Biological Control Of Root-knot Nematode Research Articles

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.

Biological control of root-knot nematodes in common beans using putative nematocidal species of Trichoderma indigenous to Pakistan

ABSTRACT The putative nematocidal strains of Trichoderma for controlling root-knot nematodes were isolated from different agricultural fields in Pakistan. The Trichoderma isolates were confirmed using morphological and molecular characterisation. The root-knot nematodes were isolated from infected common bean plants Phaseolus vulgaris and identified as Meloidogyne incognita through phenotypic characteristics. Both in vitro and in vivo assays were performed. The nematocidal activity of the selected Trichoderma spp. was assessed using culture filtrate and spore suspension assays. Parameters including J2 mortality, egg hatching inhibition, root gall index, and egg mass index were calculated. The culture filtrates of T. bevicrassum strain ISO-03 caused significantly higher J2 mortality (71%) and inhibited egg hatching (68%) as compared to the activities of culture filtrates of the other two strains used in this study. The least control activity was observed in case of the culture filtrates of T. viride strain ISO-05 with 21% J2 mortality and 19% egg hatching inhibition. Similarly, the spore suspensions of T. brevicrassum ISO-03 showed the highest mortality of M. incognita juveniles (64% with respect to control) as well as the egg-hatching inhibition rates of 59%. In the in vivo study, the same strain T. bevicrassum ISO-03 significantly reduced the root galling index and egg mass indices as compared to the control. Furthermore, T. bevicrassum ISO-03 significantly promoted plant growth compared to the control. Overall, T. bevicrassum ISO-03 was identified as a potent biocontrol strain against root-knot nematodes in addition to its plant growth-promoting characteristics.

Antagonistic potential of endophytic fungi against Meloidogyne enterolobii, M. incognita and Nacobbus aberrans sensu lato

Root-knot nematodes limit horticultural crop production in Mexico where management is mainly based on nematicides that represent a risk to health and the environment. Thus, biological alternatives, such as the use of endophytic fungi, are currently being developed. The objective of this research was to isolate, identify and evaluate the antagonistic potential of endophytic fungi against the root-knot nematodes Meloidogyne enterolobii, M. incognita and the false root-knot nematode Nacobbus aberrans sensu lato (s.l.) occurring in Mexico. Endophytic fungi from chili pepper and tomato plants with a low root galling index were isolated from three localities in Sinaloa state (Villa Juárez, Valle de Culiacan and La Cruz de Elota) and one in Mexico City (Xochimilco). Fourteen isolates from leaves and roots were evaluated to assess: i) the ability to promote growth in chili pepper and tomato plants, ii) the degree of parasitism on nematode eggs and second-stage juveniles (J2), and iii) the nematostatic and nematicidal effect of their filtrates on the J2. In the trials, the three most effective endophytic fungal isolates were Chaetomium globosum (S1TH2), Echria macrotheca (S3RT2) and Stagonospora trichophoricola (XRC3). All three fungal isolates increased growth on chili pepper plants after application, but only two (S3RT2 and XRC3) did so on tomato plants. S1TH2 parasitized M. enterolobii eggs; S3RT2 and XRC3 eggs of N. aberrans s.l.; S3RT2 also parasitized M. incognita eggs and J2 of N. aberrans s.l. The S1TH2 filtrate was nematostatic for M. incognita and N. aberrans s.l., the XRC3 filtrate was nematostatic for N. aberrans s.l., and the S3RT2 filtrate was nematostatic and nematicidal for the J2 of N. aberrans s.l. The results obtained indicate that these isolates could be involved in natural regulation and biological control of root-knot nematodes.

Biological control of Root-knot nematode (Meloidogyne javanica) by potential antagonism of endophytic fungi isolated from Taify roses

ObjectivesPlant-parasitic nematodes are a serious threat to global agricultural production worldwide. To avoid synthetic chemistries toxicity there is a dire need of the hour to develop innovative nematode control strategies. Biological control using the antagonistic fungi of the plants is considered very economical and environment friendly. MethodsEfficacy of different fungal filtrate concentrations was estimated towards the mortality and clutching of Meloidogyne javanica. To determine the antagonistic potential of Penicillium citrinum (MN518391), time of disclosure was assessed in the laboratory with the result “exposure to 8% filtrate for a clock (24 hrs.), expressively reduced the viable juveniles and hatched eggs. ResultsExposition to aforementioned filtrate of P. citrinum for a clock (24 hrs.) revealed that juvenile body turned into straight stature leading to reduction in viability of nematodes. Contrary to it most of nematodes exhibited bent body when exposed to Aspergillusniger (MK713445), or (MN513383) its filtrates. Among the various isolated antagonistic fungi, GC–MS analysis revealed 22 unique compounds e.g., quinazoline and its derivatives as the most prevalent and squalene as least occurring possess significant nematicidal properties against the rootknot nematodes. ConclusionHence, using antagonistic fungus from the described plans as BCAs in agriculture against plant-parasitic nematodes is a viable long-term biocontrol technique and provide future avenues in this area of research.

