Use of chitin for controlling plant-parasitic nematodes

Cabbage plants were grown in soil amended with Clandosan (CLA) prepared from crustacean chitin (0.3% w/w). The plants were maintained in constant temperature tanks set to 15° or 30°C, in soils naturally infested with cyst nematodeHeterodera schachtii, or inoculated with the root-knot nematode,Meloidogyne javanica, respectively. At 30°C, after the first month following inoculation, CLA caused an increase in top fresh weight of plants but no reduction in nematode—induced root galling was recorded. However, when fresh plants were planted, CLA induced a large reduction in gall formation and caused an increase in top fresh weight of nematode-inoculated plants. At 15°C, CLA significantly affected the plants only after 60 days: an increase in top fresh weight and a reduction in the number of eggs per cyst were recorded. Ammonium was not detected in soil after 30 days, at 30°C, whereas at 15°C, CLA-treated soil contained twice as much ammonium as non-treated soil. After 60 days, ammonium was not detected at all. After 30 days nitrate concentrations in soil attained higher values at 30°C than at 15°C, whereas after 60 days high levels were detected only at 15°C. At 30°C, CLA induced an increase in the number of fungi, chitinolytic bacteria, and total amount of bacteria; at 15°C, such an increase was detected only with the chitinolytic microorganisms.Contribution from the Agricultural Research Organization (ARO), Bet Dagan, Israel No. 2196-E, 1987 series.     

Role of Zinc in Rhizobacteria-Mediated Suppression of Root-Infecting Fungi and Root-Knot Nematode

Understanding the environmental factors that influence the rhizosphere and inner root colonization of the disease‐suppressive strains of fluorescent pseudomonads is an essential step towards improving the level and reliability of their biocontrol activity. Soil amendment with Zn at 0.8 or 1.6 mg/kg of soil alone or in combination with Pseudomonas aeruginosa IE‐6S⁺significantly reduced nematode penetration in tomato roots. Zn applied alone did not reduce root infection caused by Macrophomina phaseolina or Fusarium solani but did reduce when used in combination with IE‐6S⁺. Soil amendment with Zn at 0.8 or 1.6 mg/kg of soil alone or in conjunction with IE‐6S⁺ markedly suppressed Rhizoctonia solani infection. Plant height, fresh weight of shoot and protein contents of the leaves substantially improved when used with Zn, however, plants growing in the soil treated with 1.6 mg/kg of Zn in the absence of IE‐6S⁺ not only reduced plant growth but also showed necrotic symptoms on the leaves. Zn application in the soil decreased populations of IE‐6S⁺ both in the rhizosphere and root. A positive correlation between bacterial rhizosphere and inner root colonization was also observed. With an increase in nematode densities in the soil, nematode penetration and subsequent galling due to Meloidogyne javanica increased. Regardless of the nematode densities, Zn applied alone or in combination with IE‐6S⁺ caused marked suppression of M. javanica. At all the population densities of M. javanica, Zn enhanced the efficacy of IE‐6S⁺ to reduce nematode invasion and subsequent gall development. IE‐6S⁺ caused significant suppression of soil‐borne root‐infecting fungi both in Zn‐sufficient and Zn‐deficient soil although this suppressive effect accentuated in Zn‐sufficient soils. In the absence of IE‐6S⁺ and/or Zn, increased nematode densities in the soil significantly reduced plant height, fresh weight of shoot and protein contents of the shoots. With an increase in nematode densities, populations of IE‐6S⁺ in the rhizosphere and root increased regardless of the Zn application. However, Zn‐deficient soils supported larger populations of IE‐6S⁺ compared with those of Zn‐sufficient soils.     

