Root Knot Research Articles

Evaluation of F1 hybrids against root knot nematode (<i>Meloidogyne incognita</i>) resistance in Brinjal (<i>Solanum melongena</i> L.)

Brinjal is one of the most important commercial solanaceous vegetable crops. Root knot nematodes cause severe yield losses in brinjal both in open and poly house conditions. Host plant resistance is considered to be a viable solution and cost-effective method to manage the root knot nematodes. Ten genotypes along with their nineteen F1 hybrids were screened for resistance to root knot nematode and biochemical basis of resistance was assessed. Two F1 hybrids viz., IIHR-824 x VI046101, IIHR-824 x IIHR-766, parents viz., IIHR-824 and VI046103 were found to be resistance to M. incognita with gall index/ egg mass index of 1. Three F1 hybrids, IIHR-824 x IIHR-356, IIHR-824 x IIHR-835, VI046103 x IIHR-834 showed moderately resistant reaction. The root biochemical compounds analysis indicated that, total phenolic content (67.05 mg/g) and flavonoids (121.32 mg/g) were found higher in the inoculated roots of resistant line i.e. IIHR-824 indicating their role in conferring resistance. The identified F1 hybrids having resistance can be explored for commercial cultivation.

Evaluation of nematicidal potential of leaves extract of Afrohybanthus enneaspermus for management of Meliodogyne incognita in Tomato

The resistance of nematode pests to synthetic nematicides and its attendant hazards both to the crops and the ecosystem have caused growing interest. This study is aimed at investigating the nematicidal potential of the leaves extract of Afrohybanthus enneaspermus. Afrohybanthus enneaspermus is an evegreen shrub found in the tropical regions. The herbs have been used in ethonomedicine in the treatment of various ailments such as fever, diabetes, cough, skin infections and so on. According to standard methods in this study, in-vivo and In-vitro nematicidal screening of leaves extract was carried out against juvenile nematode pest (Meliodogyne incognita) while the pot experiment was carried out on tomato plants infected with root knot nematode. At the growth rate of the Tomato (Tropimech +), plant height was significantly lowered at 4 WAP (four weeks after planting) in tomato plants inoculated with 2,000 root-knot nematodes (RKN) applied with 20 g powered of Afrohybanthus enneaspermus compared with the rest of the treatments. With the application of 15% aqueous plant extracts and the inoculation of 2,000 RKN, plant height was significantly higher (32.8), followed by Plant alone and 20% aqueous plant extract. However, plant height was significantly lowered in plants applied with 20g powered of Afrohybanthus enneaspermus and nematode compared to the other treatments. At 6 weeks plant height is significantly higher in tomato plants inoculated with 5% aqueous plant extract with 2000RKN followed by others that are at the same range except 20g powered extract with 2000RKN that is significantly lowered . At 7 weeks plant height is significantly higher in tomato plants inoculated with 5% aqueous plant extract with 2000 RKN followed by others that are at the same range except 20g powdered extract with 2000 RKN that is significantly lowered. The research concluded that leaves extract of Afrohybanthus enneaspermus is effective in management of root Knot nematodes, however, in- vitro experiments, it is established that the powder form of the leave has higher effectiveness in management of nematode than its organic extract.

Nematicidal efficacy of Cymbopogon nardus, Pelargonium graveolens essential oils and Annona squamosa extract against Meloidogyne incognita and M. graminicola

A crude hexane extract of seed kernel was processed into fatty acid methyl esters (FAME) using methanolic-sulfuric acid. Herbal mixtures (seed extracts of A. squamosa and essential oils of Cymbopogon nardus (citronella) and Pelargonium graveolens (geranium)) were evaluated against root knot nematode (Meloidogyne spp). The mortality of J2s of M. incognita in hexane and methanol extracts (AHE+AME) of A. squamosa with geranium oil (GO) ranged from 50.75-89.75% to 71.50-99.00% at 31.25 to 1000 μgmL-1 in 24 to 96 hours. The number of galls after CO+AHE+AME treatment was 4.0 ± 0.0 and 5.67 ± 0.58 galls/seedling and were recorded at 1000 and 500 μgmL-1 treatments on 30 days after inoculation, compared to carbofuran (3.0 ± 0.0 and 4.3 ± 0.6 galls/seedling) at 1000 and 500 μgmL-1 and velum prime (3.6 ± 0.6 and 4.6 ± 0.6 galls/seedling) at 1000 and 500 μgmL-1. The maximum shoot length of brinjal seedlings was recorded in CO+AHE+AME treatment compared to carbofuran (47.3 ± 0.6cm) and velum prime (48.7 ± 0.6 cm) at 1000 μg mL-1 in soil drenching application. Methanol and hexane extracts (AHE+AME) obtained from Annona squamosa seeds were investigated for their nematicidal properties. M. graminicola in direct-seeded rice at the nursery level and M. incognita in brinjal (eggplant) were controlled for up to sixty days when treated with these mixtures.