Root-knot nematodes (Meloidogyne spp.) a threat to agriculture in Mexico: biology, current control strategies, and perspectives.

Root-knot nematodes (RKN) are sedentary parasites of the roots of plants and are considered some of the most damaging pests in agriculture. Since RKN target the root vascular system, they provoke host nutrient deprivation and defective water transport, causing above-ground symptoms of growth stunting, wilting, chlorosis, and reduced crop yields. In Mexico RKN infestations are primarily dealt with by treating with synthetic chemically based nematicides that are preferred by farmers over available bioproducts. However, due to environmental and human health concerns chemical control is increasingly restricted. Biological control of RKNs can help reduce the use of chemical nematicides as it is achieved with antagonistic organisms, mainly bacteria, fungi, other nematodes, or consortia of diverse microorganisms, which control nematodes directly by predation and parasitism at different stages: eggs, juveniles, or adults; or indirectly by the action of toxic diffusible inhibitory metabolites. The need to increase agricultural production and reduce negative environmental impact creates an opportunity for optimizing biological control agents to suppress nematode populations, but this endeavour remains challenging as researchers around the world try to understand diverse control mechanisms, nematode and microbe life cycles, ecology, metabolite production, predatory behaviours, molecular and biochemical interactions, in order to generate attractive products with the approval of local regulatory bodies. Here, we provide a brief review of the biology of the genus Meloidogyne, biological control strategies, and a comparison between chemical and bioproducts in the Mexican market, and guidelines emitted by national agencies to ensure safety and effectiveness of new developments.

Microorganisms in the biological control of root-knot nematode: A metanalytical study

Nematodes can cause annual losses in the order of 100 billion dollars in crops worldwide. Its control using chemical nematicides proves to be quite aggressive to the environment. For this reason, the management of microorganisms has been promising. However, it is essential to know the control potential of each organism. Thus, the objective of this study was to verify the efficiency of different microorganisms in the biological control of Meloidogyne sp. A systematic review of the literature was carried out from 2000 to 2020 with the keywords “Meloidogyne and biology control", resulting in 659 articles, of which 51 were pre-selected and, after the more detailed evaluation, was selected ten published articles. These ten articles generated a total of 83 studies for meta-analyses. Each study included a treatment group using some microorganisms (bacteria, fungus, actinomycetes) for nematode biocontrol, a control group without using biocontrol agents. From this meta-analysis, we can observe that the use of microorganisms decreased the number of galls (42.05%), the number of eggs (57.77%), the gall index (28.58%) and the eggs mass (53.48%). The use of microorganisms was also positive in increasing root mass (832.89%). We can conclude that the use of microorganisms proved to be efficient in controlling nematodes M. javanica and M. incognita. The fungi Pleurotus ostreatus and Phanerochaete chrysosporium have more significant potential for biocontrol for these species.

The carB Gene of Escherichia coli BL21(DE3) is Associated with Nematicidal Activity against the Root-Knot Nematode Meloidogyne javanica.

Biological nematicides have been widely used to lower the losses generated by phytoparasitic nematodes. The purpose of this study was to evaluate the nematicidal effects of Escherichia coli BL21(DE3) against Meloidogyne javanica and to identify nematicide-related genes. Culture filtrates of BL21(DE3) caused juvenile mortality and inhibited egg hatching in a dose-dependent manner. In the greenhouse, treatment of tomato seedlings with BL21(DE3) culture filtrates at 50 and 100% concentrations not only reduced the amount of M. javanica egg masses and galls, but improved plant root and shoot fresh weight. Culture filtrate analysis indicated that the nematicidal active ingredients of strain BL21(DE3) were non-proteinaceous, heat and cold resistant, sensitive to pH and volatile. To identify the genes associated with nematicidal activity, a BL21(DE3) library of 5000 mutants was produced using Tn5 transposase insertion. The culture filtrate of the MB12 mutant showed no nematicidal activity after 72 h of treatment and thermal asymmetrical interlaced PCR demonstrated that the carB gene was disrupted. Nematicidal activity was restored when the pH of the MB12 culture filtrate was adjusted to the original pH value (4.15) or following MB12 complementation with the carB gene, confirming a role for carB in mediating pH value and nematicidal activity. The outcomes of this pilot study indicate that BL21(DE3) is a potential microorganism for the continuable biological control of root-knot nematode in tomato and that carB affects the nematicidal activity of BL21(DE3) by modulating the pH environment.

