An integrated approach to managing Rhizoctonia solani on maize in marginal soils: field studies

Abstract

A study was conducted over two seasons in a marginal soil with an acid saturation of 54%. A plant growth promoting rhizobacterium, Bacillus megaterium, a commercial biocontrol agent, Trichoderma harzianum Strain kd (Eco-T^®), and soluble potassium silicate were used in this study. The objective was to control maize yield reduction caused by Rhizoctonia solani AG2 root rot isolated from infected maize. R. solani reduced maize yields significantly by 34% in the first season. However, the losses decreased in the second season from 34% to 10%. In the first season, combination of T. harzianum, B. megaterium and potassium silicate increased maize yields by 130%. The highest yield in the presence of R. solani was treatments with T. harzianum (216%) followed by T. harzianum plus potassium silicate (214%) and lastly T. harzianum plus B. megaterium (178%). However, in the second season, T. harzianum plus potassium silicate treatment resulted in the highest yields.     

Nematode inhibiting organic materials and a strain of Trichoderma harzianum effectively manages Meloidogyne incognita in Withania somnifera fields

The usefulness of Trichoderma harzianum was tested along with farmyard manure, cow urine, neem oil seed cake, and vermicompost separately and in combination to manage Meloidogyne incognita in Withania somnifera. A treatment combination of nematode inhibitory vermicompost and T. harzianum was found to be most effective against M. incognita.     

Efficacy of new nematicides for managing Meloidogyne incognita in tomato crop

New non‐fumigant nematicides (fluensulfone, fluopyram and fluazaindolizine) were tested in greenhouse tomato trials aiming to evaluate its efficacy on the control of Meloidogyne incognita soil and root populations and plant produtivity. Plants of the cultivar Red Gnome were transplanted into 2,500 cm³ fibre pots inoculated with 200 eggs of M. incognita/100 cm³ of soil and treated with fluensulfone, fluopyram and fluazaindolizine, in two rates each. After eight weeks of incubation the plants were evaluated for fresh root and shoot weight, weight and number of fruits, egg mass number, population density and nematode reproduction factor. All nematicide treatments reduced the root gall index, the number of M. incognita egg masses, eggs/g root and the nematode reproduction factor when compared to the non‐treated control.     

In vitro evaluation of combination of Trichoderma harzianum and chitosan for the control of sapstain fungi

In vitro assays were undertaken to evaluate the control of two sapstain fungi, Leptographium procerum and Sphaeropsis sapinea by a combination of chitosan or chitosan oligomer and an albino strain of Trichoderma harzianum. Spore germination and hyphal growth of the test fungi were assessed on media amended with chitosan or chitosan oligomer with and without T. harzianum using either simultaneous inoculation with test fungus or inoculation 1, 2, or 3 days after pre-infection with test fungus.There was no mycelial growth of the test fungi regardless of chitosan concentrations used when either L. procerum or S. sapinea was simultaneously inoculated with T. harzianum. However, the dose–response of chitosan or chitosan oligomer on the test fungi was apparent when T. harzianum was not simultaneously inoculated with test fungus but introduced later. There was a greater growth reduction at higher concentrations (0.075–0.1% v/v) of chitosan, and overall chitosan oligomer was more effective than chitosan aqueous solution.Chitosan alone was able to restrict or delay the germination of spores but the combination of chitosan and T. harzianum inhibited spore germination and hence colony formation of test fungi regardless of time delay.     

Interaction between Pseudomonas fluorescens and Meloidogyne incognita on tomato plant as influenced by the different levels of phosphorus

A pot experiment was conducted on tomato (Solanum lycopersicum cv. Pusa Ruby) to assess the effect of different phosphorus (P) levels (0, 125, 250 and 500 mg/pot) and the plant growth promoting rhizobacterium, Pseudomonas fluorescens, on the growth of tomato and on the reproduction of Meloidogyne incognita. Maximum growth of tomato occurred at P rates of 125 mg/kg soil, irrespective of whether plants were uninoculated or inoculated with P. fluorescens or M. incognita or inoculated with both the agents. Nematodes per gram of roots, egg masses per root, eggs per egg mass and galls per root significantly increased by increasing levels of P. P. fluorescens performed better than other treatments and different P levels in improving tomato growth and reducing galling and multiplication of M. incognita.     

