Nematode Management Research Articles

Evaluation of Different Fertilizer Types in the Suppression of Root Knot Nematode Infection on Sweet Potato (Ipomoea batatas) in Makurdi, Benue State

A field experiment was conducted at the Agronomy Teaching and Research Farm, Federal University of Agriculture Makurdi in the 2020/2021 planting season. To evaluate the effects of different fertilizer types in the control of root knot nematode of sweet potato. The experiment was laid out in a randomized complete block design (RCBD). The treatments were Liquid fertilizer (Super gro) and poultry dropping and control which were replicated three times. Before the treatments were applied, soil samples were collected for nematode extraction and the nematodes were extracted in the laboratory using the modified Bearmann tray technique. Super gro and geese droppings were applied at 2 weeks interval and 4 weeks interval. The results show a significant (p<0.05) reduction of root gall index, significant increase in root length, weight of roots and number of roots on the plots treated with fertilizer. This research work recommends the application of poultry droppings for the management of root knot nematode in sweet potato (Ipomoea batatas).

Genetic disruption of Arabidopsis secondary metabolite synthesis leads to microbiome-mediated modulation of nematode invasion.

In-depth understanding of metabolite-mediated plant-nematode interactions can guide us towards novel nematode management strategies. To improve our understanding of the effects of secondary metabolites on soil nematode communities, we grew Arabidopsis thaliana genetically altered in glucosinolate, camalexin, or flavonoid synthesis pathways, and analyzed their root-associated nematode communities using metabarcoding. To test for any modulating effects of the associated microbiota on the nematode responses, we characterized the bacterial and fungal communities. Finally, as a proxy of microbiome-modulating effects on nematode invasion, we isolated the root-associated microbiomes from the mutants and tested their effect on the ability of the plant parasitic nematode Meloidogyne incognita to penetrate tomato roots. Most mutants had altered relative abundances of several nematode taxa with stronger effects on the plant parasitic Meloidogyne hapla than on other root feeding taxa. This probably reflects that M. hapla invades and remains embedded within root tissues and is thus intimately associated with the host. When transferred to tomato, microbiomes from the flavonoid over-producing pap1-D enhanced M. incognita root-invasion, whereas microbiomes from flavonoid-deficient mutants reduced invasion. This suggests microbiome-mediated effect of flavonoids on Meloidogyne infectivity plausibly mediated by the alteration of the abundances of specific microbial taxa in the transferred microbiomes, although we could not conclusively pinpoint such causative microbial taxa.

Nematode Management: Options and Constraints for Organic Agriculture

Nematode Management: Options and Constraints for Organic Agriculture

Management of potato cyst nematodes with special focus on biological control and trap cropping strategies.

Potato cyst nematodes (PCNs; Globodera spp.) are one of the most difficult pests of potato to manage worldwide. Indiscriminate use of pesticides and their hazardous effects discourage the use of many chemicals for the management of PCNs. As a result, biological control agents and trap crops have received more attention from growers as safer ways to manage PCNs. The biological control agents such as Pochonia chlamydosporia, Purpureocillium lilacinum, Trichoderma spp., Pseudomonas fluorescens, Bacillus spp., Pasteuria spp., and others are recognized as potential candidates for the management of PCNs. Moreover recently, the use of trap crop Solanum sisymbriifolium also showed promise by drastically reducing soil populations of PCNs. Integration of these management strategies along with other practices including identification, conservation, and multiplication of native antagonists, will facilitate efficient management of the PCNs in potato cropping system. Some of the promising research approaches that are being used against PCNs are addressed in this review. © 2022 Society of Chemical Industry.

First Report of Xiphinema Ifacolum Luc, 1961 (Dorylaimida: Longidoridae) from Nigeria.

A population of a species of dagger nematode (Xiphinema) belonging to the non-americanum group was recovered from the fields of kola nut (Cola sp.) in southern Nigeria. The morphological and morphometric data obtained from this population were consistent with the characteristics of the species Xiphinema ifacolum. In addition, molecular identification based on D2-D3 expansion segments of 28S rRNA and partial mitochondrial COI gene regions confirmed its identity. According to our knowledge, this is the first report of the species from Nigeria, and the second report from Africa, after the original description from Foulaya, Guinea.

