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The search for natural product-based biopesticides from endophytic fungi is an effective tool to find new solutions. In this study, we studied a pre-selected fungal endophyte, isolate YCC4, from the paleoendemism Persea indica, along with compounds present in the extract and the identification of the insect antifeedant and nematicidal ones. The endophyte YCC4 was identified as Phyllosticta sp. by molecular analysis. The insect antifeedant activity was tested by choice bioassays against Spodoptera littoralis, Myzus persicae, and Rhopalosiphum padi, and the in vitro and in vivo mortality was tested against the root-knot nematode Meloidogyne javanica. Since the extract was an effective insect antifeedant, a strong nematicidal, and lacked phytotoxicity on tomato plants, a comprehensive chemical study was carried out. Two new metabolites, metguignardic acid (4) and (-)-epi-guignardone I (14), were identified along the known dioxolanones guignardic acid (1), ethyl guignardate (3), guignardianones A (5), C (2), D (7), and E (6), phenguignardic acid methyl ester (8), the meroterpenes guignardone A (9) and B (10), guignarenone B (11) and C (12), (-)-guignardone I (13), and phyllomeroterpenoid B (15). Among these compounds, 1 and 4 were effective antifeedants against S. littoralis and M. persicae, while 2 was only active on the aphid M. persicae. The nematicidal compounds were 4, 7, and 8. This is the first report on the insect antifeedant or nematicidal effects of these dioxolanone-type compounds. Since the insect antifeedant and nematicidal activity of the Phyllosticta sp. extract depend on the presence of dioxolanone components, future fermentation optimizations are needed to promote the biosynthesis of these compounds instead of meroterpenes. [ABSTRACT FROM AUTHOR]

The Mi-1.2 gene confers resistance to a wide range of Meloidogyne species, being the most important resistance factor employed in tomato breeding so far. However, many aspects related to the interaction of Mi-1.2-carrying tomato cultivars and virulent/avirulent Meloidogyne populations have not yet been clarified. Herein, comparative histopathological analyses were carried after inoculation of the homozygous (Mi-1.2/Mi-1.2) tomato rootstock 'Guardião' and the susceptible cultivar 'Santa Clara' (mi-1.2/mi-1.2) with virulent and avirulent populations of M. javanica. In the susceptible control, it was possible to visualize second stage juveniles (J2) of avirulent population and feeding sites from 2 to 30 days after infection (DAI) with females reaching maturity at 24-34 DAI. In the resistant rootstock, the Mi-1.2 gene-mediated resistance was related mainly to early defense responses (pre-infection and hypersensitive reaction), which led to an immunity-like phenotype that completely prevented the reproduction of the avirulent Meloidogyne population. On the other hand, J2s of the virulent M. javanica population were able to penetrate roots much more than the avirulent population, migrated and developed normally, showing intense and similar pattern of penetration from 4 to 34 DAI in the root tissues of both resistant and susceptible tomato genotypes. The total numbers of J2, J3, J4, and females counted in 'Santa Clara' for the virulent population of M. javanica were higher than in 'Guardião'. [ABSTRACT FROM AUTHOR]

The decline in the yield of tomato (Solanum lycopersicum L.) is largely attributed to the prevalence of nematodes belonging to the Meloidogyne species, commonly known as root-knot nematodes. The Meloidogyne species of nematodes are regarded as the most significant contributing factor to the reduction in tomato yield. Therefore, the present investigation was conducted in 2023 at the University of Limpopo to reveal that Meloidogyne javanica (Treub) Chitwood was the identified cause of the nematode. The ITS rDNA was sequenced and amplified from female nematodes, following which the blast result showed that the South African population exhibited a high similarity (99% identity) to those populations studied in the United States (AF387094 and U96305) and China (AY438555). A comparison to the USA population (AF387094), revealed four nucleotide differences. Utilizing the maximum likelihood method for phylogenetic analysis, it was demonstrated that our population and the other populations of M. javanica form a robust clade (91% bootstrap values). [ABSTRACT FROM AUTHOR]

This study aimed to assess the effects of rock dust on Meloidogyne javanica in soybean grown in autoclaved and non-autoclaved soil and investigate the impacts on plant foliar nutrition. The nematode reproduction experiment was conducted in two periods (Trials 1 and 2) in a 5 × 2 factorial design (rock dust rates of 0, 1000, 2000, 3000, and 4000 kg ha−1 × autoclaved and non-autoclaved soil). Soybean were inoculated with 2000 eggs + second-stage juveniles (J2) of M. javanica, and nematode and vegetative variables were evaluated at 60 days after inoculation (DAI). The penetration experiment followed a 2 × 2 factorial design (rock dust rates of 0 and 2500 kg ha−1 × autoclaved and non-autoclaved soil). Soybean were inoculated with 2000 eggs + J2 of M. javanica and evaluated at 5, 10, 15, 20, and 25 DAI. The shoot dry biomass from the reproduction experiment (Trial 1) was analyzed for macro- and micronutrients. In Trial 1, nematode reproduction decreased proportionally to the increase in rock dust rate in non-autoclaved soil. In Trial 2, the lowest nematode numbers were predicted to be achieved with rates of 2213 to 2309 kg ha−1, and nematode numbers were lower in autoclaved than in non-autoclaved soil. Rock dust reduced J2 penetration at 10 and 15 DAI, and there was no formation of females in treated plants. Rock dust application increased foliar levels of Fe, B, and Cu. Rock dust reduced M. javanica reproduction, penetration, and development in soybean and promoted gains in Fe, Cu, and B foliar contents. [ABSTRACT FROM AUTHOR]

Root‐knot nematodes (RKNs) are one of the most serious pests of carrot plants. Resistance cultivars are a cost‐effective and ecofriendly management strategy for nematodes. To develop these, it is essential to understand the genetic, molecular and biochemical aspects underpinning RKN infection. Here, Meloidogyne javanica penetration and development, defence reactions and antioxidant enzyme activity were investigated in a resistant carrot cultivar (TN‐99‐129) compared to the susceptible cultivar TN‐99‐62. No significant difference was found in the number of J2s penetrating the roots of both cultivars. At 2 days post‐inoculation (DPI), necrosis symptoms were observed around the head of penetrated nematodes. Cell death also increased in the roots of the nematode‐infected TN‐99‐129 cultivar. Callose deposition happened at 6 DPI, and lignin content increased with delay (21 DPI) in the inoculated resistant cultivar. In addition, the reactive oxygen species metabolism process in resistant and susceptible cultivars was significantly different. In TN‐99‐129, catalase activity inhibition was observed at the early (2 DPI) phases of infection, and increasing superoxide dismutase activity and a relative decrease in catalase activity during nematode development. The activity of guaiacol peroxidase also increased significantly in the resistant cultivar, but no significant difference was observed in the activity of ascorbate peroxidase. This study explains the process of defence reactions in the TN‐99‐129 carrot cultivar during RKN penetration and development. The exhaustive characterization of the defence mechanism of a novel source of resistance to RKN in carrots constitutes a significant step toward their use in crop breeding. [ABSTRACT FROM AUTHOR]

Summary: The chlamydospore production of three Pochonia chlamydosporia isolates from two different varieties was evaluated on flaxseed and rice husk, testing their survival on talc, kaolin and maize cob powder. The effect of each formulation in suppressing Meloidogyne javanica on tomato was also investigated in glasshouse trials. For all isolates, the number of chlamydospores produced on flaxseed was about twice that observed on rice husk (i.e. , 8 weeks after inoculation, isolate IRAN 1119 C produced 98 × 106 and 50 × 106 chlamydospores on flaxseed and rice husk, respectively). Isolate IRAN 1212 C produced more chlamydospores with longer lifespan compared with the other fungi. IRAN 1212 C on maize cob powder could reduce M. javanica by 95% at a level similar to fluopyram. This prototype formulation had a superior effect in establishing the fungus in the rhizosphere and on roots, suppressing the nematode and increasing plant growth. The three P. chlamydosporia isolates reproduced well on flaxseed and could last longer if formulated on maize cob powder, which appears suitable to produce an effective powdered formulation. [ABSTRACT FROM AUTHOR]

