Meloidogyne Research Articles

Host status of cover crops for the management of Meloidogyne izalcoensis in coffee orchards infested with root-knot nematodes

Summary The root-knot nematode Meloidogyne izalcoensis was described parasitising coffee trees and causing damage in the Izalco volcano region, Sonsonate, El Salvador. In Brazil, it was detected in coffee roots in the municipality of Indianópolis, Minas Gerais state (MG). Intercropping cover crops is a traditional practice in Brazilian coffee orchards, and the use of plants that are non-hosts or antagonistic to the nematodes is a very promising strategy for coffee in infested areas. Due to the scarce information on the host status of M. izalcoensis, the aim of this study was to evaluate 24 plants of different species of cover crops and select the non-hosts or poor hosts. Two assays were conducted at different times, and all plants were inoculated with 10 000 eggs. After 90 days, the following parameters were determined: fresh root weight, reproduction factor (RF) and final reaction. Plants with RF < 1.0 were classified as non-hosts (NH), those with RF > 1.0 were classified as hosts and using statistical analyses as: good host (GH), intermediate host (IH) and poor host (PH). Most of the botanical species tested were classified as NH or PH to M. izalcoensis: cotton, rice, white oat, black oat, ryegrass, corn, three species of grass, two cultivars of millet, two wheat cultivars, Crotalaria breviflora, C. ochroleuca, C. spectabilis, jack bean, gray mucuna bean and two species of rice grass. Only tomato and bean were classified as GH, and C. juncea and soybean were classified as IH. The plants identified as non-hosts or poor hosts can be recommended for intercropping or for crop rotation in Brazilian coffee orchards in regions infested by M. izalcoensis.

Efficient control of root-knot nematodes by expressing Bt nematicidal proteins in root leucoplasts

Root-knot nematodes (RKNs) are plant pests that infect the roots of host plants. Bacillus thuringiensis (Bt) nematicidal proteins exhibited toxicity to nematodes. However, the application of nematicidal proteins for plant protection is hampered by the lack of effective delivery systems in transgenic plants. In this study, we discovered the accumulation of leucoplasts (root plastids) in galls and RKN-induced giant cells. RKN infection causes the degradation of leucoplasts into small vesicle-like structures, which are responsible for delivering proteins to RKNs, as observed through confocal microscopy and immunoelectron microscopy. We showed that different-sized proteins from leucoplasts could be taken up by Meloidogyne incognita female. To further explore the potential applications of leucoplasts, we introduced the Bt crystal protein Cry5Ba2 into tobacco and tomato leucoplasts by fusing it with a transit peptide. The transgenic plants showed significant resistance to RKNs. Intriguingly, RKN females preferentially took up Cry5Ba2 protein when delivered through plastids rather than the cytosol. The decrease in progeny was positively correlated with the delivery efficiency of the nematicidal protein. In conclusion, this study offers new insights into the feeding behavior of RKNs and their ability to ingest leucoplast proteins, and demonstrates that root leucoplasts can be used for delivering nematicidal proteins, thereby offering a promising approach for nematode control.

Optimization andutilization ofemerging waste (fly ash) for growth performance of chickpea (Cicer arietinum L.) plant and mitigation of root-knot nematode (Meloidogyne incognita) stress.

The sustainable management of large amounts of fly ash (FA) is a concern for researchers, and we aim to determine the FA application in plant development and nematicidal activity in the current study. A pot study is therefore performed to assess the effects of adding different, FA-concentrations to soil (w/w) on the infection of chickpea plants with the root-knot nematode Meloidogyne incognita. Sequence characteristic amplified region (SCAR) and internal transcribed spacer (ITS) region-based-markers were used to molecularly confirm M. incognita. With better plant growth and chickpea yield performance, FA enhanced the nutritious components of the soil. When compared with untreated, uninoculated control (UUC) plants, the inoculation of M. incognita dramatically reduced chickpea plant growth, yield biomass, and metabolism. The findings showed that the potential of FA to lessen the root-knot nematode illness in respect of galls, egg-masses, and reproductive attributes may be used to explain the mitigating effect of FA. Fascinatingly, compared with the untreated, inoculated control (UIC) plants, the FA treatment, primarily at 20%, considerably (p ≤ 0.05) boosted plant growth, yield biomass, and pigment content. Additionally, when the amounts of FA rose, the activity of antioxidants like superoxide dismutase-SOD, catalase-CAT, and peroxidase-POX as well as osmo-protectants like proline gradually increased. Therefore, our findings imply that 20% FA can be successfully applied as a potential strategy to increase biomass yield and plant growth while simultaneously reducing M. incognita infection in chickpea plants.