Molecular characterization of internal transcribed spacer (ITS) of ribosomal RNA gene, haplotypes and pathogenicity of potato rot nematode Ditylenchus destructor in China

Potato rot nematode Ditylenchus destructor is one of the most damaging pests in potato-producing regions and causes severe yield losses worldwide. However, D. destructor has been rarely reported in potato crops in China. We collected 542 samples from 17 Chinese provinces during 2016–2020 for the detection of D. destructor using species-specific primers and universal primers targeting ribosomal internal transcribed spacer (ITS) or 28S ribosomal RNA (rRNA) sequences. D. destructor was detected in 14.94% of total samples, primarily in Inner Mongolia Autonomous Region (43 sites), Jilin Province (12 sites), and Shaanxi Province (9 sites). The nematode was for the first time detected in Guizhou Province and Ningxia Hui Autonomous Region. Phylogenetic analysis of 33 ITS sequences along with the prediction of the secondary structure of the helix H9 of ITS1 sequences revealed that haplotypes A, B, and C accounted for 6.06%, 9.09%, and 69.70% of our detections, respectively, while 15.15% were comprised of haplotypes H–L, and extensive genetic diversity of ITS sequences was detected in samples from Gansu Province. Using RNAfold software, we analyzed the haplotypes of 124 Chinese D. destructor populations based on their ITS sequences, and the results showed that haplotypes A, B, C, E, F, and new haplotypes M–P accounted for 49.19%, 12.10%, 15.32%, 3.23%, 1.61%, and 18.55% of the total sequences, respectively. Infection tests on the potato cultivar ‘Helan 15’ showed significant difference in infection capacity among different D. destructor populations. The information obtained in this study on spatial patterns of D. destructor haplotypes in China provides valuable insights into the development of an integrated approach for the management of this plant-parasitic nematode.

Hot Water Tuber Treatments for Management of Meloidogyne Arenaria in Caladium Cultivars.

Hot water treatment was evaluated for its efficacy in controlling Meloidogyne arenaria on caladium. Caladium tubers pre-infested with M. arenaria were immersed in hot water at 50°C for 0 min, 30 min, and 45 min before being planted into 16.5-cm pots filled with sterilized sandy soil. Two caladium cultivars Florida Sweetheart PP 8526 (SWT) and Postman Joyner (PJR), each with three tuber sizes [#3 (<1.5 inch), #1 (1.5–2.5 inch), and Jumbo (>2.5 inch)], were evaluated. Ninety days after the first shoot observation, the number of nematode eggs in roots and second-stage juveniles in soil were significantly reduced, but not eliminated, in both 30 min and 45 min treatments; the 45 min treatment had better results than the 30 min treatment. The efficacy of hot water treatment was affected by caladium cultivar, but not by tuber size. The treated PJR tubers had lower nematode numbers than those of the cultivar SWT. The difference in nematode number between the two caladium cultivars might be related to the morphological characteristics of caladium tubers, as the scale-like tissue on SWT tubers might provide refuge for root-knot nematodes from heat damage. Further research needs to be conducted on determining heat-tolerant thresholds for different Meloidogyne spp. and different caladium cultivars, which will help improve nematode management strategies for caladium growers.

Transient expression of a luciferase mRNA in plant-parasitic and free-living nematodes by electroporation

Despite their economic significance in agricultural cropping systems, a lack of suitable molecular tools for manipulating gene expression has hindered progress in the functional genomics of plant parasitic nematodes (PPN). Obligate sexual reproduction and the obligate nature of PPN-host interactions further complicate the development of in vivo gene delivery and expression systems in these pests. Methods such as microinjection and microprojectile bombardment have been developed for introducing gene constructs into the free-living nematode, Caenorhabditis elegans. However, these procedures can be laborious and inefficient. Electroporation has been used extensively to introduce macromolecules, including single-stranded RNAs, into eukaryotic and prokaryotic cells. The technique has also been used for the delivery of DNA and double-stranded RNA constructs into nematodes by whole-animal electroporation. Here, we describe methods for the expression of a nematode-optimized NanoLuc luciferase mRNA in the form of in vitro transcripts following whole-animal electroporation of Heterodera glycines, Meloidogyne incognita, and C. elegans. The ability to transiently express single-stranded RNA constructs in economically important PPN provides a rapid means to evaluate nematode and/or foreign genes for their biological significance and potential role in nematode management.