Summary: In this study, the accumulation of hydrogen peroxide (H2O2) in different parts (healthy root, gall, root attached to gall, aerial parts) of healthy tomato plants and plants infected by the root-knot nematode, Meloidogyne javanica , was investigated after treating the roots with β -aminobutyric acid (BABA). In addition, the effects of different concentrations of H2O2 (0-2 mM) on mortality, body structures and the digestive system of second-stage juveniles (J2) were also investigated in in vitro experiments. Results showed that exposure to concentrations of more than 1 mM H2O2 is lethal for J2, while the digestive system is not able to tolerate concentrations of more than 0.2 mM. Evaluating the activity level of enzymes related to biosynthesis and removing H2O2 in treated plants also showed that the nematode has significant suppressive effects on the biosynthesis enzymes of this compound, and this effect is greater in the site of nematode activity than in other parts of the plant. By contrast, the activity of catalase enzyme, as one of the H2O2-removing enzymes, shows a significant increase in all parts of nematode infected plants (especially in galls). [ABSTRACT FROM AUTHOR]

Summary: Root‐knot nematodes (RKN; Meloidogyne species) are plant pathogens that introduce several effectors in their hosts to facilitate infection. The actual targets and functioning mechanism of these effectors largely remain unexplored. This study illuminates the role and interplay of the Meloidogyne javanica nematode effector ROS suppressor (Mj‐NEROSs) within the host plant environment.Mj‐NEROSs suppresses INF1‐induced cell death as well as flg22‐induced callose deposition and reactive oxygen species (ROS) production. A transcriptome analysis highlighted the downregulation of ROS‐related genes upon Mj‐NEROSs expression. NEROSs interacts with the plant Rieske's iron–sulfur protein (ISP) as shown by yeast‐two‐hybrid and bimolecular fluorescence complementation.Secreted from the subventral pharyngeal glands into giant cells, Mj‐NEROSs localizes in the plastids where it interacts with ISP, subsequently altering electron transport rates and ROS production. Moreover, our results demonstrate that isp Arabidopsis thaliana mutants exhibit increased susceptibility to M. javanica, indicating ISP importance for plant immunity.The interaction of a nematode effector with a plastid protein highlights the possible role of root plastids in plant defense, prompting many questions on the details of this process. [ABSTRACT FROM AUTHOR]

The identification of novel drug targets in plant-parasitic nematodes (PPNs) is imperative due to the loss of traditional nematicides and a lack of replacements. Chemosensation, which is pivotal for PPNs in locating host roots, has become a focus in nematode behavioral research. However, its underlying molecular basis is still indistinct in such a diverse group of PPNs. To characterize genes participating in chemosensation in the Javanese root-knot nematode Meloidogyne javanica, RNA-sequencing of the second-stage juveniles (J2s) treated with tomato root exudate (TRE) for 1 h and 6 h was performed. Genes related to chemosensation in M. javanica mainly responded to TRE treatment at 1 h. Moreover, a gene ontology (GO) analysis underscored the significance of the neuropeptide G protein-coupled receptor signaling pathway. Consequently, the repertoire of putative neuropeptides in M. javanica, including FMRFamide-like peptides (FLPs), insulin-like peptides (ILPs), and neuropeptide-like peptides (NLPs), were outlined based on a homology analysis. The gene Mjflp-14a, harboring two neuropeptides, was significantly up-regulated at 1 h TRE treatment. Through peptide synthesis and J2 treatment, one of the two neuropeptides (MjFLP-14-2) was proven to influence the J2 chemotaxis towards tomato root tips. Overall, our study reinforces the potential of nematode neuropeptides as novel targets and tools for root-knot nematode control. [ABSTRACT FROM AUTHOR]

We present the chromosome-scale genome assembly of the allopolyploid root-knot nematode Meloidogyne javanica. We show that the M. javanica genome is predominantly allotetraploid, comprising two subgenomes, A and B, that most likely originated from hybridisation of two ancestral parental species. The assembly was annotated using full-length non-chimeric transcripts, comparison to reference databases, and ab initio prediction techniques, and the subgenomes were phased using ancestral k-mer spectral analysis. Subgenome B appears to show fission of chromosomal contigs, and while there is substantial synteny between subgenomes, we also identified regions lacking synteny that may have diverged in the ancestral genomes prior to or following hybridisation. This annotated and phased genome assembly forms a significant resource for understanding the origins and genetics of these globally important plant pathogens. Author summary: Root-knot nematodes represent one of the most significant crop parasites globally. Despite their agricultural importance, only limited genomic resources have been published to date, leaving a gap in the understanding of genetic mechanisms driving genome evolution and crop virulence. Here, we have used modern genomic and bioinformatic approaches to create a chromosome-scale reference assembly to investigate the origins and genomic composition of the root-knot nematode species Meloidogyne javanica. This species has an allopolyploid genome, reproduces by ameiotic parthenogenesis and is among the most damaging plant parasitic nematodes with a large and expanding plant host range. Utilising modern long-read DNA sequencing and bioinformatics approaches, we successfully phased the assembly into its constituent subgenomes, a first for this agriculturally important clade. While we find the genomic landscape is mostly syntenic between subgenomes, we identified regions of minimal similarity, and highlight structural divergence between subgenomes. [ABSTRACT FROM AUTHOR]

Soybean is the main oilseed cultivated worldwide. Even though Brazil is the world's largest producer and exporter of soybean, its production is severely limited by biotic factors. Soil borne diseases are the most damaging biotic stressors since they significantly reduce yield and are challenging to manage. In this context, the present study aimed to evaluate the potential of a bacterial strain (Ag109) as a biocontrol agent for different soil pathogens (nematodes and fungi) of soybean. In addition, the genome of Ag109 was wholly sequenced and genes related to secondary metabolite production and plant growth promotion were mined. Ag109 showed nematode control in soybean and controlled 69 and 45% of the populations of Meloidogyne javanica and Pratylenchus brachyurus, respectively. Regarding antifungal activity, these strains showed activity against Macrophomia phaseolina, Rhizoctonia solani, and Sclerotinia sclerotiorum. For S. sclerotiorum, this strain increased the number of healthy plants and root dry mass compared to the control (with inoculation). Based on the average nucleotide identity and digital DNA-DNA hybridization, this strain was identified as Bacillus velezensis. Diverse clusters of specific genes related to secondary metabolite biosynthesis and root growth promotion were identified, highlighting the potential of this strain to be used as a multifunctional microbial inoculant that acts as a biological control agent while promoting plant growth in soybean. [ABSTRACT FROM AUTHOR]

In an integrated nematode management system, the best results are generally obtained by rotating crops with resistant plants, antagonists, or poor host of parasites. Some reports indicate that Stylosanthes spp. have the potential to control nematodes. Thus, this study aimed to assess the reaction of Stylosanthes spp. 'Campo Grande' to Pratylenchus brachyurus and Meloidogyne javanica penetration and reproduction at different inoculum levels and examine the histopathology and histochemistry of parasitized plants. Stylosanthes did not prevent P. brachyurus penetration in roots. However, the number of penetrated nematodes was lower than that in soybean from 17 days after inoculation onwards. The numbers of second-stage and third-/fourth-stage juveniles of M. javanica in Stylosanthes roots were close to zero, and no females were observed. Assays conducted using increasing levels of inoculum (P. brachyurus or M. javanica) showed that Stylosanthes was resistant to the parasites, with a maximum reproduction factor of 0.59 for P. brachyurus and 0.07 for M. javanica. Histopathological analysis showed the presence of P. brachyurus in Stylosanthes, but without rupture of plant cells. M. javanica individuals were not observed. Histochemistry revealed the presence of phenolic compounds in the epidermis of Stylosanthes and proteins in plant cells. These results show that Stylosanthes spp. 'Campo Grande' can be used in crop rotation programs in fields with mixed infestation of P. brachyurus and M. javanica. [ABSTRACT FROM AUTHOR]