The Effect of Flame Sterilization on the Microorganisms in Continuously Cultivated Soil and the Yield and Quality of Tobacco Leaves

Flame disinfection is a new technology that uses high temperatures to kill pathogens and control soil-borne diseases. In order to determine the feasibility of applying flame disinfection technology to flue-cured tobacco, a field experiment was conducted in Pianpo Village (test site I) and Lühuai Village (test site II), Luquan County, Yunnan Province. The effects of flame disinfection on soil-borne disease control, flue-cured tobacco growth agronomic traits, the tobacco yield and quality, and the soil microbial community in the flue-cured tobacco field were investigated. The results were as follows. (1) After flame disinfection, the control rates of the four main soil-borne diseases—black root rot, root rot, wilt, and root knot nematodes—were all over 70%. (2) Samples were taken from the experimental site of Pianpo Village at 0 and 114 days after disinfection (tobacco boom period) to study the effects of soil microbial communities by high-throughput sequencing. Compared with the control group, after 0 days of flame disinfection, the abundance of bacterial actinobacteria, Nocardia, Streptomyces, and fungal ascomycetes decreased, while the abundance of bacterial Proteobacteria, Bacteroidetes, Arthrobacter, and mycospora increased. After 114 days of disinfection, the abundance of bacterial actinobacteria, Proteobacteria, chloromyces, and fungal ascomycetes decreased. The abundance of Mortierella was recovered, the abundance of Gibberella and Fusarium increased, and the abundance of Trichospora and Basidiomycetes decreased in both periods. (3) After flame disinfection treatment, the tobacco yield in the two experimental areas was increased by 50.80% and 54.70%, respectively, and the proportion of high-quality tobacco was also increased. In conclusion, flame disinfection before tobacco planting can improve the soil conditions, effectively control soil-borne tobacco diseases, and improve the quality and yield of tobacco leaves.

Prevalence and Distribution of Rice Root Knot Nematode in Rice Nurseries in Chitwan and Lamjung Districts of Nepal

To determine the natural infection of the rice root-knot nematode (Meloidogyne graminicola Golden & Brichfield) in rice nurseries, a survey was carried out in Chitwan and Lamjung in June and July of 2022. Rice nurseries were randomly selected based on geographical location, agro-ecological region, land type, cropping practice, and soil type. Forty rice nurseries were surveyed i.e. twenty from each district and 100 seedlings from each nursery as the sample for the study using the simple random method of sampling were evaluated. Field survey revealed that M. graminicola was widely distributed in most rice growing areas of Chitwan and Lamjung districts. Most of the rice nurseries in Lamjung district were found to be infested with M. graminicola as compared to that of the Chitwan district. Disease severity was reported up to 23.26% in Lamjung and 20.2% in Chitwan district. Additionally, the study showed that dry bed conditions were more likely to be affected by rice root-knot disease than wet bed conditions. The majority of farmers planted seedlings on upland (dry) soil, where second-stage juvenile (J2) populations and rice root-knot disease were more common. Most farmers (87.5%) have limited knowledge about rice root knot nematodes and their control methods. This suggested a significant loss in rice output and a high danger of nematode multiplication. This information will provide knowledge about the prevalence of nematode and enabling rice growers in this region to design and implement an appropriate control strategy for managing M. graminicola.

Gene markers generating polygenic resistance in melon-Fusarium wilt-FOM1.2 interaction pathosystem.

