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The root-knot nematode, Meloidogyne javanica, is one of the most damaging plant-parasitic nematodes, affecting chickpea and causing substantial yield losses worldwide. The damage potential and population dynamics of this nematode in chickpea in Ethiopia have yet to be investigated. In this study, six chickpea cultivars were tested using 12 ranges of initial population densities (Pi) of M. javanica second-stage juveniles (J2): 0, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64 and 128 J2 (g dry soil)−1 in a controlled glasshouse pot experiment. The Seinhorst yield loss and population dynamics models were fitted to describe population development and the effect on different measured growth variables. The tolerance limit (TTFW) for total fresh weight ranged from 0.05 to 1.22 J2 (g dry soil)−1, with corresponding yield losses ranging from 31 to 64%. The minimum yield for seed weight (mSW) ranged from 0.29 to 0.61, with estimated yield losses of 71 and 39%. The ‘Haberu’ and ‘Geletu’ cultivars were considered good hosts, with maximum population densities (M) of 16.27 and 5.64 J2 (g dry soil)−1 and maximum multiplication rate (a) values of 6.25 and 9.23, respectively. All other cultivars are moderate hosts for M. javanica; therefore, it is crucial to initiate chickpea-breeding strategies to manage the tropical root-knot nematode M. javanica in Ethiopia. [ABSTRACT FROM AUTHOR]

Plant-parasitic nematodes (PPNs) are significant agricultural pests that can reduce maize yields. This study examines the prevalence, abundance, and diversity of PPNs in New Zealand maize fields, focusing on the effects of territory, soil orders, crop stages, and sampling times. Seven PPN genera were identified: Pratylenchus spp. (root-lesion), Helicotylenchus spp. (spiral), Meloidogyne spp. (root-knot), Heterodera spp. (cyst), Paratylenchus spp. (pin), Criconemella spp. (ring), and Tylenchus spp. PPNs were present in 98% of the samples, with Pratylenchus spp. being the most prevalent (91%), followed by Helicotylenchus spp. (38%). Compared to Waikato and Manawatu-Whanganui, Canterbury had the highest nematode populations, particularly of Pratylenchus spp. and Helicotylenchus spp. Brown and pallic soils supported higher PPN abundances. Sampling during the maize harvesting stage and late autumn resulted in the highest nematode populations and diversity indices. Pratylenchus spp. populations often exceeded the economic threshold of 500 Pratylenchus kg−1 of soil, suggesting a significant threat to maize yield in New Zealand. The findings highlight the need for further research to assess the impact of Pratylenchus spp. on maize yield and to develop effective management practices for maize cultivation in the country. [ABSTRACT FROM AUTHOR]

Accurate identification and estimation of the population densities of microscopic, soil-dwelling plant-parasitic nematodes (PPNs) are essential, as PPNs cause significant economic losses in agricultural production systems worldwide. This study presents a comprehensive review of emerging techniques used for the identification of PPNs, including morphological identification, molecular diagnostics such as polymerase chain reaction (PCR), high-throughput sequencing, meta barcoding, remote sensing, hyperspectral analysis, and image processing. Classical morphological methods require a microscope and nematode taxonomist to identify species, which is laborious and time-consuming. Alternatively, quantitative polymerase chain reaction (qPCR) has emerged as a reliable and efficient approach for PPN identification and quantification; however, the cost associated with the reagents, instrumentation, and careful optimisation of reaction conditions can be prohibitive. High-throughput sequencing and meta-barcoding are used to study the biodiversity of all tropical groups of nematodes, not just PPNs, and are useful for describing changes in soil ecology. Convolutional neural network (CNN) methods are necessary to automate the detection and counting of PPNs from microscopic images, including complex cases like tangled nematodes. Remote sensing and hyperspectral methods offer non-invasive approaches to estimate nematode infestations and facilitate early diagnosis of plant stress caused by nematodes and rapid management of PPNs. This review provides a valuable resource for researchers, practitioners, and policymakers involved in nematology and plant protection. It highlights the importance of fast, efficient, and robust identification protocols and decision-support tools in mitigating the impact of PPNs on global agriculture and food security. [ABSTRACT FROM AUTHOR]

Jambu plants (Acmella oleracea) exhibiting necrotic angular leaf spots were collected in Belém—Pará, Brazil. Suspected to be a disease caused by nematodes, the jambu leaves were processed and the presence of nematodes from Aphelenchoides genus was observed using a light microscope. These nematodes were reared on Fusarium sp. and subsequently morphologically and molecularly characterized to species level. Aphelenchoides sp. associated with jambu exhibited morphological and morphometric characteristics similar to those within the A. besseyi complex (A. besseyi sensu stricto, A. oryzae and A. pseudobesseyi). Still, these characteristics were insufficient to confirm the identity of this population. However, the Bayesian inference analysis, utilizing the expansion segment of the large subunit (D2-D3 LSU) of nuclear ribosomal DNA, yielded results with a high posterior probability, indicating that the Aphelenchoides sp. associated with jambu belongs to the A. pseudobesseyi species. Under controlled conditions, the reproduction of the nematode in the leaf tissues (RF > 1) was observed, resulting in disease symptoms. The highest reproductive rate of A. pseudobesseyi (RF = 2.6) was observed from inoculation with 100 nematodes per leaf (500 nematodes per plant). Based on Seinhorst analysis, the tolerance limit in jambu plants infected with A. pseudobesseyi was 250 nematodes. It is concluded that A. pseudobesseyi is the etiological agent of the jambu angular leaf spot. For future evaluation of jambu resistance on A. pseudobesseyi, an inoculate maximum of 100 nematodes per leaf is recommended. [ABSTRACT FROM AUTHOR]