Interaction of Glomus mosseae and Paecilomyces lilacinus on Meloidogyne javanica of tomato

The effects of Glomus mosseae and Paecilomyces lilacinus on Meloidogyne javanica of tomato were tested in a greenhouse experiment. Chicken layer manure was used as a carrier substrate for the inoculum of P. lilacinus. The following parameters were used: gall index, average number of galls per root system, plant height, shoot and root weights. Inoculation of tomato plants with G. mosseae did not markedly increase the growth of infected plants with M. javanica. Inoculation of plants with G. mosseae and P. lilacinus together or separately resulted in similar shoots and plant heights. The highest root development was achieved when mycorrhizal plants were inoculated with P. lilacinus to control root-knot nematode. Inoculation of tomato plants with G. mosseae suppressed gall index and the average number of galls per root system by 52% and 66%, respectively, compared with seedlings inoculated with M. javanica alone. Biological control with both G. mosseae and P. lilacinus together or separately in the presence of layer manure completely inhibited root infection with M. javanica. Mycorrhizal colonization was not affected by the layer manure treatment or by root inoculation with P. lilacinus. Addition of layer manure had a beneficial effect on plant growth and reduced M. javanica infection.     

Nematicidal and allelopathic potential of Argemone mexicana,a tropical weed

Argemone mexicana L. (Papaveraceae), a tropical annual weed, is phytotoxic to many crop species. This study was designed to examine the allelochemical and nematicidal potential of A. mexicana and to better understand the role of this weed in the ecosystem. A methanol-soluble extract of the leaf material caused greater juvenile mortality of Meloidogyne javanica than did ethyl acetate or hexane extracts indicating the polar nature of the toxins. Decomposing tissues of A. mexicana in soil at 50 g kg^–1 were highly deleterious causing 80% mortality of tomato plants. At 10 g kg^–1 plant growth was enhanced, while at 30 g kg^–1 plant growth was substantially retarded. M. javanica population densities in the rhizosphere and in roots, and gall formation were significantly suppressed when 10, 30 or 50 g kg^–1 A. mexicana was allowed to decompose in the soil. To establish whether decomposition was necessary to produce phytotoxic symptoms, or whether the shoot extract alone could interfere with plant growth, an aqueous shoot extract was applied to soil. Whereas a 50% extract promoted plant growth, a 100% (100 g/500 mL distilled water) concentration significantly reduced plant height, and fresh weights of shoot and root. In general, decomposing plant material caused greater phytotoxicity compared to the aqueous extract. Addition of N as NH₄NO₃ partially alleviated the phytotoxic action of A. mexicana,and also reduced severity of root-knot disease. Adding Pseudomonas aeruginosa to soil amended with A. mexicana resulted in decreased density of M. javanicain the rhizosphere and in tomato roots, suppressed galling rates and enhanced plant growth.     

Enhanced Nematicidal Activity of Organic and Inorganic Ammonia-Releasing Amendments by Azadirachta indica Extracts

The nematicidal activities of ammonium sulfate, chicken litter and chitin, alone or in combination with neem (Azadirachta indica) extracts were tested against Meloidogyne javanica. Soil application of these amendments or the neem extracts alone did not reduce the root galling index of tomato plants or did so only slightly, but application of the amendments in combination with the neem extracts reduced root galling significantly. Soil analysis indicated that the neem extract inhibited the nitrification of the ammonium released from the amendments and extended the persistence of the ammonium concentrations in the soil. In microplot experiments, tomato plants were grown in pots filled with soils from the treated microplots. The galling indices of tomato plants grown in soil treated with ammonium sulfate or chicken litter in combination with the neem extract or a chemical nitrification inhibitor were far lower than those of plants grown in the control soil or in soil treated with chicken litter, neem extract or nitrification inhibitor alone. However, plants grown in the microplots showed only slight reductions in galling, probably because the soil amendments were inadequately mixed compared to their application in the pot experiments. The extended exposure of nematodes to ammonia as a result of nitrification inhibition by the neem extracts appeared to be the cause of the enhanced nematicidal activity of the ammonia-releasing amendments.     

Biocontrol of <Emphasis Type="Italic">Meloidogyne javanica</Emphasis> by <Emphasis Type="Italic">Rhizobium</Emphasis> and plant growth-promoting rhizobacteria on lentil