Essential oils as soil biofumigants for the control of the root‐knot nematode Meloidogyne incognita on tomato

The effectiveness of soil fumigation with 50, 100 and 200 µL kg^?1 soil of essential oils (EOs) from the plant species Eucalyptus citriodora, Eucalyptus globulus, Mentha piperita, Pelargonium asperum and Ruta graveolens was assessed against the root‐knot nematode Meloidogyne incognita on potted tomato. Plant growth parameters and number of galls, nematode eggs and juveniles on tomato roots were evaluated after two months of maintenance of the treated plants at 25°C in greenhouse. EOs of E. globulus and P. asperum significantly reduced nematode multiplication and gall formation on tomato roots at all the tested rates, whereas the EOs of E. citriodora, M. piperita and R. graveolens were more suppressive at levels greater than 50 µL kg^?1 soil. Biofumigation with EOs of E. globulus and P. asperum resulted also in the largest increase of tomato plant top and root biomass. The five samples of EOs had a different chemical composition as determined by GC and GC‐MS. Structure–activity relationship based on the main constituents of the tested EOs and their nematicidal effect on M. incognita is discussed.     

Effects of Tomato Root Exudates on Meloidogyne incognita

Plant root exudates affect root-knot nematodes egg hatch. Chemicals in root exudates can attract nematodes to the roots or result in repellence, motility inhibition or even death. However, until recently little was known about the relationship between tomato root exudates chemicals and root-knot nematodes. In this study, root exudates were extracted from three tomato rootstocks with varying levels of nematode resistance: Baliya (highly resistant, HR), RS2 (moderately resistant, MR) and L-402 (highly susceptible, T). The effects of the root exudates on Meloidogyne incognita (M. incognita) egg hatch, survival and chemotaxis of second-stage juveniles (J2) were explored. The composition of the root exudates was analysed by gas chromatography/mass spectrometry (GC/MS) prior to and following M. incognita inoculation. Four compounds in root exudates were selected for further analysis and their allopathic effect on M. incognita were investigated. Root exudates from each tomato rootstocks (HR, MR and T strains) suppressed M. incognita egg hatch and increased J2 mortality, with the highest rate being observed in the exudates from the HR plants. Exudate from HR variety also repelled M. incognita J2 while that of the susceptible plant, T, was demonstrated to be attractive. The relative amount of esters and phenol compounds in root exudates from HR and MR tomato rootstocks increased notably after inoculation. Four compounds, 2,6-Di-tert-butyl-p-cresol, L-ascorbyl 2,6-dipalmitate, dibutyl phthalate and dimethyl phthalate increased significantly after inoculation. The egg hatch of M. incognita was suppressed by each of the compound. L-ascorbyl 2,6-dipalmitate showed the most notable effect in a concentration-dependent manner. All four compounds were associated with increased J2 mortality. The greatest effect was observed with dimethyl phthalate at 2 mmol·L^-1. Dibutyl phthalate was the only compound observed to repel M. incognita J2 with no effect being detected in the other compounds. Each of the four compounds were correlated with a reduction in disease index in the susceptible cultivar, T, and tomato seedlings irrigated with L-ascorbyl 2,6-dipalmitate at 2 mmol·L^-1 showed the best resistance to M. incognita. Taken together, this study provided a valuable contribution to understanding the underlying mechanism of nematode resistance in tomato cultivars.     

