<abstract>
<title style='display:none'>Abstract</title>
Root-knot nematode, <italic>Meloidogyne mali</italic> can cause damage in trees, shrubs, and herbaceous plants, and was placed on the EPPO Alert List in 2014. In the present study, we report a population isolated from Japanese maple. The recovered population is described by detailed morphological and molecular approaches. The molecular phylogentic analysis based on 28S rRNA, ITS, and mitochondrial COI genes places the population in the clade together with other <italic>M. mali</italic> sequences available in GenBank. The cloned sequences of the 28S rRNA gene revealed a high intragenomic rRNA polymorphism where the polymorphic copies are spread across <italic>M. mali</italic> clade. Similarly, we also found high variation in the mitochondrial COI gene. Among four haplotypes in <italic>M. mali</italic>, three occur in the newly found population. Our study provides the first report of intragenomic polymorphism in <italic>M. mali</italic>, and the results suggest that intragenomic polymorphism maybe widespread in <italic>Meloidogyne.</italic>

</abstract>

Morphological and molecular analyses of a <italic>Meloidogyne mali</italic> population with high intragenomic rRNA polymorphism

<abstract>
<title style='display:none'>Abstract</title>
Vetiver, a nonhost grass for certain nematodes, was studied for the production of compounds active against the southern root-knot nematode, <italic>Meloidogyne incognita</italic>. In laboratory assays studying the effects on second-stage juvenile (J2) activity and viability, crude vetiver root and shoot extracts were nematotoxic, resulting in 40% to 70% J2 mortality, and were also repellent to J2. Vetiver oil did not exhibit activity against J2 in these assays. Gas chromatography-mass spectrometry analyses of three crude vetiver root ethanol extracts and a commercial vetiver oil determined that two of the major components in each sample were the sesquiterpene acid 3,3,8,8-tetramethyltricyclo[5.1.0.0(2,4)]oct-5-ene-5-propanoic acid and the sesquiterpene alcohol 6-isopropenyl-4,8a-dimethyl-1,2,3,5,6,7,8,8a-octahydronaphthalen-2-ol. The acid was present in higher amounts in the extracts than in the oil. These studies demonstrating nematotoxicity and repellency of vetiver-derived compounds to <italic>M. incognita</italic> suggest that plant chemistry plays a role in the nonhost status of vetiver to root-knot nematodes, and that the chemical constituents of vetiver may be useful for suppressing nematode populations in the soil.
</abstract>

Activity of Vetiver Extracts and Essential Oil against <italic>Meloidogyne incognita</italic>

<article-title xml:lang="en">ABSTRACTS FROM THE SOCIETY OF NEMATOLOGISTS ANNUAL MEETING 2021

Abstracts from The Society of Nematologists Annual Meeting 2019

<abstract>
<title style='display:none'>Abstract</title>
Millipedes may cause unexpected damage when they are introduced to new locations, becoming invaders that leave behind their old parasites and predators. Therefore, it was interesting to find numerous rhabditid nematodes within the gut of the invasive phytophagous millipede <italic>Chamberlinius hualienensis</italic> Wang, 1956 (Diplopoda, Paradoxosomatidae) from Hachijojima (Japan) in November, 2014. This millipede originated in Taiwan but was discovered in Japan in 1986. The nematodes were identified as juvenile <italic>Oscheius rugaoensis</italic> (Zhang et al., 2012) Darsouei et al., 2014 (Rhabditidae), and juvenile and adult <italic>Mononchoides</italic> sp. (Diplogastridae) based on images, morphometrics, and sequences of 18S and 28S rDNA. A novel short 28S sequence of a separate population of <italic>Oscheius necromenus</italic> SB218 from Australian millipedes was also included in a phylogenetic comparison of what can now be characterized as a species complex of millipede-associated <italic>Oscheius</italic>. The only other nematode associates of millipedes belong to Rhigonematomorpha and Oxyuridomorpha, two strictly parasitic superorders of nematodes. These nematode identifications represent new geographic and host associations.
</abstract>

Two nematodes (Nematoda: Diplogastridae, Rhabditidae) from the invasive millipede <italic>Chamberlinius hualienensis</italic> Wang, 1956 (Diplopoda, Paradoxosomatidae) on Hachijojima Island in Japan

