Root-knot Nematodes In Tomato Research Articles

Modelling the biological control of tomato root-knot nematode by predatory mites in the presence of an alternative prey

Modelling the biological control of tomato root-knot nematode by predatory mites in the presence of an alternative prey

Metagenomic Approach Deciphers the Role of Community Composition of Mycobiome Structured by Bacillus velezensis VB7 and Trichoderma koningiopsis TK in Tomato Rhizosphere to Suppress Root-Knot Nematode Infecting Tomato.

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.

Biocontrol Efficacy of Bacillus methylotrophicus TA-1 Against Meloidogyne incognita in Tomato.

Root-knot nematodes (RKNs) are harmful plant-parasitic nematodes of tomatoes which can cause significant yield losses. Therefore, there is increasing interest in exploring the application of bacterial nematicides. The bacterium Bacillus methylotrophicus TA-1 is a broad-spectrum biological control agent; however, its effect on RKNs control remains largely unclear. In this study, the toxicity of B. methylotrophicus TA-1 against Meloidogyne incognita was investigated in vitro, and the potential of B. methylotrophicus TA-1 to decrease infection of RKNs in tomato were evaluated in pot and field trials. Results showed that B. methylotrophicus TA-1 exhibited high nematicidal activity against second-stage juveniles (J2s) and eggs of M. incognita with 50% lethal concentration (LC50) values of 5.80 and 7.00 × 108 colony forming units (CFU)/ml, respectively. In the pot experiments and field trials conducted in 2020 and 2021, tomato plants treated with B. methylotrophicus TA-1 soil drench applied once at 3, 6, and 9 × 108 CFU/plant had significantly higher plant height and greater yield compared with the untreated control. Tomato yields of the treated plots with B. methylotrophicus TA-1 in 2 consecutive years' field trials were between 53.4 to 66.1 and 52.8 to 61.5 t/ha, while they were 49.7 and 48.2 t/ha in the untreated control for each year, respectively. The lowest population densities of M. incognita at 30 and 60 days after treatment were 119 and 135 J2s per 100 g soil in 2020 and 43 and 118 J2s in 2021 in TA-1-treated plots. The lowest gall index of 4.7 and 3.3 in 2020 and 2021, respectively, and the highest yield were all observed in the TA-1 at 9 × 108 CFU/plant treated plants, with no significant differences with the commercial control abamectin. These results provided a basis for further studies of B. methylotrophicus TA-1 formulations, application doses, frequencies, and mechanisms of action, which are necessary before it could be used as a component of integrated management programs to manage RKNs in tomato production.

Effect of Biosynthesized Nanoselenium on Controlling Tomato Root-Knot Nematode Meloidogyne incognita

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.

AUXIN RESPONSIVE FACTOR8 regulates development of the feeding site induced by root-knot nematodes in tomato.

Root-knot nematodes (RKN) from the genus Meloidogyne induce the dedifferentiation of root vascular cells into giant multinucleate feeding cells. These feeding cells result from an extensive reprogramming of gene expression, and auxin is known to be a key player in their development. However, little is known about how the auxin signal is transmitted during giant cell development. Integrative analyses combining transcriptome and small non-coding RNA datasets with the specific sequencing of cleaved transcripts identified genes targeted by miRNAs in tomato (Solanum lycopersicum) galls. The two auxin-responsive transcription factors ARF8A and ARF8B, and their miRNA167 regulators, were identified as robust gene-miRNA pair candidates to be involved in the tomato response to M. incognita. Spatiotemporal expression analysis using promoter-β-glucuronidase (GUS) fusions showed the up-regulation of ARF8A and ARF8B in RKN-induced feeding cells and surrounding cells. The generation and phenotyping of CRISPR (clustered regularly interspaced palindromic repeats) mutants demonstrated the role of ARF8A and ARF8B in giant cell development and allowed the characterization of their downstream regulated genes.

One-pot construction of epoxy resin nanocarrier delivering abamectin and its efficacy on plant root-knot nematodes.