Effect of Temperature on the Embryogenesis of Three Geographically Distinct Populations of Meloidogyne incognita Is Driven by Intrinsic Thermal Acclimation Reaction.

Research interest in the mechanisms enabling plant-parasitic nematodes to adjust their physiological performance and cope with changing temperatures has intensified in light of global warming. Here, we show that geographically distinct populations of the root-knot nematode Meloidogyne incognita, which is prevalent in the three main pepper-growing regions in Israel-Carmel Valley (Carmel), Jordan Valley (JV), and Arava Rift (Arava)-possess persistent differences in their thermal acclimation capacity, which affect pre- and postembryonic development. The optimal temperature for embryonic growth completion was 25°C for the Carmel population; 25 and 30°C for the JV population; and 30°C for the Arava population. Cumulative hatching percentages showed variations among populations; relative to hatching at 25°C, the Carmel population experienced hatching reduction at the higher studied temperatures 30 and 33°C, while the JV and Arava populations exhibited an increase in hatching at 30 and 33°C, respectively. Juvenile survival indicates that at the lowest temperature (20°C), the Carmel population gained the highest survival rates throughout the experimental duration, while at the same duration at 33°C, the Arava population gained the highest survival rate. Infective juveniles of the Carmel population demonstrated increased penetration of tomato roots at 25°C compared to the JV and Arava populations. Inversely, at 33°C, increased penetration was observed for the Arava compared to the Carmel and JV populations. Altogether, the Arava population's performance at 33°C might incur distinct fitness costs, resulting in consistent attenuation compared to the Carmel population at 25°C. Precisely defining a population's thermal acclimation response might provide essential information for models that predict the impact of future climate change on these populations.

Optimizing sustainable control of Meloidogyne javanica in tomato plants through gamma radiation-induced mutants of Trichoderma harzianum and Bacillus velezensis

This study investigates the efficacy of Trichoderma spp. and Bacillus spp., as well as their gamma radiation-induced mutants, as potential biological control agents against Meloidogyne javanica (Mj) in tomato plants. The research encompasses in vitro assays, greenhouse trials, and molecular identification methodologies to comprehensively evaluate the biocontrol potential of these agents. In vitro assessments reveal significant nematicidal activity, with Bacillus spp. demonstrating notable effectiveness in inhibiting nematode egg hatching (16–45%) and inducing second-stage juvenile (J2) mortality (30–46%). Greenhouse trials further confirm the efficacy of mutant isolates, particularly when combined with chitosan, in reducing nematode-induced damage to tomato plants. The combination of mutant isolates with chitosan reduces the reproduction factor (RF) of root-knot nematodes by 94%. By optimizing soil infection conditions with nematodes and modifying the application of the effective compound, the RF of nematodes decreases by 65–76%. Molecular identification identifies B. velezensis and T. harzianum as promising candidates, exhibiting significant nematicidal activity. Overall, the study underscores the potential of combined biocontrol approaches for nematode management in agricultural settings. However, further research is essential to evaluate practical applications and long-term efficacy. These findings contribute to the development of sustainable alternatives to chemical nematicides, with potential implications for agricultural practices and crop protection strategies.