The predominant plant-parasitic nematodes associated with Pattawia pineapple-cultivated areas were investigated using combined molecular and morphological techniques. In total, 134 soil samples were collected for nematode extraction from the main pineapple crops in 3 districts (Sam Roi Yot, Mueang and Hua Hin) of Prachuap Khiri Khan, Thailand. Based on the morphology, 6 plant-parasitic nematode genera were identified: Rotylenchulus sp., Meloidogyne sp., Helicotylenchus sp., Hoplolaimus sp., Mesocriconema sp. and Pratylenchus sp. The main plant-parasitic nematodes that occurred in Sam Roi Yot and Mueang districts were Rotylenchulus sp. (70.27 and 97.01 %, respectively), while in Hua Hin district, Helicotylenchus sp. (37.73 %) was dominant. Based on molecular identification, nucleotide sequence comparisons and the phylogenetic tree analyses based on the 18S and 28S rRNA genes revealed the species of the nematodes were R. reniformis and H. dihystera, showing 99 % identity with the nematode populations from Japan and China, respectively. Notably, the morphometric and morphological characters also identified these 2 species correctly; however, this technique required more time and may be less accurate. While R. reniformis has been identified as a common species in pineapple fields in the USA, India, Kenya, the Philippines and Nigeria, the current study was the 1st to report H. dihystera isolated from soil in Pattawia pineapple crops in Thailand. [ABSTRACT FROM AUTHOR]

Nematoda is a diverse phylum that is estimated to contain more than a million species. More than 4,100 of these species have the ability to parasitize plants and cause agricultural losses estimated at US $173 billion annually. This has led to considerable research into their biology to minimize crop losses via control methods. At the infancy of plant-parasitic nematode molecular biology, researchers compared nematode genomes, genes, and biological processes to the model nematode species Caenorhabditis elegans, which is a free-living bacterial feeder. This well-annotated and researched model nematode assisted the molecular biology research, e.g., with genome assemblies, of plant-parasitic nematodes. However, as research into these plant parasites progressed, the necessity of relying on the free-living relative as a reference has reduced. This is partly driven by revealing the considerable divergence between the two types of nematodes both genomically and anatomically, forcing comparisons to be redundant as well as the increased quality of molecular plant nematology proposing more suitable model organisms for this clade of nematode. The major irregularity between the two types of nematodes is the unique anatomical structure and effector repertoire that plant nematodes utilize to establish parasitism, which C. elegans lacks, therefore reducing its value as a heterologous system to investigate parasitic processes. Despite this, C. elegans remains useful for investigating conserved genes via its utility as an expression system because of the current inability to transform plant-parasitic nematodes. Unfortunately, owing to the expertise that this requires, it is not a common and/or accessible tool. Furthermore, we believe that the application of C. elegans as an expression system for plant nematodes will be redundant once tools are established for stable reverse-genetics in these plant parasites. This will remove the restraints on molecular plant nematology and allow it to excel on par with the capabilities of C. elegans research. [ABSTRACT FROM AUTHOR]

Abstract Background Plant-parasitic nematodes are economically important pests responsible for substantial losses in agriculture. Researchers focusing on plant-parasitic nematodes, especially on finding new ways of their control, often need to assess basic parameters such as their motility, viability, and reproduction. Traditionally, these assays involve visually counting juveniles and eggs under a dissecting microscope, making this investigation time-consuming and laborious. Results In this study, we established a procedure to efficiently determine the motility of two plant-parasitic nematode species, Heterodera schachtii and Ditylenchus destructor, using the WMicrotracker ONE platform. Additionally, we demonstrated that hatching of the cyst nematode H. schachtii can be evaluated using both the WMicrotracker ONE and by assessing the enzymatic activity of chitinase produced during hatching. Conclusions We present fast and straightforward protocols for studying nematode motility and hatching that allow us to draw conclusions about viability and survival. Thus, these methods are useful tools for facilitating fast and efficient evaluation in various fields of research focused on plant-parasitic nematodes.

Plant diseases are caused by various microorganisms such as bacteria, fungi, viruses, and nematodes. These diseases impact crop growth, reduce produce quality, and lead to financial losses. Plant disease can be caused by single pathogens or by interactions called "disease complexes", involving two or more pathogens. In these cases, the disease severity caused by the pathogens combined is greater than the sum of the disease caused by each pathogen alone. disease complexes formed among plant-parasitic nematodes (PPNs) with bacteria, fungi, or viruses, can occur. PPNs either enhance the other pathogen incidence and severity or are necessary for disease symptoms to be expressed. PPNs can do so by being wounding agents, vectors, modifiers of plant biochemistry and physiology, or altering the rhizosphere microbiome. This review identifies several PPNs-plant pathogens disease complexes in crop production to discuss how understanding such interactions is key for improving management practices. [ABSTRACT FROM AUTHOR]

Background: Plant-parasitic nematodes are economically important pests responsible for substantial losses in agriculture. Researchers focusing on plant-parasitic nematodes, especially on finding new ways of their control, often need to assess basic parameters such as their motility, viability, and reproduction. Traditionally, these assays involve visually counting juveniles and eggs under a dissecting microscope, making this investigation time-consuming and laborious. Results: In this study, we established a procedure to efficiently determine the motility of two plant-parasitic nematode species, Heterodera schachtii and Ditylenchus destructor, using the WMicrotracker ONE platform. Additionally, we demonstrated that hatching of the cyst nematode H. schachtii can be evaluated using both the WMicrotracker ONE and by assessing the enzymatic activity of chitinase produced during hatching. Conclusions: We present fast and straightforward protocols for studying nematode motility and hatching that allow us to draw conclusions about viability and survival. Thus, these methods are useful tools for facilitating fast and efficient evaluation in various fields of research focused on plant-parasitic nematodes. [ABSTRACT FROM AUTHOR]

Nematode abundance and diversity could indicate soil health since they play roles in the soil nutrient cycle. In a shallot field, nematode abundance and diversity from different types of organic manure treatment were examined to determine the effect of organic fertilizer on nematode abundance. This study aimed to determine the best option of organic amendment for managing the nematode population in crop soil. The research took place in the center of a shallot plantation in Kulon Progo District, Yogyakarta, Indonesia, and consisted of four treatments: cow manure+green manure; sludge+green manure; cow manure, and chicken manure as farmer control. The nematode community was processed and analised with the PCA, which indicated a cumulative value of 94.5%. The treatment of cow and green manure contributed in nematode abundance, in which nematodes clustered were predators, bacterial feeders, and omnivores. The treatment of cow and green manure could be the best option that environmentally friendly control plant-parasitic nematodes and improve beneficial nematodes abundance that could improve the soil health by their regulation in soil. [ABSTRACT FROM AUTHOR]