Plants grown without soil are believed to be less affected by soilborne diseases. However, in a commercial greenhouse in Ethiopia's Rift valley, Lavender plants grown in hydroponic showed signs of severe stunting and galled roots. To identify the cause of the problem, root samples were taken. From these samples, single egg masses were obtained and used as inoculum for tomato cv. Moneymaker seedlings. The resulting seedlings were grown to produce a pure culture. DNA was extracted from second-stage juveniles (J2) from sixteen isolates derived from pure cultures and amplified the 28S rRNA and NADH dehydrogenase subunit 5 (Nad5) region of the mtDNA. The 28S rRNA and Nad5 were sequenced for two and five randomly selected isolates. A BLAST search of 28S rRNA sequences at NCBI showed a 98.34% sequence homology with known sequences of Meloidogyne javanica isolates. Moreover, Nad5 gene analysis, female perennial pattern, and the phylogenetic trees further confirmed the correct identification of this species. This is the first report of a nematode infecting plants growing in a hydroponic greenhouse in Ethiopia. Therefore, isolating any potential contaminants of the potting media for future lavender production are important. [ABSTRACT FROM AUTHOR]

Meloidogyne nematodes, commonly known as root-knot nematodes, pose a considerable threat to crop yields, resulting in significant economic losses due to their intricate biology and limited control methods. In line with the European Union's focus on promoting organic farming and soil health to encourage sustainable agricultural practices, this study explores the efficacy of two characterized bacterial communities obtained from compost against M. javanica in tomato plants. Through pot experiments, it was demonstrated that both bacterial communities, namely SC1 and SC2, effectively suppressed nematode reproduction and root invasion, which was reflected by a reduction in the number of egg masses per root (by 63% and 28%, respectively) and a reduction in the total progeny population (by 68% and 28%, respectively), with various simultaneously enhanced growth parameters in tomatoes, i.e., aerial part fresh weight increased by 74% and 58%, aerial part dry weight increased by 90% and 55%, and plant height increased by 86% and 53%, respectively. These findings underscore the potential of compost bacterial communities as promising tools for organic or integrated pest management, thereby supporting sustainable agricultural practices and contributing to improved crop yields. [ABSTRACT FROM AUTHOR]

Summary: Chickpea is one of the most important legume crops in Ethiopia; however, its production is far below the mean international chickpea production due to biotic and abiotic stressors. Plant-parasitic nematode infestation is extensive in chickpea-growing areas worldwide. The distribution and population density of plant-parasitic nematodes in chickpea were determined during the September-December 2021 growing season. Ten plant-parasitic nematode taxa were identified from 27 localities across ten districts in the main chickpea-growing areas in Ethiopia. Pratylenchus had the highest prominence values, followed by Rotylenchulus and Meloidogyne spp. Helicotylenchus , Hoplolaimus , Scutellonema and Quinisulcius were more prevalent than Criconemoides and Ditylenchus. Sequences of different molecular markers, including D2-D3 of 28S rDNA, ITS of rDNA, and COI and Nad5 of mtDNA, revealed the presence of Meloidogyne javanica , Rotylenchulus parvus , Scutellonema clathricaudatum and Helicotylenchus caudatus. Helicotylenchus caudatus and R. parvus are the first reports from Ethiopia and chickpea, while S. clathricaudatum is the first report for chickpea. This study provides essential baseline information of nematode pest occurrence on chickpea in Ethiopia. This information will raise awareness among growers, agricultural officers, and extension advisors, enabling them to develop effective nematode management strategies for the chickpea production system in Ethiopia. [ABSTRACT FROM AUTHOR]

Integrated management is considered the best strategy to mitigate the damage caused by plant-parasitic nematodes. However, there is still limited information regarding some integrated techniques. Thus, this study aimed to assess the effects of genetic management associated with chemical control of Meloidogyne javanica in soybean (Glycine max (L.) Merr.) The experiment was installed in a greenhouse according to an 8×4 factorial design with eight replicates. The first factor was soybean cultivar (HO Juruena IPRO, resistant; Foco IPRO, HO Maracaí IPRO, and CZ 58B28 IPRO, moderately resistant; HO Mamoré IPRO, moderately susceptible; and Extrema IPRO, CZ 48B32 IPRO, and HO Aporé IPRO, susceptible). The second factor consisted of an untreated control and commercial nematicides based on abamectin, thiodicarb+imidacloprid, and fluopyram. Plants were inoculated with 2000 nematode eggs, and nematode and vegetative variables were evaluated at 65 d after inoculation. There was an interaction effect on nematode variables. Furthermore, there was an additive effect of genetic management and chemical control, mainly in resistant cultivars treated with thiodicarb+imidacloprid or fluopyram with controls of up to 69.90% and 96.86%, respectively. The application of fluopyram and the use of 'HO Juruena IPRO', 'Foco IPRO', or 'HO Maracaí IPRO' also contributed to the control of M. javanica. Vegetative variables were studied by analyzing product effects separately, but results were inconclusive. [ABSTRACT FROM AUTHOR]

Tobacco (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 <.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. [ABSTRACT FROM AUTHOR]

Plant parasitic nematodes cause severe damage to soybean crops, leading to substantial losses in yield and quality. However, more information is needed regarding the occurrence, distribution and damage status of soybean PPNs in Ethiopia. A total of 180 samples of rhizosphere and roots were collected randomly from three major soybean‐producing districts of Metekel Zone. Nematodes were extracted and identified at the genus level based on their morphological characteristics, except Meloidogyne javanica, the deadly species, which was identified using morphological and molecular techniques. Seven nematode genera were recovered: Meloidogyne, Scutellonema, Pratylenchus, Helicotylenchus, Rotylenchulus, Hemicycliophora and Criconema. The genera Meloidogyne, Scutellonema and Pratylenchus were dominant and had FO% of 98.3%, 97.5% and 81.8%, respectively. The host status of 10 soybean varieties to M. javanica infection was determined. Data on the shoot height, root length, fresh shoot and root weight, gall number and nematode density were estimated 3 months after inoculation. The results revealed that Jalele variety suppresses M. javanica multiplication while the other nine supported it. Comparatively, Pawe‐3, Awassa‐95 and Koreme varieties supported the highest nematode multiplication 24.4, 16.2 and 15.3 reproductive factors, respectively. Nova experienced the highest shoot and root relative biomass losses (84%) and roots (63%). In contrast, Jalele did not experience any loss in all parameters. However, Jalele variety resisted M. javanica, making it a promising approach towards soybean breeding programs for nematode management. [ABSTRACT FROM AUTHOR]

Meloidogyne javanica is one of the most widespread and economically important sedentary endoparasites. In this study, a comparative transcriptome analysis of M. javanica between pre-parasitic second-stage juveniles (Pre-J2) and parasitic juveniles (Par-J3/J4) was conducted. A total of 48,698 unigenes were obtained, of which 18,826 genes showed significant differences in expression (p < 0.05). In the differentially expressed genes (DEGs) from transcriptome data at Par-J3/J4 and Pre-J2, a large number of unigenes were annotated to the C-type lectin (CTL, Mg01965), the cathepsin L-like protease (Mi-cpl-1), the venom allergen-like protein (Mi-mps-1), Map-1 and the cellulase (endo-β-1,4-glucanase). Among seven types of lectins found in the DEGs, there were 10 CTLs. The regulatory roles of Mj-CTL-1, Mj-CTL-2 and Mj-CTL-3 in plant immune responses involved in the parasitism of M. javanica were investigated. The results revealed that Mj-CTL-2 could suppress programmed cell death (PCD) triggered by Gpa2/RBP-1 and inhibit the flg22-stimulated ROS burst. In situ hybridization and developmental expression analyses showed that Mj-CTL-2 was specifically expressed in the subventral gland of M. javanica, and its expression was up-regulated at Pre-J2 of the nematode. In addition, in planta silencing of Mj-CTL-2 substantially increased the plant resistance to M. javanica. Moreover, yeast co-transformation and bimolecular fluorescence complementation assay showed that Mj-CTL-2 specifically interacted with the Solanum lycopersicum catalase, SlCAT2. It was demonstrated that M. javanica could suppress the innate immunity of plants through the peroxide system, thereby promoting parasitism. [ABSTRACT FROM AUTHOR]