The complex preparation process and storage instability of nanoformulations hinders their development and commercialization. In this study, nanocapsules loaded with abamectin were prepared by interfacial polymerization at room temperature and ordinary pressure using the monomers of epoxy resin (ER) and diamine. The potential mechanisms of primary amine and tertiary amine in influencing the shell strength of the nanocapsules and the dynamic stability of abamectin nanocapsules (Aba@ER) in the suspension system were systematically researched. The tertiary amine catalyzed the self-polymerization of epoxy resin into linear macromolecules with unstable structures. The structural stability of the diamine curing agent with a primary amine group played a key role in enhancing the structural stability of the polymers. The intramolecular structure of the nanocapsule shell formed by isophorondiamine (IPDA) crosslinked epoxy resin has multiple spatial conformations and a rigid saturated six-membered ring. Its structure was stable, and the shell strength was strong. The formulation had stable dynamic changes during storage and maintained excellent biological activity. Compared with emulsifiable concentrate (EC), Aba@ER/IPDA had superior biological activity, and the field efficacy on tomato root-knot nematode was enhanced by approximately 31.28% at 150 days after transplanting. Aba@ER/IPDA, which has excellent storage stability and simple preparation technology, can provide a nanoplatform with industrial prospects for efficient pesticide delivery. © 2023 Society of Chemical Industry.

Assessment on Awareness of Root Knot Nematodes (Meloidogyne spp.) Associated with Tomato Production in Mvomero District, Morogoro, Tanzania

Root-knot nematodes (RKN) (Meloidogyne spp.) are among the serious biotic constraints to tomato growers in Tanzania but are relatively overlooked. This required a survey of growers in Mvomero District, Morogoro, Tanzania, to assess their RKN expertise. Semi-structured questionnaires were used to collect data from 100 randomly selected respondents in Mlali (33), Doma (33), and Dakawa (34). Socioeconomic status, RKN awareness, tomato varietals, seed sources, and yield were collected. RKN awareness varied significantly among responder categories. 59% were unaware of RKN. Farming experience correlated with tomato yield, RKN awareness, and RKN-resistant tomato varieties. Rio Grande (14%), Cal J (18%), Roma (10%), and Tanya (16%) were popular tomato types, while hybrids included Imara F1 (19%), Assila F1 (15%), Jarrah F1 (2%), Zara F1 (3%), Kipato F1 (2%) and Anna F1 (2%). Seventy-five root and 75 rhizosphere soil samples were taken from tomato plants at the flowering stage demonstrating stunting, chlorosis, and wilting at least 1km apart in Mlali, Doma, and Dakawa Wards. Samples were shovelled 25 cm deep, packed in sterile plastic bags, labelled, and delivered to Tanzania Agriculural Research Institute Kibaha Nematology laboratory. Results revealed the significant prevalence and incidence of RKN. Despite the occurrence and damage caused by RKN in tomato in the study areas, only one percent of respondents recognized RKN as a serious problem. Awareness campaigns on RKN will facilitate farmers’ consciousness of their existence and management.

Management of root knot nematode in tomato through Tricoderma harzianum and moringa leaf extract

Management of root knot nematode in tomato through Tricoderma harzianum and moringa leaf extract

The effect of ferula and rosemary extracts on tomato root-knot nematode

The effect of ferula and rosemary extracts on tomato root-knot nematode

Genome Sequence Resource of Sarocladium terricola TR, an Endophytic Fungus as a Potential Biocontrol Agent Against Meloidogyne incognita.

Genome Sequence Resource of Sarocladium terricola TR, an Endophytic Fungus as a Potential Biocontrol Agent Against Meloidogyne incognita.

Bacillus licheniformis JF-22 to Control Meloidogyne incognita and Its Effect on Tomato Rhizosphere Microbial Community

Meloidogyne incognita is one of the most destructive soil pests, causing serious economic losses in tomato production. Here, in vitro experiments demonstrated that the Bacillus licheniformis strain JF-22 has the potential to prevent M. incognita infection. A pot experiment confirmed that B. licheniformis strain JF-22 isolated from the tomato rhizosphere soil and planted in the tomato root-knot nematode disease area effectively prevented and controlled M. incognita, reducing its negative effect on tomato growth. Additionally, the composition of volatile substances secreted by B. licheniformis strain JF-22 was analyzed using solid-phase microextraction and gas chromatography–mass spectrometry. We detected acetoin, 2,3-Butanediol, [R-(R*,R*) ]-, and hexamethyl cyclotrisiloxane as the main components among these volatiles. Using MiSeq sequencing technology and bioinformatics, we analyzed the influence of B. licheniformis strain JF-22 on the microbial community of the tomato rhizosphere. B. licheniformis strain JF-22 changed the composition of the microbial community; particularly, it significantly reduced the diversity of the fungal community. Furthermore, using the FUNGuild and PICRUSt databases, we predicted the effect of JF-22 on microbial community function. In conclusion, B. licheniformis strain JF-22 may be considered as a potential biocontrol agent against M. incognita.

SlWRKY45 interacts with jasmonate-ZIM domain proteins to negatively regulate defense against the root-knot nematode Meloidogyne incognita in tomato.