Potential biocontrol activity of Arthrobotrys oligospora and Trichoderma harzianum BI against Meloidogyne javanica on tomato in the greenhouse and laboratory studies

In this investigation, the biological control activity of Arthrobotrys oligospora and Trichoderma harzinum BI against the root-knot nematode, Meloidogyne javanica, infecting tomato, was assessed both in in vitro and in in vivo experiments. In greenhouse experiments, tomato seedlings at six-leaf stage were inoculated with 10⁶?spores/ml of A. oligospora and T. harzianum BI and number of 2000 nematode eggs per individual seedling. In in vitro assays, the per cent inhibition of nematode eggs hatching, the death per cent of second-stage juvenile (J2) and proteolytic activity on casein hydrolysis was evaluated. Results showed that A. oligospora and T. harzianum BI decreased the mean numbers of galls, eggmasses and egg per eggmass significantly (p?<?0.05) compared with control. Percentage hatching inhibition of M. javanica treated with A. oligospora and T. harzianum BI was 25 and 52%, respectively. Moreover, A. oligospora and T. harzianum BI significantly increased (p?<?0.05) the mortality rate of M. javanica (J2) after two and four days (74, 85 and 53, 63%, respectively). A. oligospora and T. harzianum BI had a proteolytic activity of 3.9 (U/min per ml) and 2.4 (U/min per ml) at pH 5.0, respectively. Our data suggest that the application of these two fungi in tomato rhizosphere infected with root-knot nematode M. javanica had antagonistic effects on the infection and reproduction of this nematode and the ability to control its population.     

Combination of the entomopathogenic nematode Heterorhabditis bacteriophora and the nematode-trapping fungi Dactylaria brochopaga and Arthrobotrys conoides for controlling Meloidogyne incognita in tomato fields

Abstract

Effects of combining an entomopathogenic nematode (EPNs) and nematode-trapping fungi to control root-knot nematode were studied in the laboratory and in a tomato field. Bioassay effects of EPNs (Heterorhabditis bacteriophora) on growth of the two nematode-trapping fungi (Dactylaria brochopaga and Arthrobotrys conoides) attacking J2 of Meloidogyne incognita were studied in the laboratory. A field experiment was conducted in a tomato field. The mortality percentages were higher in combining EPNs and trapping fungi than either by trapping fungi or EPNs alone. Combining EPNs with A. comcaides fungi caused mortality higher than application by EPNs and trapping fungi D. brochopaga. The highest mortality percentage of combined EPNs and trapping fungi on larvae, root galls and egg-masses of M. incognita in tomato field were in the treatment of combined EPNs and D. brochopaga several times and the treatment of combined EPNs and A. comcaides several times, followed by the treatment of combined EPNs and D. brochopaga one time, and treatment of combined EPNs and A. comcaides one time. In the third stage came the treatment of D. brochopaga alone, and the treatment of A. comcaides alone, finally came effects of the treatment of EPNs alone. The highest tomato yield was recorded in treatments of combined EPNs and D. brochopaga or A. comcaides compared to the separate treatments and control. Thus, we recommend farmers to use combination of EPNs and trapping fungi for increasing the mortality of M. incognita in tomato fields.     

Effects of high grafting on tomato plants infected by Meloidogyne incognita and Ralstonia solanacearum

The root‐knot nematode Meloidogyne incognita is known to increase the severity of bacterial wilt in many solanaceous crops. In Japan, several bacterial wilt‐resistant rootstocks that have the M. incognita resistance (Mi) gene in their genome have been developed for tomatoes. In this study, we aimed to examine whether the presence of Mi gene‐breaking M. incognita population affects the development of bacterial wilt in bacterial‐wilt‐resistant tomato rootstocks with Mi in their genetic background. We also aimed to examine the possibility of using high‐grafted tomatoes to control bacterial wilt in plants infected by M. incognita. Our results indicate that the resistance to bacterial wilt was easy to break in usual‐grafted tomato plants infected with M. incognita and that M. incognita enhanced the vertical movement of Ralstonia solanacearum in the bacterial‐wilt‐resistant tomato rootstocks. In addition, our results suggest that high grafting led to significantly less wilting in the plants infected by M. incognita than did usual grafting.     