Developing melon genotypes with resistance to Fusarium oxysporum f. sp. Melonis-(FOM) race1.2 is a major goal in any breeding program. In this study, we identified the role of 11 gene markers that contribute to polygenic resistance during the FOM1.2-melon interaction. qRT-PCR analysis elucidated upregulation of candidate marker genes AMT, DXPR, Fom-2, GLUC, GalS, GRF3, MLO, PRK, RuBlsCo, TLP and WRKY in resistant 'Shante-F1' and 'Khatouni', and susceptible 'Shante-T' and 'Shahabadi' at 7, 14 and 21 days post-inoculation (dpi). We also studied changes in defence-related enzyme activity: chitinase (CHI), β-1,3-glucanase (GLU) and peroxidase (POX) in melon roots. AMT, GLUC and DXPR transcripts were upregulatied in leaf and root tissues of the resistant 'Shante-F1' and 'Shahabadi'. Transcript levels for GalS and GRF3 increased 6.77- and 6.83-fold in roots of 'Shante-F1' at 7 dpi, whereas in PRK, TLP and WRKY theye increased by 7.84-, 5.15- and 12.26-fold at 14 dpi, respectively. However, transcript levels increased by 5.18-fold for Fom-2 and 8.46-fold for MLO at 21 dpi. Also, RBC transcript level peaked at 14 dpi with 4.9-fold increase in leaves of resistant genotypes, whereas AMT increased 2.94-fold at 21 dpi, and GLUC and DXPR increased 7.11- and 2.91-fold at 14 dpi in 'Shante-F', respectively. Defence-related-enzyme activity was also upregulated three-fold in resistant varieties. The dynamic shifts in the melon transcriptome induced by FOM1.2 emphasize that resistance mechanisms are predominantly regulated through signalling pathways involving CHI, GLU, and POX defence response. Surprisingly, the AMT gene, basically resistant to downy mildew, Pseudoperonospora cubensis; GLUC, MLO and PRK resistant to powdery mildew (Sphaerotheca fusca); TLP and WRKY resistant to Phytophthora blight (Phytophthora capsici); and GRF3 and RBC resistant to root knot nematodes (Meloidogyne spp.) were upregulated in resistant genotypes, indicating a dual role of these genes in resistance to more than one disease at a time.

Biocontrol potential of nicotinamide from Arachis hypogaea roots against Meloidogyne incognita

Root knot nematode disease is a global problem that causes significant economic losses to cash crops annually, and Meloidogyne incognita is the most destructive threat. The urgent need for reliable biocontrol agents is evident. This study evaluated the nematicidal effects of various tissue extracts from Arachis hypogaea, a non-host plant of M. incognita. Subsequently, the metabolic changes in peanut roots induced by M. incognita were analyzed, and the in vitro biological activity of differential metabolites were tested. The results indicated that peanut root extracts showed the highest inhibiting effect on M. incognita, the LC50 values were 18.54 mg/mL, 11.58 mg/mL, and 8.05 mg/mL after treated 24, 36, and 48 hours, respectively. Additionally, it was found that M. incognita infestation induced distinct metabolic changes in peanut roots. Among the differential metabolites, nicotinamide exhibited strong nematicidal effects on M. incognita, and the corrected mortality of second-stage juveniles and hatching inhibition of eggs could reach 99.65% and 95.90%, respectively at a concentration of 25 mg/mL. In conclusion, nicotinamide manifested distinctive advantages as a novel nematicide for the potential applications in sustainable agriculture.

Evaluation of the efficacy of some organic substances to induce resistance in cucumber against root knot nematode, Meloidogyne spp.

The study aimed to evaluate the impact of certain biofertilizers on some growth parameters, total chlorophyll content and the concentrations of enzymes phenylalanine amino-lyase (PAL) and peroxidase (POX) pre and post infestation of cucumber with root-knot nematodes (Meloidogyne spp.). The results demonstrate that supplementing substances before or after nematode infection resulted in enhanced growth parameters of cucumbers, including shoot growth, fresh and dry weight of root, total chlorophyll content and the concentrations of the enzymes PAL and POX, with significant differences compared to non-infected plants. Among those that showed a positive effect were ascorbic acid, K2HPO4, liquid earthworms, crushed fertilizer and compost. Among the test biofertilizers evaluated, the liquid vermicompost proved to be the standout performer compared to the other treatments, demonstrating the most substantial growth improvements such as the highest increase in both shoot fresh weight (44.67 g per plant) and dry weight (5.93 g per plant). Additionally, this treatment resulted in a remarkable 83.00 % increase in total chlorophyll content and a significant increase in PAL and POX enzyme activity (18.25 and 25.29 IU g-1 respectively).

