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Plant-parasitic nematodes are a major problem for horticultural production, causing significant economic losses. Chemical nematicides are a common nematode control strategy but can negatively impact the environment and human health. In this review, we provide an overview of the use of fungi for the biological control of plant-parasitic nematodes in horticultural crops. Fungal bio-control represents an alternative, environmentally friendly strategy for managing nematodes. The use of fungi for the bio-control of nematodes has gained increasing attention due to the potential benefits of selectivity, sustainability, and long-term control. Here, we discuss the different types of fungi used for nematode management, the mechanisms of their action, the advantages and limitations of using fungi for bio-control, and the factors affecting their efficacy. Additionally, we provide several case studies of fungal bio-control against root-knot, cyst, and lesion nematodes in horticultural crops. The review concludes with a discussion of future directions and research recommendations for implementing fungal bio-control in horticultural crops. [ABSTRACT FROM AUTHOR]

Background: Meloidogyne incognita is one of the most important plant-parasitic nematodes and causes tremendous losses to the agricultural economy. Light is an important living factor for plants and pathogenic organisms, and sufficient light promotes root-knot nematode infection, but the underlying mechanism is still unclear. Results: Expression level and genetic analyses revealed that the photoreceptor genes PHY, CRY, and PHOT have a negative impact on nematode infection. Interestingly, ELONGATED HYPOCOTYL5 (HY5), a downstream gene involved in the regulation of light signaling, is associated with photoreceptor-mediated negative regulation of root-knot nematode resistance. ChIP and yeast one-hybrid assays supported that HY5 participates in plant-to-root-knot nematode responses by directly binding to the SWEET negative regulatory factors involved in root-knot nematode resistance. Conclusions: This study elucidates the important role of light signaling pathways in plant resistance to nematodes, providing a new perspective for RKN resistance research. [ABSTRACT FROM AUTHOR]

Meloidogyne enterolobii is regarded as one of the most severe and threatening pathogens worldwide. Guava production in India is quenched by the invasion of root-knot nematode, Meloidogyne enterolobii. Bacterial bio-control agents confer resistance against nematodes by producing various bioactive molecules. Exploiting these biomolecules will lead to the development of novel nematicidal formulations for managing plant parasitic nematodes. Considering this, our present investigation was focused on the isolation and identification of endophytic bacterial communities from wild guava Psidium eugeniaefolia. Amongst various endophytes, Bacillus subtilis GEB-1 exhibited a 90% reduction in the population of M. enterolobii. Cell-free supernatant extracts of B. subtilis GEB-1 revealed the presence of seventeen unique biomolecules. Attempts were made to dock these biomolecules against major protein targets of M. enterolobii such as E3 ubiquitin ligase, Neurotransmitter-gated ion-channel, G protein-coupled receptor kinase, Peptidase M12B domain-containing protein, Hyaluronidase through molecular docking techniques. The results of in-silico studies revealed that all seventeen biomolecules had a significant impact on protein targets of M. enterolobii. Among other bacterial metabolites, 2-heptanone and 2,3-butanediol were found to have a greater binding affinity with protein targets of M. enterolobii. Furthermore, the in-vitro evaluation of 2-heptanone and 2,3-butanediol at different concentrations confirmed their nematicidal activity against eggs and second-stage juveniles of M. enterolobii. Hence our present study revealed that bacterial metabolites, 2 heptanone, and 2,3-butanediol can be explored as novel nematicidal molecules against guava root-knot nematodes, M. enterolobii. [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]

The biocontrol agent Pythium oligandrum, which is a member of the phylum Oomycota, can control diseases caused by a taxonomically wide range of plant pathogens, including fungi, bacteria, and oomycetes. However, whether P. oligandrum could control diseases caused by plant root-knot nematodes (RKNs) was unknown. We investigated a recently isolated P. oligandrum strain GAQ1, and the P. oligandrum strain CBS530.74, for the control of an RKN Meloidogyne incognita infection of tomato (Solanum lycopersicum L.). Initially, P. oligandrum culture filtrates were found to be lethal to M. incognita second-stage juveniles (J2s) with up to 84% mortality 24 h after treatment compared to 14% in the control group. Consistent with the lethality to M. incognita J2s, tomato roots treated with P. oligandrum culture filtrates reduced their attraction of nematodes, and the number of nematodes penetrating the roots was reduced by up to 78%. In a greenhouse pot trial, the P. oligandrum GAQ1 inoculation of tomato plants significantly reduced the gall number by 58% in plants infected with M. incognita. Notably, the P. oligandrum GAQ1 mycelial treatment significantly increased tomato plant height (by 36%), weight (by 27%), and root weight (by 48%). A transcriptome analysis of tomato seedling roots inoculated with the P. oligandrum GAQ1 strain identified ~2500 differentially expressed genes. The enriched GO terms and annotations in the up-regulated genes suggested a modulation of the plant hormone-signaling and defense-related pathways in response to P. oligandrum. In conclusion, our results support that P. oligandrum GAQ1 can serve as a potential biocontrol agent for M. incognita control in tomato. Multiple mechanisms appear to contribute to the biocontrol effect, including the direct inhibition of M. incognita, the potential priming of tomato plant defenses, and plant growth promotion. [ABSTRACT FROM AUTHOR]

Plant parasitic nematodes are harmful agricultural pests, causing severe yield losses of a wide range of crops worldwide. The lack of effective nematode management products has increased demand for innovative nematode management tools. This work was conducted to test propolis (bee glue) at different concentrations to control the root-knot nematode (Meloidogyne spp.) under laboratory conditions. A sample of propolis was measured and ethanol solvent (95%) was added and kept at room temperature for 24 h. The nematode eggs were exposed to the propolis extract at different concentrations (i.e., 2000, 4000, and 6000 ppm) for 24, 48, and 72 h. Results showed that propolis extract caused significant decreases in egg hatching, but to varying degrees. There was a gradual decrease in egg hatching with increasing the extract concentration and the duration of exposure. [ABSTRACT FROM AUTHOR]

In Egypt, root knot nematodes (RKN) were shown to be significant plant parasites with a variety of host plants. Under laboratory and greenhouse circumstances, the current study examines the antagonistic effects of four distinct yeast isolates on Meloidogyne spp. egg hatching and larval mortality. In comparison to the control, the results showed that Pichia guilliermondii ATCC 9058 had the highest egg hatching inhibition and larval mortality, which were 93 and 100%, respectively, after 168 hours of exposure. Pichia guilliermondii ATCC 9058 at 4% of soil weight, one-week pre nematode inoculation achieved the highest reduction in nematode parameters including number of galls, egg masses, females, and number of juveniles (J2s)/250g soil, by 89.6, 90, 88.7 and 90%, respectively., followed by S. cerevisiae at 4% of soil weight, one-week pre nematode inoculation application, with 84.4, 88.3, 88.4 and 85.3%, respectively. Used yeast isolates could therefore be a useful biocontrol tool for plant parasitic nematodes. [ABSTRACT FROM AUTHOR]