Present status and future directions for management of root lesion nematode (Pratylenchus thornei) in chickpea

Chickpea is a popular legume crop in Asia and Africa's semi-arid regions. Crop production gains, on the other hand, have been modest, owing to biotic and abiotic stressors. Among the different biotic stresses, nematodes portray serious threat to chickpea production and colossal losses have been reported due to stress-free infection by other pathogens on infection with root lesion nematode (RLN). The worldwide distribution of two major species of RLN namely P. thornei and P. neglectus made them a focus research area especially on management aspect. In dryland farming areas of southeastern Australia, the P. thornei alone can cause yield losses of up to 40% in cereals and legumes. Despite the fact that chickpea breeders have been working persistently to generate superior chickpea varieties with increased resilience or tolerance to biotic and abiotic challenges, contemporary biotechnology technologies can help to speed up this process. To incorporate these tools and/or accelerate breeding programmes, identification of RLN resistant source with its genetic factor is first step in developing improved cultivars. However, study of resistance screening methods for chickpea against RLN is limited and standardization of different factors for development of a stable screening methodology distinguishing various levels of resistance is the need of the hour in RLN research.

Antimicrobial peptides producing native Bacillus spp. for the management of root-knot nematode Meloidogyne incognita infecting okra (Abelmoschus esculentus L. Moench)

In the present study, native strains of Bacillus species were isolated, characterized and evaluated for their biocontrol efficacy in laboratory, pot and field conditions to combat Meloidogyne incognita incidence in okra (Abelmoschus esculentus L. Moench). Based on the laboratory results, two Bacillus spp., Bacillus marisflavi CRB2 and Bacillus subtilis CRB7 were found most effective against M. incognita. We also profiled antimicrobial peptide (AMP) genes associated with this two Bacillus spp. Bacillus marisflavi CRB2 was found to harbour 10 AMP genes whereas, B. subtilis CRB7 had 8 AMP genes with the expression of 3 and 4 genes, respectively at the RNA level. Talc based formulation of B. marisflavi CRB2 and B. subtilis CRB7 were evaluated under pot and field conditions for the management of M. incognita in okra. Bacillus marisflavi CRB2 and B. subtilis CRB7 at dose of 5 g plant−1 were found most effective against M. incognita by reducing the nematode incidence in okra under pot conditions. Further, field application of either Bacillus marisflavi CRB2 and B. subtilis CRB7 as a combination of seed treatment 20 g kg−1 seed + soil application (5 kg ha−1) of enriched vermicompost (2 t ha−1) + soil drenching @ 1% at 30 days interval showed a significant reduction of M. incognita incidence in okra and also increased yield as compared to untreated control. Their bioefficacy was comparable with carbofuran 3G (1 kg a.i. ha−1) treatments. Thus, the native strains B. marisflavi CRB2 and B. subtilis CRB7 having diverse antimicrobial peptide genes can be used as one of the components in the integrated nematode management strategy to combat M. incognita incidence in okra.

Plant growth-promoting rhizobacteria Burkholderia vietnamiensis B418 inhibits root-knot nematode on watermelon by modifying the rhizosphere microbial community

Burkholderia vietnamiensis B418 is a multifunctional plant growth-promoting rhizobacteria (PGPR) strain with nitrogen-fixing and phosphate-solubilizing capability which can be employed for root-knot nematode (RKN) management on various crops and vegetables. Here we investigated the control efficacy of B. vietnamiensis B418 inoculation against RKN on watermelon, applied either alone or combined with nematicides fosthiazate or avermectin, and their effects on bacterial and fungal microbiomes in rhizosphere soil. The results of field experiments showed individual application of B418 displayed the highest control efficacy against RKN by 71.15%. The combinations with fosthiazate and avermectin exhibited slight incompatibility with lower inhibitory effects of 62.71% and 67.87%, respectively, which were still notably higher than these nematicides applied separately. Analysis of microbiome assemblages revealed B418 inoculation resulted in a slight reduction for bacterial community and a significant increment for fungal community, suggesting that B418 could compete with other bacteria and stimulate fungal diversity in rhizosphere. The relative abundance of Xanthomonadales, Gemmatimonadales and Sphingomonadales increased while that of Actinomycetales reduced with B418 inoculation. The predominate Sordariomycetes of fungal community decreased dramatically in control treatment with B418 inoculation whereas there were increments in fosthiazate and avermectin treatments. Additionally, nitrogen (N) cycling by soil microbes was estimated by quantifying the abundance of microbial functional genes involved in N-transformation processes as B418 has the capability of N-fixation. The copy number of N-fixing gene nifH increased with B418 inoculation, and the highest increment reached 35.66% in control treatment. Our results demonstrate that B. vietnamiensis B418 is an effective biological nematicide for nematode management, which acts through the modulation of rhizosphere microbial community.