Paenibacillus polymyxa J2-4 induces cucumber to enrich rhizospheric Pseudomonas and contributes to Meloidogyne incognita management under field conditions.

Root knot nematodes (RKNs) pose a great threat to agricultural production worldwide. The bacterial nematocides have received increasing attention due to their safe and efficient control against RKNs. Here, we investigated the biocontrol efficacy of Paenibacillus polymyxa J2-4 against Meloidogyne incognita in the field and analyzed the rhizosphere microbiome of cucumber under nematode infection after application of the J2-4 strain. Furthermore, a biomarker strain of Pseudomonas spp. was isolated from the J2-4-inoculated rhizosphere soil, and its nematocidal activity and growth-promoting effect on host plants were determined. In addition, chemotaxis assay of P. fluroescens ZJ5 toward root exudates was carried out. The field experiment demonstrated that P. polymyxa J2-4 could effectively suppressed gall formation in cucumber plants, with the galling index reduced by 67.63% in 2022 and 65.50% in 2023, respectively, compared with controls. Meanwhile, plant height and yield were significantly increased in J2-4 treated plants compared with controls. Metagenomic analysis indicated that J2-4 altered the rhizosphere microbial communities. The relative abundance of Pseudomonas spp. was notably enhanced in the J2-4 group, which was consistent with Linear discriminant analysis Effect Size results that Pseudomonas was determined as one of the biomarkers in the J2-4 group. Furthermore, the ZJ5 strain, one of the biomarker Pseudomonas strains, was isolated from the J2-4-inoculated rhizosphere soil and was identified as Pseudomonas fluorescens. In addition, P. fluorescens ZJ5 exhibited high nematicidal activity in vitro and in vivo, with 99.20% of the mortality rate of M. incognita at 24 h and 69.75% of gall index reduction. The biocontrol efficiency of the synthetic community of ZJ5 plus J2-4 was superior to that of any other single bacteria against M. incognita. Additionally, ZJ5 exhibited great chemotaxis ability toward root exudates inoculated with J2-4. Paenibacillus polymyxa J2-4 has good potential in the biological control against M. incognita under field conditions. Enrichment of the beneficial bacteria Pseudomonas fluorescens ZJ5 in the J2-4-inoculated rhizosphere soil contributes to M. incognita management. © 2024 Society of Chemical Industry.

In-vitro Study of Different Fungal Bio-agents against Root-knot Nematode, Meloidogyne incognita

To assess the antagonistic effect of fungal bio-control agents, such as Trichoderma harzianum, T. viride, Purpureocillium lilacinum, Metarhizium anisopliae, and Beauveria bassiana, on the hatching of egg masses of the root-knot nematode, Meloidogyne incognita, investigations were conducted in vitro. In comparison to the control, bio-control agents were tested at 106 and 107 dilutions on M. incognita egg hatching after 24, 48, 72, 96, and 120 hours of exposure. P. lilacinum 107 concentration and T. harzianum 106 concentration (83.90 % and 83.04 %) were found at par and significantly effective on egg hatching inhibition of M. incognita. Among different concentration, P. lilacinum at 106 concentration (85.46 %) gave maximum egg hatching inhibition followed by P. lilacinum at 107 concentration (83.90 %), T. harzianum at 106 concentration (83.04 %) and T. virideat 106 concentration (82.00 %) after 120 hrs. M. anisopliae at 107 concentration (69.46 %) was found least effective at different period of exposure. Further studies to be conducted in pot and field conditions to evaluate the efficacy of these bio-agents against root knot nematode, M. incognita.

Bio Efficacy of Different Fungal Bio-agents on Juvenile Mortality of Root Knot Nematode, Meloidogyne incognita under Laboratory Condition

An investigation was carried out in vitro to evaluate the antagonistic effect of fungal bio-control agents i.e., Trichoderma harzianum, T. viride, Purpureocillium lilacinum, Metarhizium anisopliae and Beauveria bassiana on second stage juvenile (J2) mortality of root-knot nematode (RKN) at 106 and 107 dilutions on juvenile mortality of M. incognita after 24, 48, 72, 96 and 120 hrs exposure period as compared to untreated check. Among different dilutions, T. viride at 106 dilutions (86.00 per cent) gave maximum per cent juvenile mortality followed by T. harzianum at 106 dilutions (82.00 per cent), P. lilacinum at 106 dilutions (76.00 per cent) and T. viride at 107 dilutions (72.00 per cent) after 120 hrs. M. anisopliae at 107 dilutions (38.00 per cent) was found least effective at different period of exposure.Further studies need to be conducted in pot and field conditions to evaluate the efficacy of these bio-agents against root knot nematode, M. incognita.