The prevalence and abundance of plant-parasitic nematodes (PPNs) associated with corn (Zea mays; Poaceae) in the Anuradhapura district of Sri Lanka are poorly understood. This study investigated the occurrence and population densities of major PPN genera associated with corn. Over 92% of the corn fields were positive for PPNs in all the sampled fields. Major PPN genera identified were Pratylenchus spp. (71.4%), Helicotylenchus spp. (28.6%), Meloidogyne spp. (21.4%), Criconemella spp. (21.4%), and Hoplolaimus spp. (35.7%). The mean population density of Pratylenchus spp. was 2020 nematodes kg-1 of soil, in the Anuradhapura corn fields. During the cropping season from November (2021) to February (2022), all PPN genera except Meloidogyne spp. were observed. Pratylenchus spp. were detected at levels below 1000 nematodes kg-1 of soil at the seedling stage, except in Kelenikawewa where the initial population was 1865 nematodes kg-1. At the time of harvest, Pratylenchus spp. increased by 2 to 10 folds. These findings suggest a potential impact of Pratylenchus spp. on corn yield in Anuradhapura, highlighting the need for further research to assess damage levels and the overall effect of PPNs on corn production in Sri Lanka. [ABSTRACT FROM AUTHOR]

Unlike sedentary plant-parasitic nematodes, migratory plant endoparasitic nematodes (MPENs) are unable to establish permanent feeding sites, and all developmental stages (except eggs) can invade and feed on plant tissues and can be easily overlooked because of the unspecific symptoms. They cause numerous economic losses in agriculture, forestry, and horticulture. In order to understand the pathogenetic mechanism of MPENs, here we describe research on functions and host targets focused on currently identified effectors from six MPENs, namely Radopholus similis, Pratylenchus spp., Ditylenchus destructor, Bursaphelenchus xylophilus, Aphelenchoides besseyi, and Hirschmanniella oryzae. This information will provide valuable insights into understanding MPEN effectors and for future fostering advancements in plant protection. [ABSTRACT FROM AUTHOR]

Serotonin (5-hydroxytryptamine) is an essential neurotransmitter involved in regulating various behaviors in plant-parasitic nematodes, including locomotion, egg laying, feeding, and mating. However, the functional role of serotonin in root-knot nematode invasion of host plants and the molecular mechanisms underlying feeding behavior remain poorly understood. In this study, we tested the effects of exogenous serotonin and the pharmacological compounds fluoxetine and methiothepin on the feeding behaviors of Meloidogyne graminicola. Our results suggested that M. graminicola possesses an endogenous serotonin signaling pathway and that serotonin plays a crucial role in modulating feeding behaviors in M. graminicola second-stage juveniles. We also identified and cloned the serotonin synthesis enzyme tryptophan hydroxylase (Mg-tph-1) in M. graminicola and investigated the role of endogenous serotonin by generating RNA interference nematodes in Mg-tph-1. Silencing Mg-tph-1 substantially reduced nematode invasion, development, and reproduction. According to the immunostaining results, we speculated that these serotonin immunoreactive cells near the nerve ring in M. graminicola are likely homologous to Caenorhabditis elegans ADFs, NSMs, and RIH serotonergic neurons. Furthermore, we investigated the impact of phytoserotonin on nematode invasion and development in rice by overexpressing OsTDC-3 or supplementing rice plants with tryptamine and found that an increase in phytoserotonin increases nematode pathogenicity. Overall, our study provides insights into the essential role of serotonin in M. graminicola host plant parasitism and proposes that the serotonergic signaling pathway could be a potential target for controlling plant-parasitic nematodes. [ABSTRACT FROM AUTHOR]

The management of plant-parasitic nematodes (PPNs) still relies on traditional nematicides that threaten the environment and human health. Novel solutions are urgently needed for PPN pest management that are effective while safeguarding non-target organisms. Volatile phytochemicals belong to a structurally diverse group of bioactive metabolites that are believed to hold safer environmental characteristics than synthetic pesticides. Nonetheless, not many studies have analysed the potential environmental benefits of shifting to these novel bionematicides. In the present study, 20 phytochemical volatiles with reported nematicidal activity were compared to traditional pesticides using specific parameters of environmental and human health safety available on applied online databases and predicted in silico through specialised software. Overall, the reviewed nematicidal phytochemicals were reportedly less toxic than synthetic nematicides. They were predicted to disperse to the air and soil environmental compartments and were reported to have a lower toxicity on aquatic organisms. On the contrary, the synthetic nematicides were reportedly toxic to aquatic organisms while showing a predicted high affinity to the water environmental compartment. As alternatives, β-keto or fatty acid derivatives, e.g., aliphatic alcohols or ketones, showed more adequate properties. This study highlights the importance of complementing studies on nematicidal activity with a risk assessment-based analysis to allow for a faster selection of nematicidal phytochemical volatiles and to leverage the development and implementation of bionematicides. [ABSTRACT FROM AUTHOR]