Nacobbus aberrans is an endophytic parasitic nematode that induces root galls, negatively affecting plant growth and development, and decreasing the production of economically important crops. Currently, low environmental impact alternatives are being developed for the control of nematodes, such as biological control agents, to reduce the use of soil disinfectants. Nematophagous fungi are microorganisms that can suppress nematode reproduction due to different mechanisms, such as parasitism of eggs, toxin production and stimulation of plant growth. The aim of this study was to investigate the effect of inoculation with nematophagous fungi on N. aberrans in greenhouse-grown pepper (Capsicum anuumm L.) plants and to analyze the response of the infected plants. Two fungal isolates, Purpureocillium lilacimum and Pleurotus ostreatus were tested. The plants were inoculated with these fungi at the time of transplantation in the presence and absence of N. aberrans. The reproduction factor of the nematode was 23.17; 5.90 and 36.4 for P. lilacinum, P. ostreatus and control, respectively. Both in plants parasitized and not parasitized by nematodes, the fungi increased the content of soluble proteins and photosynthetic pigments. Additionally, a favorable impact on growth parameters was also observed. This beneficial effect was also verified by a lower accumulation of proline and sugars, metabolites used by plants as osmoregulators in stress situations, and a low accumulation of malondialdehyde, a metabolite resulting from oxidative stress. These results show that both fungi are suitable for use in the biocontrol of N. aberrans and as growth promoters in plants. [ABSTRACT FROM AUTHOR]

The root‐knot nematode Meloidogyne incognita is one of the most damaging plant parasitic nematodes in the world. In this study, the effect of cystatin from Amaranthus hypochondriacus (AhCPI) as a potential control agent for M. incognita was explored. In vitro bioassays demonstrated that AhCPI affects the growth and development of eggs and the infectivity of juveniles (J2) of M. incognita, such as mortality and slower development, showing characteristic tissue damage. Mortality levels were quantified by Probit analysis, estimating LC50s of 1.4 mg/mL for eggs and 0.028 mg/mL for J2. In planta bioassays showed that infected tomato seedlings treated with 0.056 mg/mL of AhCPI showed a 60% reduction in the number of galls, as compared with untreated J2‐inoculated seedlings. Under greenhouse conditions, three applications of 10 mL of AhCPI (1.4 mg/mL) in the soil around the stem of M. incognita‐infected tomato plants, reduced the number of galls by 93 ± 8%, as compared to the control M. incognita‐infected plants. The application of AhCPI to the infected plants increased the yield (10.7%) of harvested tomato fruits, as compared to infected plants. These results show the potential of AhCPI for the control of M. incognita in tomato plants. [ABSTRACT FROM AUTHOR]

Root-knot nematodes (RKN), Meloidogyne spp., are plant-parasitic nematodes that are responsible for considerable economic losses worldwide, because of the damage they cause to numerous plant species and the inadequate biological agents available to combat them. Therefore, developing novel and eco-friendly nematicides is necessary. In the present study, Burkholderia sp. JB-2, isolated from RKN-infested rhizosphere soil in South Korea, was evaluated to determine its nematicidal and plant growth-promoting effects under in vitro and in vivo conditions. Cell-free filtrates of the JB-2 strain showed high levels of nematicidal activity against second-stage juveniles (J2) of M. incognita, with 87.5% mortality following two days of treatment. In addition, the assessment of the activity against other six plant parasitic nematodes (M. javanica, M. hapla, M. arenaria, Ditylenchus destructor, Aphelenchoides subtenuis, and Heterodera trifolii) showed that the cell-free filtrates have a broad nematicidal spectrum. The three defense-responsive (MiMIF-2, MiDaf16-like1, and MiSkn1-like1) genes were activated, while Mi-cm-3 was downregulated when treated with cell-free filtrates of JB-2 cultures on J2. The greenhouse experiments suggested that the cell-free filtrates of the JB-2 strain efficiently controlled the nematode population in soil and egg mass formations of M. incognita in tomato (Solanum lycopersicum L., cv. Rutgers). An improvement in the host plant growth was observed, in which the shoot length and fresh weights of shoots and roots increased. The treatment with 10% of JB-2 cell-free filtrates significantly upregulated the expression levels of plant defenses (SlPR1, SlPR5, and SlPAL) and growth-promoting (ACO1, Exp18, and SlIAA1) genes compared with the corresponding parameters of the control group. Therefore, JB-2 could be a promising candidate for the sustainable management of RKN. [ABSTRACT FROM AUTHOR]

Root-Knot nematodes (RKNs) are one of the major plant pathogens that can substantially reduce plant growth and development. Management of RKNs is one of the major concerns as chemical pesticides pose a potential risk to humans and other life forms and also have toxic effects to environment. There is a need to find out some alternative eco-friendly strategies for management of these parasites. Jasmonic acid (JA) and Spermine (Spm) are those plant growth regulators (PGRs) that have positive effects on plant growth and alleviates toxic effects caused by various stresses including RKNs. Keeping this in mind,present study accessed the potential of these (PGRs), JA and Spm on morphological and biochemical attributes in 45 days old Solanum lycopersicum plants under nematode stress. It was observed that nematode infection resulted in reduced plant growth and photosynthetic pigments. Application of JA and Spm improved growth parameters and photosynthetic pigments. Moreover, tomato plants after JA and Spm supplementation lowered the activities of H 2 O 2, DPPH and MDA thus decreasing nuclear and membrane damage caused by nematode stress. Additionally, enzymatic CAT (Catalase), SOD (Superoxide dismutase), GuPOX (Guaiacol peroxidase), APOX (Ascorbate peroxidase), PPO (Polyphenol oxidase), GST (Glutathione-S-transferase) and non-enzymatic (ascorbic acid, glutathione, and tocopherol) antioxidant levels increased markedly under nematode stress, but application of JA and Spm further improved these attributes. Taken together, the current study demonstrated that JA and Spm are suitable agents for managing nematode stress resistance in tomato plants. [Display omitted] • Tomato plants were inoculated with J2 stage of Meloidogyne incognita. • M.incognita decreased photosynthetic pigments and enhanced stress marker in tomato plants. • Treatment with Jasmonic acid and spermine mitigated nematode stress by enhancing Antioxidant enzymes and gases exchange parameters in tomato plants. [ABSTRACT FROM AUTHOR]

The soil microbiome is crucial for maintaining the sustainability of the agricultural environment. Concerning the role of diverse mycobiomes and their abundance toward the suppression of root-knot nematode (RKN) infection in vegetable crops, our understanding is unclear. To unveil this issue, we examined the fungal microbiome in tomato rhizosphere augmented with bioagents challenged against RKN at taxonomic and functional levels. Composition of the mycobiome in tomato rhizosphere treated with Bacillus velezensis VB7 and Trichoderma koningiopsis TK differed significantly from the infected tomato rhizosphere. The abundance and diversity of fungal species, however, were significantly higher in the combined treatments of bioagents than for individual treatments. Fungal microbiome diversity was negatively correlated in the RKN-associated soil. Network analysis of the fungal biome indicated a larger and complex network of fungal biome diversity in bioagent-treated soil than in nematode-associated tomato rhizosphere. The diversity index represented by that challenging the RKN by drenching with consortia of B. velezensis VB7 and T. koningiopsis TK, or applying them individually, constituted the maximum abundance and richness of the mycobiome compared to the untreated control. Thus, the increased diverse nature and relative abundance of the mycobiome in tomato rhizosphere was mediated through the application of either T. koningiopsis TK or B. velezensis VB7, individually or as a consortium comprising both fungal and bacterial antagonists, which facilitated engineering the community composition of fungal bioagents. This in turn inhibited the infestation of RKN in tomato. It would be interesting to explore further the possibility of combined applications of B. velezensis VB7 and T. koningiopsis TK to manage root-knot nematodes as an integrated approach for managing plant parasitic nematodes at the field level. [ABSTRACT FROM AUTHOR]

