Management Of Root-knot Nematode Research Articles

Management of Root-Knot Nematode (Meloidogyne spp.) on Kiwifruit Seedlings using Different Plant Extracts, Biocontrol Agents, and Chemical Nematicides

Root-knot nematodes (RKN), (Meloidogyne spp.), are the major biotic factor responsible for the limiting production of Kiwifruit in Nepal including Kiwifruit orchard of Warm Temperate Horticulture Center, Nepal. Hence, there is a pressing demand for nematicides that are both easily accessible and cost-effective while being environmentally friendly. A screenhouse experiment was conducted in the Summer of 2023 with an objective to evaluate the effects of different plant extracts, bio-control agents, and chemical nematicides against RKN on Kiwifruit seedlings. The experiment was set up in a Completely Randomized Design with three replications and eight treatments which include the extracts of Allium sativum and Lantana camara, Trichoderma viride, Pseudomonas fluorescens, Cartap hydrochloride, Fosthiazate, Inoculated control and Uninoculated control. The results revealed that Trichoderma viride proved to be the most effective in reducing the nematode population, displaying a low root gall index of 3.11, a minimal reproductive factor of 0.24, and a high percentage of nematode control at 91.71%. It was also found to be efficient in promoting the growth parameters of Kiwifruit seedlings. Additionally, regression analysis exhibited a significantly positive interaction between root gall index and reproductive factor, while indicating a negative interaction between reproductive factor and growth parameters. Therefore, T. viride (@ 20 gm per 2000 cm3 of soil) should be soil drenched before the seedlings are transplanted into the main field for effective and sustainable management of RKN. Nevertheless, further research is needed to determine the efficacy of T. viride in infested roots of Kiwifruit trees in field condition of Kiwifruit orchard.

Management of root-knot nematode Meloidogyne incognita infesting turmeric (Curcuma longa) under coconut (Cocos nucifera) cropping system

Field experiments were conducted during 2018–19, 2019–20 and 2020–21 at ICAR-Central Plantation Crops Research Institute, Kasaragod, Kerala for assessment of biocontrol fungi for the management of root-knot nematode (RKN), Meloidogyne incognita damaging turmeric (Cucuma longa L.) (cv. IISR-Prathibha) under coconut (Cocos nucifera L.) cropping system. Treatments included talc-based formulations of Trichoderma harzianum (ICAR- Indian Institute of Spices Research (IISR), Kerala and ICAR-Central Plantation Crops Research Institute (CPCRI), Kerala isolates) and Pochonia chlamydosporia (ICAR-Indian Institute of Spices Research, Kerala isolate), neem cake, marigold and carbosulfan 25 ec (standard check). Talc-based formulations were applied at 50 g/bed, neem cake @1 kg/bed at pre-monsoon and post-monsoon, marigold @30 plants/bed compared with untreated and standard check carbosulfan 25 ec @5 litre/bed at pre-monsoon and post-monsoon against M. incognita. Maximum reduction of RKN in the soil, as well as root, was achieved by either P. chlamydosporia (74 and 86%, respectively) or carbosulfan (67 and 87%, respectively) over the control. A number of the tillers (3.75/plant) for P. chlamydosporia and (3.23/ plant) for carbosulfan were recorded more in comparison to control (1.42/plant). The findings demonstrated that P. chlamydosporia (ICAR-Indian Institute of Spices Research) is a promising alternative to synthetic nematicides for the management of M. incognita due to its high antagonistic and good plant growth promotion activities. However, large scale field trials on these promising fungal biocontrol agents can be considered for evaluation in relation to the management of RKN under field conditions for confirmation.

Non-fumigant nematicides and root-knot nematode management in Californian carrots

Non-fumigant nematicides and root-knot nematode management in Californian carrots

Chitin-enriched insect frass fertilizer as a biorational alternative for root-knot nematode (Meloidogyne incognita) management.