Biocontrol of the root-knot nematode Meloidogyne javanica was studied on lentil using plant growth-promoting rhizobacteria (PGPR) namely Pseudomonas putida, P. alcaligenes, Paenibacillus polymyxa and Bacillus pumilus and root nodule bacterium Rhizobium sp. Pseudomonas putida caused greater inhibitory effect on the hatching and penetration of M. javanica followed by P. alcaligenes, P. polymyxa and B. pumilus. Inoculation of any PGPR species alone or together with Rhizobium increased plant growth both in M. javanica-inoculated and -uninoculated plants. Inoculation of Rhizobum caused greater increase in plant growth than caused by any species of plant growth-promoting rhizobacteria in nematode-inoculated plants. Among PGPR, P. putida caused greater increase in plant growth and higher reduction in galling and nematode multiplication followed by P. alcaligenes, P. polymyxa and B. pumilus. Combined use of Rhizobium with any species of PGPR caused higher reduction in galling and nematode multiplication than their individual inoculation. Use of Rhizobium plus P. putida caused maximum reduction in galling and nematode multiplication followed by Rhizobium plus P. alcaligens. Pseudomonas putida caused greater root colonization and siderophore production followed by P. alcaligenes, P. polymyxa and B. pumilus. Analysis of the protein bands of these four species by SDS-PAGE revealed that P. putida had a different protein band profile compared to the protein profiles of P. alcaligenes, P. polymyxa and B. pumilus. However, the protein profiles of P. acaligenes, P. polymyxa and B. pumilus were similar.     

Population Development and Pathogenicity of Meloidogyne javanica on Flue-cured Tobacco as Influenced by Ethoprop and DD

Growth of flue-cured tobacco as influenced by Meloidogyne javanica and the effectiveness of DD and ethoprop to manage this nematode were evaluated over two growing seasons. Populations of M. javanica, root galling, plant height, steam crown diameter, whole plant weight, and yield were monitored at approximately 2-week intervals beginning 28 days after transplanting. Treatment influence on nematode population development, root galling, and plant growth generally followed a pattern in descending order of efficacy: DD (187 liters/ha), ethoprop (27, 18, or 9 kg a.i./ha), and control. In all treatments, nearly season-long increases in M. javanica populations and root galling were observed. Correlation coefficients relating nematode populations or root galling to final tobacco yield suggested either method may be used successfully to evaluate nematicide efficacy in research plots. Plant growth parameters most affected by M. javanica in order of decreasing severity were cured leaf yield, whole plant weight, plant height, and stem diameter.     

Efficacy of Saccharomyces cerevisiae on controlling the root-knot nematode (Meloidogyne javanica) infection and promoting cucumber growth and yield under laboratory and field conditions

Saccharomyces cerevisiae is a promising plant growth-promoting yeast for different crops. Applicability of S. cerevisiae as a biocontrol agent of the root-knot nematode (Meloidogyne javanica) was investigated on cucumber under growth-room and field conditions. The yeast S. cerevisiae similar to the nematicide, Ethoprophos, when applied as a rhizospheric soil drench treatment led to an obvious reduction of root galling caused by M. javanica and resulted in reducing the nematode reproduction ability on cucumber under growth room and field conditions. The yeast was more effective at 10 than at 5?g/l. Furthermore, the application of S. cerevisiae resulted in improving cucumber plant growth and increasing its fruit yield. High content of total phenolics in cucumber roots of S. cerevisiae-treated plants and hydrogen peroxide-treated plants gives a clue on the ability of the yeast to induced plant resistance in a similar way to exogenous hydrogen peroxide.     

Control of Meloidogyne javanica by Formulations of Inula viscosa Leaf Extracts

Inula viscosa is a perennial plant that is widely distributed in Mediterranean countries. Formulations of I. viscosa extracts were tested for their effectiveness in control of Meloidogyne javanica in laboratory, growth chamber, microplot, and field experiments. Oily pastes were obtained by extraction of dry leaves with a mixture of acetone and n-hexane or n-hexane alone, followed by evaporation of the solvents. Emulsifiable concentrate formulations of the pastes killed M. javanica juveniles in sand at a concentration of 0.01% (paste, w/w) or greater and reduced the galling index of cucumber seedlings as well as the galling index and numbers of nematode eggs on tomato plants in growth chamber experiments. In microplot experiments, the hexane-extract formulation at 26 g paste/m² reduced nematode infection on tomato plants in one of two experiments. In a field experiment, a reduction of 40% in root galling index by one of two formulations was observed on lettuce plants. The plant extracts have potential as a natural nematicide, although the formulations need improvement.     