Isolation and Characterization of a (Surfactin-Like Molecule) Produced by Bacillus subtilis: Antagonistic Impact on Root-Knot Nematodes

Plant-parasitic nematodes are severe soil-borne pathogens that cause significant damage to agricultural products each year, resulting in substantial financial losses globally. Thus, there is an urgent need to identify novel biological control agents or nematicides. The nematicidal potential of Bacillus subtilis-derived lipopeptides against Meloidogyne incognita was investigated at various concentrations (35 ppm, 25 ppm, 15 ppm, 5 ppm) under in vitro conditions. Egg hatching inhibition and mortality of second-stage juveniles (J2s) of M. incognita were analyzed after exposure for 6, 12, 24, 48, and 96 hours. Data showed that with the increase in concentration and exposure period, egg hatching inhibition and percent mortality increases. Maximum percent mortality of J2s was reported at 35ppm i.e., 45%, 55%, 67.75%, 77% and 85% at 6, 12, 24, 48 and 96 hrs, respectively. The maximum ovicidal activity was reported at 35ppm concentration, with 84.61% of eggs hatching inhibition on 96 hrs of the exposure period. The bacterial culture suspension of Bacillus subtilis and Pseudomonas putida at1.2x108cfu/ml, and the crude lipopeptide (35ppm) was also investigated as a biological control agent against M. incognita on tomato in a pot experiment under glasshouse condition. Combinational treatment of P. putida and B. subtilis culture, prior to inoculation of M. incognita on tomato plant caused a significant increase in plant growth attributes and in biochemical parameters over the inoculated control. In the same treatment, the maximum reduction in nematode population and root galling was recorded. However, in the crude lipopeptide experiment study, root dip and inoculation of crude lipopeptide in tomato after the introduction of M. incognita caused a major augment in all the parameters over the inoculated control. MALDI-TOF MS analysis of crude lipopeptide shows surfactin like molecules at m/z 1058 [M+Na]+. It is concluded that crude lipopeptide or combinational treatment of B. subtilis and P. putida culture suspension can be employed as a biocontrol agent against M. incognita and may act as a source of a novel nematicidal agent of bacterial origin.

Building accelerated plant breeding pipelines: Screening to evaluate lima bean resistance to root-knot nematode in diverse inbred lines and segregating breeding populations.

Lima beans (Phaseolus lunatus) are a cornerstone crop of Delaware's processing vegetable industry. Root-knot nematodes (RKN; Meloidogyne spp.) cause galling of root systems which severely reduces yield. Durable host resistance is an effective management strategy for RKN, but availability of resistant lima bean cultivars is limited. To overcome these challenges, breeding pipelines must simultaneously advance pre-commercial lines and identify new resistance sources with potential for incorporation into the breeding program. Inoculated field trials were conducted in 2021-2022 to evaluate three M. incognita resistant, pre-commercial experimental lines for resistance traits and yield potential in comparison to commercial standards, 'Cypress' and 'C-elite Select'. DE1306635 had the highest yield and reduced galling and reproduction compared to 'Cypress', and is a candidate for commercial release. To continue the breeding pipeline, 256 lima bean inbred accessions from around the world were assessed from 2022-2023 in greenhouse and field screenings to identify novel sources of resistance in the lima bean gene pool. This method allows for evaluation and/or advancement of three generations per year. The full panel was initially evaluated for root galling and 60 accessions were selected for additional field and greenhouse screening: 25 large- and 25 small-seeded with the lowest gall ratings, 5 high-gall controls, and 5 commercial standards. Seven accessions with reduced M. incognita galling and reproduction were identified, including two known resistant lines and five newly identified genotypes. The resistance carried by these genotypes will be further characterized to assess their potential use in lima bean RKN resistance breeding.

Metabolomics and histopathological analysis of two tomato cultivars after co-infection with soil-borne pathogens (Southern root-knot nematode and Fusarium wilt fungus)