Enhanced biological control of root-knot nematode, Meloidogyne incognita, by combined inoculation of cotton or soybean seeds with a plant growth-promoting rhizobacterium and pectin-rich orange peel.

LC-MS analysis of plant growth-promoting rhizobacterium (PGPR) Bacillus velezensis AP203 supernatants indicated the presence of nematode-inhibiting compounds that increased in abundance when B. velezensis AP203 was grown on orange peel. Meloidogyne incognita J2 were incubated with B. velezensis AP203 spores and orange peel, spores alone, orange peel alone, or with a non-inoculated control, and the combination of B. velezensis AP203 with orange peel resulted in 94% mortality of M. incognita juveniles (p ≤ 0.05). The J2 mortality rate for B. velezensis alone was 53%, compared to 59% mortality with orange peel, and the non-inoculated control exhibited 7% mortality. When tested on soybeans raised in a greenhouse, it was observed that when grown in the presence of orange peel, B. velezensis AP203 culture broth, cell suspension or supernatant reduced the numbers of M. incognita eggs per g of root at 45 days after planting (DAP) compared to inoculated controls in soybean and cotton (p ≤ 0.05). Likewise, soybean root length and fresh root weight significantly increased after inoculation with B. velezensis AP203 amended with orange peel. In cotton, shoot and root length significantly increased after inoculation with cell pellets of B. velezensis AP203 amended with orange peel compared to the M. incognita inoculated control. These data indicate that B. velezensis AP203 responds to growth on pectin-rich orange peel by production of biologically active secondary metabolites that can promote plant growth and inhibit root-knot nematode viability.

KETEPATAN WAKTU APLIKASI Paecilomyces lilacinus DALAM MENGENDALIKAN NEMATODA BENGKAK AKAR (Meloidogyne spp.) PADA TANAMAN TOMAT

Root-knot nematodes (Meloidogyne spp.) have been reported to be one of the primary pathogens that decreased tomato production in Indonesia. Biological control of root-knot nematodes by using parasitic fungus as like as Paecilomyces lilacinus is still limited. An effective application of parasitic fungi could be successful by managing a suitability application time. The study aimed to determine the suitability of the application time of the P.lilacinus in controlling root-knot nematodes on tomato. The study was conducted in farmers' land that was infected by root-knot nematodes. The experiment was done in a randomized block design with applying P.lilacinus isolates on 12, 8, and 4 days before planting, planting time, and 4, 8, 12 days after planting. All treatments were repeated four times. The application of P. lilacinus onto tomato root at planting time was better at suppressing the development of root-knot nematode compared to applications made before or after planting. P. lilacinus was able to suppress the number of root-knot (66.08%), the number of egg groups (77.33%), the number of eggs (26.79%), and the number of nematodes in the soil (82.20%). Keywords: Application time, Meloidogyne spp., Paecilomyces lilacinus, tomato

Combined releases of soil predatory mites and provisioning of free-living nematodes for the biological control of root-knot nematodes on ‘Micro Tom tomato’

Soil predatory mites feed on a diverse diet making them excellent candidates for conservation biocontrol. Free-living nematodes (FLN) are commonly found in soils and serve as prey for many acarine predators. Our goal was to determine whether conservation biological control of plant-parasitic nematodes by predators could be enhanced by provisioning FLN with their culture medium (FLNCM) under semi-field conditions. We conducted two experiments on dwarf tomato plants, the first until the beginning of flowering and the second until harvest. The treatments evaluated were with and without: 1) the root-knot nematode Meloidogyne incognita, 2) the predator Stratiolaelaps scimitus, and 3) the FLN Rhabditella axei in its culture medium. In both experiments, gall abundance was lowest in the combined treatment of FLN and predators. Similar reduction in gall abundance occurred when only predators or only FLNCM was added to the soil mix. Additionally, in the FLNCM treatment, foliar macronutrients N and K were significantly higher than the negative control. Our original aim was to use FLN as a supplementary food source for predators in conservation IPM. Based on the significant reduction in gall numbers, and the increase in foliar macronutrients, it is clear that the FLNCM treatment played additional roles. Finally, for demonstration, the predation of M. incognita was visualized in high resolution imaging using a low-temperature-scanning electron microscope. Accordingly, we recommend that future research focus on identifying soil amendments that will foster the establishment of beneficial microbiota, FLN and soil predators for the conservation biological control of soil pests.