Abstract Background Transposable elements (TEs) are mobile DNA sequences that propagate within genomes, occupying a significant portion of eukaryotic genomes and serving as a source of genetic variation and innovation. TEs can impact genome dynamics through their repetitive nature and mobility. Nematodes are incredibly versatile organisms, capable of thriving in a wide range of environments. The plant-parasitic nematodes are able to infect nearly all vascular plants, leading to significant crop losses and management expenses worldwide. It is worth noting that plant parasitism has evolved independently at least three times within this nematode group. Furthermore, the genome size of plant-parasitic nematodes can vary substantially, spanning from 41.5 Mbp to 235 Mbp. To investigate genome size variation and evolution in plant-parasitic nematodes, TE composition, diversity, and evolution were analysed in 26 plant-parasitic nematodes from 9 distinct genera in Clade IV. Results Interestingly, despite certain species lacking specific types of DNA transposons or retrotransposon superfamilies, they still exhibit a diverse range of TE content. Identification of species-specific TE repertoire in nematode genomes provides a deeper understanding of genome evolution in plant-parasitic nematodes. An intriguing observation is that plant-parasitic nematodes possess extensive DNA transposons and retrotransposon insertions, including recent sightings of LTR/Gypsy and LTR/Pao superfamilies. Among them, the Gypsy superfamilies were found to encode Aspartic proteases in the plant-parasitic nematodes. Conclusions The study of the transposable element (TE) composition in plant-parasitic nematodes has yielded insightful discoveries. The findings revealed that certain species exhibit lineage-specific variations in their TE makeup. Discovering the species-specific TE repertoire in nematode genomes is a crucial element in understanding the evolution of genomes in plant-parasitic nematodes. It allows us to gain a deeper insight into the intricate workings of these organisms and their genetic makeup. With this knowledge, we are gaining a fundamental piece in the puzzle of understanding the evolution of these parasites. Moreover, recent transpositions have led to the acquisition of new TE superfamilies, especially Gypsy and Pao retrotransposons, further expanding the diversity of TEs in these nematodes. Significantly, the widely distributed Gypsy superfamily possesses proteases that are exclusively associated with parasitism during nematode-host interactions. These discoveries provide a deeper understanding of the TE landscape within plant-parasitic nematodes.

Biosecurity in agriculture is essential for preventing the introduction and spread of plant-parasitic nematodes (PPNs) which threaten global food security by reducing crop yields and facilitating disease spread. These risks are exacerbated by increased global trade and climate change, which may alter PPN distribution and activity, increasing their impact on agricultural systems. Addressing these challenges is vital to maintaining the integrity of the food supply chain. This review highlights significant advancements in managing PPN-related biosecurity risks within the food supply chain, particularly considering climate change's evolving influence. It discusses the PPN modes of transmission, factors increasing the risk of infestation, the impact of PPNs on food safety and security, and traditional and emerging approaches for detecting and managing these pests. Literature suggests that implementing advanced biosecurity measures could decrease PPN infestation rates by up to 70%, substantially reducing crop yield losses and bolstering food security. Notably, the adoption of modern detection and management techniques, (molecular diagnostics and integrated pest management) and emerging geospatial surveillance and analysis systems (spectral imaging, change-detection analysis) has shown greater effectiveness than traditional methods. These innovations offer promising avenues for enhancing crop health and securing the food supply chain against environmental shifts. The integration of these strategies is crucial, demonstrating the potential to transform biosecurity practices and sustain agricultural productivity in the face of changing climatic conditions. This analysis emphasizes the importance of adopting advanced measures to protect crop health and ensure food supply chain resilience, providing valuable insights for stakeholders across the agricultural sector. [ABSTRACT FROM AUTHOR]

Main conclusion: Upon systemic S. indica colonization in split-root system cyst and root-knot nematodes benefit from endophyte-triggered carbon allocation and altered defense responses what significantly facilitates their development in A. thaliana. Serendipita indica is an endophytic fungus that establishes mutualistic relationships with different plants including Arabidopsis thaliana. It enhances host’s growth and resistance to different abiotic and biotic stresses such as infestation by the cyst nematode Heterodera schachtii (CN). In this work, we show that S. indica also triggers similar direct reduction in development of the root-knot nematode Meloidogyne javanica (RKN) in A. thaliana. Further, to mimick the natural situation occurring frequently in soil where roots are unequally colonized by endophytes we used an in vitro split-root system with one half of A. thaliana root inoculated with S. indica and the other half infected with CN or RKN, respectively. Interestingly, in contrast to direct effects, systemic effects led to an increase in number of both nematodes. To elucidate this phenomenon, we focused on sugar metabolism and defense responses in systemic non-colonized roots of plants colonized by S. indica. We analyzed the expression of several SUSs and INVs as well as defense-related genes and measured sugar pools. The results show a significant downregulation of PDF1.2 as well as slightly increased sucrose levels in the non-colonized half of the root in three-chamber dish. Thus, we speculate that, in contrast to direct effects, both nematode species benefit from endophyte-triggered carbon allocation and altered defense responses in the systemic part of the root, which promotes their development. With this work, we highlight the complexity of this multilayered tripartite relationship and deliver new insights into sugar metabolism and plant defense responses during S. indica–nematode–plant interaction. [ABSTRACT FROM AUTHOR]

Pre-parasitic second-stage juveniles (pre-J2s) of Meloidogyne graminicola are non-feeding in soil, and their migration, localization and successful invasion of host roots are essential for survival. Chemotaxis is thought to play a central role in host localization, but the mechanisms of chemotaxis are poorly understood. In this study, we cloned and evaluated the molecular characteristics and functions of four chemosensory genes, including Mg-odr-3, Mg-odr-1, Mg-tax-4, and Mg-osm-9. Quantitative real-time PCR (qRT‒PCR) analysis revealed that Mg-odr-3 and Mg-osm-9 tended to be expressed in pre-J2s and parasitic J2s (par-J2s), while Mg-odr-1 and Mg-tax-4 were expressed in par-J2s, consistent with their functions during the host-seeking period and establishment of suitable feeding sites in root tips. Root signals from eight plant root extracts, namely, rice, barnyard grass (Echinochloa crus-galli), wheat, soybean, pepper, tomato, eggplant, and marigold, were repulsive to J2s of M. graminicola. Moreover, RNAi silencing of Mg-odr-3, Mg-odr-1, Mg-tax-4, and Mg-osm-9 in J2s attenuated their repulsion to the rice root extract. Furthermore, we found that the response of J2s to root exudates was concentration-dependent, with high concentrations of root exudates repelling J2s. Silenced J2s also showed reduced repulsion in response to high concentrations of rice root exudates. Conversely, M. graminicola J2s were attracted to the root tips of the eight plants, while RNAi-J2s showed defective attraction to root tips. In conclusion, our results showed that chemosensory genes are crucial for the chemotactic host-seeking behaviour of M. graminicola. [ABSTRACT FROM AUTHOR]