Southern root-knot nematode (Meloidogyne incognita) and Fusarium wilt fungus (Fusarium oxysporum) are one of the most predominant pathogens responsible for substantial agricultural yield reduction of tomato. The current study planned to assess the effects of M. incognita (Mi) and F. oxysporum (Fo) and their co-infection on two tomato cultivars, Zhongza 09 (ZZ09) and Gailing Maofen 802 (GLM802). The present study examined the effects of co-infection on leaf morphology, chlorophyll content, leaf area, and histopathology. The present study used metabolomics to evaluate plant-pathogen interactions. The outcomes of the current study revealed that chlorophyll content and leaf area decreased more in GLM802 during co-infection. In co-infection (Fo + Mi), the chlorophyll content reduction in ZZ09 was 11%, while in GLM802 the reduction reached up to 31% as compared to control. Moreover, the reduction in leaf are in ZZ09 was 31%, however, in the GLM802 reduction was observed 54% as compared to control plants. Similarly, GLM802 stems exhibited larger brown patches on their vascular bundles than ZZ09 stems. The rate of browning of GLM802 stems was 247% more than ZZ09, during co-infection. Moreover, GLM802 roots exhibited a higher abundance of hyphae and larger galls than ZZ09 roots. In metabolic studies, glutathione, succinic acid, and 2-isopropylmalic acid decreased, whereas spermine and fumaric acid increased in GLM802 co-infected stems. It indicates that GLM802 is weakly resistant; therefore, F. oxysporum and other pathogens readily damage tissue. In the co-infected stem of ZZ09, L-asparagine and shikimic acid increased, but pipecolic acid, L-saccharine, and 2-isopropylmalic acid declined. L-asparagine was crucial in preserving the stability of nitrogen metabolism, chlorophyll synthesis, and leaf growth in ZZ09. Shikimic acid's substantial accumulation could explain the limited extent of browning observed in the vascular bundles of ZZ09. Thus, the present study provides insight into M. incognita and F. oxysporum co-infection in two tomato cultivars, which may aid breeding efforts to generate commercially viable resistant cultivars. However, further research on the relationship between M. incognita and F. oxysporum in different host plants is required in the future.

THE POTENTIAL OF TEQUIL, A PLANT EXTRACT BASED ON QUILLAJA SAPONARIA, IN SUSTAINABLE AGRICULTURE

More attention is being given to researches of eco-sustainable solutions to be implemented in agriculture, particularly in the presence of plant parasitic nematodes, whose damages have significant global importance. Unsustainable practices, such as fumigation and monoculture, have led to depletion of biodiversity, allowing harmful trophic groups (bacteria, fungi, and nematodes) to prevail, and their negative synergistic action further exacerbating yield losses. Considering the notable and progressive restriction of usable molecules, nematode control strategies must necessarily consider the appropriate integration of methods. The main objective of control is to limit pathogen populations below the damage threshold, rather than aiming at their eradication as mistakenly pursued in the past. This goal can be achieved with the help of solutions that promote plant development through biostimulation of root systems, which are often affected by various organisms in the biosphere. Tequil, through its well-documented synergy of saponins, tannins, and polyphenols, produces invigorating, biostimulating, and strengthening effects on the root system. Indeed, in vitro tests and field trials have highlighted Tequil’s appreciable activity in containing trophic groups, particularly root-knot nematodes of the Meloidogyne genus. Therefore, its use could indirectly contribute to nematode control and limit yield losses. Key Words: Quillaja saponaria, nematodes, bio stimulation, biocontrol, abiotic stresses resistance.

Distinct changes in tomato-associated multi-kingdom microbiomes during Meloidogyne incognita parasitism

BackgroundThe interplay between root-knot nematode (RKN) parasitism and the complex web of host-associated microbiota has been recognized as pivotal for effective management of the pest. However, studies assessing this relationship have focussed on the bacterial and fungal communities, neglecting the unicellular eukaryotic members. Here, we employed amplicon sequencing analysis of the bacterial 16S rRNA, fungal ITS and eukaryotic 18S rRNA genes, and comprehensively examined how the microbiome composition, diversity and networking developed with time in the rhizospheres and roots of RKN-inoculated and non-inoculated tomato plants.ResultsAs expected, infection with the RKN Meloidogyne incognita decreased plant growth. At individual timepoints, we found distinct bacterial, fungal and eukaryote community structures in the RKN-inoculated and non-inoculated rhizospheres and roots, and RKN inoculation affected several taxa in the root-associated microbiome differentially. Correlation analysis revealed several bacterial and fungal and few protist taxa that correlated negatively or positively with M. incognita. Moreover, network analysis using bacterial, fungal and eukaryotic data revealed more dynamic networks with higher robustness to disturbances in the RKN-inoculated than in the non-inoculated rhizospheres/roots. Hub taxa displayed a noticeable successional pattern that coincided with different phases of M. incognita parasitism. We found that fungal hubs had strong negative correlations with bacteria and eukaryotes, while positive correlations characterized hub members within individual kingdoms.ConclusionOur results reveal dynamic tomato-associated microbiomes that develop along different trajectories in plants suffering M. incognita infestation and non-infested plants. Overall, the results identify stronger associations between RKN and bacterial and fungal taxa than between eukaryotic taxa and RKN, suggesting that fungal and bacterial communities could play a larger role in the regulation of RKN. The study identifies several putative RKN-antagonistic bacterial and fungal taxa and confirms the antagonistic potential previously identified in other taxa.