Considered one of the most devastating plant parasitic nematodes worldwide, Meloidogyne spp. (commonly known as the root-knot nematodes (RKNs)) are obligate sedentary endoparasites that establish in the roots, causing hyperplasia and hypertrophy of surrounding cells, triggering the formation of galls. These galls will affect root development and physiology, leading to substantial yield losses. During 2017–2022, an extensive survey of Meloidogyne species was undertaken in Portugal (mainland and islands). A total of 1,071 samples were collected by the National Plant Protection Organization (DGAV) and private farmers from different regions of the country and were analysed at the Laboratory of Nematology (NemaINIAV). Samples in which the presence of Meloidogyne sp. was detected were used to perform bioassays to obtain females and juveniles for further studies. Since the accurate identification of RKNs is an important aspect of crop management, morphological and biochemical characterisation was performed. The most common morphological features were observed, showing consistency with previous descriptions of the genus. The biochemical identification using the esterase (EST) phenotype revealed the phenotypes of Meloidogyne arenaria, M enterolobi, M. hispanica, M. hapla, M. incognita, M javanica, and M. luci. Meloidogyne incognita and M. javanica were found to be the most prevalent species in the different regions followed by M. arenaria and M. hapla. This is the first distribution report performed in Portugal on RKNs, contributing to the development of management strategies and to updated information on the status of these pests in Europe. [ABSTRACT FROM AUTHOR]

Tomato is a globally important fruit crop, which is easily susceptible to infection by plant-parasitic nematodes during growth. In this study, selenium nanoparticles were biosynthesized through the selenite reduction pathway in a wild-type Pseudomonas stutzeri BB19 and were characterized by uniform nanostructured needle-like forms with an average size of 95.2 nm. The nematicidal effect of biosynthesized selenium nanoparticles (BioSeNPs) at different concentrations (2, 6, and 10 ppm) during the pre- or post-infection of tomato root-knot nematode (RKN), Meloidogyne incognita, was assessed under greenhouse conditions. The BioSeNPs were applied as a foliar spray or a soil drench, compared to ethoprophos nematicide (100 mL/pot). The results showed that the ethoprophos nematicide significantly reduced the number of galls, egg mass, and eggs/egg mass of M. incognita by 94.2, 92.8, and 49.8%, respectively. BioSeNPs, as foliar sprays, significantly reduced the number of galls in post-treated infected tomato plants at 10 ppm and in pre-treated infected tomato plants at 2 ppm by 91.9 and 91.4%, respectively. Concerning the egg mass, BioSeNPs significantly reduced it in pre-treated infected tomato plants at 2 ppm as a foliar spray by 90.9%. Moreover, BioSeNPs significantly reduced the eggs/egg mass in pre-treated infected tomato plants at 2 ppm as a soil drench by 43.3%. On the other hand, the BioSeNPs considerably improved tomato growth, chlorophyll a and b, carotenoid content, and enzymes (i.e., catalase and peroxidase) activity compared to untreated infected tomato plants (negative control). Hence, the BioSeNPs show a significant application potential as a cost-effective and environmentally friendly biocontrol agent for RKN management in tomato plants. [ABSTRACT FROM AUTHOR]

Root‐knot nematodes (Meloidogyne spp.) are the major group of plant parasitic nematodes impeding the cultivation of fruiting Solanaceous vegetable crops i.e., tomato, pepper, and eggplant worldwide. In the last two decades, significant progress has been achieved in the development of management strategies, however, the management of root-knot nematodes is still a serious concern due to their wide diversity of species and host range. Host plant resistance is the most viable and eco-friendly strategy. The knowledge of the available genetic resources of the cultivated and their related wild species with resistance to root-knot nematodes, gene action, and available molecular markers associated with resistance is crucial for breeding resistant/tolerant varieties/hybrids. With advances in next-generation sequencing technologies, fine mapping and the development of precise markers will aid in accelerated marker-assisted breeding. Recently grafting, which explores resistant rootstocks for managing root-knot nematodes has also been shown to be highly promising in Solanaceous vegetable crops. The current review highlights the present understanding of root-knot nematodes, resistant genetic resources, breeding of rootstocks, and advancements made in traditional and marker-assisted breeding for root-knot nematode resistance in tomato, pepper, and eggplant globally. [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]

Summary: To establish persistent infections in host plants, herbivorous invaders, such as root‐knot nematodes, must rely on effectors for suppressing damage‐induced jasmonate‐dependent host defenses. However, at present, the effector mechanisms targeting the biosynthesis of biologically active jasmonates to avoid adverse host responses are unknown.Using yeast two‐hybrid, in planta co‐immunoprecipitation, and mutant analyses, we identified 12‐oxophytodienoate reductase 2 (OPR2) as an important host target of the stylet‐secreted effector MiMSP32 of the root‐knot nematode Meloidogyne incognita. MiMSP32 has no informative sequence similarities with other functionally annotated genes but was selected for the discovery of novel effector mechanisms based on evidence of positive, diversifying selection.OPR2 catalyzes the conversion of a derivative of 12‐oxophytodienoate to jasmonic acid (JA) and operates parallel to 12‐oxophytodienoate reductase 3 (OPR3), which controls the main pathway in the biosynthesis of jasmonates. We show that MiMSP32 targets OPR2 to promote parasitism of M. incognita in host plants independent of OPR3‐mediated JA biosynthesis.Artificially manipulating the conversion of the 12‐oxophytodienoate by OPRs increases susceptibility to multiple unrelated plant invaders. Our study is the first to shed light on a novel effector mechanism targeting this process to regulate the susceptibility of host plants. [ABSTRACT FROM AUTHOR]

Background: Root-knot nematodes (RKN) are among the most important root-damaging plant-parasitic nematodes, causing severe crop losses worldwide. The plant rhizosphere and root endosphere contain rich and diverse bacterial communities. However, little is known about how RKN and root bacteria interact to impact parasitism and plant health. Determining the keystone microbial taxa and their functional contributions to plant health and RKN development is important for understanding RKN parasitism and developing efficient biological control strategies in agriculture. Results: The analyses of rhizosphere and root endosphere microbiota of plants with and without RKN showed that host species, developmental stage, ecological niche, and nematode parasitism, as well as most of their interactions, contributed significantly to variations in root-associated microbiota. Compared with healthy tomato plants at different developmental stages, significant enrichments of bacteria belonging to Rhizobiales, Betaproteobacteriales, and Rhodobacterales were observed in the endophytic microbiota of nematode-parasitized root samples. Functional pathways related to bacterial pathogenesis and biological nitrogen fixation were significantly enriched in nematode-parasitized plants. In addition, we observed significant enrichments of the nifH gene and NifH protein, the key gene/enzyme involved in biological nitrogen fixation, within nematode-parasitized roots, consistent with a potential functional contribution of nitrogen-fixing bacteria to nematode parasitism. Data from a further assay showed that soil nitrogen amendment could reduce both endophytic nitrogen-fixing bacteria and RKN prevalence and galling in tomato plants. Conclusions: Results demonstrated that (1) community variation and assembly of root endophytic microbiota were significantly affected by RKN parasitism; (2) a taxonomic and functional association was found for endophytic nitrogen-fixing bacteria and nematode parasitism; and (3) the change of nitrogen-fixing bacterial communities through the addition of nitrogen fertilizers could affect the occurrence of RKN. Our results provide new insights into interactions among endophytic microbiota, RKN, and plants, contributing to the potential development of novel management strategies against RKN. -jDL8NUj-q41CTzHNcAR Video Abstract [ABSTRACT FROM AUTHOR]