Parasitic root-knot nematodes (RKNs) cause a severe reduction in crop yield and seriously threaten agricultural production. The phytohormones jasmonates (JAs) are important signals regulating resistance to multiple biotic and abiotic stresses. However, the molecular mechanism for JAs-regulated defense against RKNs in tomato remains largely unclear. In this study, we found that the transcription factor SlWRKY45 interacted with most JA-ZIM domain family proteins (JAZs), key repressors of the JA signaling. After infection by the RKN Meloidogyne incognita, the slwrky45 mutants exhibited lower gall numbers and egg numbers per gram of roots than wild type, whereas overexpression of SlWRKY45 attenuated resistance to Meloidogyne incognita. Under M. incognita infection, the contents of jasmonic acid (JA) and JA-isoleucine (JA-Ile) in roots were repressed by SlWRKY45-overexpression. Furthermore, SlWRKY45 bound to and inhibited the promoter of the JA biosynthesis gene ALLENE OXIDE CYCLASE (AOC), and repressed its expression. Overall, our findings revealed that the SlJAZ-interaction protein SlWRKY45 attenuated RKN-regulated JA biosynthesis and repressed defense against the RKN M. incognita in tomato.

Dissipation and residue of fosthiazate in tomato and cherry tomato and a risk assessment of dietary intake.

In this study, the safety and risk of fosthiazate as a nematicide against root-knot nematode in tomato and cherry tomato were evaluated. The dissipation and residue of fosthiazate for 28 days in tomatoes and cherry tomatoes were determined and studied by HPLC after simple, rapid pre-treatment. The mean recovery was 83.79~94.18%, and the relative standard deviations were 3.97~7.40%. Results showed that the half-lives of fosthiazate in tomatoes (4.81~5.37 days) were significantly lower than that in cherry tomatoes (5.25~5.73 days). At the pre-harvest interval (PHI) of 21 days, the residues of tomatoes and cherry tomatoes were 0.032~0.046 mg/kg, which were lower than the maximum residue level (MRL) established in China. The potential risks of fosthiazate exposure through the dietary intake of tomatoes and cherry tomatoes to different populations were also studied. According to the results of dietary risk assessment, the residual levels of fosthiazate were within the acceptable range of long-term dietary risk in different populations in China within the sampling interval of 21 days after the application of fosthiazate. Our results show that fosthiazate at 2250 g.a.i./ha in the field control of root-knot nematode has high safety and low risk, and can provide a reference for the safe and reasonable use of fosthiazate as a nematicide in the field.

The carB Gene of Escherichia coli BL21(DE3) is Associated with Nematicidal Activity against the Root-Knot Nematode Meloidogyne javanica.

Biological nematicides have been widely used to lower the losses generated by phytoparasitic nematodes. The purpose of this study was to evaluate the nematicidal effects of Escherichia coli BL21(DE3) against Meloidogyne javanica and to identify nematicide-related genes. Culture filtrates of BL21(DE3) caused juvenile mortality and inhibited egg hatching in a dose-dependent manner. In the greenhouse, treatment of tomato seedlings with BL21(DE3) culture filtrates at 50 and 100% concentrations not only reduced the amount of M. javanica egg masses and galls, but improved plant root and shoot fresh weight. Culture filtrate analysis indicated that the nematicidal active ingredients of strain BL21(DE3) were non-proteinaceous, heat and cold resistant, sensitive to pH and volatile. To identify the genes associated with nematicidal activity, a BL21(DE3) library of 5000 mutants was produced using Tn5 transposase insertion. The culture filtrate of the MB12 mutant showed no nematicidal activity after 72 h of treatment and thermal asymmetrical interlaced PCR demonstrated that the carB gene was disrupted. Nematicidal activity was restored when the pH of the MB12 culture filtrate was adjusted to the original pH value (4.15) or following MB12 complementation with the carB gene, confirming a role for carB in mediating pH value and nematicidal activity. The outcomes of this pilot study indicate that BL21(DE3) is a potential microorganism for the continuable biological control of root-knot nematode in tomato and that carB affects the nematicidal activity of BL21(DE3) by modulating the pH environment.

Potential of nicotinamide adenine dinucleotide (NAD) for management of root-knot nematode in tomato.