Seasonal Fluctuations in Plant-Parasitic Nematode Vertical Distributions and Their Interactions with Edaphic Factors in Vegetable Fields of South Georgia, U.S.A.

Plant-parasitic nematodes (PPNs) can be found deep in the soil profile, compounding nematode management decisions and detection. This study aimed to understand how seasonal fluctuations in edaphic factors are associated with the vertical distribution of PPNs in south Georgia's vegetable cropping systems. Five-core composite soil samples were taken monthly (March 2020 to February 2022) at three random locations in six vegetable fields. Fields represented three cropping systems (vegetable plasticulture, bare ground cucumber, and plastic bed watermelon rotation) and two regions (north and south) sampled from five 15-cm strata (0 to 15, 15 to 30, 30 to 45, 45 to 60, and 60 to 75 cm). Only soil temperatures and precipitation had seasonal fluctuations; the other edaphic factors were vertically stratified. Latitude and stratum had the strongest associations with nematode composition, showing a clear separation between the north and south regions. Variations in soil texture, porosity, moisture, and PPN vertical distribution suggested that the illuvial zone in the north region was the main factor in the differences observed between regions and strata. Seasonal fluctuations in vertical distribution were found among Meloidogyne incognita and Nanidorus spp. Higher abundances of deep-dwelling PPNs were limited to the south region in the winter for deep-dwelling M. incognita and summer and winter for Nanidorus spp., probably due to the illuvial zone barrier in the north region. Because most root-knot nematodes dwell at ≤30 cm during the summer, fumigant/nematicide applications are recommended during this season to minimize the risk of deep-dwelling escapees.

Nematicidal Activity of Volatiles against the Rice Root-Knot Nematode and Environmental Safety in Comparison to Traditional Nematicides.

The rice root-knot nematode (RRKN), Meloidogyne graminicola Golden and Birchfield 1965, is a dangerous crop pest that affects rice production on a global scale. The largest rice-producing countries struggle with the impacts of RRKN infestation, namely, underdeveloped plants and a reduction in rice grain that can reach up to 70% of crop yield. In addition, the shift to strategies of sustainable pest management is leading to a withdrawal of some of the most effective pesticides, given the dangers they pose to the environment and human health. Volatile metabolites produced by plants can offer safer alternatives. The present study characterized the nematicidal activity of volatile phytochemicals against the RRKN and compared the most active with commercial nematicides concerning their safety to the environment and human health. Rice plants were used to grow large numbers of RRKNs for direct-contact bioassays. Mortality induced by the volatiles was followed for four days on RRKN second-stage juveniles. Of the 18 volatiles tested, carvacrol, eugenol, geraniol, and methyl salicylate showed the highest mortalities (100%) and were compared to traditional nematicides using (eco)toxicological parameters reported on freely available databases. While methyl salicylate had a faster activity, carvacrol had more lasting effects. When compared to synthetic nematicides, these volatile phytochemicals were reported to have higher thresholds of toxicity and beneficial ecotoxicological parameters. Ultimately, finding safer alternatives to traditional pesticides can lower the use of damaging chemicals in farming and leverage the transition to agricultural practices with a lower impact on biodiversity.

Local and systemic transcriptome and spliceome reprogramming induced by the root-knot nematode Meloidogyne incognita in tomato.