Root-knot nematodes (Meloidogyne spp.) are serious pests of most food crops, causing up to 100% yield loss. Nevertheless, commercial nematicides are costly and harmful to the environment. While the nematicidal potential of crustacean and synthetic chitin has been demonstrated globally, research on the potential of insect-derived chitin for nematode control has received limited attention. Here, seven chitin-fortified black soldier fly frass fertilizer extracts (chFE) were assessed for their suppressiveness of Meloidogyne incognita and impacts on spinach growth in comparison with a commercial nematicide using in vitro and in vivo bioassays. The performance of chFE and control treatments was assessed by determining their effects on nematode egg hatchability; infective juvenile (J2) mortality and paralysis; number of galls, egg masses, and J2s per plant; and spinach root and shoot biomass. In vitro results showed that chFE and commercial nematicide suppressed nematode egg hatchability by 42% and 52%, respectively, relative to the control (sterile distilled water). Up to 100% paralysis was achieved when M. incognita J2s were exposed to either chFE or commercial nematicide. Further, the J2 mortality achieved using chFE (95%) was comparable to the value achieved using commercial nematicide (96%); in all treatments, mortality increased with exposure time. Similarly, up to 85% suppression of gall development was achieved when spinach plants were grown in soil drenched with chFE; up to 79% reduction in egg mass formation and 68% suppression of J2 development in the root system were achieved using chFE. Also, chFE application significantly increased spinach root and shoot biomass by 54%-74% and 39%-58%, respectively, compared to commercial nematicide. Our findings demonstrate the nematicidal potential of chFE and its benefits on crop production. Thus, chFE could be considered as a promising multipurpose, regenerative, and cost-effective input for sustainable management of plant-parasitic nematodes and enhancement of crop yield.

Isolation of Pasteuria penetrans, an obligate hyper-parasite, infecting root knot nematode, Meloidogyne spp. from the rhizosphere of pulses in India

BackgroundPasteuria penetrans is a mycelial, endospore forming, obligate, bacterial parasite that has shown enormous potential for biological control of root-knot nematode, Meloidogyne spp. In the present study, the effort has been made to isolate effective and high temperature tolerant indigenous strains from pulse rhizosphere in India.ResultsSurveys were carried out in four different agro-climatic zones and collected 106 root-knot nematode infected soil and plant samples from pulses rhizosphere. Of these, we observed Pasteuria spore attachment on root knot nematode juveniles from seven samples: three from Varanasi, two from Salem and one each from Deoria and Kushinagar. The pure cultures of these seven isolates (named as IIPR-Pp-1 to IIPR-Pp-7 from single infected female, respectively) were developed in 7 cm pot and soil-less CYG medium. The nematode host species was identified as Meloidogyne incognita by perineal pattern and confirmed by sequencing of ITS region. The host range study with M. incognita and Heterodera cajani showed the spore attachment was specific to M. incognita revealed that the species of the parasite was Pasteuria penetrans. SEM study on morphometrics of Pasteuria spores belong to two groups. In vitro assay on endospore attachment assay with pre-treated endospores at 20, 30, 40, 50, 60 and 70 °C revealed that maximum number of endospore attachment of all isolates was observed at 30 °C followed by 40 °C, and the least number of them was observed at 60 °C and above. The isolate Pp3 exhibited maximum number of spore attachments among all isolates at 30 °C treatment (14) and 40 °C treatment (10.67). Endospore attachment assay with pre-treated J2 at 20, 25, 30, 35, 40 and 45 °C revealed that maximum number of attachment of all isolates was observed at 30 °C treatment, and no attachment was observed at 40 °C and above.ConclusionPasteuria penetrans isolate IIPR-Pp3 exhibited high temperature tolerance and can be used further to develop Pasteuria-based biopesticide for management of root-knot nematode, M. incognita in pulses.