Root-knot nematodes (Meloidogyne species) are the most important group of plant nematodes in potato-producing regions of South Africa. Prior to the withdrawal of synthetic chemical fumigant nematicides from the agrochemical markets, Meloidogyne species were viewed as a minor pest in potato-producing regions. Currently, it has been established that all potato cultivars are host to Meloidogyne species, with the preferred management option of the genus being the use of resistant crops. However, the host status of most crops used in potato-based crop rotations intended to manage nematode population densities of the genus had not been established. Globally, M. incognita is viewed as being more aggressive than M. javanica, whereas in South Africa the opposite is true. Therefore, the objective of the study was to determine whether the reproduction potential (RP) values of M. javanica on 16 crops used in potato crop rotation systems would be below unity. The experiment was conducted under greenhouse conditions at the University of Limpopo during autumn (February-April) 2022 and validated in spring (September-November) of the same year in South Africa. Treatments (16 crops) were laid out in a randomized complete block design, with six replications. The crops were inoculated with 250 eggs + second-stage juveniles (J2). At 56 days after inoculation, nematodes variables were collected and expressed as RP, which demonstrated that there were similarities and differences in RP of the 16 crops to infection by M. javanica, but with the values being below one in white maluti oats, tillage radish, forage sorghum, and jap radish. In conclusion, the four crops with RP values below one could be used in a potato-crop rotation system intended to manage the population densities of M. javanica. [ABSTRACT FROM AUTHOR]

Summary: Bush tea (Athrixia phylicoides) is an aromatic, perennial, leafy shrub that is endemic to the northeastern mountain ranges of South Africa and has a high potential for commercialisation as an alternative to caffeine-containing tea. During the summer and winter of 2018-2019, a survey was carried out at nine localities in the northeastern regions of South Africa to study the diversity of nematodes associated with bush tea and, in terms of frequency of occurrence and abundance, identify the dominant plant-parasitic nematodes. Twenty-one plant-parasitic nematode species belonging to 14 genera were identified in 90 rhizosphere soil and root samples. Meloidogyne and Helicotylenchus were the dominant plant-parasitic nematode genera. Meloidogyne javanica and Scutellonema brachyurus were found at all localities, followed by M. enterolobii , Pratylenchus brachyurus , Rotylenchulus parvus , H. martini and S. truncatum (found at 7-8 localities). Other species identified included Criconema corbetii , C. sphaerocephalus , C. xenoplax , Criconemoides ihlathum , C. parvus , Discocriconemella glabrannulata , H. dihystera , H. erythrinae , H. paraplatyurus , Hemicycliophora typica , M. hapla , M. incognita , Rotylenchulus unisexus and R. clavicaudatus. Individuals of Crossonema , Paratylenchus , Ogma , the Xiphinema americanum -group and X. americanum sensu lato could not be identified to species level due to the low number of specimens present in the samples. Comparison of the two methods used to identify the Meloidogyne populations to species level shows that morphological identification (particularly perineal pattern morphology) provided a more complete picture of the Meloidogyne species present in the samples compared with the molecular SCAR-PCR technique. High levels of Cu, K and pH were associated with the highest relative population densities (RPD% = average population density of a nematode genus/total nematode population density × 100) of Meloidogyne , whilst high levels of Al and soil resistivity were associated with the lowest RPD% of Meloidogyne. By contrast, high levels of K and pH were associated with the lowest RPD% of Helicotylenchus , whilst high levels of Al and soil resistivity were associated with the highest RPD% of Helicotylenchus. [ABSTRACT FROM AUTHOR]

Root and crown rot incited by an oomycete, Phytophthora melonis, causes significant yield losses in commercial pumpkin (Cucurbita pepo) production worldwide. Currently, resistant cultivars and knowledge of molecular mechanism of C. pepo against P. melonis are scarce. Here, we analysed the quantitative gene expression changes of 10 candidate gene markers (bHLH87, ERF014, HSF, MYB, PR-1, WRKY21, CPI, POD, PSK, SGT) in pumpkin roots and leaves at three time points (h post-inoculation, hpi) following inoculation with P. melonis in two resistant (Ghelyani and Tanbal), and two susceptible (Marmari and Khoreshti) varieties of pumpkin. Gene expression using quantitative real time PCR along a time course revealed the strongest transcriptomic response at 48 and 72 hpi in resistant genotypes, 1.1-2.7-fold in roots and leaves, respectively, with a high significant correlation (r = 0.857**-0.974**). We also found that CPI, PSK, SGT1 and POD act as a dual regulator that similarly modulate immunity not only against P. melonis, but also against other diseases such as early blight (Alternaria cucumerina), powdery mildew (Podosphaera xanthii), downy mildews (Pseudoperonospora cubensis), and pathogenic plant nematodes (Meloidogyne javanica). Furthermore, significantly higher activities of the ROS scavenging defence enzymes, catalase (1.6-fold increase) and peroxidase (6-fold increase) were observed in the roots of resistant cultivars at different hpi compared with non-inoculated controls. In addition, the biomass growth parameters including leaf and root length, stem and root diameter, root fresh weight and volume were significantly different among studied genotypes. Cumulatively, the transcriptome data provide novel insights into the response of pumpkins for improving pumpkin breeding to P. melonis. [ABSTRACT FROM AUTHOR]

The Mi-1 gene in tomato confers resistance against insects and nematodes. The mechanisms involved in the functioning of this gene are not completely known, and they differ depending on the damaging organism (insect or nematode). Transcription factors (TF) from different families are essential for plant defence, and the TGAs, members of the Basic Leucine Zipper (bZIP) TF family, are relevant in different pathosystems. In this work, the implication of TGA 1a and TGA 2.1 genes in Mi-1 resistance against the root-knot nematode Meloidogyne javanica was studied, by virus-induced gene silencing (VIGS) based on Tobacco rattle virus (TRV). Results showed that infiltration with the empty TRV vector did not alter Mi-1-mediated resistance, confirming the adequacy of this method. Silencing of the TGA 1a gene resulted in a decrease in resistance to M. javanica, as the numbers of egg masses were significantly higher than those on non-silenced plants. This decrease in resistance was similar to that caused by silencing the Mi-1 gene. However, the silencing of the TGA 2.1 gene caused a limited loss of resistance, with infestation levels intermediate between those of resistant and susceptible varieties. Thus, our results demonstrate the requirement of TGA 1a in Mi-1-mediated resistance to M. javanica, while the incomplete silencing of TGA 2.1 impaired a specific determination of its role. [ABSTRACT FROM AUTHOR]

Arabidopsis thaliana is a suitable host for phytoparasitic nematodes of the genus Meloidogyne. Successful nematode infection leads to the formation of root galls. We tested for natural genetic variation and inoculation density effects on nematode reproductive success in the interaction between A. thaliana and Meloidogyne javanica. We inoculated different Arabidopsis genotypes with two sources of nematodes at two different doses, using a mild protocol for inoculum preparation. We counted root galls and egg masses 2 months after inoculation. We obtained a high number of successful nematode infections. Infection success differed among Arabidopsis genotypes in interaction with the nematode source. Overall, infection success and reproductive success of nematodes were lower at a higher inoculum dose of nematodes. Our results indicate that natural genetic variation in both host plants and nematodes, as well as short‐ and long‐term negative density effects, shape nematode reproductive success. [ABSTRACT FROM AUTHOR]