Pathogenicity and life cycle of Meloidogyne javanica on broccoli

A pathogenicity trial conducted against root-knot nematode, Meloidogyne javanica on broccoli indicated that a gradual increase in the nematode inoculum from 500 to 8000 juveniles/kg soil was associated with a progressive decline in all the plant growth parameters and reproduction factor of the nematode. Although 8000 juveniles/kg soil showed maximum plant growth reduction and root knot index, statistical analysis of the data revealed that the population of 1000 juveniles/kg soil was associated with a significant decline in plant growth. Hence, this level was indicative of being the pathogenic level. The significant reduction in seedling emergence was recorded at and above 2000 juveniles/kg soil and it decreased further with increasing inoculum levels. Meloidogyne javanica required 27 days to complete the life cycle on broccoli at a temperature range of 28–35°C.     

Effect of root-rot fungus (Macrophomina phaseolina) on the life cycle of root-knot nematode (Meloidogyne javanica) Race-2 on balsam

The penetration of second stage juveniles of Meloidogyne javanica started within 12 hours after inoculation and the rate of penetration gradually increased with the passage of time up to the fifth day in the plants inoculated with root-knot nematode alone and up to the sixth day when plants were infected with root-knot nematode and root-rot fungus. Mostly, the penetration of second stage juveniles of Meloidogyne javanica took place in the meristematic region but in some cases the juveniles also penetrated into the root tips and oriented themselves near the stellar region almost parallel to the longitudinal axis of the roots. The life cycle of Meloidogyne javanica on balsam was completed within 25 days, whereas the duration of the life cycle and fecundity of females was adversely affected in the presence of fungus (Macrophomina phaseolina) and it took about 33 days to complete the life cycle, i.e. the presence of Macrophomina phaseolina delayed the life cycle of the root-knot nematode (Meloidogyne javanica) by eight days.     

Effect of amino acids on root-knot nematode (Meloidogyne javanica) infecting tomato plant

Six amino acids viz. DL-methionine, DL-valine, DL-serine, DL-phenylalanine, L-proline and L-histidine were tested against root knot of tomato caused by Meloidogyne javanica. All amino acids showed significant response in plant growth characters with corresponding reduction in the number of galls, adult females, egg masses and juvenile stages within the treated plants. DL-phenylalanine gave significantly higher response in reducing the hatch of egg masses and survival of juveniles in in vitro test compared to control. The highest plant growth and maximum reduction of galling incidence of tomato were recorded in the DL-phenylalanine- treated plants followed by L-proline and L-histidine. All the amino acids gave positive response in suppressing the development of the nematode in the treated plants.     

Development of Multi-Component Transplant Mixes for Suppression of Meloidogyne incognita on Tomato (Lycopersicon esculentum)

The effects of combinations of organic amendments, phytochemicals, and plant-growth promoting rhizobacteria on tomato (Lycopersicon esculentum) germination, transplant growth, and infectivity of Meloidogyne incognita were evaluated. Two phytochemicals (citral and benzaldehyde), three organic amendments (pine bark, chitin, and hemicellulose), and three bacteria (Serratia marcescens, Brevibacterium iodinum, and Pseudomonas fluorescens) were assessed. Increasing rates of benzaldehyde and citral reduced nematode egg viability in vitro. Benzaldehyde was 100% efficacious as a nematicide against juveniles, whereas citral reduced juvenile viability to less than 20% at all rates tested. Benzaldehyde increased tomato seed germination and root weight, whereas citral decreased both. High rates of pine bark or chitin reduced plant growth but not seed germination, whereas low rates of chitin increased shoot length, shoot weight, and root weight; improved root condition; and reduced galling. The combination of chitin and benzaldehyde significantly improved tomato transplant growth and reduced galling. While each of the bacterial isolates contributed to increased plant growth in combination treatments, only Brevibacterium iodinum applied alone significantly improved plant growth.     