<abstract>
<title style='display:none'>Abstract</title>
One new and one known species of the genus <italic>Aphelenchoides</italic> from Iran are studied. <italic>Aphelenchoides giblindavisi</italic> n. sp. is mainly characterized by having five lines in the lateral fields at mid-body, and a single mucro with several tiny nodular protuberances, giving a warty appearance to it, as revealed by detailed scanning electron microscopic (SEM) studies. The new species is further characterized by having a body length of 546 to 795 μm in females and 523 to 679 μm in males, rounded lip region separated from the rest body by a shallow depression, 10 to 11 μm long stylet with small basal swellings, its conus shorter than the shaft (<italic>m</italic> = 36–43), 52 to 69 µm long postvulval uterine sac (PUS), males with 16 to 18 μm long arcuate spicules, and three pairs of caudal papillae. The new species was morphologically compared with two species of the genus having five lines in the lateral fields namely <italic>A. paramonovi</italic> and <italic>A. shamimi</italic> and species having a warty-surfaced mucro at tail end and similar morphometric data ranges. The morphological features and morphometrics of the second studied species, <italic>A. helicus</italic>, agreed well with the data given for the type population. However, detailed study of fresh females revealed it has three drop-shaped stylet knobs and long PUS, making it typologically similar to the genus <italic>Robustodorus</italic>, meriting its taxonomic revision, i.e., transferring to it. In molecular phylogenetic analyses using partial small and large subunit ribosomal RNA gene (SSU and LSU rDNA) sequences, the new species formed a clade with <italic>A. heidelbergi</italic> in both SSU and LSU D2-D3 trees. The species <italic>A. helicus</italic>, however, clustered inside a well-supported clade of the genus <italic>Robustodorus</italic> in both trees, corroborating its newly proposed taxonomic placement as <italic>Robustodorus helicus</italic> n. comb.
</abstract>

Description of <italic>Aphelenchoides giblindavisi</italic> n. sp. (Nematoda: Aphelenchoididae), and Proposal for a New Combination

<abstract>
<title style='display:none'>Abstract</title>
Nematodes play a vital ecological role in soil and marine ecosystems, but there is limited information about their dietary diversity and feeding habits. Due to methodological challenges, the available information is based on inference rather than confirmed observations. The lack of correct dietary requirements also hampers rearing experiments. To achieve insight into the prey of mononchid nematodes, this study employed high-throughput Illumina paired-end sequencing using universal eukaryotic species 18S primers on 10 pooled mononchid nematode species, namely <italic>Mylonchulus brachyuris, M. brevicaudatus, Mylonchulus</italic> sp., <italic>Clarkus parvus, Prionchulus</italic> sp. <italic>M. hawaiiensis, M. sigmaturellus, M. vulvapapillatus, Anatonchus</italic> sp. and <italic>Miconchus</italic> sp. The results indicate that mononchids are associated with a remarkable diversity of eukaryotes, including fungi, algae, and protists. While the metabarcoding approach, first introduced here for mononchids, proved to be a simple and rapid method, it has several limitations and crucial methodological challenges that should be addressed in future studies. Ultimately, such methods should be able to evaluate the dietary complexity of nematodes and provide a valuable avenue for unraveling the dietary requirements of previously unculturable nematodes. This can contribute to the methodology of understanding their feeding habits and contributions to ecosystem dynamics.
</abstract>

Exploring the use of metabarcoding to reveal eukaryotic associations with mononchids nematodes

<abstract>
<title style='display:none'>Abstract</title>
Plant-parasitic nematodes (PPN) are an understudied pathogen group in the Oregon cool-season grass seed cropping system. In this survey, the PPN associated with annual ryegrass, bentgrass, fine fescue, orchardgrass, perennial ryegrass, and tall fescue were determined. Thirty-seven fields were sampled in the 2022 or 2023 growing season by collecting 10 soil cores in each of six 100-m transects for nematode extraction and visual identification. PerMANOVA testing indicated significant differences in PPN community composition across grass host and sampling time. <italic>Pratylenchus</italic> and <italic>Meloidogyne</italic> were the most commonly encountered nematodes, with maximum population densities of 1,984 and 2,496 nematodes/100 g soil, respectively. Sequencing of the COX1 gene region indicated the presence of <italic>P. crenatus, P. fallax, P. neglectus, P. penetrans</italic>, and <italic>P. thornei</italic>, with some of these species being detected for the first time on these grass hosts. The only <italic>Meloidogyne</italic> sp. found in these grasses was <italic>M. nassi</italic>, based upon sequencing of the ITS gene region. This first-of-its-kind survey indicates the need for further assessment of the impact of these PPNs on yield and stand longevity in cool-season grass seed fields in Oregon.
</abstract>