Summary: A bioassay was developed to characterise the effects of nematicidal compounds and tested using low concentrations (0.125 and 0.25 mg l−1) of three nematicides: fluensulfone, fluopyram and fluazaindolizine. Germinating lettuce seeds with ca 2-3 mm roots were planted in a 5.5-cm-diam. Petri dish on agar containing the nematicides. Second-stage juveniles (J2) of Meloidogyne javanica and M. incognita were introduced to the agar plate immediately after planting. Alternatively, lettuce seeds were planted 48 h after introducing J2 to the plate. The number of J2 attracted to a root tip and J2 mobility were recorded 19 h after inoculation or planting, and infection rate and root length were recorded 5 days after planting. The three nematicides showed different effects on J2 of the Meloidogyne species. Fluensulfone did not inhibit infection by either species if the lettuce was planted immediately after inoculation, but their infection rates, and especially those of M. incognita , were reduced when lettuce seeds were planted 2 days later. Fluopyram reduced infection with M. javanica J2 at higher rates (>83.3%) than for M. incognita J2 (<58.4%) compared to the control, even without 48 h exposure before planting. Fluazaindolizine reduced M. incognita infection at high rates (>83.3%), although the J2 were attracted to the lettuce roots. Root lengths also showed differences in infection severity. This assay distinguished the effects of the three nematicides on the two Meloidogyne species and can also serve to screen compounds that inhibit nematode infection without killing Meloidogyne J2. [ABSTRACT FROM AUTHOR]

Objective: In this study, a series of synthetic hydroxylated (5-10) and prenylated (10-17) acetophenones, chalcones (18-20) and a flavone (21) have been synthesized and evaluated on the nematode Meloidogyne javanica. Additional phenolic compounds, including salicylic acid, isopropyl salicylate, thymol, carvacrol, cumic acid, eugenol, vanillin, and vanillic acid (22-29), were also tested. Methods: Compounds 5-21 have been synthesized by a sequence of reactions and were isolated and identified by ¹H-NMR, 13C-NMR, and HRMS. The in vitro nematicidal effects of the compounds were tested on J2 juveniles. The nematicidal activity was confirmed by their egg hatching inhibition effects, tested at the minimum lethal concentration (minimum dose to give 100% J2 mortality). Results: Compounds 5-18 have been previously reported and 19-21 are described here for the first time. The 2'-hydroxylated acetophenones (5-9) showed strong nematicidal effects, being 7-9 the most active. Salicylic (22) and cumic (26) acids were effective compounds. Compounds 7, 12, 22-26, active on M. javanica J2 juveniles, were also egg hatching inhibitors. Conclusions: A C-2/C-4 dihydroxylation or C-2/C-4/C-3 trihydroxylation of the acetophenone moiety improved the activity, while introducing a hydrophilic isoprene chain (10-17) eliminated the effect, with only one prenylated acetophenone (12) being active. Among the additional phenolic compounds (22-29), these with a carboxyl group instead of the acyl side were better nematicides. These results generate molecular leads for developing new nematicidal phenolic compounds. [ABSTRACT FROM AUTHOR]

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The strains in Lysobacter spp. have the potential to control plant-parasitic nematodes. In our experiment, L. gummosus YMF3.00690 showed antagonistic effects against plant root-knot nematode. Nine metabolites were isolated and identified from cultures of L. gummosus YMF3.00690, of which compound 1 was identified as a new metabolite tetrahydro-4,4,6-trimethyl-6-[(tetrahydro-6,6-dimethyl-2-oxo-4(1H)-pyrimidinylidene) methyl]-2(1H)-pyrimidinone. The activity assay showed that two compounds, 5-(hydroxymethyl)-1H-pyrrole-2-carbaldehyde (2) and 1H-pyrrole-2-carboxylic acid (3), had nematicidal activities against Meloidogyne javanica with mortalities of 69.93 and 90.54% at 400 ppm for 96 h, respectively. These two compounds were further tested for the inhibition activity of eggs hatching, and compound 3 showed a significant inhibition rate of 63.36% at 50 ppm for 48 h. In the chemotactic activity assay, three compounds (1 to 3) were found to have concentration-dependent chemotactic activity, of which compound 1 showed attractive activity. This experiment explored the active metabolites of L. gummosus YMF3.00690 against M. javanica and laid the foundation for biopesticide development. [ABSTRACT FROM AUTHOR]

The involvement of WRKY transcription factors in plant-nematode interactions, and in particular, how these WRKYs participate in regulating the complex morphological and physiological changes occurring after nematode infection, are the topic of active research. We characterized the functional role of the unstudied tomato WRKY genes SlWRKY16 and SlWRKY31 in regulating tomato roots' response to infection by the root-knot nematode Meloidogyne javanica. Using promoter–GUS reporter gene fusions and qRT-PCR, we show that both SlWRKYs are predominantly expressed during the first half of the parasitic life stages, when feeding-site induction and construction occur. Expression of SlWRKY16 increased sharply 15 days after inoculation, whereas SlWRKY31 was already induced earlier, but reached its maximum expression at this time. Both genes were downregulated at the mature female stage. To determine biological function, we produced transgenic lines overexpressing SlWRKY16 and SlWRKY31 in tomato hairy roots. Overexpression of both genes resulted in enhanced M. javanica infection, reflected by increased galling occurrence and reproduction. Expression profiling of marker genes responsive to defense-associated phytohormones indicated reductions in salicylic acid defense-related PR-1 and jasmonic acid defense-related PI in inoculated roots overexpressing SlWRK16 and SlWRKY31, respectively. Our results suggest that SlWRKY16 and SlWRKY31 function as negative regulators of plant immunity induced upon nematode infection. [ABSTRACT FROM AUTHOR]

Background: The efficacy of drip‐applied nematicides depends on adequate product distribution, which can be difficult in sandy soils. Three new non‐fumigant nematicides (fluazaindolizine, fluensulfone, fluopyram), together with two old nematicides, oxamyl and metam potassium, were evaluated when applied via single and double drip tapes to control root‐knot nematode in cucumber and squash in Florida between February 2020 and December 2022. Results: Nematicide applications via double drip tapes resulted in lower root gall infection (and tend to have higher yield) as compared to a single tape for fluopyram, but no difference was noted between single and double tapes for oxamyl and fluazaindolizine. Fluensulfone response was somewhere in between and metam potassium had higher squash yield when applied with double tapes. Root‐knot infection was higher in cucumber than in squash, and metam potassium had the highest yields and lowest nematode infection compared to other nematicide treatments. Conclusion: The benefit of double versus single drip tapes depended on the type of nematicide that was applied and was evident for nematicides that have poor water solubility like fluopyram. Some benefit was noted for metam potassium, but no or limited benefit was noted for oxamyl, fluazaindolizine and fluensulfone. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Summary: Finger millet (Eleusine coracana) is a staple crop for subsistence farmers and is primarily cultivated in arid and semi-arid regions. Nevertheless, there are limited data available on the occurrence of plant-parasitic nematodes that specifically target finger millet, and the damage arising from such infections. In this study, we investigated the population dynamics, damage threshold and tolerance of the lesion nematode, Pratylenchus n. sp., and the root-knot nematode, Meloidogyne javanica , on finger millet 'P-224'. We used 11 initial population densities (P i) of second-stage juveniles (J2): 0, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, 32 and 64 J2 (g soil)−1 for M. javanica and the same densities of mixed life-stages for Pratylenchus n. sp. The logistic growth model, Seinhorst yield loss and population dynamic models were fitted to the shoot height, plant biomass and final nematode population density. Based on the population dynamics model parameters, maximum multiplication rates and maximum population densities for each nematode species were estimated. The maximum multiplication rates (a) were 32.39 and 17.46, whilst the maximum population densities (M) were 18.83 nematodes (g soil)−1 and 19.78 J2 (g soil)−1 for Pratylenchus n. sp. and M. javanica respectively. The maximum height reached (C) was negatively affected by increasing P i for both nematode genera, while the rate of growth (B) and the time to reach 0.5 × C was not affected based on the logistic model. A tolerance limit (T) of 1.70 nematodes (g soil)−1 and 0.65 J2 (g soil)−1; relative minimum grain yield (m) of 0.23 and 0.40 for Pratylenchus n. sp. and M. javanica was found, respectively. The results indicate that 'P-224' is a good host for both Pratylenchus n. sp. and M. javanica , which significantly reduce yield. These findings can be used as a base to develop effective nematode management strategies for finger millet. [ABSTRACT FROM AUTHOR]