Effects of nitrogen fertilisers on the Javanese root-knot nematode Meloidogyne javanica and its interaction with cucumber

The influence of different nitrogen salts at five electrical conductivity levels (EC 2, 4, 6 and 8 mmhos/cm) on the Javanese root-knot nematode (RKN) (Meloidogyne javanica) and its interaction with cucumber was evaluated under in vitro, growth chamber and greenhouse conditions. Percentages of egg-hatching and second-stage juvenile viability of M. javanica were greatly reduced when NH₄Cl, (NH4)₂SO₄ and NH₄NO₃ were used especially at the higher levels of EC and accompanied with reduction in cucumber root galling. The lower root galling (less than 2.5) was accompanied with NH₄Cl, (NH₄)₂SO₄ and (NH₄)₂HPO₄, while KNO₃ and NH₄NO₃ resulted in moderate root galling. In contrast to the nitrogen salts, NaCl caused a reduction in both nematode infection and root growth especially at higher EC levels and this could be due to salinity effect. Diammonium phosphate was superior over the tested salts in increasing plant and root fresh and dry weights and cucumber phosphorus content, while KNO₃ was superior in increasing in plant content of potassium.     

Plant Sources of Chinese Herbal Remedies: Laboratory Efficacy,Suppression of Meloidogyne javanica in Soil,and Phytotoxicity Assays

Extracts of Chinese herbal medicines from plants representing 13 families were tested for their ability to suppress plant-parasitic nematodes. Effective concentration (EC₅₀ and EC₉₀) levels for 18 of the extracts were determined in laboratory assays with Meloidogyne javanica juveniles and all stages of Pratylenchus vulnus. Efficacy of 17 extracts was tested against M. javanica in soil. Generally, EC₅₀ and EC₉₀ values determined in the laboratory were useful indicators for application rates in the soil. Extracts tested from plants in the Liliaceae reduced galling of tomato by M. javanica and were not phytotoxic. Similarly, isothiocyanate-yielding plants in the Brassicaceae suppressed root galling without phytotoxicity. Other plant extracts, including those from Azadirachta indica, Nerium oleander, and Hedera helix, suppressed root galling but were phytotoxic at the higher concentrations tested. Many of these plant sources have been tested elsewhere. Inconsistency in results across studies points to the need for identification of active components and for determination of concentration levels of these components when plant residues or extracts are applied to soil.     

Role of cyanide production by Pseudomonas fluorescens CHA0 in the suppression of root-knot nematode, Meloidogyne javanica in tomato

Summary Pseudomonas fluorescens strain CHA0 produces hydrogen cyanide (HCN), a secondary metabolite that accounts largely for the biocontrol ability of this strain. In this study, we examined the role of HCN production by CHA0 as an antagonistic factor that contributes to biocontrol of Meloidogyne javanica, the root-knot nematode, in situ. Culture filtrate of CHA0, resulting from 1/10-strength nutrient broth yeast extract medium amended with glycine, inhibited egg hatch and caused mortality of M. javanica juveniles in vitro. The bacterium cultured under high oxygen-tension conditions exhibited better inhibitory effects towards nematodes, compared to its cultivation under excess oxygen situation. Growth medium amended with 0.50 or 1.0 mM FeEDDHA further improved hatch inhibition and nematicidal activity of the strain CHA0. Strain CHA77, an HCN-negative mutant, failed to exert such toxic effects, and in this strain, antinematode activity was not influenced by culture conditions. Exogenous cyanide also inhibited egg hatch and caused mortality of M. javanica juveniles in vitro. Strains CHA0 or CHA77 applied in unsterilized sandy-loam soil as drench, caused marked suppression of root-knot disease development incited by M. javanica in tomato seedlings. However, efficacy of CHA77 was noticeably lower compared to its wild type counterpart CHA0. An increased bioavailability of iron following EDTA application in soil substantially improved nematode biocontrol potential of CHA0 but not that of CHA77. Soil infestation with M. javanica eggs resulted in significantly lower nematode population densities and root-knot disease compared to the juveniles used as root-knot disease-inducing agents. Strain CHA0 significantly suppressed nematode populations and inhibited galling in tomato roots grown in soil inoculated with eggs or juveniles and treated with or without EDTA. Strain CHA0 exhibited greater biocontrol potential in soil inoculated with eggs and treated with EDTA. To demonstrate that HCN synthesis by the strain CHA0 acts as the inducing agent of systemic resistance in tomato, efficacy of the strain CHA0 was compared with CHA77 in a split root trial. The split-root experiment, guaranteeing a spatial separation of the inducing agent and the challenging pathogen, showed that HCN production by CHA0 is not crucial in the induction of systemic resistance in tomato against M. javanica, because the HCN-negative-mutant CHA77 induced the same level of resistance as the wild type but exogenous cyanide in the form of KCN failed to trigger the resistance reaction. In the root section where both nematode and the bacterium were present, strain CHA0 reduced nematode penetration to a greater extent than CHA77, suggesting that for effective control of M. javanica, a direct contact between HCN-producing CHA0 and the nematode is essential.     

