<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

Abstracts from The Society of Nematologists Annual Meeting 2019

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

Morphological Variation in the Rice Root Nematode, <italic>Hirschmanniella Oryzae</italic> (Van Breda De Haan, 1902) Luc &amp; Goodey, 1964 from Korea, with Inferences from its Ribosomal and Mitochondrial DNA

<abstract>
<title style='display:none'>Abstract</title>
Midwest crop production is dominated by two summer annual crops grown in rotation, viz., corn (<italic>Zea mays</italic> L.) and soybean (<italic>Glycine max</italic> L.). Winter oilseed crops, such as pennycress (<italic>Thlaspi arvense</italic> L.), can provide ecosystem and economic benefits when added to the corn–soybean rotation. However, adding a new crop adds risks, such as increased pest pressure. The objectives of this study were to (i) evaluate population development of three soybean cyst nematode (SCN; <italic>Heterodera glycines</italic>) biotypes on three pennycress genotypes and susceptible soybean and (ii) determine whether SCN inoculation level influenced plant biomass. SCN population density and biomass were determined after 60 d in the greenhouse. At the inoculation level of 2,000 eggs/100 cm3 soil, the average egg density for the three pennycress genotypes was 1,959 eggs/100 cm3 soil, lower than that for the susceptible soybean ‘Sturdy’ (9,601 eggs/100 cm3 soil). At the inoculation level of 20,000 eggs/100 cm3 soil, the average egg density for the three pennycress genotypes was 6,668 eggs/100 cm3 soil, lower than that for ‘Sturdy’ (40,740 eggs/100 cm3 soil). The inoculation level did not affect plant biomass. Pennycress is an alternative host to SCN under greenhouse conditions but is a less suitable host than soybean.
</abstract>

Soybean Cyst Nematode Population Development and Its Effect on Pennycress in a Greenhouse Study

<abstract>
<title style='display:none'>Abstract</title>
Root-knot nematodes (RKN) cause yield losses in eggplant-growing areas. There are no known varieties of eggplant (<italic>Solanum melongena</italic> L.) that are resistant to RKNs. However, the wild relative of eggplant, <italic>S. torvum</italic> (Sw.), provides resistance to some RKN species and is used as a rootstock for cultivated eggplants. Therefore, determination of the reproductive capacity of nematodes on eggplant rootstocks developed from <italic>S. torvum</italic> is required for effective management of RKNs that are widely present in vegetable growing areas. In the present study, the degree of reproduction of <italic>Mi-1.2</italic>-virulent and avirulent isolates of <italic>M</italic>. <italic>incognita</italic>, <italic>M</italic>. <italic>javanica</italic>, and <italic>M</italic>. <italic>luci</italic> on eggplant rootstocks, Hawk and Boğaç, was evaluated in a plant growth chamber. Hawk and Boğaç were resistant (&lt; 10 egg masses per whole root system) to all avirulent and virulent isolates of <italic>M</italic>. <italic>incognita</italic>, <italic>M</italic>. <italic>javanica</italic>, and <italic>M</italic>. <italic>luci.</italic> This study is the first report on the resistance of <italic>S. torvum</italic> to virulent isolates of <italic>M. luci</italic>. Results indicate that <italic>S. torvum</italic> offers broad-spectrum resistance against RKNs.
</abstract>

<article-title xml:lang="en">Degree of resistance of <italic>Solanum torvum</italic> cultivars to <italic>Mi-1.2</italic>-virulent and avirulent isolates of <italic>Meloidogyne incognita</italic>, <italic>Meloidogyne javanica</italic>, and <italic>Meloidogyne luci</italic>

<abstract>
<title style='display:none'>Abstract</title>
Mermithidae is a family of nematodes that parasitize a wide range of invertebrates worldwide. Herein, we report nematodes that were unexpectedly found in three of 486 adult stable flies (<italic>Stomoxys calcitrans</italic>) captured from three farms (F1, F2, and F3) in different regions of Gifu Prefecture, Japan. We aimed to characterize these nematodes both at the morphological and molecular level. Morphological studies revealed that the nematodes were juveniles of Mermithidae. Phylogenetic analysis based on 18S and 28S rDNA indicated that the mermithids from farms F1 and F2 could be categorized into the same cluster as <italic>Ovomermis sinensis</italic> and <italic>Hexamermis</italic> sp., whereas the mermithid from farm F3 clustered with <italic>Amphimermis</italic> sp. Additionally, these mermithids could be categorized within the same clusters as related mermithids detected in Japan that parasitize various arthropod orders. Our findings suggest that these stable flies may have been parasitized by mermithids already present in the region and that genetically distinct species of mermithids occur across Japan. To the best of our knowledge, this is the first report of mermithids parasitizing adult stable flies in Japan.
</abstract>

First Report of Mermithidae (Enoplea: Mermithida) Parasitizing Adult Stable Flies in Japan

<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>
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>
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

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