Plant-parasitic Nematodes Associated with Grasses Grown for Seed in the Willamette Valley of Oregon

<abstract>
<title style='display:none'>Abstract</title>
In the southern United States, corn earworm, <italic>Helicoverpa zea</italic> (Boddie), and soybean looper, <italic>Chrysodeixis includens</italic> (Walker) are economically important crop pests. Although Bt crops initially provided effective control of target pests such as <italic>H. zea</italic>, many insect pests have developed resistance to these Bt crops. Alternative approaches are needed, including biological control agents such as entomopathogenic nematodes (EPNs). However, the effectiveness of EPNs for aboveground applications can be limited due to issues such as desiccation and ultraviolet radiation. Effective adjuvants are needed to overcome these problems. Ten strains of EPNs were tested for virulence against eggs, first to fourth instars, fifth instars, and pupae of <italic>H. zea</italic> and <italic>C. includens</italic> in the laboratory. These 10 EPN strains were <italic>Heterorhabditis bacteriophora</italic> (HP88 and VS strains), <italic>H. floridensis</italic> (K22 strain), Hgkesha (Kesha strain), <italic>Steinernema carpocapsae</italic> (All and Cxrd strains), <italic>S. feltiae</italic> (SN strain), <italic>S. rarum</italic> (17c+e strain), and <italic>S. riobrave</italic> (355 and 7–12 strains). EPNs could infect eggs of <italic>H. zea</italic> or <italic>C. includens</italic> in the laboratory, but the infection was low. The mortality caused by 10 EPN strains in seven days was significantly higher for the first to fourth instars of <italic>H. zea</italic> compared to the control, as was the fifth instars of <italic>H. zea</italic>. Similarly, for the first to fourth and fifth instars of <italic>C. includens</italic>, the mortality was significantly higher compared to the controls, respectively. However, only <italic>S. riobrave</italic> (355) had significantly higher mortality than the control for the pupae of <italic>H. zea</italic>. For the pupae of <italic>C. includens</italic>, except for <italic>H. bacteriophora (HP88)</italic>, <italic>S. rarum (17c+e)</italic>, and <italic>H. floridensis</italic> (K22), the mortality of the other seven strains was significantly higher than the control. Subsequently, <italic>S. carpocapsae</italic> (All) and <italic>S. riobrave</italic> (7–12) were chosen for efficacy testing in the field with an adjuvant 0.066% Southern Ag Surfactant (SAg Surfactant).
In field experiments, the SAg Surfactant treatment significantly increased the mortality and EPN infection for <italic>S. carpocapsae</italic> (All) on first instars of <italic>H. zea</italic> in corn plant whorls. On soybean plants, with the SAg Surfactant, <italic>S. carpocapsae</italic> (All) was more effective than <italic>S. riobrave</italic> (7–12) on fifth instars of <italic>C. includens</italic>. This study indicates that EPNs can control <italic>H. zea</italic> and <italic>C. includens</italic>, and SAg Surfactant can enhance EPN efficacy.
</abstract>

The Efficacy of Entomopathogenic Nematodes Plus an Adjuvant against <italic>Helicoverpa zea</italic> and <italic>Chrysodeixis includens</italic> in Aboveground Applications

<abstract>
<title style='display:none'>Abstract</title>
Viviparity is generally considered to be rare in animals. In nematodes, only six species of Rhabditida are viviparous. Five of these species have been identified in association with <italic>Onthophagus</italic> dung beetles, with <italic>Tokorhabditis atripennis</italic> being repeatedly isolated from the dung beetle <italic>Onthophagus atripennis</italic> in Japan. <italic>T. atripennis</italic> is easy to culture in a laboratory setting, and its host, <italic>O. atripennis</italic>, is distributed all over Japan. Therefore, <italic>T. atripennis</italic> is an ideal candidate for ecological and evolutionary studies on viviparity. However, the extent of their distribution and relationship with dung beetles, as well as habitats, remain unclear. In the present study, we conducted field surveys and successfully isolated 27 strains of viviparous nematodes associated with tunneler dung beetles from various regions of Japan, all of which were identified as <italic>T. atripennis</italic>. <italic>T. atripennis</italic> exhibited a strong association with <italic>Onthophagus</italic> dung beetles, especially <italic>O. apicetinctus</italic> and <italic>O. atripennis</italic>. And it was predominantly found in specific anatomical locations on the beetle bodies, such as the ‘groove between pronotum and elytron’ and the ‘back of the wings’. Our findings suggest that <italic>Onthophagus</italic> species are the primary hosts for <italic>T. atripennis</italic>, and <italic>T. atripennis</italic> exhibits a close relationship with the living environments of tunneler beetles. This association may play a significant role in the evolution of viviparity in nematodes.
</abstract>