Nicotinamide adenine dinucleotide (NAD) has been shown to induce plant defense responses to different plant pathogens, including reducing northern root-knot nematode, Meloidogyne hapla, penetration and increasing plant mass in tomato. We wanted to further evaluate NAD that are effective against the more economically important species, M. incognita and whether NAD treatments of tomato seedlings in transplant trays can protect plants in the field. Different NAD concentrations (1 mM, 0.1 mM and 0.01 mM) and three application timings (pre; post; pre and post inoculation) were evaluated in growth room and greenhouse trials. The highest tested NAD concentration (1 mM) suppressed second-stage juveniles (J2) infection for all three application methods. Root gall ratings at 30 days after inoculation (DAI) were also suppressed by 1 mM NAD compared to the other two concentrations, and egg mass number was significantly suppressed for all concentrations and application timings compared to the non-treated control. The rate of 1 mM NAD for all three application timings also improved plant growth at 30 DAI. Long-term effects of 1 mM NAD (pre, pre + post, or post applications) on nematode infection, growth and yield of tomato were evaluated in two additional experiments. All NAD applications suppressed root galls after 60 days, but only the pre + post 1 mM NAD application suppressed gall severity at 105 days, as well as suppressed egg counts by 50% at 60 DAT. No significant difference in plant biomass and fruit yield after 105 days was observed among the treatments. Two field trials were conducted in spring and fall 2020 using tomato seedlings (cv. HM 1823) treated with two different NAD concentrations (1 mM and 5 mM in spring; 5 mM and 10 mM in fall) and transplanting seedlings in fumigated (chloropicrin ± 1,3-dichloropropene) and non-fumigated plastic-mulch beds. No significant impact of NAD in terms of reducing RKN severity or overall tomato growth and production was seen in fumigated beds, but in non-fumigated beds 5 mM NAD slightly increased early fruit yield in spring, and 10 mM NAD reduced root-knot soil populations in fall.

Evaluating a new non-fumigant nematicide fluopimomide for management of southern root-knot nematodes in tomato

The southern root-knot nematode (Meloidogyne incognita) is one of the most damaging diseases affecting tomato production in China and worldwide. There is an increasing need to find environmentally friendly non-fumigant nematicides of low-toxicity to manage M. incognita because of the phase-out of methyl bromide and restrictions on the use of highly toxic non-fumigant nematicides. Fluopimomide is a novel fungicide with a chemical structure similar to fluopyram, another fungicide exhibiting nematicidal properties. However, the nematicidal potential of fluopimomide to suppress M. incognita and its effect on tomato plant growth was hitherto unknown. In the present study, the nematicidal efficacy of fluopimomide was evaluated in vitro and under greenhouse conditions against M. incognita and its effect on tomato plant growth was determined. In vitro, fluopimomide had a high toxicity to second-stage juveniles (J2s) and eggs of M. incognita with median lethal concentrations (LC50) of 23.4 and 9.5 mg L−1 after 48 h exposure, respectively. Under greenhouse conditions, fluopimomide at 250, 500 and 1000 g ha−1 was effective in reducing root galling at 30 and 60 days after treatment (DAT), with the value of the galling index being reduced by 19.3%–23.8% and 35.7%–52.7%, respectively, and increasing plant height, stem diameter and above-ground biomass. Fluopimomide at all rates significantly reduced populations of M. incognita in the soil by 26.2–46.5% and 65.6%–82.1% at 30 and 60 DAT, respectively, compared with the untreated control. Moreover, there were no significant differences in reduction of M. incognita J2s by fluopimomide at 1000 g ha−1 compared to fluopyram or abamectin. Application of fluopimomide significantly increased plant height with or without inoculation of M. incognita, indicating that plant growth promotion was attributed to treatment with fluopimomide itself. Overall, fluopimomide demonstrated strong nematicidal activity in vitro against M. incognita, and application of fluopimomide effectively reduced root galling and the populations of M. incognita, meanwhile enhancing tomato plant growth under greenhouse conditions.

Nematocidal activity of fermented extracts from Lantana camara plant parts against Meloidogyne javanica on tomato

ABSTRACT Root-knot nematode (Meloidogyne sp.) is a major concern due to difficulty of control. Secondary metabolites naturally occurring in plants offer a method for combating invasion by root-knot nematode . The study was conducted to investigate nematocidal effects of plant parts of fermented Lantana camara L. collected around the Visage, George and Mooketsi areas, Limpopo Province, South Africa. Effective dosages of plant extracts, which could be applied through a drip irrigation system, on tomato (Solanum lycopersicum L) were determined against nematode infection. Extracts of L. camara were evaluated at aqueous concentrations of 0.92%, 2.76%, or 3.68% (v/v) for effects on plant parameters. Mortality rate of Meloidogyne javanica J2 treated with fermented Lantana camara at varying extract concentration, location and tissue was significant. Nematocidal activity of the extracts were mainly due to plant part and concentration. There was a significant location × tissue interaction for wet plant biomass, Meloidogyne javanica galling index, root egg mass, and soil egg mass. The reduction in final nematode population, root-knot index and soil egg hatching after 8 weeks following transplanting in pot trials is indicative of nematocidal activity of L. camara. There was no difference in location × tissue interaction for plant height, stem diameter, and number of fruit. Treatment with fermented L. camara was not phytotoxic. Fermented L. camara plant extracts may be used for management of root-knot nematode in tomato, but this must be validated in field trials.