Root-knot nematodes (Meloidogyne spp.) are widely spread root parasites that infect thousands of vascular plant species. These highly polyphagous nematodes engage in sophisticated interactions with host plants that results in the formation of knot-like structures known as galls whose ontogeny remains largely unknown. Here, we determined transcriptome changes and alternative splicing variants induced by Megalaima incognita in galls and neighboring root cells at two distinct infective stages. M. incognita induced substantial transcriptome changes in tomato roots both locally in galls and systemically in neighboring cells. A considerable parallel regulation of gene expression in galls and neighboring cells were detected, indicative of effective intercellular communications exemplified by suppression of basal defense responses particularly during the early stage of infection. The transcriptome analysis also revealed that M. incognita exerts a tight control over the cell cycle process as a whole that results in an increase of ploidy levels in the feeding sites and accelerated mitotic activity of the gall cells. Alternative splicing analysis indicated that M. incognita significantly modulates pre-mRNA splicing as a total of 9064 differentially spliced events from 2898 genes were identified where intron retention and exon skipping events were largely suppressed. Furthermore, a number of differentially spliced events were functionally validated using transgenic hairy root system and found to impact gall formation and nematode egg mass production. Together, our data provide unprecedented insights into the transcriptome and spliceome reprogramming induced by M. incognita in tomato with respect to gall ontogeny and nematode parasitism.

Utilizing endophytic plant growth-promoting bacteria and the nematophagous fungus Purpureocillium lilacinum as biocontrol agents against the root-knot nematode (Meloidogyne incognita) on tomato plants

AbstractThe present investigation was designed to assess how administering biocontrol agents (BCAs) made from the nematophagous endophytic fungus MR20 (Purpureocillium lilacinum) or a mixture of endophytic plant growth-promoting bacteria MR12 (Pseudomonas fluorescens), and MR25 (Serratia marcescens), could enhance tomato growth and resistance to Meloidogyne incognita under in vivo conditions. The three strains’ cell-free culture filtrates showed a strong nematocidal impact (P < 0.05) on M. incognita infective second-stage juveniles (J2s). The highest mortality rates by the three BCAs were at concentrations of 80%, followed by 60%, 40%, and 20%. The in vitro hatching of free eggs was found to be considerably (P < 0.05) reduced as the concentrations of the endophytic bacteria MR12, and MR25 were increased in the order 1 × 105, 1 × 106, 1 × 107, 0.5 × 108, to 1 × 108 colony forming units (CFU)/mL, and the maximum nematicidal activity in killing M. incognita free eggs occurred at 1 × 108 CFU/mL. A statistically significant (P < 0.05) reduction in the percentage of M. incognita-free eggs retrieved was seen in vitro when various concentrations of the endophytic fungus MR20 were applied compared to the negative control (distilled water). The endophytic fungus MR20 had the highest nematicidal activity against M. incognita free eggs at a concentration of 3 × 106 CFU/mL. The application of P. lilacinum or a combination of P. fluorescens and S. marcescens to tomato plants in the presence of M. incognita under greenhouse conditions resulted in a significant increase (P < 0.05) in root and shoot fresh weight, number of leaves, weight of leaves, and stem diameter when compared to the positive control treatment that contained only M. incognita. Treatment with P. lilacinum was more effective (P < 0.05) than P. fluorescens and S. marcescens in reducing egg masses per root, J2s per 100 g of soil, egg masses per 100 g of soil, J2s + eggs of M. incognita per 100 g of soil, reproduction factor, and reduction percentage after 60 days under greenhouse conditions. Nevertheless, the reduction of M. incognita gall size categorization (> 4 mm, 2–4 mm, and < 2 mm) was more effectively achieved by treatment with P. fluorescens and S. marcescens than by treatment with P. lilacinum. Under in vivo conditions, the tested P. lilacinum or a mixture of P. fluorescens and S. marcescens effectively controlled nematode population densities below the economic threshold.

Nematicidal Potential of Green Chiretta Extracts Against Meloidogyne enterolobii and M. Incognita: In vitro Assessment for Agricultural Application