The use of green nano-amendments is a promising approach for improving soil health and providing sustainable options to reduce root-knot nematodes (RKN) and thus increase yields. Therefore, the purpose of this research was to identify the characteristics of nano-amendments such as nanobiochar (nB), green nanobiochar (GnB), and magnetic nanobiochar (MnB) and their effect on the root-knot nematodes and tomato yield at levels of 3 and 6 mg kg−1 in sandy loam soil. The results showed that the GnB and MnB contain many functional groups (such as O-H, C=C, S-H, H-C=O, C-O, and H–O–H) and minerals (such as magnetite, ferrous sulfate monohydrate, and quartz), and they also had an elevated specific surface area. The application of the investigated soil nano-amendments significantly increased soil organic matter (OM) and microbial biomass carbon (MBC) and decreased the root-knot nematodes, playing a major role in increasing tomato growth. The highest significant values of OM and MBC were found in the soil amended by GnB at 6 mg kg−1, with increases of 84.7% and 71.5% as compared to the control, respectively. GnB6 significantly decreased the number of root galls, the egg mass, and number of nematodes per 250 cm3 soil by 77.67, 88.65, and 74.46%, respectively, compared to the control. Green nanobiochar was more efficient in accelerating the growth and yield components of the tomato plant. The addition of GnB is an effective strategy and an environmentally friendly technology to control plant parasitic nematodes and increase tomato yield. Therefore, the results recommend adding GnB at a rate of 6 mg kg−1 in sandy loam soil. [ABSTRACT FROM AUTHOR]

Root-knot nematode disease occurs frequently due to continuous monocropping and excessive water and nitrogen input. The disease degree and gall index are often used to evaluate the damage of root-knot disease. However, the weak correlation between these two indicators to tobacco leaf dry weight has often been reported. The objective of this study was to verify whether the use of the root-knot density (RKD)—the root-knot number per unit root weight or volume—as a new indicator could describe the damage of root-knot disease to tobacco growth and yield quantitatively. A total of 3000 tobacco plants from 60 independent plots were classified according to the damage symptom of leaves in situ. A total of 6 plants in each plot were selected and sampled to represent six damage levels in a total of 360 plants. The responding roots were taken out with a root auger. The dry weight of the leaves, stems, roots and root knots as well as the root volume, root-knot number and volume, disease degree, and gall index were determined for all 360 plants separately. Our results showed that: (1) the disease degree and gall index of the root-knot nematodes had a weak negative correlation with the tobacco leaf dry weight while the leaf dry weight and the dry weight, volume, and number of root knots were not correlated; (2) the root dry weight, volume, and length of roots with a diameter ≥2 mm were significantly positively correlated with the leaf dry weight; (3) the RKD of roots with a diameter ≥2 mm was significantly negatively correlated with the leaf dry weight; and (4) the dry weight of the leaves, stems, and roots decreased significantly with the increase in the average RKD of roots with a diameter ≥2 mm in the reclassified groups, which was significantly positively correlated with the average reclassified disease degree and gall index. Our results highlighted that the proposed RKD in this paper can be used to evaluate the damage degree of root-knot disease quantitatively as a new indicator in future research and the practical diagnosis of root-knot nematodes. [ABSTRACT FROM AUTHOR]

Summary: Problems with plant-parasitic nematodes remain a major challenge in most field vegetable crops worldwide. In agricultural fields in Belgium, these problems have increased in recent years. A major problem is the quarantine root-knot nematode Meloidogyne chitwoodi. The host plant status of the most commonly grown cultivars of spinach (Spinacia oleracea) and the damage threshold for M. chitwoodi were determined in a climate-controlled glasshouse and in a naturally infested field. The yield data with the final population densities were fitted to Seinhorst's yield and population dynamic models, respectively. The damage threshold values (T) for the relative fresh weight yield were 0.14, 1.08, 11.53 J2 (100 cm3 soil)−1, minimum yield (m) of 0.84, 0.64, 0.52 and maximum yield ( Y max ) of 12.51, 12.44 and 9.60 for 'Gnu', 'Meerkat' and 'Whale' spinach cultivars, respectively. The maximum multiplication rates (a) were 3.81, 2.38 and 2.72, whilst the maximum population densities (M) were 563, 916, and 922 J2 (100 cm3 soil)−1 for 'Gnu', 'Meerkat' and 'Whale', respectively. Meloidogyne chitwoodi had an impact on the spinach yield. The higher the nematode density the lower the yield and vice versa. The tested cultivars were all hosts for M. chitwoodi but differences between cultivars occurred. 'Kolibri' and 'Rhino' were tested as the least sensitive cultivars for M. chitwoodi during the host screening test and bring opportunities for resistance breeding. This is the first report of spinach as a host for M. chitwoodi. [ABSTRACT FROM AUTHOR]

Root-knot nematodes possess a major threat to agricultural production of various crops worldwide. The intensive use of chemical nematicides to control plant parasitic nematodes has adverse effects on our environment and human health. Owing to the importance of developing new strategies, an experiment was conducted to reveal the influence of arbuscular mycorrhizal fungus, Rhizoglomus fasciculatum and nematophagous fungus, Paecilomyces lilacinus alone or in combination with various organic amendments such as superphosphate, green and organic manure to control the infection of root-knot, nematode Meloidogyne incognita in a vegetable crop Capsicum annuum. These two fungi along with soil amendments significantly improved plant growth and fruit yield and effectively controlled infection of M. incognita. The dual inoculation of P. lilacinus and R. fasciculatum reduced the number of galls and egg masses, thereby revealing the controlled proliferation of M. incognita infection in C. annuum roots. The beneficial effect of these fungi further increased on supplementation of soil with organic or green manures. Inoculation of C. annuum with these two fungi showed a significant increase in egg parasitization; however, maximum effect was detected on dual inoculation. Amongst the soil amendments, the best response was obtained in case of green manure along with mycorrhizal fungus and P. lilacinus. Present study revealed that nematophagous and AM fungi, in combination with green manure were effective in controlling M. incognita, thus suggesting the use of such agents for biocontrol of plant parasitic nematodes in agriculture. [ABSTRACT FROM AUTHOR]

The pathogenic potential of Beauveria bassiana (bals.) Vuill was explored against Meloidogyne incognita (Kofoid and White) Chitwood under laboratory condition using conidial suspensions @ 2.6×106 conidia/mL (1x) with further dilutions. The mortality and inhibition of root-knot nematode eggs hatching were directly proportional to the concentration of B. bassiana culture filtrates. No egg hatching was observed at 1x (original concentration). There was a spike in eggs hatching with the increase in dilutions. The mortality of J2 and inhibition of hatching of the nematode species were also directly proportional to the concentration of culture filtrate of B. bassiana. Soil drenching with culture filtrate of B. bassiana significantly reduced the population of nematodes in the soil and gall formation in tomato plants under pot conditions. [ABSTRACT FROM AUTHOR]