Microbial communities and high trophic level nematodes in protected argan soil show strong suppressive effect against Meloidogyne spp.

In many agroecosystems, soil suppressiveness to root knot nematodes (RKN) is of great interest in defining the biological agents controlling population density, especially with growing concerns about the environmental and human health impacts of chemicals. In this study, we evaluated the suppressiveness to Meloidogyne spp. in two land use soils: a protected argan soil from the Souss Massa National Park (SMNP), Morocco, and a conventional soil from an adjacent non-protected area. Using next-generation sequencing (NGS) technology, we characterized the fungal and bacterial communities in these soils for the first time. Nematodes belonging to different trophic guilds were also analyzed to further understand ecological factors that enable suppressive organisms to function and persist in the soil. The experiment was conducted in a greenhouse with tomato plants grown in untreated and autoclaved soils, each inoculated with 800 Meloidogyne infective juveniles (J2). We found that omnivore-predator nematode abundance, structure, and maturity indices were higher in the protected soil indicating the presence of a well-structured soil food web and a stable ecosystem. After sixty-seven days, RKN population density and gall index were reduced by 79.6 % and 81.5 % in the protected soil, respectively. 50 % autoclaved protected soil was also suppressive, but not 75 % and totally autoclaved soil. In contrast, conventional soil amplified the RKN population by 1319 %. More than 6770 bacterial and 558 fungal taxa were detected in this study, with Firmicutes, Actinobacteria, Mortierellales, Orbiliales, Agaricales, Diversisporales, and Pleosporales being consistently associated with RKN suppression. We found that fungal diversity was higher in SMNP-protected soil. In conclusion, soil protection enhances soil ecosystem resilience and that protected argan soils can serve as a valuable source of biological agents for the sustainable management of phytoparasitic nematodes.

Piriformospora indica modifies cucumber’s tolerance to Meloidogyne incognita by regulating various agro-physiological traits, antioxidant enzymes, and abscisic acid pathway genes

Root knot nematode (RKN), Meloidogyne incognita, is considered a major soil-borne pathogen that can cause severe yield losses for vegetables and diverse crops. Usually, reducing of M. incognita damage is mainly relies on the application of nematicides and good agricultural practices. However, the use of synthetic nematicides is restricted due to concerns about their impact on the environment and human health. As a result, the use of alternative strategies is becoming necessary to combat RKN resistance. This study evaluates the antagonistic impact of the root mutualistic fungus Pirforomospora indica on M. incognita. It also assesses its influence on the nutritional status, photo-synthesis, antioxidant enzyme activity, endogenous abscisic acid (ABA) levels, and selected ABA related-responsive genes in cucumber plants. Roots of cucumber seedlings were inoculated with P. indica and the second-stage juveniles (1000 J2 per plant). The results demonstrated that P. indica significantly reduced M. incognita invasion in roots, resulting in a 24% reduction in root galling and 42.6% decline in final population. Inoculating plants with both P. indica and RKN increased performance of root fresh and dry weight, as well as improved photochemical efficiency of PSII (Fv/Fm), photosystem II efficiency (PSII), catalase (CAT), peroxidase (POD), and superoxide dis-mutase (SOD). Furthermore, P. indica colonization, either alone or in combination with M. incognita, significantly improved number of fruits per plant, average fruit weight, the plant's marketable yield, and leaf nutrient content (N, P, K and Mg), Moreover, there was an increase in IAA content combined with a decrease in ABA content in roots of dual inoculation plants, if compared to M. incognita infested plants. The highest ABA content was recorded in the root of RKN-cucumber plants. The decline in ABA content due to P. indica treatment was consistent with the modulation of ABA pathway genes, specifically PP2C, PYL1, RK2,1, and RK2,2. The mixed of P. indica and M. incognita led to a decrease in the expression of PP2C, PLY1, RK2,1, and RK2,2 in comparison to the control group. These results indicate that P. indica application could help reduce the negative effects of RKN on important crops.