Nematode egg parasitic fungus, Purpureocillium lilacinum: efficacy of indigenous strains for the management of Meloidogyne incognita in chickpea

BackgroundNematode egg parasitic fungus, Purpureocillium lilacinum is the most effective biocontrol agent and has been widely used commercially in many countries for the management of root-knot nematode, Meloidogyne incognita. Availability of indigenous potential strains specific to an agro ecosystem is very crucial for their successful commercial exploitation for suppression of nematode population. Hence, an attempt was made to isolate, characterize, evaluate and identify potential indigenous strains of P. lilacinum from pulse ecosystem for root-knot nematode management in chickpea.ResultsThe fungal colony was initially white and when spore was formed it turned into pink colour in 72 to 96 h. Hyphae was hyaline and septate, conidiophore was blunt, and phialides were with wide base and long neck bearing round to oval conidia in chains. Molecular identification of the species, P. lilacinum was carried out based on ITS1-5.8S-ITS2 region of the genomic DNA. In vitro bioassay of cultural filtrates on juvenile mortality revealed that maximum percentage of mortality was observed in IIPR-Pl-11 (88.36%). Spectrophotometric assay on chitinolytic activity showed that the strain IIPR-Pl-11 produced significantly high chitinolytic activity, chitinase enzyme and total protein content (0.139, 51.1 and173.75 µg/ml at 5days); (0.245, 90.1 and 272.67 µg/ml at 10 days) and (0.273, 100.4 and 306.25 µg/ml), respectively, at 15 days of culturing in colloidal chitin-enriched medium C. 2D gel electrophoresis of the crude chitinase suspension showed the presence of chitinase (32, 46 kDa size) in the sample from chitinase-induced medium C. In vitro bioassay of the cultural filtrates of the fungus grown in chitin-enriched medium C on inhibition on egg hatching revealed that the highest percent inhibition on egg hatching showed by IIPR-Pl-8 strain at 5 days of inoculation (42.6%) and IIPR-Pl-11 at 10 and 20 days of inoculation (62.80 and 93.50%), respectively. In vivo pot experiment revealed that among all strains, IIPR-Pl-11 was efficient in promoting plant growth very effectively by reducing gall number (41.3 per plant), egg mass (28.3 per plant) and soil population (284.3 per 200cc of soil) compared to control.ConclusionP. lilacinum strain IIPR-Pl-11 was the highest potential strain from pulse rhizosphere for the management of root-knot nematode, M. incognita in chickpea.

Management of root-knot nematodes (Meloidogyne spp.) in pulses by crop rotation

Management of root-knot nematodes (Meloidogyne spp.) in pulses by crop rotation

EFFICACY OF AQUEOUS AND POWDERED LEAF EXTRACTS OF Chromolaena odorata (ASTERALES: ASTERACEAE) AND Ficus mucuso (ROSALES: MORACEAE) BOTANICALS ON ROOT-KNOT NEMATODE INFECTING WATERMELON IN KWARA STATE, NIGERIA

Watermelon production in Kwara State, Nigeria, is affected by root-knot nematode (RKN), as all varieties of the crop are susceptible. The aim of this study was to identify readily available and environmentally safe nematicides for the management of RKN. The field was located at the Teaching and Research Farm of the University of Ilorin and set out in a randomised complete block design, with four replications. Aqueous and powdered extracts of Chromolaena odorata (L) King and Robinson and Ficus mucuso Welw. ex Ficalho were applied alone and in combination. There were seven total treatments: C. odorata aqueous, F. mucuso aqueous, C. odorata powder, F. mucuso powder, C. odorata and F. mucuso aqueous, C. odorata and F. mucuso powder, and the control. Data were collected on growth, yield and nematode populations. All data collected were subjected to analysis of variance, and treatments were compared using Duncan’s multiple range test at a 5% level of significance. The essential oil of each botanical was determined using gas chromatography-mass spectrometry. The vine length (185.61) and yield (2401.05) of plants treated with botanicals were significantly higher than those of the control at P<0.005. The nematode population was also significantly lower in plants treated with botanicals than in the control (318.30 and 230.00, first and second year, respectively) at P<0.005. Among the treatments, the combination of C. odorata and F. mucuso powders was the most effective, with higher growth and yield performance. The experiment showed that aqueous and powdered extracts of C. odorata and F. mucuso were effective in managing RKN in the field.