Algal application as a biological control method of root-knot nematode Meloidogyne incognita on cucumber under protected culture conditions and its impact on yield and fruit quality

This study was conducted during seasons 2016 and 2017 to control the root-knot nematode Meloidogyne incognita in cucumber, cultivated in infected soil, using some algal treatments under greenhouse conditions, at Kaha Farm, Qaluobia Governorate, Egypt. Six algal treatments were tested: two foliar applications of Spirulina and Amphora, two drenched soil applications of Spirulina and Amphora, two treatments using Spirulina, as spraying and drenching, and Amphora, as spraying and drenching, in addition to the Rugby nematicide (10% Ebufos, at the rate of 5 g/m2) and control. Rugby was applied by a soil prepared in its experimental units. After 15 days from transplanting, the algal extract treatments were applied twice monthly for 3 months. The same concentration (2 g/l) of both types of algae was applied in both foliar and drench treatments. The control was sprayed only by water. The results indicated that the soil drenched with Amphora or Spirulina extracts had significant increments in vegetative growth, yield, and fruit quality. In contrast, the control plants had the lowest values in all criteria. Amphora (sprayed with soil drenched) treatment gave 2.5 and 2.69 folds the control in marketable yield in 2016 and 2017 seasons, respectively. The combination of sprayed and soil drenched with Amphora was more effective in nematode’s control or in enhancing plant resistance for nematode as shown at most nematode parameters, especially the rate of nematode reproduction factor (RF), which reached 0.42 and 0.45 in both seasons, respectively. It had insignificant differences compared with the nematicide. Therefore, using algae for the biological control of root-knot nematodes is recommended, especially in sustainable agriculture for maintaining the soil and improve fertility.

Screening of locally available organic materials as substrates for production of Pochonia chlamydosporia in Kenya

Pochonia chlamydosporia is a nematophagous fungus with high potential for the biological control of root-knot nematodes (Meloidogyne spp.). The fungus is commonly produced in colonised rice substrate, but non-staple and more affordable substrates may encourage the production and use of this biological control agent. An in vitro study was conducted to screen different organic materials, including green and animal manures and industrial by-products as substrates for local production of viable fungal chlamydospores. Chlamydospore yield from sugarcane filter mud, bean straw, sunn hemp, goat manure, African marigold, wild sunflower, maize cobs, and velvet beans substrates was equal to or significantly greater than production using rice (standard substrate). In addition, the percentage viability of chlamydospores produced in most organic substrates was greater than 50%. The use of non-staple substrates deserves further investigation as a viable, and economical local option to rice substrate for mass production of P. chlamydosporia inoculum in Sub-Saharan Africa.

Biological control of root-knot nematode on sugarcane in soil naturally or artificially infested with Pasteuria penetrans

Soil was collected from a sugarcane field where most of the second-stage juveniles of root-knot nematode (Meloidogyne javanica) were encumbered with endospores of Pasteuria penetrans. A pot experiment was established to determine whether the bacterium was present at levels capable of reducing populations of the nematode. Endospores of the bacterium were eliminated by autoclaving the soil and then eggs of Meloidogyne javanica were inoculated into Pasteuria-free and naturally-infested soil. When the experiment was harvested 19 and 37 weeks later, the root-knot nematode population was respectively 96 and 99% lower in the naturally-infested field soil, indicating that this soil was highly suppressive to the nematode. Pasteuria penetrans was also mass-produced on its nematode host and a further experiment was set up to determine the effect of endospore concentration in soil on multiplication of root-knot nematode. Sugarcane was grown in pasteurised sand containing 0, 6000, 12,000, 24,000 and 50,000 endospores/g soil and treatment effects were assessed after 6, 13 and 20 months. The results showed that regardless of harvest time, the severity of root galling and the number of nematode eggs produced per plant decreased as the endospore concentration increased. The lowest endospore concentration significantly reduced the number of eggs per plant at all three harvest times while the highest concentration reduced egg numbers by 96, 88 and 81% at 6, 13 and 20 months, respectively. These results suggest that when high endospore concentrations are continually maintained in the root zone, P. penetrans will markedly reduce populations of root-knot nematode, a particularly important pest of sugarcane.