Summary: The legume cavalcade, Centrosema pascuorum , is used extensively as a cover crop and as a component of conservation agriculture systems. It is also an attractive rotation or cover crop for the management of root-knot nematodes (RKN; Meloidogyne spp.) as it is a non-host. RKN are persistent pests that are well known to be difficult to control. However, the mechanisms governing the non-host status of cavalcade is unknown. The current study established that cavalcade leaves are toxic to RKN as either aqueous extracts or soil amendments. Bioassays conducted using Meloidogyne javanica showed that a 90% concentration of aqueous extract derived from 1-month-old cavalcade leaves (89 mg crude extract ml−1) suppressed nematode hatch (82.9%) and killed infective second-stage juveniles of M. javanica (85.3%). Soil amendments with 1% (w/w) of 1-month-old cavalcade leaves (0.99 mg crude extract g−1 soil) also provided effective control of M. javanica in the glasshouse on okra. One-month-old leaves appeared more effective than 2- or 3-month-old leaves. The soil amendments had no adverse phytotoxic effect on okra seed germination. Our study demonstrates the potential for using cavalcade leaves or extracts to manage RKN. This may be due to the nematicidal activity of the various compounds in the leaves, such as flavonoids, phenols and terpenoids, which should be further assessed. [ABSTRACT FROM AUTHOR]

Root-knot nematodes (Meloidogyne spp.) are dangerous parasites of many crops worldwide. The threat of chemical nematicides has led to increasing interest in studying the inhibitory effects of organic amendments and bacteria on plant-parasitic nematodes, but their combination has been less studied. One laboratory and four glasshouse experiments were conducted to study the effect on M. javanica of animal manure, common vermicompost, shrimp shells, chitosan, compost and vermicompost from castor bean, chinaberry and arugula, and the combination of arugula vermicompost with some bacteria, isolated from vermicompost or earthworms. The extract of arugula compost and vermicompost, common vermicompost and composts from castor bean and chinaberry reduced nematode egg hatch by 12–32% and caused 13–40% mortality of second-stage juveniles in vitro. Soil amendments with the combination vermicompost of arugula + Pseudomonas. resinovorans + Sphingobacterium daejeonense + chitosan significantly increased the yield of infected tomato plants and reduced nematode reproduction factor by 63.1–76.6%. Comparison of chemical properties showed that arugula vermicompost had lower pH, EC, and C/N ratio than arugula compost. Metagenomics analysis showed that Bacillus, Geodermatophilus, Thermomonas, Lewinella, Pseudolabrys and Erythrobacter were the major bacterial genera in the vermicompost of arugula. Metagenomics analysis confirmed the presence of chitinolytic, detoxifying and PGPR bacteria in the vermicompost of arugula. The combination of arugula vermicompost + chitosan + P. resinovorans + S. daejeonense could be an environmentally friendly approach to control M. javanica. [ABSTRACT FROM AUTHOR]

BACKGROUND: Several benzenoid aromatic compounds were found to attract second‐stage juveniles (J2) of Meloidogyne species in previous studies. Here, the attraction of Meloidogyne J2 to the nematicides fluopyram and fluensulfone, with and without aromatic attractants, was evaluated on agar plates and in sand. RESULTS: Fluensulfone mixed with 2‐methoxybenzaldehyde, carvacrol, trans‐cinnamic acid, and 2‐methoxycinnamaldehyde, attracted Meloidogyne javanica J2 on an agar plate, whereas fluensulfone alone did not. In contrast, fluopyram alone attracted J2 of M. javanica, Meloidogyne hapla, and Meloidogyne marylandi, although higher numbers of M. javanica J2 were attracted to the nematicide with the aromatic compounds. Trap tubes loaded with 1 and 2 μg fluopyram attracted M. javanica, Meloidogyne incognita, M. hapla, and M. marylandi J2 in the sand. Fluopyram‐treated tubes attracted 4.4–6.3 times higher numbers of M. javanica and M. marylandi J2 than fluensulfone. Potassium nitrate (KNO3), a Meloidogyne J2 repellent, did not abolish fluopyram's attractiveness to M. marylandi. These results indicate that high numbers of Meloidogyne J2 near fluopyram on an agar plate or in sand are caused by the attractiveness of the nematicide and not by the accumulation of dead J2 after their random encounter with the nematicide. CONCLUSION: Aromatic attractants have the potential to attract Meloidogyne J2 to nematicides; however, fluopyram itself was attractive to Meloidogyne J2. The attractiveness of fluopyram to Meloidogyne J2 might contribute to its high control efficacy, and elucidation of the attraction mechanism could be useful for nematode‐control strategies. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Cowpea, Vigna unguiculata, is a legume adapted to regions with a tropical climate and limited water resources, and it has become a basic food source and income generator. Root‐knot nematodes (Meloidogyne spp.) cause substantial damage to the root system, resulting in yield losses. Genetic resistance is one of the most efficient management methods. The objective of this study was to generate information on genetic resistance to Meloidogyne incognita and Meloidogyne javanica of Brazilian cowpea genotypes. For this, 18 accessions of cowpea from the collection of Embrapa Meio‐Norte and six control accessions of cowpea were tested in completely randomized design with six replications, evaluated 60 days after inoculation, and carried out twice in time. To assess root penetration of nematodes and root gall formation in NIL‐CB3‐isoline, which allows reproduction but limits gall formation, nematodes inside the roots were stained with acid fuchsin, after inoculation with 5000 J2, with estimates at 72 h time‐points up to 28 days. None of the 18 accessions from Embrapa showed resistance to M. javanica, but accessions MNC06‐895‐1, MNC04‐14, MNC06‐909‐6, 98, MNCO4‐907‐35, and Am60‐15 showed resistance to M. incognita. There was a reduction in the number and size of galls in the NIL‐CB3 egg isoline, and an increase in formation of males, which are not important for parasitism. Given the importance and prospects for expansion of the cowpea crop throughout Brazil, the results of this study contribute to the knowledge on the reaction of Brazilian cowpea genotypes to the root‐knot nematode. Core Ideas: There are sources of resistance in Brazilian germplasm banks for the management of Meloidogyne.Six accessions were considered resistant to M. incognita.No accession was resistant to M. javanica, thus, requiring a continuous search for resistance in cowpea genotypes.The life cycle of M. incognita in cowpea roots was 24 days.The NIL‐CB3‐egg isoline genotype affected the development of females in the root. [ABSTRACT FROM AUTHOR]

Commercial tomatoes are usually complex F1 hybrids with multiple resistances genes from different wild Solanum species. The response of tomato cultivars with resistance to root-knot nematodes (RKN) and Tomato yellow leaf curl virus (TYLCV) as infected by Meloidogyne javanica was determined in a controlled environment and field conditions. Four treatments were tested, viz. tomato cultivars with (i) RKN resistance alone; (ii) combination of RKN and TYLCV resistance (RKN + TYLCV); (iii) TYLCV resistance alone; and (iv) control (susceptible to the nematode and virus). The RKN-resistant plants effectively suppressed nematode infection and reproduction both in a controlled environment and in field conditions. The RKN + TYLC-resistant plants were less effective (p < 0.001) than the RKN plants in a controlled environment, and their resistance levels were significantly reduced in the field. Nonetheless, the RKN + TYLCV plants supported lower (p < 0.001) nematode infection and reproduction than the susceptible control plants. The TYLCV-resistant plants reduced (p < 0.001) nematode infection and reproduction compared to the susceptible control in a controlled environment and in field conditions. The divergent response of tomato cultivars with resistance to TYLCV via infection by M. javanica can be attributed to the genetic background of the cultivars. [ABSTRACT FROM AUTHOR]