Efficacy of Purpureocillium lilacinum AUMC 10149 as biocontrol agent against root-knot nematode Meloidogyne incognita infecting tomato plant.

Root-knot nematode Meloidogyne incognita is among the biotic factors which has greatly affected both the yield and the quality of the tomato crop. The egg parasitic nematode, Purpureocillium lilacinum (Pl) is considered as one of the most promising agents in controlling and overcoming this plant pathogen. The nematicidal effect of the native isolate Pl AUMC 10149 on second stage juvenile's survival and egg hatching of M. incognita at different times of exposure was tested in vitro. The obtained data showed that Pl gave a maximum percentage of J2 mortality (97.6%) and egg hatching inhibition (79.8%) after 72 hours of exposure. The potentiality of Pl as well as Bio-Nematon to control M. incognita infecting tomato was conducted using different times of application in vivo. Nine treatments with five replicates were used for such bioagents compared with the nematicide Oxamyl. Each seedling was inoculated with 1000 J2s of nematode/pot and 10 mL of Pl (1x1010 CFU/mL) or Bio-Nematon spore suspension (1x108 CFU/mL) 10mL/pot. The results indicated that the most effective treatments in reducing nematode population, number of galls and egg masses of M. incognita in plant roots was performed with treatment by Pl pre-planting and post-infection with Pl (Rf 1.9) giving a significant enhancement in plant length (64.9%), fresh weight (72.52%) and shoot dry weight (163.41%) without negatively impacting environment. Therefore, the present study confirmed that using P. lilacinum AUMC 10149 can be used as a practical supplement to environmentally friendly disease management of root-knot nematodes in Egypt.

Effect of neem cake in the management of root knot nematode

Neem enrichment extract (NEE) was used at different concentrations viz., 0, 2.5, 5 and 10% to check its effect on second stage juveniles of Meloidogyne spp. Root knot nematode bio-assay in Petri Plates as well as in pot culture experiments were carried out with NEE.The results indicated that neem cake extracts was effective to control the root knot nematodes due to the presence of biological substance (azadirachtin, salannin, nimbin) and its derivative compounds (triterpenoid, limonoid).

Nematode-suppressive and plant growth-enhancing effects of Citrus spp. derivatives against Meloidogyne incognita on tomato

Plant-based derivatives (powders, pellets or extracts) are amongst the most effective types of organic soil amendments for the management of root-knot nematodes (Meloidogyne spp.). The objective of this study was to examine the effect of derivatives (juice, powder and oil) of fruits of several Citrus species (sweet orange, lemon, lime, mandarin and grapefruit) on the reproduction of Meloidogyne incognita race 2 on susceptible tomato plants, and on the vegetative growth of the crop under glasshouse conditions. Results show that juices of sweet orange, and possibly also lemon, applied as soil amendments either before planting or after planting, can significantly suppress the build-up of damaging root population densities of M. incognita on infected tomato plants, limit root galling and improve plant growth. Data confirm the nematode-suppressive and plant-growth enhancing effects reported for Citrus fruit-based plant derivatives, applied either as a compost, powder, extract or pellet.

Volatile organic compounds produced by Paenibacillus polymyxa J2-4 exhibit toxic activity against Meloidogyne incognita.