In Belgium and worldwide, agriculture has been under threat from plant-parasitic nematodes. Root-lesion nematodes (Pratylenchus spp.) cause yield loss in many vegetable, arable and horticultural crops. Increased use of cover crops can affect population build ups. This study evaluated the reproductive potential of Pratylenchus penetrans on different cultivars of cover crops both, in pot tests and field experiments. Twenty-three different cultivars were evaluated against P. penetrans at low (10 P. penetrans per 100 cm3 soil) and high (100 P. penetrans per 100 cm3 soil) initial inoculum density in a pot experiment under glasshouse conditions. Based on their reproductive factor (Rf) after 8 weeks, they were classified under five different categories: Non-host, Poor host, Maintenance host, Good host, and Excellent host. At low Pi, fodder radish 'Defender' and 'Doublet' and birds foot trefoil 'Lotar' were poor hosts. At high Pi, birds foot trefoil 'Lotar' and 'Franco', fodder radish 'Doublemax', 'Maximus' and 'Contra', black oat 'Pratex', phacelia 'Natra', Italian ryegrass 'Meroa' and 'Fedra', rye 'Dukato' and 'Matador' reduced the P. penetrans population. Under field conditions, fodder radish 'Doublet', Japanese oat 'Delux', yellow mustard 'Chacha', Phacelia 'Natra', Italian ryegrass 'Fedra' and Tagetes patula reduced the root-lesion nematode population. The infectious process of P. penetrans on some of these cultivars, proven to be poor hosts, was screened using Cone tainers™. Penetration, development and multiplication of P. penetrans was assessed. The information opens possibilities for further resistance breeding. Based on our results we can conclude that with proper choice of selected cultivars of cover crops, P. penetrans can be controlled but that further breeding efforts are needed. [ABSTRACT FROM AUTHOR]

Parasitic nematodes rely on host tissues for energy and nutrition, yet there remains a lack of detailed knowledge regarding their specific nutrient preferences. Recent advances have provided critical insights into their nutritional needs and metabolic dependencies, such as the intriguing discovery of cross-kingdom compartmentalization in vitamin B5 biosynthesis within certain parasitic nematodes. Leveraging these newfound insights into their nutritional vulnerabilities provides a promising avenue for developing effective management and control strategies, addressing the substantial challenges posed by these nematodes to both agriculture and public health. Nematodes, a diverse group of roundworms, exhibit a wide range of dietary habits, including parasitism of animals and plants. These parasites cause substantial economic losses in agriculture and pose significant health challenges to humans and animals. This review explores the unique adaptations of parasitic nematodes, emphasizing their nutritional requirements and metabolic dependencies. Recent research has identified cross-kingdom compartmentalization of vitamin B5 biosynthesis in some parasitic nematodes, shedding light on coevolutionary dynamics and potential targets for control strategies. Several open questions remain regarding the complexity of nematode nutrition, host manipulation, evolutionary adaptations, and the influence of environmental factors on their metabolic processes. Understanding these aspects offers promising avenues for targeted interventions to manage and control these economically and medically important parasites. [ABSTRACT FROM AUTHOR]

Plant diseases are caused by various microorganisms such as bacteria, fungi, viruses, and nematodes. These diseases impact crop growth, reduce produce quality, and lead to financial losses. Plant disease can be caused by single pathogens or by interactions called “disease complexes”, involving two or more pathogens. In these cases, the disease severity caused by the pathogens combined is greater than the sum of the disease caused by each pathogen alone. disease complexes formed among plant-parasitic nematodes (PPNs) with bacteria, fungi, or viruses, can occur. PPNs either enhance the other pathogen incidence and severity or are necessary for disease symptoms to be expressed. PPNs can do so by being wounding agents, vectors, modifiers of plant biochemistry and physiology, or altering the rhizosphere microbiome. This review identifies several PPNs-plant pathogens disease complexes in crop production to discuss how understanding such interactions is key for improving management practices.

This study was conducted to investigate the plant-parasitic nematodes of ornamental foliage plants, citrus orchards, and tea plantations from July to December 2022. As a result of the investigation of plant-parasitic nematodes in 415 foliage plants, root-lesion nematodes were detected most frequently, followed by root-knot nematodes, pin nematodes, and other nematodes. In tea plantations, spiral nematodes, cyst nematodes, and root-knot nematodes were detected. Citrus nematodes, ring nematodes, and root-knot nematodes were discovered in citrus orchards. In foliage plants, tea plantations, and citrus orchards, the detection rate of plant-parasitic nematodes was not high, but root-lesion nematodes were detected. Therefore, it is necessary to apply appropriate control methods to manage root-lesion nematodes during the cultivation of foliage, tea, and citrus plants.

Accurate identification and estimation of the population densities of microscopic, soil-dwelling plant-parasitic nematodes (PPNs) are essential, as PPNs cause significant economic losses in agricultural production systems worldwide. This study presents a comprehensive review of emerging techniques used for the identification of PPNs, including morphological identification, molecular diagnostics such as polymerase chain reaction (PCR), high-throughput sequencing, meta barcoding, remote sensing, hyperspectral analysis, and image processing. Classical morphological methods require a microscope and nematode taxonomist to identify species, which is laborious and time-consuming. Alternatively, quantitative polymerase chain reaction (qPCR) has emerged as a reliable and efficient approach for PPN identification and quantification; however, the cost associated with the reagents, instrumentation, and careful optimisation of reaction conditions can be prohibitive. High-throughput sequencing and meta-barcoding are used to study the biodiversity of all tropical groups of nematodes, not just PPNs, and are useful for describing changes in soil ecology. Convolutional neural network (CNN) methods are necessary to automate the detection and counting of PPNs from microscopic images, including complex cases like tangled nematodes. Remote sensing and hyperspectral methods offer non-invasive approaches to estimate nematode infestations and facilitate early diagnosis of plant stress caused by nematodes and rapid management of PPNs. This review provides a valuable resource for researchers, practitioners, and policymakers involved in nematology and plant protection. It highlights the importance of fast, efficient, and robust identification protocols and decision-support tools in mitigating the impact of PPNs on global agriculture and food security.

