Plant-parasitic Nematodes Research Articles

Parasitic nematode populations associated with developmental stages of mango in production regions of Ghana

Nematode (Phylum nematoda) infestation is a major set back in mango (Mangifera indica) production world-wide. Control of nematodes requires understanding of their diversity, distribution and population densities. The objective of this study was to identify plant-parasitic nematodes associated with mangoes and their population densities at seedling and maturity stages in production regions of Ghana. The study was conducted in Greater Accra (Manya and Klagon) and the Eastern region (Somanya) during December 2016 to January 2018. Mango farmlands were surveyed for soil and root samples, from which nematodes were extracted, identified and quantified. Twenty-four nematode genera were identified in mango seedlings and matured trees from Somanya; and 14 genera dentified in seedlings and 22 in matured trees from Manya; while at Klagon, 15 nematode genera were identified in matured trees. Helicotylenchus spp. were the most populated in seedlings obtained from Somanya and Manya, with relative abundance of 23.29%. Tylenchus spp. had the highest population in mature trees, with relative abundance of 24.49% at Somanya and 38.86% at Manya; while Helicotylenchus spp. had the highest relative abundance of 43.96% at Klagon. Mature trees had higher nematode population densities, compared to seedlings. There were significant variation in nematode populations between seedlings and matured stages of mango.

Green fabrication of titanium dioxide nanoparticles via Syzygium cumini leaves extract: characterizations, photocatalytic activity and nematicidal evaluation

ABSTRACT The most significant plant parasitic nematode in terms of economic impact is root-knot nematode (Meloidogyne incognita), which severely harms essential crops used for agriculture. This study investigated green fabrication of titanium dioxide nanoparticles (TiO2 NPs) utilizing Syzygium cumini (SC) leaf extract and evaluated its nematotoxic activity against M. incognita in vitro and in pots. During experiments, second-stage juveniles (J2s) and egg masses of M. incognita were treated with different concentrations (125, 250, 375 and 500 ppm) of SC-TiO2 NPs. After 48 h and five days of exposure, respectively, lowest J2s mortality and per cent inhibition in egg hatching was discovered at 125 ppm, and highest J2s mortality and maximum per cent inhibition in egg hatching determined at 500 ppm. The treatment of SC TiO2 NPs considerably reduced M. incognita infection and enhanced carrot plants' growth and physiological characteristics. The characterization of green synthesized SC-TiO2 NPs made by X-ray diffraction, Photoluminescence, FTIR, SEM, UV-Visible Diffuse Reflectance Spectrophotometer, TEM, and photocatalytic activity also examined. In conclusion, it can be said that SC-TiO2 NPs possess nematode-toxic potential against M. incognita and are used as substitutes for high-risk chemical nematicides without causing any phytotoxicity.

Rhizosphere-Associated Microbiota Strengthen the Pathogenicity of Meloidogyne incognita on Arabidopsis thaliana

Microorganisms associated with nematodes or enriched in galls have been reported previously to aid plant-parasitic nematodes (PPNs) in infecting and establishing parasitism in the host plants. However, the rhizosphere-associated microbiota, which strengthens the pathogenicity of PPNs, remains largely unknown. This study illustrated rhizosphere bacteria enhancing Meloidogyne incognita infection on Arabidopsis thaliana by comparing the gall numbers of the treatments between natural soil and the sterile soil or soils drenched with antibiotics. By culture-dependent and pot testing methods, sixteen bacterial combinations from rhizosphere soils of A. thaliana were demonstrated to enhance M. incognita pathogenicity, including the most effective Nocardioides. Single-strain inoculation from the Nocardioides combination significantly resulted in M. incognita forming more galls on roots than the control, in which N. nematodiphilus R-N-C8 was the most effective strain. Strain R-N-C8 could substantially facilitate the M. incognita second-stage juveniles (J2s) moving towards the roots of A. thaliana and infecting the roots by releasing chemoattractant to attract J2s. The chemoattractant from strain R-N-C8 was determined to be L-lysine. This study furnishes vital insights for understanding the infection of root-knot nematodes associated with rhizosphere microbes.