Root knot nematodes cause great damage to crops worldwide. Due to the negative effects of the application of fumigant and old chemical nematicides, biological nematicides have drawn increasing attention in recent years. Here we tested the fumigant activity of the volatile organic compounds (VOCs) blends emitted from Paenibacillus polymyxa and pure commercial VOCs against M. incognita. In this study, we investigated whether P. polymyxa strain J2-4 could produce VOCs that exhibit nematicidal activity. In vitro assays indicated that J2-4 VOCs were highly toxic to second stage juveniles (J2s) and could inhibit egg hatching. Three-layered pot experiments showed that the number of nematodes that penetrating in cucumber roots was reduced by 69.27% after the application of J2-4 VOCs under greenhouse conditions. We identified 14 volatiles using solid-phase micro-extraction gas chromatography-mass spectrometry. The efficacy of six commercially available VOCs, namely 2-isobutyl-3-methylpyrazine, 2,4-dimethoxybenzaldoxime, 2-dodecanone, 2-tridecanol, 2-tridecanone, and 2-tetradecanol, against M. incognita were examined. Except for 2,4-dimethoxybenzaldoxime, the remaining five VOCs showed strong direct-contact nematicidal activity against J2s of M. incognita, and only 2-isobutyl-3-methylpyrazine showed strong fumigant activity against J2s of M. incognita. In pot experiments, 2-isobutyl-3-methylpyrazine and 2-dodecanone reduced the number of root galls by about 70%, and 2-tridecanone reduced the number of root galls and egg masses by about 63% compared with controls. Paenibacillus polymyxa strain J2-4 exhibited high fumigant activity against M. incognita. Our results provide evidence for the use of J2-4 and its VOCs as biocontrol agents in the management of root-knot nematodes. © 2023 Society of Chemical Industry.

Efficiency of Vinasse Application on Root-Knot Nematodes in Soybean

Vinasse is not only effectively used in pest control but also creates a conducive environment for the growth of antagonistic microorganisms. Thus, this study aimed to evaluate the potential of vinasse applied via soil for the management of root-knot nematodes in soybean culture. The experimental design was entirely random, in a factorial scheme (2 × 6), consisting of two species of nematodes, Meloidogyne incognita and M. javanica, under vinasse application at five concentrations (20, 40, 60, 80, and 100%) and one control (water), with five repetitions. Soybean plants Intacta cv. M-Soy 8644 IPRO were inoculated with 4000 eggs/juveniles of each species separately. At 60 days after the first application of vinasse, evaluations of parasitism and agronomic characteristics in soybean were performed. Stillage resulted in the highest average values for root volume and root fresh mass in plants inoculated with M. incognita, showing respective increases of 24.33% and 14.92% compared to plants inoculated with M. javanica. However, concentrations exceeding 60% had a detrimental effect on all agronomic variables of soybean. For parasitism, an interaction among the factors was observed, with a significant effect (p < 0.01) for most of the evaluated variables, except for the number of eggs in the soil. The concentration equivalent to 60% vinasse promoted a sharp reduction in parasitism for the two nematode species, making reproduction on plant roots unfeasible.

Allelopathic Interactions of Solanum stramonifolium Jacq. Might Be Used for Meloidogyne incognita Management

The root-knot nematode (RKN) Meloidogyne incognita infects a large host range causing enormous agricultural losses. Although the control of this pest is mainly based on the use of chemical pesticides, natural alternatives are currently being largely considered, especially the use of plant-derived molecules, as allelochemicals and plant extracts. Solanum stramonifolium is a plant of the Solanaceae family and has been studied for its potential to control RKN, either by the use aqueous extracts of its seeds, or due to its immunity to nematode penetration. Our studies demonstrate that S. stramonifolium has an efficient defense mechanism against RKN completely preventing its penetration into its root system. Additionally, the compounds exuded by this plant in the soil can affect nematode infection in nearby grown Nicotiana benthamiana (-89% biomass for treatment I respectively, and -61% and +57% of galls for the treatments and Solanum lycopersicum (-79% biomass for treatment I, and -83% of galls for the treatments I and II). Herein, external (ED, < 3.5 kDa) and internal (ID, > 3.5 kDa) dialysates were prepared from the extract of S. stramonifolium seeds. Arabidopsis thaliana Col-0 inoculated with RKN treated with the dialysates showed a reduced gall diameter in 45% and 35% for ED and ID respectively. Additionally, a significant reduction in biomass was observed in germinated seeds after treatment with ID. In addition, Arabidopsis roots showed changes in their ploidy levels when treated with ED and ID, compared to the untreated control, indicating its effect on endoreduplicating cells. Finally, a partial identification of glycoalkaloids present in the ED and root extracts may help to explain plant immunity to root-knot nematode infection. Results obtained shed light on the defense mechanisms of S. stramonifolium against M. incognita, its allelopathic potential in co-cultivated plants and its biotechnological potential of dialysates obtained from its seeds, representing a strong alternative to the management of RKN in conventional agriculture.