Plant-parasitic nematodes are one of the most economically important pests of crops. It is widely accepted that horizontal gene transfer—the natural acquisition of foreign genes in parasitic nematodes—contributes to parasitism. However, an apparent paradox has emerged from horizontal gene transfer analyses: On the one hand, distantly related organisms with very dissimilar genetic structures (i.e. bacteria), and only transient interactions with nematodes as far as we know, dominate the list of putative donors, while on the other hand, considerably more closely related organisms (i.e. the host plant), with similar genetic structure (i.e. introns) and documented long-term associations with nematodes, are rare among the list of putative donors. Given that these nematodes ingest cytoplasm from a living plant cell for several weeks, there seems to be a conspicuous absence of plant-derived cases. Here, we used comparative genomic approaches to evaluate possible plant-derived horizontal gene transfer events in plant parasitic nematodes. Our evidence supports a cautionary message for plant-derived horizontal gene transfer cases in the sugar beet cyst nematode, Heterodera schachtii. We propose a 4-step model for horizontal gene transfer from plant to parasite in order to evaluate why the absence of plant-derived horizontal gene transfer cases is observed. We find that the plant genome is mobilized by the nematode during infection, but that uptake of the said "mobilome" is the first major barrier to horizontal gene transfer from host to nematode. These results provide new insight into our understanding of the prevalence/role of nucleic acid exchange in the arms race between plants and plant parasites. [ABSTRACT FROM AUTHOR]

The present investigation aimed to analyze the community structure and its relationship with selected soil parameters in the Gangetic plains. In total, 60 soil samples were collected from the fields of vegetable crops at different pH. Thirty-nine soil-inhabited nematodes were isolated and identified to the species level where possible. The most prevalent nematodes encountered were Hoplolaimus indicus followed by Helicotylenchus californicus and Pratylenchus thornei with 66.67, 53.33, and 40.00% frequency, respectively. Prominence Value of H. indicus (271.62), H. californicus (115.87), and P. thornei (31.62) was higher as compared to other PPN species. The result indicated that there is a significant correlation between the plant-parasitic species and pH (e.g., Rotylenchus reniformis; r = 0.991). On the other hand, EC showed a significant negative correlation with R. reniformis (r = –0.965). However, organic carbon and sand percentage significantly correlated with PPN. Organic carbon was highly correlated (r = 1.00) with R. reniformis. In contrast, organic carbon showed a significant positive correlation with Rhabditis and no correlation with Mesodorylaimus. In conclusion, the high-producing regions suggested a considerable range of plant-parasitic and free-living nematodes, with the highest diversity in Baghpat (H' = 0.604 ± 0.14). Therefore, further studies are required to evaluate the ecological and threshold level of damage by the PPN. Additionally, the current finding suggests that soil fertility in upper 'Gangetic plains' agricultural fields was reduced due to the high load of PPN infection. However, ecological indices could help assess the plant and soil health of all the regions in future investigations. [ABSTRACT FROM AUTHOR]

Nematodes are highly abundant soil organisms, and their presence can have profound effects on soil health and plant growth. Among them, Rotylenchus species are known for their economic importance as root ectoparasites or semi-endoparasites, inflicting damage on a wide variety of economically important plants. Their impact on agricultural crops, ornamentals, and fruit and forest trees makes them significant subjects for study. In this paper, we present an updated species list of Rotylenchus spp., a genus of spiral plant-parasitic nematodes belonging to the family Hoplolaimidae. As of the current research, 107 species within the Rotylenchus genus have been recognized. To facilitate the identification of Rotylenchus species, we introduce a novel browser-based interactive key for the identification of such huge number of species. This web-assisted tool utilizes a list of 48 diagnostic character-states belonging to 11 characters for identifying 107 Rotylenchus species, providing an easy and accurate method for the identification of these plant-parasitic nematodes. This paper contributes to the understanding of Rotylenchus species' diversity and their taxonomy while offering a valuable tool to aid researchers, agricultural professionals, and plant pathologists in accurate species identification and subsequent management strategies. [ABSTRACT FROM AUTHOR]

Nematodes, commonly called roundworms, represent one of the largest phyla of animals. Plant‐parasitic nematodes cause significant economic losses in major crops worldwide, and cyst nematodes (Heterodera spp. and Globodera spp.) are among the most damaging species. This review focuses on three main species, Globodera pallida, Globodera rostochiensis and Globodera ellingtonae, collectively known as potato cyst nematodes (PCNs). G. rostochiensis and G. pallida are the most commonly occurring species in potato‐growing areas and are considered to have originated from the Andes region in South America and introduced then to Europe in the 1850s and now occur globally in more than 75 countries. PCNs feed entirely inside the root and produce distinctive cysts containing eggs. PCNs reduce root development, stunt the growth of potato plants and ultimately lead to the production of fewer and smaller tubers. PCNs are feared because of their ability to survive for up to 40 years in the soil in the absence of potatoes, and once established they are incredibly difficult to eradicate. Five case studies in this review provide an historical overview of how scientists and potato experts have responded to PCN pandemics and the effectiveness of management strategies. [ABSTRACT FROM AUTHOR]

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Chile is one of the world's leading walnut producers, but the endoparasitic migratory nematode Pratylenchus vulnus considerably affects walnut plants and decreases crop yield. This study assessed the biological control effects of three selected native rhizobacteria species (Bacillus weihenstephanensis FB25M, Brevibacterium frigoritolerans FB37BR, and Oerskovia turbata FB55) against P. vulnus and its damage to walnut plants. The direct effect of the bacterial filtrates of the three species on population of P. vulnus was evaluated in vitro for 72 h at 20 °C and nematode mortality registered every 24 h. The antagonistic effect of a bacterial suspension was measured under greenhouse conditions using 3-month-old potted walnut plants. The growing substrate of the plants was inoculated with a suspension of 1 × 106 colony-forming units (CFU/ml) of each rhizobacteria strain or their mixture, followed by P. vulnus inoculation. As control treatments, two commercial products (chemical: cadusafos; and biological: rhizobacterial mix) and unbacterized plants with and without nematodes were used. Results under in vitro conditions showed that after 72 h exposure of P. vulnus to rhizobacterial filtrates, all bacterial treatments were effective in controlling the nematode (P < 0.01), reaching values between 98 and 100% and exhibiting nematicidal and nemastatic effects. The greenhouse experiments had consistent results; rhizobacteria-treated walnut plants exhibited the maximum biocontrol (mortality) values (67–77%) (P < 0.05). Similarly, rhizobacterial treatments demonstrated the highest root weight compared with the untreated and chemical control treatments (P < 0.05). The evaluated rhizobacterial species showed nematicidal and root growth-promoting effects, which can offer a potential alternative for controlling and protecting walnut plants from P. vulnus. [ABSTRACT FROM AUTHOR]