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Copyright of Egyptian Journal of Agronematology is the property of Egyptian Society for Agronematology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Plant parasitic nematodes are highly abundant in all agrosystems and some species can have a major impact on crop yields. To avoid the use of chemical agents and to find alternative methods to manage these pests, research studies have mainly focused on plant resistance genes and biocontrol methods involving host plants or natural enemies. A specific alternative method may consist in supporting non-damaging indigenous species that could compete with damaging introduced species to decrease and keep their abundance at low level. For this purpose, knowledge about the biodiversity, structure and functioning of these indigenous communities is needed in order to carry out better risk assessments and to develop possible future management strategies. Here, we investigated 35 root crop fields in eight regions over two consecutive years. The aims were to describe plant parasitic nematode diversity and to assess the potential effects of cultivation practices and environmental variables on communities. Community biodiversity included 10 taxa of plant parasitic nematodes. Despite no significant abundance variations between the two sampling years, structures of communities varied among the different regions. Metadata collected for the past six years, characterizing the cultural practices and soils properties, made it possible to evaluate the impact of these variables both on the whole community and on each taxon separately. Our results suggest that, at a large scale, many variables drive the structuration of the communities. Soil variables, but also rainfall, explain the population density variations among the geographical areas. The effect of the variables differed among the taxa, but fields with few herbicide applications and being pH neutral with low heavy metal and nitrogen concentrations had the highest plant parasitic nematode densities. We discuss how these variables can affect nematode communities either directly or indirectly. These types of studies can help to better understand the variables driving the nematode communities structuration in order to support the abundance of indigenous non-damaging communities that could compete with the invasive species. [ABSTRACT FROM AUTHOR]

New data on the effect of colloidal silicon nanoparticles on the content of nutrients and photosynthetic pigments in tomato plants invaded by root-knot nematode Meloidogyne incognita are presented. Foliar treatment of plants with colloidal solutions of silicon nanoparticles at concentrations of 0.5 and 1.0 μg/mL revealed an increase in the content of photosynthetic pigments and a number of biogenic elements (P, Mg, K, S, and Fe) in tomato leaves, indicating an improvement in the physiological state of the invaded plants. The stimulating effect of nanosilicon on the development and growth of plants and the inhibiting effect on the susceptibility of plants by nematodes and the morpho-physiological parameters of the parasite is shown. [ABSTRACT FROM AUTHOR]

Plant parasitic root‐knot nematodes (RKN) such as Meloidogyne incognita cause significant crop losses worldwide. Although RKN are polyphagous, with wide host ranges, races with differing host compatibilities have evolved. Associations between genotype and infection phenotype in M. incognita have not yet been discovered. In this study, 48 M. incognita isolates were collected from geographically diverse fields in Japan and their genomes sequenced. The isolates exhibited various infection compatibilities to five sweetpotato (SP) cultivars and were assigned to SP races. Genome‐wide association analysis identified 743 SNPs affecting gene coding sequences, a large number of which (575) were located on a single 1 Mb region. To examine how this polymorphic region evolved, nucleotide diversity (Pi) was scanned at the whole genome scale. The SNP‐rich 1 Mb region exhibited high Pi values and was clearly associated with the SP races. SP1 and 2 races showed high Pi values in this region whereas the Pi values of SP3, 4, and 6 were low. Principal component analysis of isolates from this study and globally collected isolates showed selective divergence in this 1 Mb region. Our results suggest for the first time that the host could be a key determining factor stimulating the genomic divergence of M. incognita. [ABSTRACT FROM AUTHOR]

The southern root-knot nematode (RKN), Meloidogyne incognita (Kofoid & White) Chitwood, is one of most destructive species of plant parasitic nematodes, causing significant economic losses to numerous crops including cucumber (Cucumis sativus L. 2n = 14). No commercial cultivar is currently available with resistance to RKN, severely hindering the genetic improvement of RKN resistance in cucumber. An introgression line, IL10-1, derived from the interspecific hybridization between the wild species Cucumis hystrix Chakr. (2n = 24, HH) and cucumber, was identified with resistance to RKN. In this study, an ultrahigh-density genetic linkage bin-map, composed of high-quality single-nucleotide polymorphisms (SNPs), was constructed based on low-coverage sequences of the F2:6 recombinant inbred lines derived from the cross between inbred line IL10-1 and cultivar 'Beijingjietou' CC3 (hereinafter referred to as CC3). Three QTLs were identified accounting for 13.36% (qRKN1-1), 9.07% and 9.58% (qRKN5-1 and qRKN5-2) of the resistance variation, respectively. Finally, four genes with nonsynonymous SNPs from chromosome 5 were speculated to be the candidate RKN-resistant related genes, with annotation involved in disease resistance. Though several gaps still exist on the bin-map, our results could potentially be used in breeding programs and establish an understanding of the associated mechanisms underlying RKN resistance in cucumber. [ABSTRACT FROM AUTHOR]

A study of the processes of lipid peroxidation and the activity of the peroxidase enzyme, as well as photosynthetic pigments in susceptible tomato plants treated with salicylic acid (SA), during infection with the root-knot nematode Meloidogyneincognita. It was shown that, in the roots of SA-treated plants, the activity of lipid peroxidation is higher compared to the untreated plants, especially in the case of nematode invasion. A significant increase in the activity of lipid peroxidation in SA-treated invasive plants compared with untreated was noted during the transition of larvae to the sedentary stage and the beginning of the formation of feeding areas—giant cells (3–5 days after invasion). This, apparently, contributes to the inhibition of the development of the parasite and the reduction of plant infection and also indicates the involvement of oxidative processes in the mechanism of the induced resistance of plants to root-knot nematodes. In the SA-treated plants, the qualitative and quantitative composition of photosynthetic pigments, disturbed by invasion, was restored and corresponded to the control level. [ABSTRACT FROM AUTHOR]

Copyright of Egyptian Journal of Agronematology is the property of Egyptian Society for Agronematology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Plant parasitic root-knot nematodes (RKN) have evolved sophisticated strategies for exploiting plants, and they cause devastating yield losses in many susceptible crops. The RKN Meloidogyne arenaria is the most predominant pathogenic nematode affecting cultivated peanut (Arachis hypogaea L.). Resistance against the M. arenaria has been identified in the wild peanut relative, Arachis stenosperma. Transcriptome studies on A. stenosperma–M. arenaria interaction revealed candidate genes potentially involved in the first stages of this resistance response, including a temperature-induced lipocalin (TIL) protein. Plant TILs have a protective role against harmful molecules produced in response to a number of stresses. In this study, the characterization of the RKN-responsive TIL from A. stenosperma (AsTIL) provides new insights into the role of plant lipocalins in nematode resistance. The AsTIL gene has a 2-exon/1-intron structure and encodes a 21.4 kDa polypeptide. It contains three structurally conserved regions, which are a signature for plant lipocalins. Overexpression of AsTIL in transgenic hairy roots from a susceptible peanut cultivar led to the reduction of M. arenaria galls and egg masses 60 days after inoculation. This is the first report of a possible involvement of plant lipocalins in RKN resistance. It also reveals a promising candidate gene for peanut breeding to produce cultivars resistant to M. arenaria. [ABSTRACT FROM AUTHOR]