Potential of cavalcade, Centrosema pascuorum, leaves for controlling Meloidogyne javanica and quantification of active phytochemicals

Summary The legume cavalcade, Centrosema pascuorum, is used extensively as a cover crop and as a component of conservation agriculture systems. It is also an attractive rotation or cover crop for the management of root-knot nematodes (RKN; Meloidogyne spp.) as it is a non-host. RKN are persistent pests that are well known to be difficult to control. However, the mechanisms governing the non-host status of cavalcade is unknown. The current study established that cavalcade leaves are toxic to RKN as either aqueous extracts or soil amendments. Bioassays conducted using Meloidogyne javanica showed that a 90% concentration of aqueous extract derived from 1-month-old cavalcade leaves (89 mg crude extract ml−1) suppressed nematode hatch (82.9%) and killed infective second-stage juveniles of M. javanica (85.3%). Soil amendments with 1% (w/w) of 1-month-old cavalcade leaves (0.99 mg crude extract g−1 soil) also provided effective control of M. javanica in the glasshouse on okra. One-month-old leaves appeared more effective than 2- or 3-month-old leaves. The soil amendments had no adverse phytotoxic effect on okra seed germination. Our study demonstrates the potential for using cavalcade leaves or extracts to manage RKN. This may be due to the nematicidal activity of the various compounds in the leaves, such as flavonoids, phenols and terpenoids, which should be further assessed.

Deciphering the synergistic effect of Jasmonic acid and Spermine in mitigating root-knot nematode stress in tomato plants through enhancing growth and activity of antioxidant enzymes

Root-Knot nematodes (RKNs) are one of the major plant pathogens that can substantially reduce plant growth and development. Management of RKNs is one of the major concerns as chemical pesticides pose a potential risk to humans and other life forms and also have toxic effects to environment. There is a need to find out some alternative eco-friendly strategies for management of these parasites. Jasmonic acid (JA) and Spermine (Spm) are those plant growth regulators (PGRs) that have positive effects on plant growth and alleviates toxic effects caused by various stresses including RKNs. Keeping this in mind,present study accessed the potential of these (PGRs), JA and Spm on morphological and biochemical attributes in 45 days old Solanum lycopersicum plants under nematode stress. It was observed that nematode infection resulted in reduced plant growth and photosynthetic pigments. Application of JA and Spm improved growth parameters and photosynthetic pigments. Moreover, tomato plants after JA and Spm supplementation lowered the activities of H2O2, DPPH and MDA thus decreasing nuclear and membrane damage caused by nematode stress. Additionally, enzymatic CAT (Catalase), SOD (Superoxide dismutase), GuPOX (Guaiacol peroxidase), APOX (Ascorbate peroxidase), PPO (Polyphenol oxidase), GST (Glutathione-S-transferase) and non-enzymatic (ascorbic acid, glutathione, and tocopherol) antioxidant levels increased markedly under nematode stress, but application of JA and Spm further improved these attributes. Taken together, the current study demonstrated that JA and Spm are suitable agents for managing nematode stress resistance in tomato plants.

Assessment of nematicidal and plant growth-promoting effects of Burkholderia sp. JB-2 in root-knot nematode-infested soil.