A root-knot nematode effector targets the Arabidopsis cysteine protease RD21A for degradation to suppress plant defense and promote parasitism.

Meloidogyne incognita is one of the most widely distributed plant-parasitic nematodes and causes severe economic losses annually. The parasite produces effector proteins that play essential roles in successful parasitism. Here, we identified one such effector named MiCE108, which is exclusively expressed within the nematode subventral esophageal gland cells and is upregulated in the early parasitic stage of M. incognita. A yeast signal sequence trap assay showed that MiCE108 contains a functional signal peptide for secretion. Virus-induced gene silencing of MiCE108 impaired the parasitism of M. incognita in Nicotiana benthamiana. The ectopic expression of MiCE108 in Arabidopsis suppressed the deposition of callose, the generation of reactive oxygen species, and the expression of marker genes for bacterial flagellin epitope flg22-triggered immunity, resulting in increased susceptibility to M. incognita, Botrytis cinerea, and Pseudomonas syringae pv. tomato (Pst) DC3000. The MiCE108 protein physically associates with the plant defense protease RD21A and promotes its degradation via the endosomal-dependent pathway, or 26S proteasome. Consistent with this, knockout of RD21A compromises the innate immunity of Arabidopsis and increases its susceptibility to a broad range of pathogens, including M. incognita, strongly indicating a role in defense against this nematode. Together, our data suggest that M. incognita deploys the effector MiCE108 to target Arabidopsis cysteine protease RD21A and affect its stability, thereby suppressing plant innate immunity and facilitating parasitism.

Omnipolyphilins A and B: Chlorinated Cyclotetrapeptides and Naphtho-α-pyranones from the Plant Nematode-Derived Fungus Polyphilus sieberi.

Chemical exploration for two isolates of the recently described ascomycete species Polyphilus sieberi, derived from the eggs of the plant parasitic nematode Heterodera filipjevi, afforded the identification of many compounds that belong to various metabolite families: two previously undescribed chlorinated cyclotetrapeptides, omnipolyphilins A (1) and B (2), one new pyranonaphthoquinone, ventiloquinone P (3), a 6,6'-binaphto-α-pyranone dimer, talaroderxine D (4) in addition to nine known metabolites (5-13) were isolated from this biocontrol candidate. All isolated compounds were characterized by comprehensive 1D, 2D NMR, and HR-ESI-MS analyses. The absolute configurations of the cyclotetrapeptides were determined by a combination of advanced Marfey's method, ROE correlation aided by conformational analysis, and TDDFT-ECD calculations, while ECD calculations, Mosher's method, and experimental ECD spectra were used for ventiloquinone P (3) and talaroderxine D (4). Among the isolated compounds, talaroderxine D (4) showed potent antimicrobial activities against Bacillus subtilis and Staphylococcus aureus with MIC values of 2.1 and 8.3 μg mL-1, respectively. Additionally, promising inhibitory effects on talaroderxine D (4) against the formation of S. aureus biofilms were observed up to a concentration of 0.25 μg mL-1. Moreover, ophiocordylongiiside A (10) showed activity against the free-living nematode Caenorhabditis elegans.

Phylogenetic position of Pratylenchus sp. (Nematoda: Pratylenchidae) associated with grasslands using 28S rDNA from South Africa