In vitro and in planta nematicidal activity of black pepper (Piper nigrum L.) leaf extracts

In this study, biological control of root-knot nematode (Meloidogyne incognita) by aqueous leaf extracts of black pepper was investigated. Results revealed that the leaf extracts inhibited nematode survival and other life parameters in a dose-dependent manner. Black pepper leaf extract was able to penetrate the nematode egg mass matrix and significantly reduce the percentage of egg hatching along with fatal effects on J2s and simultaneous enhancement of tomato plant growth. Egg viability after treatment was found to be less sensitive to the aqueous extracts than J2s, based on LC50 values. Complete mortality of J2s was recorded for 40, 60, and 80% dilutions of extracts, while 100% egg inhibition was only observed with the undiluted standard extracts (SE). The leaf extracts significantly inhibited egg production and egg hatching after treatment. Specific activities of the resistance-related enzymes; peroxidase (POX), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) increased significantly as a result of treatment with leaf extracts. Maximum activities of POX, PPO and PAL were observed at the fifth day after treatment. Results suggested that aqueous leaf extracts of black pepper show significant, sustainable and eco-friendly nemato-toxic effects through inactivation of growth and eradication of M. incognita. This study provides information for use of black pepper leaf extracts for control of M. incognita and could be a possible replacement for synthetic nematicides with fewer side effects in the soil and on crops.

Biological Control of Root-Knot Nematodes (Meloidogyne spp.): Microbes against the Pests

Root-knot nematodes (Meloidogyne spp.) are important pests of many cultivated plants. Recently, the most efficient chemical control products (e.g. methyl bromide) have now been restricted due to their toxic characteristics. Research on agents that work against root-knot nematodes and do not have a detrimental impact on the environment is becoming increasingly important. Advances in the last decades produced quite a number of biocontrol products that are already marketed. Some of the well-accepted commercial products contain bacteria Bacillus firmus and Pasteuria penetrans, and fungus Purpureocillium lilacinus. In this review we summarize the antagonistic activity of bacteria and fungi, with their advantages and limitations in biocontrol of root-knot nematodes.

Biological control of root-knot nematode (Meloidogyne javanica) disease by Pseudomonas fluorescens (Chao)

Plant growth-promoting Rhizobacteria is currently developed as an biocontrol agent against many plant pathogens. In this research, biological control of root-knot nematode (Meloidogyne javanica) by Pseudomonas fluorescens was investigated in greenhouse and laboratory experiments. Results showed that 109 (CFU/ml) of P. fluorescens decreased nematode infection and other parameters significantly, compared to the control. P. fluorescens was able to cause destruction of nematode egg mass matrix and significantly decreased nematode egg hatching level. Specific activities of resistance-related enzymes, namely peroxidase (POX) and phenylalanine ammonia lyase (PAL), increased significantly in P. fluorescens-inoculated plants. Maximum activities of POX and PAL were observed at the 5 days after inoculation, respectively. Results suggested that the destruction of eggs and plant defence mechanisms leading to systemic resistance are two main suppression mechanisms used by P. fluorescens against nematode.

Bacillus cereus X5 Enhanced Bio-Organic Fertilizers Effectively Control Root-Knot Nematodes (Meloidogyne sp.)

The efficacy of Bacillus cereus X5 as a potential biological control agent against root-knot nematodes was evaluated in vitro by examining second-stage juvenile mortality and egg hatching rate under addition of culture filtrate and in planta by application of bio-organic fertilizers enhanced with B. cereus X5, B. thuringiensis BTG, or Trichoderma harzianum SQR-T037 alone or together in greenhouse and field experiments. The biofumigation of the root-knot nematode-infested soil with organic materials (chicken manure, pig manure and rice straw) alone or in combination with B. cereus X5 was also conducted in greenhouse experiments. In laboratory, the filtrate of B. cereus X5 more effectively reduced egg hatching rates during the incubation period for 14 d and more effectively killed the second-stage juvenile during the incubation period of 24 h than that of B. thuringiensis BTG. The highest dry shoot weights for greenhouse tomatoes and field muskmelons were found in both the treatment consisting of the bio-organic fertilizer enhanced with the three biocontrol agents and the treatment consisting of the bio-organic fertilizer enhanced only with B. cereus X5. The two bio-organic fertilizers achieved better nematicidal effects than those enhanced only with B. thuringiensis BTG or T. harzianum SQR-T037. B. cereus X5 also enhanced effect of biofumigation, which resulted in increased plant biomass and reduced nematode counts in the roots and rhizosphere soil. Therefore, these results suggested that biological control of root-knot nematodes both in greenhouses and fields could be effectively achieved by using B. cereus X5 and agricultural wastes.