Effect of Paecilomyces lilacinus on tomato plants and the management of root knot nematodes

Effect of Paecilomyces lilacinus on tomato plant growth and the management of root knot nematodes in tomato was studied. The research work was conducted in Microbiology & Bio-control Laboratory, Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh and in Net-house of Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh, during the period from July, 2016 to October, 2017. In net-house pot culture experiment, four different treatments were used viz., T1: Inoculation of egg masses (10 egg masses/plant) of Nematodes (Meloidogyne spp.), T2: Application of P. lilacinus, T3: Application of egg masses of Nematodes and P. lilacinus simultaneously, and T4: Control (non-treated). Spore suspension (10×105 Conc.) of P. lilacinus was mixed with the soil before transplantation and Meloidogyne spp. was inoculated on three days after transplantation. Application of P. lilacinus in soil enhanced the plant growth parameters of tomato plants. Inoculation of Meloidogyne spp. reduced plant growth and the reduction was increased with the increase of inoculum density of Meloidogyne spp. Maximum plant growth reduction was recorded when Meloidogyne spp. was inoculated alone. The maximum plant growth was recorded in case of application of P. lilacinus to soil. A high percentage (85%) of egg masses of Meloidogyne spp. was infected by P. lilacinus when applied together
 J. Bangladesh Agril. Univ. 17(1): 9–13, March 2019

Resistance induction efficiency of silicon dioxide against Meloidogyne incognita in tomato

The tomato root-knot nematode is one of the main phytosanitary problems in crops. Chemical control is the phytosanitary method most used by farmers, and the study of alternative management of phytonematodes is crucial. The objective of this study was to evaluate the effect of silicon dioxide (SiO2) on the initial development of tomato plants, as well as to determine the best dose of SiO2 for inducing resistance to parasitism by M. incognita. This experiment was set up under a completely randomized design with ten treatments and five replicates in a 5×2 factorial arrangement consisting of five concentrations of SiO2 (0, 0.15, 0.3, 0.45 and 0.6 g dm-³ of soil) with the presence and absence of M. incognita, under greenhouse conditions. The following variables were evaluated: plant height; number of leaves; fresh and dry weight of shoot; percentage of shoot dry matter; root fresh weight; number of galls; final population of nematodes; and population per gram of root. The M. incognita infection affected plant height, number of leaves and shoot fresh weight, while the application of SiO2 negatively affected the formation of galls in the roots of the inoculated plants and the population per gram of root, reducing the final population of nematodes in the root system. SiO2 also provided greater development in the tomato plants, with a significant effect on plant height. The ideal dose was 0.34 g dm-3 of SiO2.

Strigolactones positively regulate defense against root-knot nematodes in tomato.

Strigolactones (SLs) are carotenoid-derived phytohormones that are known to influence various aspects of plant growth and development. As root-derived signals, SLs can enhance symbiosis between plants and arbuscular mycorrhizal fungi (AMF). However, little is known about the roles of SLs in plant defense against soil-borne pathogens. Here, we determined that infection with root-knot nematodes (RKNs; Meloidogyne incognita) induced SL biosynthesis in roots of tomato (Solanum lycopersicum). Silencing of SL biosynthesis genes compromised plant defense against RKNs, whilst application of the SL analog racGR24 enhanced it. Accumulation of endogenous jasmonic acid (JA) and abscisic acid (ABA) in the roots in response to RKN infection was enhanced by silencing of SL biosynthetic genes and was suppressed by application of racGR24. Genetic evidence showed that JA was a positive regulator of defense against RKNs while ABA was a negative regulator. In addition, racGR24 enhanced the defense against nematode in a JA-deficient mutant but not in an ABA-deficient mutant. Silencing of SL biosynthetic genes resulted in up-regulation of MYC2, which negatively regulated defense against RKNs. Our results demonstrate that SLs play a positive role in nematode defense in tomato and that MYC2 negatively regulates this defense, potentially by mediating hormone crosstalk among SLs, ABA and JA.