogenetic relationships among species were reconstructed using 18S- and 28S-rRNA gene sequences. The phylogenies showed well-supported sister relations of Paractinolaimus uljinensis n. sp. with P. sahandi, P. macrolaimus, and P. decraemerae. In addition, the ITS-rRNA gene sequences of Paractinolaimus uljinensis n. sp. were supplied, representing the first characterization of the gene for the genus.

Cretan dittany (Origanum dictamnus L.) is an aromatic and medicinal plant, local endemic of the island of Crete, Greece, occurring naturally to high rocky mountain habitats. Due to its commercial interest, cultivation of this plant has been recently expanded. Since natural infestations by Meloidogyne spp. in field cultivated plants have not been found, its response to infection by M. javanica, M. incognita, M. arenaria, M. hapla and M. luci was investigated in pot experiments. In all experiments, roots of dittany plants exhibited neither galls nor egg masses in contrast to the roots of tomato plants used as controls. Therefore, Cretan dittany appears to be resistant to the five Meloidogyne species tested.

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.