Changes in antioxidative enzyme activities in cucumber plants with regard to biological control of root-knot nematode, Meloidogyne incognita with Cinnamomum cassia Crude Extracts

Cucumber plants were infected with the root-knot nematode Meloidogyne incognita and were then treated with Cinnamomum cassia crude extracts (CCE). The activities of antioxidative enzymes such as superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), and ascorbate peroxidase (APX, EC 1.11.1.11, class I peroxidase) were detected in the cucumber leaves. On day 28 after treatment of C. cassia (0, 1, 5, and 10 mg/mL), the relative galling formation decreased significantly in a dose-dependent manner. The C. cassia crude extracts also effectively inhibited the growth of M. incognita in soil and roots. The number of second-stage juveniles was significantly decreased as the concentration of the C. cassia crude extracts increased. Twenty-eight days after treatment with CCE, the SOD activities of plant leaves treated with 5 and 10 mg/mL CCE were greater than that of leaves treated with nematode (Ne) only. In addition, the CAT and ascorbate peroxidase (APX) activities increased as the concentration of CCE increased. The relative activities of the antioxidative enzymes decreased as the galling formation in the roots increased in response to M. incognita infection. Polyacrylamide gel electrophoresis (PAGE) with activity staining revealed active bands of SOD corresponding to at least five isozymes (93, 79, 71, 66, and 41 kDa), including three Fe-SOD bands (71, 66, and 41 kDa) and two Mn-SOD bands (93 and 79 kDa). Analysis of the cucumber leaves revealed one active band corresponding to the CAT isozyme (>97 kDa) on 10% native gels. At least four bands corresponding to APX were observed in 10% polyacrylamide, including one major band (>97 kDa) and three minor bands (79, 71, and 66 kDa). Compared with the leaves of cucumber plants that received other treatments, SOD (41 kDa) and APX (70 kDa) isozymes in the leaves of plants treated with Ne only showed intensified bands in PAGE gels.

Biological control of root-knot nematode; Meloidogyne incognita in the medicinal plant; Withania somnifera and the effect of biocontrol agents on plant growth.

The medicinally important plant; Withania somnifera, is highly susceptible to root knot nematode; Meloidogyne incognita. Various nematode antagonistic fungi have been studied for their use as biocontrol agents. In the experiment, the potential of fungi Trichoderma harzianum, Paecilomyces lilacinus and Arthrobotrys oligospora along with natural organic compound (Neem compound mix) to control the nematode; M. incognita was evaluated. Also, their potential to control nematodes was compared with that achieved by using the chemical control agent; carbofuran. The fungal agents evaluated significantly controlled nematode population and enhanced plant growth.

Biological control of the root-knot nematode Meloidogyne javanica by Trichoderma harzianum

The filamentous fungi Trichoderma spp. is currently developed as biocontrol agents against many plant pathogens. Recent studies have shown that these fungi are able to infect nematode eggs and juveniles. In this research, biological control of root-knot nematode ( Meloidogyne javanica) by Trichoderma harzianum BI was investigated in greenhouse and laboratory experiments. Results showed that different concentrations (10 2–10 8 spores/ml) of T. harzianum BI decreased nematode infection and other parameters significantly, compared to control. T. harzianum BI was able to penetrate nematode egg mass matrix and significantly decreased nematode egg hatching level. Specific activities of resistance-related enzymes, namely peroxidase (POX), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) increased significantly in T. harzianum BI inoculated plants. Maximum activities of POX, PPO and PAL were observed at the 5, 5 and 6 days after inoculation, respectively. Chitinase activity was also increased in culture filtrates of T. harzianum BI grown on wheat bran moistened with salt solution supplemented with colloidal chitin or nematode eggs. Maximum activity of chitinase was recorded at the 4 days after inoculation, in media supplemented with colloidal chitin (1.15 U/min per ml) and nematode eggs (0.85 U/min per ml). Results suggested that direct parasitism of eggs through the increase in extracellular chitinase activity, which would be indicator of eggs infection capability, and inducing plant defense mechanisms leading to systemic resistance are two main suppression mechanisms used by T. harzianum BI against nematode.