Fusarium wilt [caused by the fungus Fusarium oxysporum f. sp. niveum (FON)] has been a consistent problem in watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] production worldwide. One method for combatting this pathogen in the field is to graft a susceptible, high-yielding scion on to a fusarium wilt-resistant rootstock. A concerning issue with rootstocks resistant to fusarium wilt is that they have not been tested for their susceptibility to plant pathogenic nematodes--specifically, root-knot nematodes (RKNs; Meloidogyne spp.) and the reniform nematode (Rotylenchulus reniformis). Preliminary findings have demonstrated that many of these Fusariumresistant rootstocks are highly susceptible to RKNs. Research was conducted during the Spring and Fall 2015 and 2016 to evaluate the resistance to RKN and reniform nematode in rootstocks with known resistance to fusarium wilt. Six rootstocks were evaluated over the course of four experiments. A nematode-susceptible interspecific hybrid [Cucurbitamaxima (Duchesne)×C.moschata (Duchesne)] rootstock 'Carnivor' was included as a susceptible control in both years. Results demonstrated that several Citrullus lanatus var. citroides (L.H. Bailey) rootstocks ('Carolina Strongback', USVL246-FR2, USVL252-FR2, and USVL-360) and 'SP-6' (a commercially available pollinizer cultivar) exhibited resistance to plant parasitic nematodes when compared with the susceptible control. Partial resistance was observed in USVL-482351. When compared with the control, these rootstocks also had fewer Meloidogyne spp. and R. reniformis in root tissue. These findings indicate that rootstocks may be available to manage both fusarium wilt and RKN in grafted cucurbit production system. [ABSTRACT FROM AUTHOR]

A critical factor in alleviating nematode menace in horticultural crops is discerning the nature of microbial communities associated with roots and rhizosphere. Root-knot nematodes (Meloidogyne spp.) are one of the major constraints for obtaining high yields of vegetable crops. Root-knot nematode-infected and uninfected plants occur in agricultural fields. Most biocontrol strategies used for nematode management focus on introducing a single bioagent. Recently, microbiome transplant has been found effective in curing human diseases and is also used to cure animals. Here we evaluated the role played by the microbial communities in managing M. incognita infection on tomatoes grown in protected cultivation by transplanting the microbial slurry extracted from the rhizosphere soil of the healthy plants and those infected with the root-knot nematode. The relative abundance of Gram-negative bacteria (11.11 % and 16.08 %) and anaerobes (39.58 % and 16.59 %) phospholipid fatty acids (PLFA) was significantly higher in healthy roots and rhizosphere soil. In contrast, Gram-positive bacteria (21.52 % and 37.61 %) were comparatively higher in nematode-infected roots and rhizosphere soil. Nematode penetration and reproduction indices were significantly reduced (34–43 %) by inoculating the healthy plant's unfiltered microbial slurry. However, inoculation with unfiltered microbial slurry from the rhizosphere soil of infected plants increased (8–26 %) nematode penetration and reproduction. Plant growth and fruit yield (13.1 %) of tomatoes were positively influenced by unfiltered microbial slurry from the rhizosphere soil of healthy plants. The significant role of the healthy microbiome transplant in reducing nematode invasion and reproduction and increasing the crop yield of tomatoes grown in protected cultivation suggests that microbial transplants could be an approach to managing plant nematodes. [Display omitted] • Protected structures have both healthy & root-knot infected tomato plants. • Microbial communities differ in healthy & root-knot infected tomato plants. • The rhizosphere microbiota of healthy plants suppresses nematodes. • Plant growth & fruit yields elevate with healthy-rhizosphere microbiome transplant. • Microbiome transplant reduces nematode severity in tomatoes. [ABSTRACT FROM AUTHOR]

Plant-parasitic root-knot nematodes induce the formation of giant cells within the plant root, and it has been recognized that auxin accumulates in these feeding sites. Here, we studied the role of the auxin transport system governed by AUX1/LAX3 influx proteins and different PIN efflux proteins during feeding site development in Arabidopsis thaliana roots. Data generated via promoter-reporter line and protein localization analyses evoke a model in which auxin is being imported at the basipetal side of the feeding site by the concerted action of the influx proteins AUX1 and LAX3, and the efflux protein PIN3. Mutants in auxin influx proteins AUX1 and LAX3 bear significantly fewer and smaller galls, revealing that auxin import into the feeding sites is needed for their development and expansion. The feeding site development in auxin export (PIN) mutants was only slightly hampered. Expression of some PINs appears to be suppressed in galls, probably to prevent auxin drainage. Nevertheless, a functional PIN4 gene seems to be a prerequisite for proper nematode development and gall expansion, most likely by removing excessive auxin to stabilize the hormone level in the feeding site. Our data also indicate a role of local auxin peaks in nematode attraction towards the root. [ABSTRACT FROM AUTHOR]

Linked and/or gene-based molecular markers have been used widely in markerassisted selection (MAS) to differentiate resistant and susceptible genotypes. Resistance to Meloidogyne spp. in Beta vulgaris L. is mediated by a single dominant gene (R6m-1). Using allele-specific primers (ASPs), an SNP marker harboring a single nucleotide polymorphism (A/G), linked to the resistance gene was developed to differentiate resistant genotypes. The differentiation among the resistant and susceptible genotypes was elucidated in the polymorphic bands of 555, 478 and 124 bp in size, using PCR amplification. The genotyping data using the SNP marker was firmly associated with the bioassay evaluation in the greenhouse for 100 sugar beet genotypes. This data indicated that the present robust marker allowed reliable, sensitive, faster, and cheaper large scale screening of B. vulgaris genotypes for nematode resistance breeding programs. [ABSTRACT FROM AUTHOR]

Abstract: The nematode trapping ability of nematophagous fungi Dactylaria brochopaga and Monacrosporium eudermatum to colonize tomato root and parasitize and kill root-knot nematode Meloidogyne incognita was evaluated, along with the capability of the fungi to induce the accumulation of defence-related biomolecules in tomato plants under the greenhouse and field conditions. Co-inoculation of D. brochopaga Dp-5 and M. eudermatum Mv-1 significantly reduced root-knot disease in tomato (89.63%) and increased the accumulation of total chlorophyll (125.34, 140.53 and 152.67 mg g−1 fresh wt.), total phenolic compounds (TPC) (37.40, 48.32 and 59.63 μg of gallic acid equivalent), and phenylalanine ammonia lyase (PAL) activity (58.45, 69.05 and 74.57 mM cinnamic acid h−1 g−1 fresh wt.) after 10, 20 and 30 days of inoculation, respectively, in the greenhouse. However, in the field experiments, the total chlorophyll content in leaves of M. incognita infected tomato plants co-inoculated with D. brochopaga Dp-5 and M. eudermatum Mv-1 (152.70 mg g−1 fresh wt.) was higher than the plants treated with D. brochopaga Dp-5 or M. eudermatum Mv-1 individually (130.87 and 144.73 mg g−1 fresh wt., respectively) and M. incognita treated plants (19.47 mg g−1 fresh wt.). TPC and PAL activity were found to be higher in tomato leaves co-inoculated with D. brochopaga Dp-5 and M. eudermatum Mv-1 (62.90 μg of gallic acid equivalent and 79.33 mM cinnamic acid h−1 g−1 fresh wt., respectively) than the plants treated with D. brochopaga Dp-5 or M. eudermatum Mv-1 individually, whereas in M. incognita inoculated and control plants, the induction of these two compounds was found to be very low after 30 days of inoculation. The results of this study showed that these fungi reduced root-knot disease and enhanced accumulation of defence related biomolecules in tomato plants and has potential to serve as a biocontrol agents against root-knot nematodes. [Copyright &y& Elsevier]