Geographical distribution and phoretic associations of the viviparous nematode <italic>Tokorhabditis atripennis</italic> with <italic>Onthophagus</italic> dung beetles in Japan

<abstract>
<title style='display:none'>Abstract</title>
The reniform nematode, <italic>Rotylenchulus reniformis</italic>, is a major yield-limiting pest of upland cotton (<italic>Gossypium hirsutum</italic>) in the United States that has been steadily increasing in incidence in many states. Reniform nematode-resistant cotton cultivars have recently become commercially available for cotton producers; however, few field trials have evaluated their efficacy as a nematode management tool. The aim of this study was to evaluate reniform nematode population development, plant growth, and seed cotton yield of reniform nematode-resistant cotton cultivars in two nematode-infested fields in Louisiana. Replicated small-plot field trials were conducted in St. Joseph, LA (NERS field) and Winnsboro, LA (MRRS field) during the 2022 and 2023 growing seasons. In 2022, cultivars evaluated included: (1) DP 1646 B2XF (susceptible/tolerant), (2) DP 2141NR B3XF (resistant), (3) PHY 332 W3FE (resistant), (4) PHY 411 W3FE (resistant), and (5) PHY 443 W3FE (resistant). In 2023, an additional susceptible cotton cultivar, PHY 340 W3FE, was also included. All nematode-resistant cotton cultivars evaluated provided suppression of reniform nematode population development relative to that of the susceptible cotton cultivars, with suppression of nematode soil population densities at harvest ranging from 49 – 81% relative to DP 1646 B2XF. The resistant cultivar PHY 411 W3FE provided the most consistent suppression of reniform nematode population development, reducing reniform nematode soil population densities at harvest in both field locations and both trial years. In contrast, DP 2141NR B3XF only reduced soil population densities at harvest in the NERS field in 2023. Despite relatively consistent nematode suppression and improvements in plant vigor ratings and canopy coverage associated with the resistant cotton cultivars, a yield increase was only observed with PHY 332 W3FE and PHY 411 W3FE planted at the NERS field in 2023. Despite strong resistance to reniform nematode in the evaluated cotton cultivars, nematode soil population densities still increased during the growing season in plots planted with resistant cotton cultivars, emphasizing the need for additional management tactics to use alongside host resistance. This study indicates that new reniform nematode-resistant cotton cultivars show promising potential to reduce nematode population development during the growing season in Louisiana.
</abstract>

Cotton host resistance as a tool for managing <italic>Rotylenchulus reniformis</italic> in Louisiana

<abstract>
<title style='display:none'>Abstract</title>
Infective second-stage juveniles (J2) of <italic>Meloidogyne</italic> spp. migrate towards host roots, which depends on several factors, including root exudates and soil temperature. Although <italic>Meloidogyne enterolobii</italic> is a highly virulent nematode that affects major agricultural crops worldwide, there is limited ecological data about it. The objective of this study was to determine the J2 migration pattern vertically in 14-cm long segmented soil columns towards tomato (<italic>Solanum lycopersicum</italic>) and marigold (<italic>Tagetes patula</italic>) roots, each grown at two soil temperatures (20 or 26ºC). Bottomless cups with tomatoes or marigolds were attached to the top of each column; cups with no plants were used as untreated controls. Juveniles (1,000/column) were injected into a hole located 1 cm from the bottom of each column. The apparatuses were placed in growth chambers at 20 or 26ºC, and J2 were allowed to migrate for 3, 6, 9, or 12 days after injection (DAI). At each harvest, J2 were extracted from each ring of the columns and counted to compare their distribution, and root systems were stained to observe root penetration. <italic>M. enterolobii</italic> migrated over 13 cm vertically 3 DAI regardless of temperature, even without plant stimuli. The vertical migration was greater at 26ºC, where 60% of active J2 were found at distances &gt;13 cm at 12 DAI. Temperature did not affect root penetration. Overall, a greater number of J2 was observed in tomato roots, and root penetration increased over time.
</abstract>

Vertical Migration of Second-stage Juveniles of <italic>Meloidogyne enterolobii</italic> as Influenced by Temperature and Host

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