Two formulations of Alltech Crop Science products (ACS), a proprietary blend of fermentation products and plant extracts with micronutrients (ACS5075), and a microbial based product (ACS3048), were tested to understand (1) their impact on the tomato plant immune response and (2) whether they are priming a resistance response in plants against root knot nematodes (RKN). Research findings reported previously indicate that tomato plants pre-treated with ACS5075 and ACS3048 were found less sensitive to Meloidogyne javanica infection. In the current study, the expression of six defence-related genes (PR-1, PR-3, PR-5T, ACO, CAT and JERF 3), relative to a housekeeping gene, were monitored via RT-PCR. Results suggest that the treatment with ACS5075 enhanced ACO and PR-1 gene expression levels, both post- treatment and post-infection with M. javanica. Reduced M. javanica infestation that was reported in the previous study could be attributed to the increased expression of these genes in the ACS5075-treated plants. Tomato plants treated with ACS3048, but without RKN infection, also demonstrated higher levels of ACO and PR-1 gene expression. Subsequently, 2D-gel electrophoresis was performed to study the differential protein expression in leaf tissues of treated tomato plants in an effort to elucidate a possible mechanism of action for these products. Protein spot 1 was identified as 'disease resistance protein RPP13-like', protein spot 2 as 'phosphatidylinositol 4-phosphate 5-kinase 2', spot 3 as 'protein SABRE like' and protein spot 4 as 'uncharacterized protein'. Overall research findings indicate that the ACS products could be used as plant immunity-boosting agents, as they play a significant role in the expression of certain genes and proteins associated with plant defence. [ABSTRACT FROM AUTHOR]

Ambarella (Spondias dulcis) tropical fruit showing typical galling symptoms caused by root-knot nematode was discovered in the orchard located in Phaya Yen, Pak Chong district Nakhon Ratchasima province, Thailand. The nematode was identified based on morphological and molecular information and its pathogenicity was confirmed through inoculation of second-stage juveniles into ambarella seedlings under greenhouse conditions. This was the first report of Meloidogyne javanica infecting S. dulcis. [ABSTRACT FROM AUTHOR]

Background: Plant-parasitic nematodes (PPNs) that cause most damage include root-knot nematodes (RKNs) which are a major impediment to crop production. Root-knot nematodes, like other parasites, secrete proteins which are required for parasite proliferation and survival within the host during the infection process. Results: Here, we used various computational tools to predict and identify classically and non-classically secreted proteins encoded in the Meloidogyne javanica genome. Furthermore, functional annotation analysis was performed using various integrated bioinformatic tools to determine the biological significance of the predicted secretome. In total, 7,458 proteins were identified as secreted ones. A large percentage of this secretome is comprised of small proteins of ≤ 300 aa sequence length. Functional analyses showed that M. javanica secretome comprises cell wall degrading enzymes for facilitating nematode invasion, and migration by disintegrating the complex plant cell wall components. In addition, peptidases and peptidase inhibitors are an important category of M. javanica secretome involved in compatible host-nematode interactions. Conclusion: This study identifies the putative secretome encoded in the M. javanica genome. Future experimental validation analyses can greatly benefit from this global analysis of M. javanica secretome. Equally, our analyses will advance knowledge of the interaction between plants and nematodes. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the efficacy of Ascophyllum nodosum extract, in combination or not with biocontrol agents, in the management of Meloidogyne javanica in soybean, assess treatment effects on soil biological activity, and determine the total phenolic content of the extract. The experiment was conducted according to a 5 × 2 factorial design, with three biocontrol agents (Bacillus methylotrophicus, Pochonia chlamydosporia, and Trichoderma harzianum), a chemical nematicide (abamectin, positive control), and an untreated (negative) control, each in the presence and absence of A. nodosum extract. Treatments included six replications. Nematode inoculation (2000 eggs + juveniles of M. javanica per plant) was performed at the time of sowing. Sixty days later, plants were evaluated for height, shoot weights, numbers of M. javanica eggs and J2 extracted from roots, and soil biological activity. Biological and chemical nematicide treatments were effective in reducing M. javanica multiplication. There was a synergic effect of A. nodosum extract on M. javanica multiplication for the treatments with A. nodosum + T. harzianum, A. nodosum + abamectin (Trial 1) and A. nodosum + P. chlamydosporia (Trial 2). B. methylotrophicus and T. harzianum treatments enhanced plant development and soil microbial biomass carbon. Higher values of soil basal respiration and metabolic quotient (qCO2) were observed in the A. nodosum + abamectin treatment. A. nodosum extracts at 75 g L−1 had a total phenolic content of 13 255 and 11 608 mg GAE 100−1 g in Trials 1 and 2, respectively. [ABSTRACT FROM AUTHOR]

Summary: Selected strains of Pasteuria species from the endospore-forming Gram-positive bacteria group have the potential to be developed into control agents for plant-parasitic nematodes. If Pasteuria is to be deployed successfully as a control agent, endospores of the bacterium initially have to adhere to the cuticle of the infective juvenile. Studies of the bacteria isolated from root-knot nematodes have suggested that collagen-like fibres on the endospore surface interact with a cuticle receptor on the second-stage juvenile through a host specific 'Velcro-like' mechanism. However, very little is known regarding the biochemical nature of the mechanism in Pasteuria strains isolated from cyst nematodes. Here, using several polyclonal antibodies raised to whole endospores and to synthetic collagen-like peptides, we compare two Pasteuria populations, one a strain from a root-knot nematode, Meloidogyne javanica , and another from cowpea cyst nematode, Heterodera cajani. We demonstrate that there is differential adhesion of endospores to the beet cyst nematode H. schachtii and that the sugar moieties on the endospore surface may protect the collagen-like fibres on the endospore from proteolytic digestion and be involved in the endospore's specificity. [ABSTRACT FROM AUTHOR]

Eggplant (Solanum melongena L.) is one of the premier vegetables and is widely cultivated. One of the most important reasons for reduced yield of eggplant is root-knot (Meloidogyne species) nematode. So, it is important to control this pest; therefore, an investigation was conducted in 2022 at the Aquaculture Research Unit lab to evaluate the effectiveness of moringa (Moringa oleifera Lam.) application in controlling root-knot nematode in eggplant. During this study, Meloidogyne javanica (Treub) was identified from the rhizosphere soil samples. Fresh leaf extracts of moringa, including positive control (fenamiphos), were investigated in vivo for efficacy against M. javanica in root and soil. Seedlings of eggplant were inoculated with 3000 eggs and second-stage juveniles (J2) of M. javanica in pot trials, with treatments comprising fresh leaf extracts of moringa (M. oleifera) in a series of concentrations. Fifty-six days after inoculation, the Phyto nematicide had reduced eggs and J2 in soil by 62-89%, gall number by 58-87%, and gall index by 35-87%. The best treatment was moringa (80 ppm) which was significantly superior to moringa (40 ppm) and moringa (60 ppm) (P < 0.05). However, fenamiphos had no significant difference (P > 0.05). The results showed that moringa (80 ppm) was the best treatment for controlling root-knot nematode in eggplant. [ABSTRACT FROM AUTHOR]