Plant-parasitic nematodes are the main nematodes that live in the soil, causing yield loss in various crops. As endoparasites, Pratylenchus species can reduce the yield of grass and other plants by feeding on their roots. Because of its parasitic nature on plants, this species requires careful identification; in South Africa's Limpopo Province, grasslands are among the most vital agricultural resources. Therefore, this molecular study was conducted in 2023 at Limpopo University to identify the nematode from South Africa's soils using 28S rDNA marker. The recovered nematode was extracted using the tray method, and then its DNA was extracted using the chelex method. The nematode was identified as Pratylenchus. Afterward, 28S rDNA was amplified using specific primers to identify the nematode at the molecular level. The Nblast analysis based on the large subunit ribosomal DNA showed South African Pratylenchus had 99% similarity (OQ343703) with the South African population. Phylogenetic analysis using maximum likelihood placed this species with those molecularly identified as Pratylenchus in the same clade with highly supported (100) bootstrap values. In conclusion, this species was identified using 28S rDNA; however, other rDNA markers, such as ITS rDNA and mtDNA is recommended for a better understanding of Pratylenchus phylogeny.

Evaluation of Soybean Genotypes (Glycine max and G. soja) for Resistance to the Root-Knot Nematode, Meloidogyne enterolobii.

Potential resistance to the root-knot nematode (RKN) Meloidogyne enterolobii in 72 Glycine soja and 44 G. max soybean genotypes was evaluated in greenhouse experiments. Approximately 2,500 eggs of M. enterolobii were inoculated on each soybean genotype grown in a steam sterilized 1:1 sand to soil mixture. Sixty days postinoculation, plants were destructively harvested to determine the host status. The host status of each soybean genotype was determined by assessing root galling severity and calculating the final eggs per root system divided by the initial inoculum, or the reproduction factor (Rf). Five G. soja soybean genotypes were identified as resistant (Rf < 1) to M. enterolobii: '407202', '407239', '424083', '507618', and '639621'. None of the tested G. max soybean genotypes were identified as resistant to M. enterolobii. Some of the G. max genotypes determined to be susceptible to M. enterolobii include 'Hagood', 'Avery', 'Rhodes', 'Santee', and 'Bryan'. The genotype 'Bryan' had the lowest Rf values among the group at 5.06 and 6.67 in two independent trials, respectively, which represents a five- to sixfold increase in reproduction of M. enterolobii. Plant genotypes resistant to RKNs are effective in managing the disease and preserving yield, cost-efficient, and environmentally sustainable, and host resistance is often regarded as the most robust management tactic for controlling plant-parasitic nematodes. Resistance to RKNs in soybean genotypes has been identified for other Meloidogyne species, yet there is currently limited data regarding soybean host status to the highly aggressive nematode M. enterolobii. This study adds to the knowledge of potential native resistance to M. enterolobii in wild and cultivated soybean.

Identification of Plant Parasitic Nematodes Associated with Citrus in Dibrugarh District

The present investigation was carried out to determine the occurrence and distribution of plant parasitic nematodes associated with citrus plants of different citrus orchards in Dibrugarh district. A total of 149 soil and root samples were collected randomly from the rhizosphere of citrus plants from the twenty four different citrus orchards of seven blocks from Dibrugarh district. Eight genera of plant parasitic nematodes were found to be associated with citrus plants of Dibrugarh district. Genera of plant parasitic nematodes recorded were namely Tylenchulus, Hoplolaimus, Helicotylenchus, Tylenchorhynchus, Meloidogyne, Xiphinema, Paratylenchus and also nematodes genera found under criconematids. Among them Hoplolaimus sp., Helicotylenchus sp., Tylenchorhynchus sp. and T. semipenetrans were found to be present in most of the samples. Community analysis of plant parasitic nematodes revealed that the genus Hoplolaimus ranked first in relative frequency, absolute frequency, absolute density, relative density and prominence value. Genus Helicotylenchus ranked second in absolute density, relative density and prominence value and genus Tylenchorhynchus ranked third in case of absolute density absolute frequency and prominence value. Results shown that Tylenchulus semipenetrans ranked second in absolute frequency and relative frequency and fourth in prominence value.

Assessment of Common Factors Associated with Droplet Digital PCR (ddPCR) Quantification of Paratrichodorus allius in Soil.