Differential expression of sweetpotato nodulin 26-like intrinsic protein (NIP) genes in response to infection with the root knot nematode

Differential expression of sweetpotato nodulin 26-like intrinsic protein (NIP) genes in response to infection with the root knot nematode

Volatile organic compounds released from entomopathogenic nematode-infected insect cadavers for the biocontrol of Meloidogyne incognita.

Root-knot nematodes (RKNs), Meloidogyne spp., are one of the most destructive polyphagous plant-parasitic nematodes. They pose a serious threat to global food security and are difficult to control. Entomopathogenic nematodes (EPNs) show promise in controlling RKNs. However, it remains unclear whether the volatile organic compounds (VOCs) emitted from EPN-infected cadavers can control RKNs. We investigated the fumigation activity of VOCs released from cadavers infected by five different species of EPNs on RKNs in Petri dishes, and found that VOCs released from Steinernema feltiae (SN strain) and S. carpocapsae (All strain) infected cadavers had a significant lethal effect on second-stage juveniles (J2s) of Meloidogyne incognita. The VOCs released from the cadavers infected with S. feltiae were analyzed using SPME-GC/MS. Dimethyl disulfide (DMDS), tetradecane, pentadecane, and butylated hydroxytoluene (BHT), were selected for a validation experiment with pure compounds. The DMDS compound had significant nematicidal activity and repelled J2s. DMDS also inhibited egg hatching and the invasion of tomato roots by J2s. In a pot experiment, the addition of S. feltiae-infected cadavers and cadavers wrapped with a 400-mesh nylon net also significantly reduced the population of RKNs in tomato roots after 7 days. The number of root knots and eggs was reduced by 58% and 74.34%, respectively, compared to the control. These results suggested that the VOCs emitted by the EPN-infected cadavers affected various developmental stages of M. incognita and thus have the potential to be used in controlling RKNs through multiple methods. © 2024 Society of Chemical Industry.

Native Arbuscular Mycorrhizal Fungi Promote Plukenetia volubilis Growth and Decrease the Infection Levels of Meloidogyne incognita.

The use of arbuscular mycorrhizal fungi (AMF) offers promising benefits to agriculture in the Amazon regions, where soils are characteristically acidic and nutrient-poor. The purpose of this research was to investigate the potential effects of two recently described species of AMF (Nanoglomus plukenetiae and Rhizoglomus variabile) native to the Peruvian Amazon for improving the plant growth of Plukenetia volubilis (inka nut or sacha inchi) and protecting the roots against soil pathogens. Two assays were simultaneously conducted under greenhouse conditions in Peru. The first focused on evaluating the biofertilizer effect of AMF inoculation, while the second examined the bioprotective effect against the root knot nematode, Meloidogyne incognita. Overall, the results showed that AMF inoculation of P. volubilis seedlings positively improved their development, particularly their biomass, height, and the leaf nutrient contents. When seedlings were exposed to M. incognita, plant growth was also noticeably higher for AMF-inoculated plants than those without AMF inoculation. Nematode reproduction was significantly suppressed by the presence of AMF, in particular R. variabile, and especially when inoculated prior to nematode exposure. The dual AMF inoculation did not necessarily lead to improved crop growth but notably improved P and K leaf contents. The findings provide strong justification for the development of products based on AMF as agro-inputs to catalyze nutrient use and uptake and protect crops against pests and diseases, especially those that are locally adapted to local crops and cropping conditions.

Bringing light into the dark—plant electrophysiological monitoring of root knot nematode infestation and real-time nematicide efficacy

Bringing light into the dark—plant electrophysiological monitoring of root knot nematode infestation and real-time nematicide efficacy

Biochemical and nanotechnological approaches to combat phytoparasitic nematodes.