Root-knot nematodes pose a persistent threat to various economically important crops in Thailand, with limited available management strategies for farmers. This study aimed to assess the efficacy of aqueous (AE), methanolic (ME), ethanolic (EE), ethyl acetate (EAE), and chloroform (CE) crude extracts derived from green chiretta in controlling Meloidogyne enterolobii and M. incognita under laboratory conditions. The results demonstrated significant inhibitory effects of all crude extracts, except for CE, against both nematode species. Notably, AE (10 and 20 mg/mL), ME (20 mg/mL), and EE (20 mg/mL) treatments exhibited maximum inhibition of hatching, leading to a considerable reduction in nematode hatch rates by 87.5 - 96.8 % for M. enterolobii and 88.5 - 96.5 % for M. incognita, compared with distilled water (DW). In terms of second-stage juveniles (J2s) mortality, AE (10 and 20 mg/mL), ME (20 mg/mL), and EAE (20 mg/mL) demonstrated the highest nematicidal activity, resulting in mortality rates of 94.2 - 100 % for M. enterolobii and 92.2 - 99.2 % for M. incognita. Chemotaxis assays revealed a repellent effect of all extracts on both nematode species, except for the ethyl acetate extract (EAE), which attracted M. incognita J2s without affecting M. enterolobii J2s. The observed efficacy was attributed to the higher concentrations of bioactive compounds, including flavonoids, phenolics, and terpenoids, in the extracts compared to CE. Based on these in vitro findings, it is suggested that AE, ME, EE, and EAE of green chiretta exhibit significant nematicidal activity against M. enterolobii and M. incognita. Further evaluation under greenhouse and field conditions is warranted to ascertain the practical applicability and effectiveness of these extracts in a real-world agricultural setting.

Integrated Analysis of the lncRNA-miRNA-mRNA Expression Profiles in Response to Meloidogyne incognita in Radish (Raphanus sativus L.)

Radish is an important root vegetable that is widely grown in Asia. The root-knot nematode (RKN) Meloidogyne incognita seriously affects the growth and development of radish root and causes poor appearance quality. However, the molecular mechanism of radish response to RKNs remains poorly understood. In this study, a total of 220 lncRNAs, 1144 mRNAs, 20 miRNAs and 153 proteins were differential expressed between the RKN-infected and WT samples. Correlation analysis of all DEPs compared with all DGEs showed that 8 mRNAs-DEPs showed a changed abundance. The results showed that 18 DEmiRNAs have 167 target DEGs in 220 miRNA-target modules and 29 DElncRNAs were predicted as putative targets of 16 DEmiRNAs in 37 miRNA-target modules. In all, 6 DGEs in the ABA pathway and 2 DGEs in the JA pathway were identified under RKN infection, respectively. The four regulatory networks of lncRNA-miRNA-mRNA were constructed in response to RKN infection. qRT-PCR analysis found that the expression pattern of 6 DElncRNAs, 6 DEmRNAs, 6 DEmiRNAs and 6 DEPs were consistent with sequencing results. These results provide a theoretical basis for studying the molecular mechanism of radish in response to M. incognita and breeding resistant varieties to this nematode.

Pathogenicity of Root-knot Nematode, Meloidogyne incognita on Tuberose (Polianthes tuberosa L.)

A pot experiment was carried out in the net house of Department of Nematology, Assam Agricultural University, Jorhat, to study the pathogenicity of root-knot nematode, Meloidogyne incognita, on tuberose. The study found that as the inoculum level of M. incognita increased from 10 to 10,000 second-stage juveniles (J2) per pot (containing 1 kg of sterilized soil), all plant growth parameters of tuberose decreased progressively. At the highest inoculum level, the plants became severely stunted, chlorotic, and produced very few bulblets. It was noted that at the highest inoculum level, the root systems were significantly reduced, with larger and mostly coalescent galls. The treatments with no nematode (check and associated check) were free from galls and eggmasses. An initial inoculum level of 100 J2 of M.incognita per kg of soil caused significant reduction in all growth parameters and proved to be pathogenic to the tuberose plants. The number of galls and eggmasses increased gradually in the plants with an initial inoculum level of 10 to 1000 J2 of M.incognita per kg of soil, but it declined at highest inoculum level of 10,000 J2 per kg of soil. The experiment also recorded the variation in nematode population in the soil as well as their reproductive rates. These findings can be used to develop effective, targeted methods for minimizing the damage caused by root-knot nematode in tuberose crops.