Enhanced tolerance of Mentha arvensis against Meloidogyne incognita (Kofoid and White) Chitwood through mutualistic endophytes and PGPRs

The use of herbs in pharmaceutical preparation is ever increasing, and the demand for pesticides free material by the concern industries is on the rise. Consequently the need to grow disease-free plants using non-chemical fertilizers and pesticides is the need of the hour. Mentha arvensis cv. kosi is highly infested with Meloidogyne incognita (Kofoid and White) Chitwood, and severe oil yield loss occurs due to this nematode pest. Employing ecofriendly ways of nematode management, the mutualistic endophytes (Trichoderma harzianum strain Thu, Glomus intraradices) and plant growth promoting rhizobacteria (Bacillus megaterium and Pseudomonas fluorescens) were assessed individually and in combination on plant biomass, oil yield of menthol mint (M. arvensis cv. kosi), reproduction potential and population development of root knot nematode, M. incognita under glasshouse conditions. These microbes enhanced the plant biomass and percent oil yield both with and without M. incognita inoculation. Dual application of mutualistic fungal endophytes and Plant Growth Promoting Rhizobacteria (PGPRs) may be a wise option for enhancing the oil yield and tolerance of menthol mint against M. incognita infection.     

Biological control of root-knot nematode,Meloidogyne incognita infesting tomato

Talc based formulations of two antagonistic fungi, Acremonium strictum W. Gams and Aspergillus terreus Thom were tested separately and together for their ability to suppress the development of root-knot disease of tomato caused by the root-knot nematode, Meloidogyne incognita Kofoid & White in two consecutive trials (2007–08). Tomato seedlings were each inoculated with M. incognita at 2 infective second stage juveniles /g of soil. M. incognita caused up to 48% reduction in plant growth parameters compared to un-inoculated control. Control efficacy achieved by combined soil application of both fungi, in terms of galls/root system and soil population/50 ml of soil, was 66 and 69% respectively at 60 days of inoculation compared to control. Soil application by individual fungus did not achieve as much effectiveness as the biocontrol agents applied together. The combined treatment was found to have antagonistic effect on M. incognita development and increased plant vigor. Incorporation of fine powder of chickpea pod waste with talc powder was beneficial in providing additional nutrients to both plant and biocontrol agents and increased the activity of the nematophagous fungi in soil. A. strictum and A. terreus were successfully established in the rhizosphere of tomato plants up to the termination of the experiment.     

Studies on interaction of Meloidogyne incognita (Kofoid and White) Chitwood and Fusarium solani (Mart.) Sacc forming a disease complex in lentil (Lens culinaris Medik.)

Abstract

An experiment was conducted to study the effects of interaction between Meloidogyne incognita and Fusarium solani on plant length, fresh and dry weights, number of pods, chlorophyll, carotenoid, nitrogen and phosphorus contents and nitrate reductase activity in lentil plants. The results reveal a maximum damage occurring in all the plant growth, biochemical and nutrient parameters, in plants inoculated with M. incognita 10 days prior to F. solani (Mi?→?Fs). This was followed by simultaneous (Mi?+?Fs) inoculations, fungus inoculation 10 days prior to nematode (Fs?→?Mi), M. incognita alone and F. solani alone treatments. Nematode reproduction factor and root galling were highest in individual inoculation of M. incognita, while root rotting percentage was highest when nematode was inoculated 10 days prior to fungus followed by simultaneous inoculation with both nematode and fungus.     

Der Besatz von Beta-Rüubensaatgut rait Wurzelbranderregern und der Einfluß von Umweltfaktoren auf das Auftreten des samenbüurtigen Wurzelbrandes

The root knot nematode Meloidogyne incognita was controlled more effectively when P. lilacinus and G. mosseae were applied together in a pot experiment than either was applied alone. Inoculation of tomato plant with G. mosseae did not markedly increase the growth of plant infected with M. incognita. Inoculation of plant with G. mosseae and P. lilacinus together or alone resulted in a similar shoot and plant height. The highest root development was achieved when mycorrhizal plant were inoculated with P. lilacinus to combat root knot nematode. Inoculation of tomato plant with P. lilacinus suppressed galls/root system and eggs/egg masses, compared to seedling inoculated with M. incognita alone. The mycorrhizal colonization was not affected by inoculation of P. lilacinus.     