This research investigated the factors associated with the quantitative detection of Paratrichodorus allius in soil using droplet digital PCR (ddPCR). Small-sized nematodes exhibited significantly lower DNA quantities compared to their medium and large counterparts. Soil pre-treatments (room temperature drying and 37 °C oven-drying) demonstrated no substantial impact on ddPCR detection, and soil storage (0-3 months at 4 °C) exhibited negligible alterations in DNA quantities. A commercial DNA purification kit improved the resulting quality of ddPCR, albeit at the cost of a notable reduction in DNA quantity. Upon assessing the impact of inhibitors from soil extracts, a higher inhibitor concentration (5%) influenced ddPCR amplification efficiency. Incorporating bovine serum albumin (BSA) (0.2 μg/μL or 0.4 μg/μL) into the ddPCR setup mitigated the issue. In brief, while ddPCR exhibits minimal sensitivity to soil pre-treatments and storage, higher concentrations of PCR inhibitors and the DNA purification process can influence the results. Despite ddPCR's capability to detect nematodes of all sizes, quantification may not precisely reflect soil population. Incorporating BSA into the ddPCR setup enhances both detection and quantification capacities. This study represents the first comprehensive investigation of its kind for plant-parasitic nematodes, providing crucial insights for application of ddPCR in nematode diagnosis directly from the soil DNA.

Eksplorasi Populasi dan Kepadatan Genus Nematoda Parasit pada Rizosfir Tanaman Kopi di Kota Solok, Sumatera Barat

Coffee is a plantation crop that has high economic value among other plantation crops and plays an important role as a source of foreign exchange for the country. The decline and low productivity of coffee plants in coffee production centers in Solok City, West Sumatra is one of the causes of plant parasitic nematode attacks. This nematode attack causes disrupted plant growth and reduces the value of crop production both in quantity and quality. This study aims to determine the diversity and population density of parasitic nematodes in the rhizosphere of coffee plants in Solok City, West Sumatra. This research was conducted from March to July 2023 at the Laboratory of Biological Control, Department of Plant Protection, Faculty of Agriculture, Andalas University. Soil samples were taken in two central areas of coffee plantations in Solok City, West Sumatra. In the rhizosphere of coffee plants in Solok City, four genera of parasitic nematodes were found, namely: the genera Pratylenchus, Helicotylenchus, Meloidogyne, Rotylenchulus, Paratylenchus, and Tylenchorhynchus. The highest frequency of presence of nematodes, namely the genus Rotylenchulus, was 50.99 belonging to the medium category in Jorong Kayu Aro, and 44.80 in the rare category in Jorong Kayu Jao.

Chitin-enriched insect frass fertilizer as a biorational alternative for root-knot nematode (Meloidogyne incognita) management.

Root-knot nematodes (Meloidogyne spp.) are serious pests of most food crops, causing up to 100% yield loss. Nevertheless, commercial nematicides are costly and harmful to the environment. While the nematicidal potential of crustacean and synthetic chitin has been demonstrated globally, research on the potential of insect-derived chitin for nematode control has received limited attention. Here, seven chitin-fortified black soldier fly frass fertilizer extracts (chFE) were assessed for their suppressiveness of Meloidogyne incognita and impacts on spinach growth in comparison with a commercial nematicide using in vitro and in vivo bioassays. The performance of chFE and control treatments was assessed by determining their effects on nematode egg hatchability; infective juvenile (J2) mortality and paralysis; number of galls, egg masses, and J2s per plant; and spinach root and shoot biomass. In vitro results showed that chFE and commercial nematicide suppressed nematode egg hatchability by 42% and 52%, respectively, relative to the control (sterile distilled water). Up to 100% paralysis was achieved when M. incognita J2s were exposed to either chFE or commercial nematicide. Further, the J2 mortality achieved using chFE (95%) was comparable to the value achieved using commercial nematicide (96%); in all treatments, mortality increased with exposure time. Similarly, up to 85% suppression of gall development was achieved when spinach plants were grown in soil drenched with chFE; up to 79% reduction in egg mass formation and 68% suppression of J2 development in the root system were achieved using chFE. Also, chFE application significantly increased spinach root and shoot biomass by 54%-74% and 39%-58%, respectively, compared to commercial nematicide. Our findings demonstrate the nematicidal potential of chFE and its benefits on crop production. Thus, chFE could be considered as a promising multipurpose, regenerative, and cost-effective input for sustainable management of plant-parasitic nematodes and enhancement of crop yield.