IN SILICO STUDIES OF IDENTIFIED COMPOUNDS FROM ETHANOLIC EXTRACT OF CELOSIA TRIGYNA AGAINST NEMATODE (Meloidogyne incognita)

Plant-parasitic nematodes (PPNs) have been found to be a major cause of considerable economic burden on the horticultural crops industry. Celosia genus have been renown to purpose antimicrobial activity. This study tends to swing the antimicrobial activity of one species of this genus i.e. Celosia trigyna against root-knot nematodes employing molecular docking methods. The identification of compounds in the leaf extract with the potential to inhibit Meloidogyne incognita was carried out in silico. Liquid Chromatography Mass Spectrometry (LCMS) was employed for analysis of the ethanolic leaf extract of this plant, it revealed the presence of cis-9-tetradecanoic acid, vitexin-glucoside, 6”-O-deoxyhexoside, gallic acid, malic acid, sinapic acid, 3-feruloylquinic acid in the extract. Site-directed multiligand docking of the identified compounds was performed on protein 2MIF of Meloidogyne incognita and employing Bifenazate and Boscalid as positive controls. The binding affinity of 3-feruloylquinic (– 4.2 kcal/mol) was significantly higher than the positive control compounds i.e. Bifenazate and Boscalid (– 4.0 kcal/mol and – 3.9 kcal/mol). The interactions of this molecule with the amino acids of the protein showed that the mechanism of its inhibitory action is similar to that of the cocrystallized ligand. This result validates that the antimicrobial activity of the ethanolic extract of the leaves of C. trigyna could be employed against root-knot nematodes for sustainable agriculture.

Botanicals as Phyto-nematicides Against Root-knot Disease Caused by the Root-knot Nematode (Meloidogyne incognita) via Promoting growth, Yield, and Biochemical Performance of Cabbage Crop

Botanicals as Phyto-nematicides Against Root-knot Disease Caused by the Root-knot Nematode (Meloidogyne incognita) via Promoting growth, Yield, and Biochemical Performance of Cabbage Crop

Bacillus, Pseudomonas and Serratia control Meloidogyne incognita (Rhabditida: Meloidogynidae) and promote the growth of tomato plants

Plant-parasitic nematodes cause significant losses in agriculture worldwide. Among these parasites, the root-knot nematode (Meloidogyne spp.) stands out. Consequently, control methods are being developed to combat this pest. Among these methods is biological control, the main agents of which are bacteria. This study aimed to evaluate the impact of 102 bacterial isolates on the mortality of Meloidogyne incognita J2 juveniles, hypothesizing that certain isolates could effectively control the nematode and promote tomato plant growth. Five experiments were conducted to test this hypothesis. First, the effect of the 102 bacterial isolates on J2 mortality was assessed under laboratory conditions. Second, five isolates (Bacillus cereus IBCBb130, Bacillus cereus IBCBb116, Pseudomonas aeruginosa IBCBb122, Bacillus proteolyticus IBCBb136, and Serratia sp. IBCBb118), which showed >68% J2 mortality, were evaluated over 72 h. Third, these isolates were tested at seven different concentrations. Fourth, their efficacy in controlling M. incognita on tomato plants was assessed in a greenhouse setting. Fifth, their potential to promote tomato plant growth without nematode inoculation was evaluated. The results revealed that the 102 bacterial isolates caused mortality ranging from 2 to 79.57% for M. incognita J2. At a 10% dilution, five isolates (B. cereus IBCBb130, P. aeruginosa IBCBb122, B. cereus IBCBb116, B. proteolyticus IBCBb136, and Serratia sp. IBCBb118) maintained mortality rates above 68%. Among these strains, B. cereus IBCBb130 and P. aeruginosa IBCBb122 were particularly effective, with B. cereus IBCBb130 showing high mortality rates under laboratory conditions and P. aeruginosa IBCBb122 significantly reducing nematode populations in greenhouse pots. Additionally, Serratia sp. IBCBb118 demonstrated notable potential for promoting tomato plant growth. In conclusion, specific bacterial isolates exhibit strong potential for the biocontrol of M. incognita and enhancement of tomato plant growth, suggesting a viable alternative to chemical nematicides. These findings provide insight into the development of sustainable agricultural practices through targeted manipulation of the soil microbiota. Future research should explore the underlying mechanisms of these interactions and their long-term effects on crop yield and soil health.