Filtrates of mixed Bacillus spp inhibit second-stage juvenile motility of root-knot nematodes

The global expansion of soybean (Glycine max (L.) Merr.) exposes it to more diseases and pests such as nematodes. In South Africa particularly, Meloidogyne incognita and M. javanica are considered the predominant genera infecting soybean, but a more pathogenic root-knot species, M. enterolobii, was recently reported in the Mpumalanga Highveld of South Africa. The use of chemicals to manage these pests is usually preferred although various concerns exist regarding their potential impact on the environment. An increasing need for the development of less toxic alternatives for nematode management thus exists. This study determined the nematicidal activity of Bacillus spp. mixtures isolated from soybean rhizospheres on the motility of second-stage juveniles (J2) of mixed Meloidogyne communities co-occurring in these rhizospheres. Roots and soil from 10 soybean fields in the Mpumalanga Highveld were collected and Bacillus spp. isolated, while the population density and molecular identification of the co-existing Meloidogyne spp. were also done. The filtrates of the Bacillus spp. were then used in in vitro assays to determine their potential nematicidal activity. Results confirmed the presence of M. enterolobii (100%) M. incognita (50%) and M. javanica (40%) in the sampled fields, with single populations found in 20% and mixed communities in 80% of the fields. The filtrate mixture of B. cereus, B. megaterium, B. subtilis and B. thuringiensis caused approximately 85–90% immobility of Meloidogyne spp. J2 after 96 h. The results show that the use of Bacillus spp. mixtures can aid in the development of biocontrol products to combat root-knot nematodes and might be more effective than products from a single species in limiting J2 motility.

Production of Purpureocillium lilacinum and Pochonia chlamydosporia by Submerged Liquid Fermentation and Bioactivity against Tetranychus urticae and Heterodera glycines through Seed Inoculation.

Pochoniachlamydosporia and Purpureocillium lilacinum are fungal bioagents used for the sustainable management of plant parasitic nematodes. However, their production through submerged liquid fermentation and their use in seed treatment have been underexplored. Therefore, our goal was to assess the effect of different liquid media on the growth of 40 isolates of P. lilacinum and two of P. chlamydosporia. The most promising isolates tested were assessed for plant growth promotion and the control of the two-spotted spider mite (Tetranychus urticae) and the soybean cyst nematode (Heterodera glycines). Most isolates produced > 108 blastospores mL−1 and some isolates produced more than 104 microsclerotia mL−1. Microsclerotia of selected isolates were used to inoculate common bean (Phaseolus vulgaris L.) seeds in greenhouse trials. All fungal isolates reduced the T. urticae fecundity in inoculated plants through seed treatment, while P. chlamydosporia ESALQ5406 and P. lilacinum ESALQ2593 decreased cyst nematode population. Purpureocillium lilacinum was more frequently detected in soil, whereas P. chlamydosporia colonized all plant parts. Pochonia chlamydosporia ESALQ5406 improved the root development of bean plants. These findings demonstrate the possibility of producing submerged propagules of P. chlamydosporia and P. lilacinum by liquid culture, and greenhouse trials support the applicability of fungal microsclerotia in seed treatment to control P. vulgaris pests.