Biosecurity in agriculture is essential for preventing the introduction and spread of plant-parasitic nematodes (PPNs) which threaten global food security by reducing crop yields and facilitating disease spread. These risks are exacerbated by increased global trade and climate change, which may alter PPN distribution and activity, increasing their impact on agricultural systems. Addressing these challenges is vital to maintaining the integrity of the food supply chain. This review highlights significant advancements in managing PPN-related biosecurity risks within the food supply chain, particularly considering climate change’s evolving influence. It discusses the PPN modes of transmission, factors increasing the risk of infestation, the impact of PPNs on food safety and security, and traditional and emerging approaches for detecting and managing these pests. Literature suggests that implementing advanced biosecurity measures could decrease PPN infestation rates by up to 70%, substantially reducing crop yield losses and bolstering food security. Notably, the adoption of modern detection and management techniques, (molecular diagnostics and integrated pest management) and emerging geospatial surveillance and analysis systems (spectral imaging, change-detection analysis) has shown greater effectiveness than traditional methods. These innovations offer promising avenues for enhancing crop health and securing the food supply chain against environmental shifts. The integration of these strategies is crucial, demonstrating the potential to transform biosecurity practices and sustain agricultural productivity in the face of changing climatic conditions. This analysis emphasizes the importance of adopting advanced measures to protect crop health and ensure food supply chain resilience, providing valuable insights for stakeholders across the agricultural sector.

The management of plant-parasitic nematodes (PPNs) still relies on traditional nematicides that threaten the environment and human health. Novel solutions are urgently needed for PPN pest management that are effective while safeguarding non-target organisms. Volatile phytochemicals belong to a structurally diverse group of bioactive metabolites that are believed to hold safer environmental characteristics than synthetic pesticides. Nonetheless, not many studies have analysed the potential environmental benefits of shifting to these novel bionematicides. In the present study, 20 phytochemical volatiles with reported nematicidal activity were compared to traditional pesticides using specific parameters of environmental and human health safety available on applied online databases and predicted in silico through specialised software. Overall, the reviewed nematicidal phytochemicals were reportedly less toxic than synthetic nematicides. They were predicted to disperse to the air and soil environmental compartments and were reported to have a lower toxicity on aquatic organisms. On the contrary, the synthetic nematicides were reportedly toxic to aquatic organisms while showing a predicted high affinity to the water environmental compartment. As alternatives, β-keto or fatty acid derivatives, e.g., aliphatic alcohols or ketones, showed more adequate properties. This study highlights the importance of complementing studies on nematicidal activity with a risk assessment-based analysis to allow for a faster selection of nematicidal phytochemical volatiles and to leverage the development and implementation of bionematicides.

Chickpea (Cicer arietinum L.) is classed among the most important leguminous crops of high economic value in Ethiopia. Two plant-parasitic nematode species, Pratylenchus delattrei and Quinisulcius capitatus, were recovered from chickpea-growing areas in Ethiopia and characterized using molecular and morphological data, including the first scanning electron microscopy data for P. delattrei. New sequences of D2-D3 of 28S, ITS rDNA and mtDNA COI genes have been obtained from these species, providing the first COI sequences for P. delattrei and Q. capitatus, with both species being found for the first time on chickpea in Ethiopia. Furthermore, Pratylenchus delattrei was recovered in Ethiopia for the first time. The information obtained about these nematodes will be crucial to developing effective nematode management plans for future chickpea production.

Plant-parasitic nematodes infect and cause substantial yield losses in numerous crops. Growing concern over chemical nematicides has attracted attention to safe alternatives. Meloidogyne incognita is one of the plant parasitic nematode species in the tropics and subtropics, which have a drastic economic effect on crops. This nematode is polyphagous, attacking both monocotyledons and dicotyledons crops. This study aimed to investigate the management of M. incognita using six botanical viz., Commelina benghalensis, Evolvulus nummularius, Gomphrena celosioides, Lindenbergia indica, Scoparia dulcis, and Vernonia cinerea under the pots condition. It was found that the pots treated with the amendment of fresh leaves (60 g) of selected botanicals with dried powder 10 g of L. indica efficiently reduced the infestation caused by M. incognita on carrots along with significantly increased growth and biochemical attributes. Out of the six botanicals, GC–MS analysis was performed with the two most effective plants, namely, L. indica and S. dulcis. Results from GC–MS analysis showed various volatile compounds in leaves extract of both plants, out of which phytol was a major compound. Our study concluded that various compounds, along with phytol shown by GC–MS analysis, suppress the infestation of M. incognita and increase the yield of carrots.