Parasitic nematodes are widespread in Musa cropping systems in African lowlands where they are known to limit crop production. However, their distribution is very poorly known in the large parts of the East African Highland banana ecology. We carried out a survey in 188 fields in Rwanda to assess and understand nematode occurrence and damage under a wide range of agroecological conditions. Altitude varied from 900 to 1800 m above sea level and soil types were distinctly different in the five eco-regions sampled and derived from diverse parent materials; i.e., Ruhengeri (Andosol), Gitarama-Butare (Acrisol), Kibungo (Nitisol), Gashonga (Ferralsol) and Bugarama (Fluvisol and Vertisol). Crop management practices, root health parameters and nematode infection in roots were recorded for a single East African highland banana cultivar (Intuntu, AAA-EA). Plant-parasitic nematodes from five genera were identified: Pratylenchus goodeyi, Helicotylenchus multicinctus, Meloidogyne spp., Radopholus similis and Hoplolaimus pararobustus. Pratylenchus goodeyi was the dominant species in all eco-regions except in Bugarama (lowland). Only the presence of P. goodeyi significantly correlated with root necroses. Altitude was strongly correlated with root densities of P. goodeyi and R. similis. A possible negative impact by P. goodeyi on banana yields was masked by the fact that nematode populations were positively correlated with high plant density and/or mulching practices, which led to relatively high plant vigour irrespective of soil type. Therefore, controlled field experiments will be needed to assess whether root necrosis caused by P. goodeyi at high altitude (>1400 m) actually has a detrimental impact on banana yields, similar to that observed for root-lesion nematodes at lower altitudes. [ABSTRACT FROM AUTHOR]

Nematode-suppressive soils are characterized by the ability of soil microbial communities to reduce populations of plant-parasitic nematodes (PPN) either directly or by inducing systemic resistance in plants. Various microorganisms have been recognized as antagonists of PPN in suppressive soils using culture-dependent and culture-independent methods. However, the associations that PPN form with microorganisms in nematode-conducive soils have been poorly studied. Here we drenched tomato rhizospheres with microbial suspensions from nine different soils and followed their effects on plant growth and root invasion of the infective second-stage juveniles (J2) of the northern root-knot nematode species Meloidogyne hapla. Based on the number of invaded J2, four soils were determined as nematode-suppressive, while five soils were categorized as nematode-conducive. To reveal bacteria attached to the J2 cuticle in soils with varying suppressiveness, we incubated J2 in suspensions from three suppressive and three conducive soils, and analyzed J2-attached bacteria using amplicon sequencing of the V3-V4 region of 16S rRNA gene. Our results suggest that the soil origin had a major effect on the composition of J2-attached bacteria, while the highest bacterial abundance and richness were observed on J2 from two suppressive soils. In addition, the highest number of indicator amplicon sequence variants (ASVs) was associated with J2 in two suppressive soils, but they had a very distinct bacterial profile. Further studies are needed to resolve the complexity of nemato-microbial interactions in soil and to determine the exact function of nematode-attached microorganisms in suppressive and conducive soils and their role in nematode suppression and protection. [Display omitted] • Microbiomes from nine soils uniquely affected root invasion by Meloidogyne hapla J2. • J2 attached different bacteria upon incubation in suppressive and conducive soils. • Soil origin had a major effect on the composition of J2-attached bacteria. • Higher bacterial diversity and richness were found on J2 from suppressive soils. [ABSTRACT FROM AUTHOR]

The molecular events underlying the resistance of Upland cotton ( Gossypium hirsutum L.) to the root-knot nematode (RKN) are largely unknown. In this report, we further characterize the previously identified MIC3 gene including the identification of 14 related MIC cDNAs in nematode-infected roots of allotetraploid cotton that show >85% identity with MIC3. A time-course analysis of RKN infection in resistant and susceptible cotton lines showed that maximum MIC transcript accumulation occurred immediately prior to the phenotypic manifestation of resistance. MIC expression was not induced by mechanical wounding or by virulent reniform nematode infection. MIC expression was undetectable in cotton leaves undergoing a hypersensitive response to Xanthomonas campestris. A time-course analysis of defense gene expression ( PR10, ERF5, CDNS, LOX1, POD4, POD8) in resistant and susceptible cotton roots showed that RKN infection specifically elicits the induction of MIC in resistant roots and not other common defense-signaling pathways. These results suggest that cotton resistance to RKN involves novel defense-signaling pathways and further supports the idea that the MIC genes are intimately involved in this resistance response and represent a group of root-specific defense-related genes in cotton. [ABSTRACT FROM AUTHOR]

Plant-parasitic nematodes are important pests of horticultural crops grown in tropical and subtropical regions of Australia. Burrowing nematode (Radopholus similis) is a major impediment to banana production and root-knot nematodes (predominantly Meloidogyne javanica and M. incognita) cause problems on pineapple and a range of annual vegetables, including tomato, capsicum, zucchini, watermelon, rockmelon, potato and sweet potato. In the early 1990s, nematode control in these industries was largely achieved with chemicals, with methyl bromide widely used on some subtropical vegetable crops, ethylene dibromide applied routinely to pineapples and non-volatile nematicides such as fenamiphos applied up to four times a year in banana plantations. This paper discusses the research and extension work done over the last 15 years to introduce an integrated pest management approach to nematode control in tropical and subtropical horticulture. It then discusses various components of current integrated pest management programs, including crop rotation, nematode monitoring, clean planting material, organic amendments, farming systems to enhance biological suppression of nematodes and judicious use of nematicides. Finally, options for improving current management practices are considered. [ABSTRACT FROM AUTHOR]

The non-pathogenic endophytic Fusarium oxysporum strain 162 (FO162) has been selected for its capacity to reduce root-knot nematode galling on tomato. The objectives of this study were to investigate the influence of this fungus on invasion of tomato roots by Meloidogyne incognita. The number of M. incognita that invaded roots of plants treated with FO162 was significantly lower (reductions of 36.0-55.9%) than in the non-treated controls in linked twin-pot chambers. The results demonstrated that colonisation of the roots by FO162 affects the number of M. incognita that penetrate the roots. The results of a choice test in the absence of a plant indicated that the tomato root exudates collected from plants colonised by FO162 are either less attractive or they exude substances that have repellent activity toward M. incognita juveniles. [ABSTRACT FROM AUTHOR]

An obligate parasite bacterium of the root-knot nematode, Pasteuria penetrans strain P10, isolated from Meloidogyne incognita females on banana roots in Imperatriz Maranhão State, Brazil, was evaluated in glasshouse conditions, using two doses of a dry root bionematicide (107 endospores (5.0 g/seedling) and 106 endospores (0.5 g/seedling)) on seedlings of cv. Mundo Novo coffee. The soil in which coffee seedlings were raised was inoculated previously with these two doses of P. penetrans and after 2 months the plants were transferred to soils of different textures: clay-sandy soil (38% clay, 2% silt and 60% sand) and sandy soil (17% clay, 0% silt and 83% sand). When the coffee plants were 30 cm high, they were inoculated with 20 000 eggs/plant of M. incognita race 1. The coffee plants were examined 8, 16 and 24 months after nematode plant infestation. The effectiveness of the biological control was determined by the reduction of nematode reproduction factor, which ranged from 62 to 67% in clay-sandy soil and 80 to 85% in sandy soil. The mechanism of suppression caused by the bacterium was evaluated by the percentage of infected second-stage juveniles (J2), number of endospores attached/J2 and number of infected females. The high levels of suppression were related to time, increasing from 8 to 24 months, and to the percentage of sand in the soil. [ABSTRACT FROM AUTHOR]

The article presents the summaries of several research regarding plant diseases. They include "The Incidence of Root-Knot Nematodes Meloidogyne arenaria, M. incognita, and M. javanica on Vegetables and Weeds in Montenegro," "Impatients necrotic spot virus and Tomato spotted wilt virus Diagnosed in Phalaeonopsis Orchids from Two Florida Nurseries," and "Momordica charantia is a Weed Host Reservior for Papaya ringspot virus Type P in Jamaica." Meanwhile, the authors, the references and the date of publication of each research are also presented in the article.