Nematicidal Activity of Phytochemicals against the Root-Lesion Nematode Pratylenchus penetrans.

Plant-parasitic nematodes (PPNs) are highly damaging pests responsible for heavy losses in worldwide productivity in a significant number of important plant crops. Common pest management strategies rely on the use of synthetic chemical nematicides, which have led to serious concerns regarding their impacts on human health and the environment. Plant natural products, or phytochemicals, can provide a good source of agents for sustainable control of PPNs, due to their intrinsic characteristics such as higher biodegradability, generally low toxicity for mammals, and lower bioaccumulation in the environment. In this work, the nematicidal activity of 39 phytochemicals was determined against the root-lesion nematode (RLN) Pratylenchus penetrans using standard direct and indirect contact methodologies. Overall, the RLN was tolerant to the tested phytochemicals at the highest concentration, 2 mg/mL, seldom reaching full mortality. However, high activities were obtained for benzaldehyde, carvacrol, 3-octanol, and thymol, in comparison to other phytochemicals or the synthetic nematicide oxamyl. These phytochemicals were seen to damage nematode internal tissues but not its cuticle shape. Also, the environmental and (eco)toxicological parameters reported for these compounds suggest lower toxicity and higher safety of use than oxamyl. These compounds appear to be good candidates for the development of biopesticides for a more sustainable pest management strategy.

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

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. Pratylenchus and Meloidogyne 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 P. crenatus, P. fallax, P. neglectus, P. penetrans, and P. thornei, with some of these species being detected for the first time on these grass hosts. The only Meloidogyne sp. found in these grasses was M. nassi, 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.

Simple, inexpensive, and rapid approach to detect changes in the structure of soil free-living nematodes.

A general limitation of ecological investigations based on nematodes is related to the difficult and time-consuming taxonomic identification of species. Therefore, nematologists are investing many efforts to develop alternative approaches as proxies applicable in biomonitoring assessment. Recently, an alternative method that combines morpho-functional traits was proposed for detecting assemblage changes of marine nematodes. In view of the promising results, it was tested the same approach to document taxonomic structure changes of soil free-living and plant parasitic nematodes. Specifically, this attempt was carried out using three data sets that include studies from various European regions and different types of ecosystems: forests, grasslands and maize crops. Multivariate statistical analysis revealed that the simple combination of the four traits (i.e., buccal cavity cuticularization occurrence, amphideal fovea size and shape, morphology of the cuticle and pharynx) in a single code number perfectly mirrors the taxonomic structure trends of the nematode assemblage at genus level. Therefore, we predict that similar results can be also obtained by directly encoding nematode specimens with the selected traits and we point to new important advances if this procedure can be coupled with advanced machine learning.

Comparative analysis of soil nematode biodiversity from five different fruit orchards in Osmaneli district, Bilecik, Türkiye.

Nematode population densities were determined in 60 soil and root samples collected from 6 fruit orchards in the Bilecik province (western Turkey), between April 2022 and June 2022. The total number of identified nematodes have reached up to 2418 individuals (number of female: 1036; male: 154; and juvenile: 1228). They belong to 54 species, 54 genera, 33 families and 11 orders. Plant parasitic nematodes that were detected mostly are listed as follows: Helicotylenchus (6,12 %), Pratylenchus (5,74 %), Paratylenchus (4.83 %), Xiphinema (3,06 %), Tylenchorhynchus (2,19 %), Malenchus (1.94 %) and Tylenchus (1.19 %). According to the maturity index analysis, mean values showed the highest maturity level at peach trees (MI value: 3,52), followed by; walnut trees (MI value: 2.49), cherry trees (MI value: 2.15), nectarine trees (MI value: 1.86), plum trees (MI value: 1.57), and olive trees (MI value: 1.42). Mostly the diverse group in terms of species richness was within the order Dorylaimida. The nematodes associated with peach and walnut trees here showed the most stable environments in terms of soil nematode community structure.