Sensitivity of potato cyst nematodes to fluazaindolizine

Summary Potato cyst nematodes (PCN), Globodera spp., cause damage to potatoes in more than 60 countries and several management strategies, including the application of chemical nematicides, are commonly used for their control. However, due to stringent regulations in Europe several nematicides have been, or are being, removed from the market due to their potential toxic effects on the environment and human health. New solutions and nematode management strategies are being sought to control these challenging and economically important nematodes. In this study, the effects of Salibro™, a novel sulfonamide nematicide based on the active ingredient fluazaindolizine (Reklemel™ active), were evaluated on the hatching, motility, infectivity and reproduction of PCN in the laboratory. Depending upon the duration of nematode pre-exposure, Salibro™ at concentrations of 5-250 mg fluazaindolizine (active substance) (a.s.) kg−1 (equivalent to 5-250 ppm a.s.) affected hatching, motility and infectivity of second-stage juveniles of G. pallida and G. rostochiensis, whereas the reproduction of G. pallida was only influenced at 5-50 mg a.s. kg−1. Salibro™, under laboratory conditions, has intrinsic activity against both PCN species and could be a promising additional tool for the integrated management of PCN. Further studies are needed to demonstrate Salibro™ efficacy under field conditions.

Insights Into the Genetics of the Zhonghua 11 Resistance to Meloidogyne graminicola and Its Molecular Determinism in Rice

Meloidogyne graminicola is a widely spread nematode pest of rice that reduces crop yield up to 20% on average in Asia, with devastating consequences for local and global rice production. Due to the ban on many chemical nematicides and the recent changes in water management practices in rice agriculture, an even greater impact of M. graminicola can be expected in the future, stressing the demand for the development of new sustainable nematode management solutions. Recently, a source of resistance to M. graminicola was identified in the Oryza sativa japonica rice variety Zhonghua 11 (Zh11). In the present study, we examine the genetics of the Zh11 resistance to M. graminicola and provide new insights into its cellular and molecular mechanisms. The segregation of the resistance in F2 hybrid populations indicated that two dominant genes may be contributing to the resistance. The incompatible interaction of M. graminicola in Zh11 was distinguished by a lack of swelling of the root tips normally observed in compatible interactions. At the cellular level, the incompatible interaction was characterised by a rapid accumulation of reactive oxygen species in the vicinity of the nematodes, accompanied by extensive necrosis of neighbouring cells. The expression profiles of several genes involved in plant immunity were analysed at the early stages of infection during compatible (susceptible plant) and incompatible (resistant plant) interactions. Notably, the expression of OsAtg4 and OsAtg7, significantly increased in roots of resistant plants in parallel with the cell death response, suggesting that autophagy is activated and may contribute to the resistance-mediated hypersensitive response. Similarly, transcriptional regulation of genes involved in hormonal pathways in Zh11 indicated that salicylate signalling may be important in the resistance response towards M. graminicola. Finally, the nature of the resistance to M. graminicola and the potential exploitation of the Zh11 resistance for breeding are discussed.

Nitrogen fertilizer alleviates root-knot nematode stress in beetroot by suppressing the pathogen while modulating the antioxidant defense system and cell viability of the host

The ongoing removal of environmentally harmful nematicides from the global market necessitates the development of new nematode management strategies. Therefore, alternate approaches that are eco-friendly are preferable to manage the menace of root-knot disease in agroecosystems. The current study sought to evaluate and determine the optimum level of nitrogen fertilizer with respect to its plant growth promoting and nematicidal activities. Among the different concentrations of nitrogen fertilizer supplemented to the soil, U150Mi (150 kg/h N) was found most optimum to considerably (P ≤ 0.05) improve the growth and yield attributes of beetroot inoculated with Meloidogyne incognita. Scanning electron microscopy demonstrated the improvement in stomatal attributes of beetroot at U150Mi (150 kg/h N) as compared to the untreated inoculated control. Confocal laser microscopy confirmed the dose-dependent nematicidal properties of nitrogen fertilizer under laboratory conditions. The cell viability of beetroot was also markedly improved at U150Mi (150 kg/h N) nitrogen fertilizer level. The formation of galls and egg masses was suppressed significantly with the application of nitrogen fertilizer at U150Mi (150 kg/h N) level. The PCA (principal component analysis) accounted for 99.61% for the total-data variability in plants inoculated with M. incognita and treated with different nitrogen fertilizer levels.