Root-knot nematodes ( Meloidogyne spp.) are obligate, sedentary endoparasites that infect many plant species causing large economic losses worldwide. Available nematicides are being banned due to their toxicity or ozone-depleting properties and alternative control strategies are urgently required. We have produced transgenic tobacco ( Nicotiana tabacum) plants expressing different dsRNA hairpin structures targeting a root-knot nematode ( Meloidogyne javanica) putative transcription factor, MjTis11. We provide evidence that MjTis11 was consistently silenced in nematodes feeding on the roots of transgenic plants. The observed silencing was specific for MjTis11, with other sequence-unrelated genes being unaffected in the nematodes. Those transgenic plants able to induce silencing of MjTis11, also showed the presence of small interfering RNAs. Even though down-regulation of MjTis11 did not result in a lethal phenotype, this study demonstrates the feasibility of silencing root-knot nematode genes by expressing dsRNA in the host plant. Host-delivered RNA interference-triggered (HD-RNAi) silencing of parasite genes provides a novel disease resistance strategy with wide biotechnological applications. The potential of HD-RNAi is not restricted to parasitic nematodes but could be adapted to control other plant-feeding pests. [ABSTRACT FROM AUTHOR]

Cotton breeding for resistance to root-knot nematode (RKN) [Meloidogyne incognita (Kofoid and White) Chitwood] is hindered by the lack of convenient and reliable screening methods for resistant plants. The identification of molecular markers closely linked to RKN resistance will facilitate the development of RKN resistant cultivars through marker-assisted selection (MAS). Our objective was to identify and develop new DNA markers that are associated with RKN resistance in cotton. Using three pairs of nearisogenic (NIL) resistant (R) and susceptible (S) lines, two AFLP markers, two RAPD markers, and three RGA markers were identified to be polymorphic between the NIL-R and NIL-S lines. One RAPD marker was converted into a sequence-tagged site (STS) marker. In an F2 population of ‘ST 474’ × ‘Auburn 634 RNR’, the two RAPD markers and the STS marker were mapped to the same linkage group containing several markers that were previously reported to be linked with the RKN resistance gene rknl on chromosome 11 in ‘Acala NemX’. All these markers were found to be associated with a major RKN resistance gene, presumably Mi2 in the resistant line Auburn 634 RNR, suggesting that rknl and Mi2 are either allelic or closely linked. In addition, no susceptible recombinants were found in a resistance screen of 200 F2 plants from the cross Acala NemX × Auburn 634 RNR. The utility of the two RAPD markers and the converted STS marker were evaluated using 23 R and 8 S germplasm lines. The RAPD and STS markers, along with other previously reported markers associated with RKN resistance will be useful in germplasm screening, MAS for RKN resistance, and map-based cloning for RKN resistance genes. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the effects of Hirsutella minnesotensis (Hm), an endoparasitic fungus, and N-Viro Soil® (NVS), a recycled municipal biosolid, on Meloidogyne hapla greenhouse populations from Rhode Island (RI), Connecticut (CT), Geneva, New York (NYG), Lyndonville, New York (NYL), and Michigan (MI). In a greenhouse experiment, tomato (cv. Rutgers) seedlings were inoculated with 0 or 600 eggs of each nematode population and exposed to Hm mycelium (0 or 0.1 g fresh) and NVS (0 or 1 g 0.1 L-1 of soil) in a factorial design. Hirsutella minnesotensis reduced nematode densities by 31-83% across nematode populations in one test, but only slightly reduced densities of NYG and CT populations in another test. NVS reduced nematode densities by 33-92% across populations in two repeated tests. The combination of the two agents resulted in greater nematode reduction compared with Hm alone, but not compared with NVS alone. Across all Hm and NVS treatments, reduction of nematode densities were generally greater in NYG, CT, and RI than in MI and NYL populations. This study demonstrated that Hm and NVS may be used to suppress different M. hapla populations. [ABSTRACT FROM AUTHOR]

The root-knot nematode ( Meloidogyne spp.) is a major plant pathogen, affecting several solanaceous crops worldwide. In Capsicum annuum, resistance to this pathogen is controlled by several independent dominant genes—the Me genes. Six Me genes have previously been shown to be stable at high temperature in three highly resistant and genetically distant accessions: PI 322719, PI 201234, and CM334 (Criollo de Morelos 334). Some genes ( Me4, Mech1, and Mech2) are specific to certain Meloidogyne species or populations, whereas others ( Me1, Me3, and Me7) are effective against a wide range of Meloidogyne species, including M. arenaria, M. javanica, and M. incognita, the most common species in Mediterranean and tropical areas. These genes direct different response patterns in root cells depending on the pepper line and nematode species. Allelism tests and fine mapping using the BSA-AFLP approach showed these genes to be different but linked, with a recombination frequency of 0.02–0.18. Three of the PCR-based markers identified in several genetic backgrounds were common to the six Me genes. Comparative mapping with CarthaGene software indicated that these six genes clustered in a single genomic region within a 28 cM interval. Four markers were used to anchor this cluster on the P9 chromosome on an intraspecific reference map for peppers. Other disease resistance factors have earlier been mapped in the vicinity of this cluster. This genomic area is colinear to chromosome T12 of tomato and chromosome XII of potato. Four other nematode resistance genes have earlier been identified in this area, suggesting that these nematode resistance genes are located in orthologous genomic regions in Solanaceae. [ABSTRACT FROM AUTHOR]

Resistance to root-knot nematode ( Meloidogyne incognita) is determined by a single major gene rkn1 in Gossypium hirsutum Acala NemX cotton. Bulked segregant analysis (BSA) combined with amplified fragment length polymorphism (AFLP) was used to identify molecular markers linked to rkn1. DNA pools from homozygous susceptible (S) and resistant (R) bulks of an F2:3 originating from the intraspecific cross NemX × SJ-2 were screened with 128 EcoR1/ Mse1 primer combinations. Putative AFLP markers were then screened with 60 F2:7 RIL plants and four AFLP markers were found linked to rkn1. The linkage of AFLP markers to rkn1 was also confirmed in a F2 population. The closest AFLP marker was converted to a cleaved amplified polymorphic sequence (CAPS) marker (designated GHACC1) by aligning the sequences from both susceptible and resistant parents. GHACC1 linkage to rkn1 was confirmed in the F2 (1R:3S), F2:7 RIL (1R:1S) and the backcross population SJ-2 × F1 (NemX × SJ-2) (1 heterozygous: 1 homozygous). The four AFLP markers, GHACC1 plus two SSR markers (CIR316 and BNL1231) linked to rkn1 from previous work were mapped to intervals of 2.6–14.2 cM from the rkn1 locus, and the genomic region around rkn1 was spanned to about 28.2 cM in the F2:7 population. The PCR-based GHACC1 and CIR316 markers were tested on 21 nematode resistant and susceptible cotton breeding lines and cultivars. GHACC1 was suitable for nematode resistance screening within G.␣hirsutum, but not G. barbadense, whereas CIR316 was useful in both species, indicating their␣potential for utilization in marker-assisted selection. [ABSTRACT FROM AUTHOR]