Unveiling the Diversity: Plant Parasitic Nematode Effectors and Their Plant Interaction Partners.

Root-knot and cyst nematodes are two groups of plant parasitic nematodes that cause the majority of crop losses in agriculture. As a result, these nematodes are the focus of most nematode effector research. Root-knot and cyst nematode effectors are defined as secreted molecules, typically proteins, with crucial roles in nematode parasitism. There are likely hundreds of secreted effector molecules exuded through the nematode stylet into the plant. The current research has shown that nematode effectors can target a variety of host proteins and have impacts that include the suppression of plant immune responses and the manipulation of host hormone signaling. The discovery of effectors that localize to the nucleus indicates that the nematodes can directly modulate host gene expression for cellular reprogramming during feeding site formation. In addition, plant peptide mimicry by some nematode effectors highlights the sophisticated strategies the nematodes employ to manipulate host processes. Here we describe research on the interactions between nematode effectors and host proteins that will provide insights into the molecular mechanisms underpinning plant-nematode interactions. By identifying the host proteins and pathways that are targeted by root-knot and cyst nematode effectors, scientists can gain a better understanding of how nematodes establish feeding sites and subvert plant immune responses. Such information will be invaluable for future engineering of nematode-resistant crops, ultimately fostering advancements in agricultural practices and crop protection. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 "No Rights Reserved" license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2024.

Drivers of plant parasitic nematode community structures associated with tobacco‐growing areas in southern Brazil

AbstractTobacco (Nicotiana tabacum L.) is one of the most important crops in southern Brazil, but little is known about the distribution and diversity of plant parasitic nematodes (PPNs). We surveyed the occurrence and diversity of PPNs in 36 tobacco‐growing areas in southern Brazil as well as evaluated their relationship with 19 bioclimatic variables. For these purposes, extracted nematodes (from soil and roots) were identified based on morphological and biochemical traits and estimates of incidence and abundance were obtained, which were used to compute diversity indices. Furthermore, the relationship between taxa and diversity and the influence of bioclimatic variables were studied using principal component analysis (PCA) and generalized linear models (GLMs), respectively. We observed diversity across the sampled sites, with values varying from 0.03 to 1.22 and from 0.05 to 0.76 according to the Shannon‐Wiener and Pielou's evenness indices, respectively. Seven genera of PPNs (Meloidogyne, Helicotylenchus, Tylenchus, Xiphinema, Pratylenchus, Paratylenchus and Mesocriconema) were identified, highlighting taxa with high incidence and abundance, such as Meloidogyne (100%; 1800 to 41,850 specimens/250 cm3), Helicotylenchus (100%; 50 to 9850 specimens/250 cm3), and Pratylenchus (86.1%; 50 to 1950 specimens/250 cm3). The PCA disclosed the major roles of Meloidogyne, Tylenchus, and Helicotylenchus in the structure of the PPN communities and their interplays. Among root‐knot nematodes, Meloidogyne javanica, M. arenaria and M. incognita were the predominant species. Using GLMs, we found that average annual temperature and annual precipitation strongly influenced the abundance of PPNs as well as the diversity indices (p &lt; .01), with negative and/or positive interactions. Collectively, our findings fill gaps in knowledge about the current impact of PPNs and provide insights into future scenarios, including for other host crops.

Depth distribution of plant-parasitic nematodes on bentgrass golf greens in Missouri and Indiana.