Biological Control of Root-Knot Nematode <i>Meloidogyne incognita</i> in <i>Psoralea corylifolia</i> Plant by Enhancing the Biocontrol Efficacy of <i>Trichoderma harzianum</i> Using Press Mud

Meloidogyne incognita is a plant pathogen causing root-knot disease and loss of crop yield. The present study aimed to use Trichoderma harzianum as a biocontrol agent against plant-parasitic nematodes and used press mud, which is a solid waste by-product of sugarcane, as a biocontrol agent and biofertilizer. Therefore, the combined application of T. harzianum and press mud may enhance nematode control and plant growth. Elemental analysis of press mud using scanning electron microscopy (SEM) integrated with an Energy Dispersive X-ray (EDX) analyzer revealed the presence of different elements such as C, O, Mg, Si, P, K, Ca, Cu and Zn. In addition, a greenhouse study was conducted to investigate the combined effects of press mud and T. harzianum on M. incognita reproduction and growth and the biochemical features of Psoralea corylifolia. The results showed that plant length, dry biomass, leaf area, the number of seeds per plant, chlorophyll a, chl b, carotenoid content, nitrate reductase, carbonic anhydrase, and nitrogen content were significantly increased (P ≤ 0.05) in the T2 plants (plants were treated with 100 g of press mud + 50 mL T. harzianum before one week of M. incognita inoculation), over inoculated plants (IC). Antioxidant enzyme activity of ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) in the foliage of P. corylifolia was significantly increased when plants were treated with press mud + T. harzianum. A significant reduction in the number of egg masses, nematode population, and root-knot index (RKI) was found in plants with T2 plants. These results suggest that the combined application of T. harzianum and press mud has the potential to control the M. incognita infection and can be used as an environmentally safe alternative to chemical nematicides and also help in the removal of sugarcane waste that causes environmental pollution.     

Activity of four nematicides against Meloidogyne incognita race 2 on tomato plants

Meloidogyne incognita is one of the most important causes of disease in protected vegetable cultivation in North China Plain, but chemical control options for it are currently limited. In the present study, we measured activity of four nematicides with M. incognita race 2 in the laboratory and greenhouse pots. Fluensulfone and fluopyram had a greater negative effect on the motility of M. incognita second-stage juveniles (J2) than avermectin B1a (AV-B1a) and fosthiazate had, especially at low concentration, with respective EC₅₀ values of 0.29, 0.13, 0.68 and 2.48 mg/L. AV-B1a significantly and uniquely inhibited egg hatching, which indicated that it was the only nematicide that could readily be transported across the eggshell. In greenhouse pots, fluensulfone (10 mg⁻¹) and fluopyram (1 and 10 mg⁻¹) caused the greatest inhibition of formation of galls in tomato roots, with decreases of 98.6%, 96.2% and 99.2%, respectively. This indicated that some M. incognita J2 lost their root penetration ability without losing their motility.     

Nematicidal effect of an Amaranthus hypochondriacus L. cystatin (AhCPI) on the root-knot nematode Meloidogyne incognita (Kofoid and White) Chitwood

The root-knot nematode Meloidogyne incognita is one of the most damaging plant parasitic nematodes in the world. In this study, the effect of cystatin from Amaranthus hypochondriacus (AhCPI) as a potential control agent for M. incognita was explored. In vitro bioassays demonstrated that AhCPI affects the growth and development of eggs and the infectivity of juveniles (J2) of M. incognita, such as mortality and slower development, showing characteristic tissue damage. Mortality levels were quantified by Probit analysis, estimating LC₅₀s of 1.4 mg/mL for eggs and 0.028 mg/mL for J2. In planta bioassays showed that infected tomato seedlings treated with 0.056 mg/mL of AhCPI showed a 60% reduction in the number of galls, as compared with untreated J2-inoculated seedlings. Under greenhouse conditions, three applications of 10 mL of AhCPI (1.4 mg/mL) in the soil around the stem of M. incognita-infected tomato plants, reduced the number of galls by 93 ± 8%, as compared to the control M. incognita-infected plants. The application of AhCPI to the infected plants increased the yield (10.7%) of harvested tomato fruits, as compared to infected plants. These results show the potential of AhCPI for the control of M. incognita in tomato plants.     