The devastating root-knot nematodes (Meloidogyne spp.) can cause severe damage to greenhouse crops. Due to high economic losses, alternative products are essential to replace banned, or strictly regulated nematicides that affect human health and/or the environment. Studies were carried out at the Maritsa Vegetable Crops Research Institute, Plovdiv, to determine the biological activity of the product Nemguard and the microbioagent Trichoderma asperellum Bulgarian strain T6, as well as the combination between them against root-knot nematodes (Meloidogyne spp.) in cucumber varieties Defense F1 and Kiara grown in greenhouses. The combined application of Nemguard + Trichoderma asperellum strain T6 according to the scheme is distinguished by the best effectiveness against root-knot nematodes, the best biometric indicators and yield of cucumbers in greenhouse conditions. [ABSTRACT FROM AUTHOR]

Plant-parasitic nematodes (PPN), especially sedentary endoparasitic nematodes like root-knot nematodes (RKN), pose a significant threat to major crops and vegetables. They are responsible for causing substantial yield losses, leading to economic consequences, and impacting the global food supply. The identification of PPNs and the assessment of their population is a tedious and time-consuming task. This study developed a state-of-the-art deep learning model-based decision support tool to detect and estimate the nematode population. The decision support tool is integrated with the fast inferencing YOLOv5 model and used pretrained nematode weight to detect plant-parasitic nematodes (juveniles) and eggs. The performance of the YOLOv5-640 model at detecting RKN eggs was as follows: precision = 0.992; recall = 0.959; F1-score = 0.975; and mAP = 0.979. YOLOv5-640 was able to detect RKN eggs with an inference time of 3.9 milliseconds, which is faster compared to other detection methods. The deep learning framework was integrated into a user-friendly web application system to build a fast and reliable prototype nematode decision support tool (NemDST). The NemDST facilitates farmers/growers to input image data, assess the nematode population, track the population growths, and recommend immediate actions necessary to control nematode infestation. This tool has the potential for rapid assessment of the nematode population to minimise crop yield losses and enhance financial outcomes. [ABSTRACT FROM AUTHOR]

Outdoor vegetable cultivation is an important economic activity, both for fresh consumption and for the frozen vegetable industry within Flanders, Belgium. In recent years, due to the intensive nature of vegetable cultivation in the open air, nematode problems increased. The quarantine root-knot nematode Meloidogyne chitwoodi causes economic damage to the most important arable crops and vegetables grown in Flanders. However, for some vegetable crops knowledge on host plant status and damage potential is scarce or lacking. The host sensitivity for M. chitwoodi and damage thresholds of the most commonly field-grown cultivars of pea and celeriac were determined, both in glasshouse and field conditions. The damage threshold values (T) for the relative fresh pod weight of pea were 10, 1, 0.2 and 0 J2 (100 cm3 soil)-1 for pea 'Cher', 'Electra', 'Geneva' and 'Pixia' respectively with up to 70% yield loss. For celeriac 'Prinz', the damage threshold was 11.0 J2 (100 cm3 soil)-1 with maximum 22% yield loss. Based on our pot trials, all pea cultivars were considered to be a good host with their high maximum population density (M) and maximum multiplication rate (a) values in the pot trials and reproductive factor (Rf) from the field trials. Celeriac proved to be an excellent host in the pot test but on the field the M. chitwoodi population declined. However, on plots with lowest yield a substantial number of M. chitwoodi was found in the roots. This is the first report of celeriac as host for M. chitwoodi. [ABSTRACT FROM AUTHOR]

The increase in the populations of root-knot nematode Meloidogyne enterolobii in various vegetables such as tomatoes grown under greenhouse conditions as well as increasing restrictions on the use of certain chemical nematicides have led to the search for new, effective management strategies, preferably ones that are sustainable biological alternatives. In this work, two formulations of the nematophagous fungus Metarhizium carneum, one concentrated suspension and one wettable powder, were evaluated under greenhouse conditions to reduce the M. enterolobii infestation in tomato plants. In addition, the effectiveness of the liquid formulation of M. carneum was compared with two biological and three chemical commercial nematicides. The results show that the two M. carneum formulations reduced the M. enterolobii population density by 78 and 66% in relation to the control treatment. In comparison, the liquid formulation of M. carneum and Purpureocillium lilacinum treatments reduced nematode population density by 72 and 43%, respectively, while for metam sodium preplanting applications followed by M. carneum applications during the tomato growth stage, the reduction was 96%. The alternate use of some chemical compounds plus the application of M. carneum as a biocontrol is a good starting strategy for managing M. enterolobii populations. These results confirm that M. carneum is a serious candidate for the short-term commercialization of an environmentally friendly biological nematicide. [ABSTRACT FROM AUTHOR]

Plant parasites take advantage of host developmental plasticity to elicit profound developmental and physiological changes. In the case of plant-parasitic nematodes (PPNs), these changes can result in the development of new plant organs. Despite the importance of the development- and physiology-altering abilities of these parasites in pathology, research has historically focused on their abilities to suppress immunity. We argue that, given the dramatic changes involved in feeding site establishment, it is entirely possible that development- and physiology-altering abilities of PPNs may, in fact, dominate effector repertoires – highlighting the need for novel high-throughput screens for development- and physiology-altering 'tools'. Uncovering this portion of the nematode 'toolbox' can enable biotechnology, enhance crop protection, and shed light on fundamental host biology itself. Plant-parasitic nematodes (PPNs) profoundly alter plant development, but there is a paucity of information about nematode effectors that alter development and physiology. The recent advances in gland-cell-specific transcriptomics have allowed us to access the full effector repertoire of PPNs. The development of a novel, reproducible, high-throughput screen for development- and physiology-altering effector function will be essential to accelerate the field. [ABSTRACT FROM AUTHOR]

Worldwide, the ornamental plant industry is estimated to be valued at $70 billion, with the United States’ ornamental plant industry valued at $4.8 billion in 2020. Ornamental plants are cultivated for numerous reasons worldwide, such as decorative, medicinal, social, and utility purposes, making the ornamental field a high growth industry. One of the main pathogen groups affecting the yield and growth of the ornamental plant industry is plant-parasitic nematodes, which are microscopic roundworms that feed on plant parts causing significant yield loss. There are many kinds of plant-parasitic nematodes that affect ornamental plants, with the main genera being Meloidogyne spp., Aphelenchoides spp., Paratylenchus spp., Pratylenchus spp., Helicotylenchus spp., Radopholus spp., Xiphinema spp., Trichodorus spp., Paratrichodorus spp., Rotylenchulus spp., and Longidorus spp. The aim of this review is to focus on the effects, hosts, and symptoms of these major plant-parasitic nematodes on ornamental plants and synthesize current management strategies in the ornamental plant industry.