Control of plant-parasitic nematodes (PPNs) on golf putting greens with nematicides is dependent on the seasonal occurrence and depth distribution of target PPN populations. This study aimed to determine if plant-parasitic nematode populations on golf course putting greens in Missouri and Indiana peaked at a targetable depth at a specific time in the year, focusing primarily on lance (Hoplolaimus spp.) and root-knot (Meloidogyne spp.) nematodes. To elucidate species diversity in the region, rDNA from a subset of lance and root-knot nematodes was sequenced and analyzed, with additional micromorphology of a lance nematode assessed in scanning electron micrographs (SEM). Soil samples were taken to a depth of 25 cm and stratified into 5 cm increments during April, June, August and October at seven sites across Missouri, three in the Kansas City metro of Kansas in 2021 and in ten sites across Indiana in 2022. Samples were stratified in five-centimeter increments and aggregated for a total of 100 cm3 of soil at each depth for each sampling. Samples were processed using a semi-automatic elutriator followed by the sucrose-flotation method, and populations were counted using a hemocytometer and recorded. For molecular characterization, rDNA was extracted and analyzed from 31 individual lance nematodes from one site in Missouri and eight sites in Indiana, and 13 root-knot nematodes from nine sites across Indiana. A significant interaction occurred between sampling month and depth for lance and ring nematodes Missouri/KS, with both PPN populations peaking at the 0-5 cm depth during October, which is well after most targeted nematicide applications are applied. Ring nematodes in Indiana did not follow this trend and were most abundant in August at a depth of 0-5 cm. No significant interaction between depth and month occurred for lance or root-knot nematodes in Indiana, or root-knot nematodes in Missouri/KS. Hoplolaimus stephanus and H. magnistylus were the lance species identified on golf greens, and Meloidogyne naasi, M. graminicola and M. marylandi were the root-knot species identified. Scanning-electron micrographs confirmed morphological characteristics unique to H. stephanus.

First report of Meloidogyne hapla on hemp (Cannabis sativa) in Oregon.

Hemp is a crop that has gained interest in Washington and Oregon. As with other crops, hemp production faces challenges due to biotic factors, including plant-parasitic nematodes. During a survey for plant-parasitic nematodes associated with hemp, Meloidogyne sp. was found in a composite root sample collected in Oregon. Morphological characterization of second-stage juveniles identified the nematode as Meloidogyne hapla. Molecular identification confirmed the population as M. hapla. To our knowledge, this is the first report of M. hapla on hemp in the Pacific Northwest of the United States.

Morphological and molecular characterizations of Pratylenchus coffeae infecting Ming aralia and coffee in Vietnam.

Pratylenchus coffeae, belonging to the root-lesion nematode group, is a highly prevalent and destructive plant-parasitic nematode that is able to infest a wide range of host plants. Although this species' devastating impacts on coffee plantations across the world are widely known on other host plants, its association with Ming aralia has never been reported. Our study characterized two popu lations of P. coffeae (associated with Ming aralia and coffee) and compared them with other popu lations from previous studies in Vietnam and other countries in the world. The identification of P. coffeae in our study was confirmed by the comprehensive analysis encompassing morphological examination, morphometric data, and molecular characterizations of the COI mtDNA and D2D3 of 28S rRNA regions. The cluster and MDS analyses revealed that the two populations of P. coffeae from Vietnam are closely related to those from Japan and Indonesia. The D2-D3 sequences of 28S rRNA and COI mtDNA regions exhibited high similarity among these populations, indicating a stable genetic profile. Our research contributes to a better understanding of the distribution and genetic characterizations of P. coffeae by offering new morphological and molecular insights into the presence of this nematode in Vietnam. Additionally, this nematode species was found to be associated with host plant's symptoms such as chlorotic leaves, stunted growth and root lesion in both hosts. Given the economic significance of both Ming aralia and coffee crops in Vietnam, as well as the damaging potential of P. coffeae, this study emphasizes the need of proactive nematode management measures to control this destructive pest.