Impact of biocontrol agents in combination with Prosopis juliflora (Swartz) DC. in controlling the root-infecting fungi of leguminous crops

Biocontrol agents, viz., Rhizobium meliloti, Pseudomonas aeruginosa, Aspergillus niger and Trichoderma harzianum, are used as seed dressing and soil is amended with Prsosopis juliflora (Swartz) DC. plant parts like stem, leaves and flower at 1% w/w for the control of root-rot fungi. All antagonists suppressed the infection of root-rot fungi viz., Fusarium spp., Rhizoctonia solani and Macrophomina phaseolina whereas the infection of R. solani and M. phaseolina was controlled when cowpea (Vigna unguiculata L.) and mungbean (Vigna radiata L.) seeds were treated with P. aeruginosa and T. harzianum and the soil was amended with P. juliflora leaves’ powder at 1% w/w. However, germination of both the crops was observed in all treatments. Growth parameters like shoot and root length, shoot and root weight, and leaf area significantly increased in all the treatments as compared to the control parameters. P. aeruginosa and T. harzianum in combination with soil amendment with P. juliflora plant parts at 1% w/w were the most effective for the control of root-rot fungi of leguminous plants.     

Combining the oomycete Pythium oligandrum with two other antagonistic fungi: Root relationships and tomato grey mold biocontrol

To reduce Pythium oligandrum biocontrol variability and improve its efficacy, experiments were performed by combining the oomycete with two other antagonistic fungi, Fusarium oxysporum strain Fo47 and Trichoderma harzianum. In Petri dishes, Fo47 or T. harzianum hyphae destroyed P. oligandrum cells by antibiosis and mycoparasitism processes; in the rhizosphere of tomato plants (Lycopersicon esculentum), the same antagonistic features were observed. However, in the rhizosphere, hyphae are frequently separated by a certain distance; this allows the coexistence and the persistence of the three microorganisms on the root systems. When introduced in the rhizosphere, Fo47 and P. oligandrum were able to penetrate the root tissues with Fo47 limited to the epidermal and upper layers of cortical cells while P. oligandrum colonized deeper tissue at a faster rate. The two antagonists were killed in few days within roots following elicited plant-defense reactions. T. harzianum was not able to penetrate root tissues. Root colonization with either P. oligandrum alone or in combination with Fo47 and/or T. harzianum resulted in systemic plant resistance which provided plant protection against Botrytis cinerea infection of leaves. The level of control and the expression of pathogenesis-related proteins (PR-proteins) in leaves were similar whatever the antagonistic microbial treatment applied to roots.     

Effects of varying environmental factors on the biological control of Meloidogyne incognita in tomato by Bacillus cereus strain BCM2

The root-knot nematode (Meloidogyne spp.), which represents a global threat to agricultural production, can cause serious losses in both the yield and quality of many crops. Endophytic bacteria are known to have great potential against Meloidogyne incognita. The colonisation ability of endophytic Bacillus cereus BCM2 in tomato roots and its biological control efficacy of M. incognita were investigated. By the end of the growth period of tomato plants, the population of BCM2 in the rhizosphere soils and roots of the tomato were 5.86 and 3.38 log CFU g^?1, respectively, indicating that BCM2 can colonise tomato roots for long periods of time. Pre-inoculation with BCM2 resulted in a significant reduction in the population of M. incognita and the gall index of tomato compared to the untreated control, and there was an increase in the tomato yield of 47.4%. Colony counts showed that the population of BCM2 in tomato roots was affected by soil type and pH, and the colonisation of BCM2 in tomato rhizosphere soils was influenced by soil water and organic matter contents. We observed that the biocontrol effects of BCM2 were best when soil pH was 7. Pre-inoculation with BCM2 can inhibit the formation of tomato galls more effectively when soil water content is 25%, and rich organic matter content was conducive to a reduction in the number of M. incognita second stage juveniles (J2s) in soil. These results demonstrated that B. cereus BCM2 has great potential for controlling M. incognita in tomato plants.