Root-knot nematodes (RKNs) are important nematode pests, causing huge economic losses on vegetable crops worldwide. A decline in the yield of Swiss chard (Beta vulgaris L.) which was associated with RKNs was observed on an organic vegetable farm in the Western Cape Province of South Africa. Nematodes were extracted from galled plant roots and identified using molecular tools. PCR-based Sequence Characterised Amplified Region (SCAR) primers was used to confirm the specie of the RKN associated with the infected plants. Thereafter, a pot assay was conducted to determine the response of artificially infected Swiss chard plants to varying concentrations of bio-synthesized silver nanoparticle Ag-NP (1 μg/mL, 2 μg/mL, and 3 μg/mL) under controlled conditions. The results of the study showed that Swiss chard is highly susceptible to M. javanica with an egg-laying-female index of >5 in all infected plants. Significantly lower values (at P=0.05) in egg masses (EM), juveniles (J2s), and reproduction factor (RF) of nematodes were recorded on plants treated with 3 μg/mL, indicating a potential for nematode control. A negative correlation was also observed in the number of egg masses, J2s, and RF of the nematodes with increasing concentrations of the Ag-NP. This study confirms that Swiss chard is highly susceptible to M. javanica and demonstrates the potential nematicidal property of Ag-NP in controlling the nematode pest of Swiss chard. [ABSTRACT FROM AUTHOR]

Root-knot nematodes (RKN; Meloidogyne spp.) are obligatory endoparasites with worldwide distribution which cause severe damage to agricultural crops. The present study aimed to define the nematicidal activity of thymol on different life stages of the root-knot nematode Meloidogyne javanica (Treub) Chitwood, at concentrations of 37.5–1000 μL/L. This study is the first to report the effect of thymol on egg differentiation and also its vapor and sublethal concentration activities. A mortality of greater than 90% of M. javanica second-stage juveniles (J2s) occurred after 96 h of exposure at a concentration of 500 μL/L. At this concentration, thymol inhibited 59.7% of nematode hatching. In addition, the use of thymol at sublethal concentrations reduced the number of females per gram in tomato roots in a pot test, as well as inhibiting egg differentiation. On the contrary, no nematostatic effects were observed in paralysis bioassays. The results presented here indicate that the use of thymol may show its potential as a source of a new sustainable nematicidal product. [ABSTRACT FROM AUTHOR]

Background: In our continuing search for biologically active natural enemies from North of Africa with special reference to Tunisian fungi, our teamwork screened fungi from different ecological habitats in Tunisia. Our previous study on the comparative effectiveness of filamentous fungi in the biocontrol of Meloidogyne javanica, a taxon (Lecanicillium) showed high potentiality against M. javanica. We undertook the present study to evaluate the ability and understand the mechanism of this fungal parasite as a biological control candidate against the root-knot nematode M. javanica. This study used in vitro bioassays with fungal filtrate cultures, scanning electron microscopy (SEM) observation, and isobaric tag for relative and absolute quantitation (iTRAQ) methodology to characterize the biological and molecular features of this fungus. Results: The microscopic and SEM observation revealed that Lecanicillium sp. exhibited exceptional hyperparasitism against M. javanica eggs. The hyphae of this fungi penetrated the eggs, causing destructive damage to the outer eggshell. The exposure to five concentrations of Lecanicillium sp. filtrate cultures showed high inhibition of egg hatching, which increases depending on the exposure time; the best results are recorded at 50%, 75%, and 100% dilutions after seven days of exposure. The SEM observation of nematode-parasitized eggs and juveniles suggests that the production of lytic enzymes degrades the egg cuticle and fungal hyphae penetrate unhatched M.javanica juveniles. Forty-seven unique proteins were identified from the Lecanicillium sp. isolate. These proteins have signalling and stress response functions, bioenergy, metabolism, and protein synthesis and degradation. Conclusion: Collectively, Lecanicillium sp. had ovicidal potentiality proved by SEM and proteomic analysis against root-knot nematode' eggs. This study recommended applying this biological control candidate as a bio-agent on vegetable crops grown in situ. [ABSTRACT FROM AUTHOR]

Antagonistic and non-host plants are some of the main strategies for nematode control, but the reaction of several plant species to these parasites remains to be investigated. This study aimed to evaluate the reaction of buckwheat to Pratylenchus brachyurus and Meloidogyne javanica and to assess the effect of buckwheat aqueous extract on P. brachyurus and M. javanica mortality and M. javanica hatching. Experiments were conducted under greenhouse and laboratory conditions. Treatments consisted of buckwheat 'IPR-92 Altar' and soybean 'M6410 IPRO' inoculated with different levels of P. brachyurus or M. javanica according to each experiment. Buckwheat was found to be a non-host to P. brachyurus. The RF of M. javanica on buckwheat ranged from 1.33 to 4.11, whereas the RF on soybean was 24.00. Buckwheat shoot extracts were effective in promoting nematode mortality and reducing M. javanica hatching. These findings indicate that buckwheat has potential as a cover crop for the control of P. brachyurus, but care is needed when introducing this plant to areas infested with M. javanica. [ABSTRACT FROM AUTHOR]

Nematodes of the Meloidogyne genus are among the main limiting factors of world agricultural productivity. Its management is quite complex and alternative methods such as the use of extracts have been widely studied. This study aimed to evaluate the penetration and development of M. javanica in soybean (Glycine max (L.) Merr.) treated with Ascophyllum nodosum extract and assess this algal product and its nutrient components in nematode management. Experiment 1 comprised five sampling times (5, 10, 15, 20, and 25 d after nematode inoculation) and three application methods (planting hole, foliar spraying, and untreated control). Soybean plants were inoculated with 2000 eggs+second-stage juveniles of M. javanica and treated with algal extract. Total nematode number, number of nematodes per developmental stage, and population density (nematodes g-1 root) were determined. Experiment 2 consisted of 11 treatments: Algal extract, N, K, P, Ca, Mg, Cu, Zn, Mn, Fe, combined nutrients, and untreated control. Soybean crops were evaluated for total nematode number, population density, gall index, plant height, root fresh weight, shoot fresh weight, and shoot dry weight. In Experiment 1, algal extract reduced nematode penetration, regardless of application method. There was a decrease in the total number of nematodes and number of nematode g-1 root by 83% and 56% in the application via furrow and 68% and 70% via foliar application, respectively. In Experiment 2, all nutrient treatments reduced at least one nematode parameter, with P, Ca, Mg, Fe, and combined nutrients (Trial 1) and algal extract, P, Ca, Mg, Cu, Zn, Mn, Fe and combined nutrients (Trial 2) achieving 83% to 95% reductions in population density. Nutrient treatments positively influenced vegetative development, as a 20% increase in height for the nutrients A. nodosum, N, K, P, Ca, Mg, Cu and Fe. Ascophyllum nodosum and its nutrient components have potential in the management of M. javanica in soybean. [ABSTRACT FROM AUTHOR]

Brevundimonas diminuta is broadly distributed in terrestrial and aquatic environments and has various biological activities. In this study, we found that B. diminuta exhibited nematicidal activity against the plant root-knot nematode, Meloidogyne javanica. A total of 42 volatile organic compounds (VOCs) from B. diminuta were identified using gas chromatography–mass spectrometry (GC-MS). The nematicidal activity of the 10 main VOCs was tested against M. javanica. Butyl butanoate (4 µL) caused the mortality of 80.13% of M. javanica after 4 h. The nematicidal activity of an additional 38 butyl-butyrate-like volatile esters was also investigated. Of these, seven had strong nematicidal activity against M. javanica, five of which showed egg-hatching inhibitory activity. This study is the first to report that butyl butanoate, ethyl 2-methylbutanoate, ethyl 4-methylpentanoate, ethyl pent-4-enoate, and methyl undecanoate have nematicidal activity against M. javanica. The results indicated that B. diminuta could serve as a candidate microorganism for the biocontrol of plant root-knot nematodes, showing that volatile esters have great potential as nematicides. [ABSTRACT FROM AUTHOR]