Comprehensive Perception Approach of Adoption: Innovative Wrap &amp; Plant Technology for Nematodes Management on Yam

ABSTRACT&#x0D; A new agricultural practice, wrap &amp; plant technology, was experimented in yam fields on three different sites in the centre-north of Benin. These sites were "Savalou", site 1, "Savè", site 2 and “Glazoué”, site 3. The research sought to highlight the perception of various actors from the vegetative to the culinary phases. Two improved practices were introduced: treatment A (wrapping of seed yam cv. Klatchi with banana-fibre paper, impregnated with micro-doses of abamectin), treatment B (wrapping of seed yam of cv. Klatchi using banana-fibre paper alone). On the basis of a Comparative Appraisal Index (CBI), that is, the practice introduced was well appreciated by enumerators if the difference in perception scores of characteristics was greater than zero. In terms of results, treatment A seemed to be the most popular practice on sites 1 and 2. On site 3, treatment B seemed to substitute for A. While in the first two sites, the sensory characteristics of dishes and the agro-morphological descriptors constituted a main component of favourable perception, the descriptors from agro-morphological and harvest phases were very much important at site 3. In terms of the decision to adopt a treatment, it depended significantly amongst other socioeconomic characteristics of the respondents on the sex, number of years of experience, membership in an association, level of education, other income generating activity and the site. For future expansion of introduced practices, agricultural research needs to address socioeconomic characteristics and to improve agro-morphological descriptors.&#x0D; Key-words: Abamectin, actors, Dioscorea spp., nematode management, sensory selectivity, Benin

Effect of differential addition of water on mobility of fluopyram in two different soils of Kerala

ABSTRACT Fluopyram, a pyridyl ethyl benzamide broad-spectrum fungicide and nematicide, used for the management of plant parasitic nematodes and soil-borne fungi, is recommended for use in crops like tomato, potato and tobacco. Fluopyram being a pesticide used for drenching soil, there is every possibility of it getting leached down with water, ultimately leading to contamination of waterbodies. An experiment was conducted to study the downward movement of fluopyram in laterite and red loam soils in Kerala, India. Fluopyram and fluopyram benzamide, each at150 µg, were loaded separately on top of the respective soil column and were eluted separately with 20, 40, 80 and 160 mL each of water equivalent to 50, 100, 200 and 400 mm rainfall. It was observed that 76.84% and 74.85% of fluopyram and 73.48% and 64.24% of fluopyram benzamide were confined to the top 0–10 cm soil with application of 20 mL water in laterite and red loam soil, respectively. More than 50% of fluopyram and fluopyram benzamide were detected in the top 0–10 cm layer of soil with the application of 40 and 80 mL water. With the application of 160 mL water, considerable reduction in the concentration of both compounds was observed and the residues moved beyond 30 cm. Leaching of residues was more in laterite soil than in red loam soil, and they are in direct relation to the volume of water applied and the residues moved beyond 30 cm depth with 160 mL water.

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.

Bacterial Volatile-Mediated Suppression of Root-Knot Nematode (Meloidogyne incognita).

Root-knot nematodes (Meloidogyne spp.) are obligate plant parasites that cause severe economic losses to agricultural crops worldwide. Because of serious health and environmental concerns related to the use of chemical nematicides, the development of efficient alternatives is of great importance. Biological control through exploiting the potential of rhizosphere microorganisms is currently accepted as an important approach for pest management in sustainable agriculture. In our research, during screening of rhizosphere bacteria against the root-knot nematodes Meloidogyne incognita, Ochrobactrum pseudogrignonense strain NC1 from the rhizosphere of healthy tomatoes showed strong nematode inhibition. A volatile nematicidal assay showed that the cell-free fermentation filtrate in the first-row wells of 12-well tissue culture plates caused M. incognita juvenile mortality in the second-row wells. Gas chromatography-mass spectrometry analysis revealed that dimethyl disulfide (DMDS) and benzaldehyde were the main volatile compounds produced by strain NC1. The nematicidal activity of these compounds indicated that the lethal concentration 50 against the M. incognita juveniles in the second-row wells and the fourth-row wells were 23.4 μmol/ml and 30.7 μmol/ml for DMDS and 4.7 μmol/ml and 15.2 μmol/ml for benzaldehyde, respectively. A greenhouse trial using O. pseudogrignonense strain NC1 provided management efficiencies of root-knot nematodes of 88 to 100% compared with the untreated control. This study demonstrated that nematode-induced root-gall suppression mediated by the bacterial volatiles DMDS and benzaldehyde presents a new opportunity for root-knot nematode management.