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

Study on Some Species of Trichoderma for the Management of Root Knot Nematode (Meloidogyne spp.) in Tomato

Pot experiment was conducted to find out the competence of some commercial product of Trichoderma spp. on the management of root knot nematode in tomato crop. The experiment was conducted in RCBD having seven treatments of six different Trichoderma spp. including one control in three replications. Each treatment had five pots. Twenty five days old seedling of Shrijana hybrid tomato was transplanted and inoculated with 1500 eggs of Meloidogyne spp. in soil after five days of transplanting of tomato seedlings. The spore suspensions of different Trichoderma spp. adjusted to 1 × 106 spores/ml and also inoculated per pot with 30 ml after one week of nematode inoculation. The same concentration and amount of Trichoderma spores solution was again inoculated after one month from the date of first application. Sixty five days after transplanting, all tomato plants were uprooted and the number of galls in root, galling index and fresh root weight were determined based on a 0-10 scale. The result showed that the treatments varied significantly in root knot index and number of galls per root system and fresh root weight per plant. The lowest gall index was observed in T. harzianum - Nemastin (1.6), followed by T. harzianum (T22) - Rootshield Plus (2.37) and T. viride (Ashtha TV) (3.43). Similarly, lowest numbers of galls (9.13) was observed in T. harzianum - Nemastin than all other treatments. There was no significant difference in fresh root weight per plant of tomato among the treatments except T. harzianum and T. harzianum (T22). Significantly highest suppressive effect on the nematode population was achieved by T. harzianum- Nemastin (Rf 0.45), followed by T. harzianum, (T22) (Rf 0.61), and T. viride, (Ashtha TV) (Rf 1.43). Different isolates of T. harzianum suppressed root knot disease of tomato as compare the isolates of T. viride. Hence, T. harzianum - Nemastin can be applied as a biological control agent to reduce the nematode population.

Investigation on Management of Root-Knot Nematode, Meloidogyne incognita through Soil Application of Bio-control Agents in Field Pea

The pot experiment was conducted at AICRP on vegetables, Pusa farm, Dr. Rajendra Prasad Central Agricultural University during 2020-21. The bio-control agents viz. Glomus fasciculatum (85-90 spores/g), Trichoderma harzianum 1.0% WP (2×106 cfu/g), Pseudomonas fluorescens 1.0% WP (1×108 cfu/g), Purpureocillium lilacinum 1.0% WP (2×106 cfu/g) either singly or in combined application shown significant improvement in plant growth and development and in declining nematode population. The combined application of P. fluorescens 1.0% WP (1×108 cfug-1) and P. lilacinum 1.0% WP (2×106 cfug-1) when applied 10g per pot each is efficient in improving plant growth and on other hand, plants treated with Cartap hydrochloride 4G (5g per pot) had the lowest nematode population, galls per plant, and Reproduction factor (Rf). P. lilacinum 1.0% WP (2×106 cfu/g) demonstrated promising effects in plants when just single bio-control agent i.e., 10g/pot was used. This study discovered that utilizing a mixture of bio-control agents was more effective than using bio-control agents alone in reducing the population of M. incognita. According to the study, bio-control agents had the same effects as Cartap hydrochloride 4G. As a result, bio-control agents can be used instead of nematicides.

Antagonistic Bacteria Bacillus velezensis VB7 Possess Nematicidal Action and Induce an Immune Response to Suppress the Infection of Root-Knot Nematode (RKN) in Tomato.

Meloidogyne incognita, the root-knot nematode (RKN), a devastating plant parasitic nematode, causes considerable damage to agricultural crops worldwide. As a sedentary root parasite, it alters the root's physiology and influences the host's phytohormonal signaling to evade defense. The sustainable management of RKN remains a challenging task. Hence, we made an attempt to investigate the nematicide activity of Bacillus velezensis VB7 to trigger the innate immune response against the infection of RKN. In vitro assay, B. velezensis VB7 inhibited the hatchability of root-knot nematode eggs and juvenile mortality of M. incognita by 87.95% and 96.66%, respectively at 96 hrs. The application of B. velezensis VB7 challenged against RKN induced MAMP-triggered immunity via the expression of transcription factors/defense genes by several folds pertaining to WRKY, LOX, PAL, MYB, and PR in comparison to those RKN-inoculated and healthy control through RT-PCR. Additionally, Cytoscape analysis of defense genes indicated the coordinated expression of various other genes linked to immune response. Thus, the current study clearly demonstrated the effectiveness of B. velezensis VB7 as a potential nematicide and inducer of immune responses against RKN infestation in tomato.