The foundation of most food production systems underpinning global food security is the careful management of soil resources. Embedded in the concept of soil health is the impact of diverse soil-borne pests and pathogens, and phytoparasitic nematodes represent a particular challenge. Root-knot nematodes and cyst nematodes are severe threats to agriculture, accounting for annual yield losses of US$157 billion. The control of soil-borne phytoparasitic nematodes conventionally relies on the use of chemical nematicides, which can have adverse effects on the environment and human health due to their persistence in soil, plants, and water. Nematode-resistant plants offer a promising alternative, but genetic resistance is species-dependent, limited to a few crops, and breeding and deploying resistant cultivars often takes years. Novel approaches for the control of phytoparasitic nematodes are therefore required, those that specifically target these parasites in the ground whilst minimizing the impact on the environment, agricultural ecosystems, and human health. In addition to the development of next-generation, environmentally safer nematicides, promising biochemical strategies include the combination of RNA interference (RNAi) with nanomaterials that ensure the targeted delivery and controlled release of double-stranded RNA. Genome sequencing has identified more than 75 genes in root knot and cyst nematodes that have been targeted with RNAi so far. But despite encouraging results, the delivery of dsRNA to nematodes in the soil remains inefficient. In this review article, we describe the state-of-the-art RNAi approaches targeting phytoparasitic nematodes and consider the potential benefits of nanotechnology to improve dsRNA delivery.

Transcriptional regulation modulates saponin biosynthesis of Panax notoginseng response to root knot nematodes

Root knot nematodes (RKNs) are highly destructive pests that pose a negative impact on the growth of Panax notoginseng and also affect its quality. P. notoginseng is widely known for its medicinal properties regarded to ginsenosides which are chemically triterpene saponins. However, the effect of RKNs infection on the saponin content in the roots and the transcriptional regulation mechanisms of their synthesis are not well understood. Our study aimed to assess the impact on saponin content and investigate the expression pattern of key genes related to saponin synthesis in RKN-infected P. notoginseng. Our results highlight that RKNs infection significantly affected the content of notoginseng R1 in the main root, with a major impact on the levels of ginsenoside Rg1 and Rb1 in lateral roots. Furthermore, the expression of saponin synthesis key genes in RKN-infected P. notoginseng varied as compared with the healthy plant. Specifically, various genes including HMGS2, DS1, and DS2, were up-regulated in response to RKNs infection of grade I and II. In contrast, except for DXS5, various genes were down-regulated when the infection degree of RKNs reached grade II and III. In addition, our study highlights the strong correlation between transcription factor families and triterpenoid saponin synthesis genes, such as AP2/ERF-ERF, bHLH, WRKY, GRAS and MYB. It was found that the expression pattern of the PnMYB61 transcription factor closely reflected that of squalene epoxidase (SE2), a key gene that controls the biosynthesis of 2,3-oxidosqualene, following RKNs infection. Molecular docking analysis also suggested that PnMYB61 may play a crucial regulatory role in expression of SE2 protein. Overall, our findings contribute to the quality evaluation of RKN-infected P. notoginseng roots and provide valuable insights into the identification of key regulators involved in ginsenoside biosynthesis.

Evaluation of the Efficiency of some Nanoparticles and Chemical Nematicides in Controlling Root-Knot Nematodes Meloidogyne Incognita (on Eggplant)

Objectives: This study was carried out to investigate the effectiveness of some nanoparticles in inhibiting the growth of the root knot nematode. Methods: This study was carried out to investigate the effectiveness of aluminum oxide Alo-NPs and silver Ag-NPs, and chemical nematicides (Velum prime and Furadan granules), in inhibiting the growth of the root knot nematode (Meloidogyne incognita) on two different types of eggplant cultivars, Barcelona and Thuraya. Results: The result obtained indicated that chemical nematicides and nanoparticles were highly effective in lowering the nematode invasion level expressed as number of knots per root and a gall index based on a 0-5 scale. Velum prime at concentrations of 300 and 400 ppm was the most effective and gave 0.67 and 0.17 knots/root average on both eggplant cultivars, respectively. In addition, the ALO-NPs treatment reduced infection to 1.17 knots/root compared to initial infection of 37.33 knots/root. The use of Ag-NPs at the concentration of 4000 ppm reduced infection to a low average of 2.83 knots/root for both eggplant varieties. All treatments average reduced the gall index to 0.95 (cv. Barcelona) and 1.20 (cv. Thuraya) compared to 3.33 and 4.00 for the infected non-treated controls, respectively. Conclusions: Nanoparticles have a role in controlling root-knot galls as alternatives to chemical pesticides that are dangerous to the environment and humans, and reducing the number of galls on the plant indicates the inhibition of eggs and second stage juveniles (J2).