Control of Late Blight (Phytophthora capsici ) in Pepper Plant with a Compost Containing Multitude of Chitinase-producing Bacteria

Compost sustaining a multitude of chitinase-producing bacteria was evaluated in a greenhouse study as a soil amendment for the control of late blight (Phytophthora capsici L.) in pepper (Capsicum annuum L.). Microbial population and exogenous enzyme activity were measured in the rhizosphere and correlated to the growth and health of pepper plant. Rice straw was composted with and without a chitin source, after having been inoculated with an aliquot of coastal area soil containing a known titer of chitinase-producing bacteria. P. capsici inoculated plants cultivated in chitin compost-amended soil exhibited significantly higher root and shoot weights and lower root mortality than plants grown in pathogen-inoculated control compost. Chitinase and β-1,3-glucanase activities in rhizosphere of plants grown in chitin compost-amended soil were twice that seen in soil amended with control compost. Colony forming units of chitinase-producing bacteria isolated from rhizosphere of plants grown in chitin compost-amended soil were 10³ times as prevalent as bacteria in control compost. These results indicate that increasing the population of chitinase-producing bacteria and soil enzyme activities in rhizosphere by compost amendment could alleviate pathogenic effects of P. capsici.     

Use of Cucumis metuliferus as a Rootstock for Melon to Manage Meloidogyne incognita

Root-knot nematode-susceptible melons (Cantaloupe) were grown in pots with varying levels of Meloidogyne incognita and were compared to susceptible melons that were grafted onto Cucumis metuliferus or Cucurbita moschata rootstocks. In addition, the effect of using melons as transplants in nematode-infested soil was compared to direct seeding of melons in nematode-infested soil. There were no differences in shoot or root weight, or severity of root galling between transplanted and direct-seeded non-grafted susceptible melon in nematode-infested soil. Susceptible melon grafted on C. moschata rootstocks had lower root gall ratings and, at high nematode densities, higher shoot weights than non-grafted susceptible melons. However, final nematode levels were not lower on the grafted than on the non-grafted plants, and it was therefore concluded that grafting susceptible melon on to C. moschata rootstock made the plants tolerant, but not resistant, to the nematodes. Grafting susceptible melons on C. metuliferus rootstocks also reduced levels of root galling, prevented shoot weight losses, and resulted in significantly lower nematode levels at harvest. Thus, C. metuliferus may be used as a rootstock for melon to prevent both growth reduction and a strong nematode buildup in M. incognita-infested soil.     

Plant Species, Host Age and Host Genotype Effects on Meloidogyne incognita Biocontrol by Pseudomonas fluorescens Strain CHA0 and its Genetically-Modified Derivatives

Pseudomonas fluorescens strain CHA0 and its antibiotic overproducing derivative CHA0/pME3424 repeatedly reduced Meloidogyne incognita galling on tomato, brinjal, mungbean and soya bean roots but not in chilli. An antibiotic‐deficient derivative, CHA89, did not reduce nematode invasion in any of the plant species tested. When plant species were compared, bacterial inoculants afforded better protection to tomato, mungbean and soya bean roots against root‐knot nematodes than to brinjal and chilli. Antibiotic overproducing strain CHA0/pME3424 markedly reduced fresh shoot weights of chilli and mungbean while antibiotic‐deficient strain CHA89 enhanced fresh shoot weights of mungbean. While strains CHA0 had no significant impact on fresh root weights of any of the plant species, strain CHA0/pME3424 consistently reduced fresh root weights of brinjal and mungbean. In none of the plant species the bacterial strains had an influence on protein contents of the leaves. Regardless of the plant species, the three bacterial strains did not differ markedly in their rhizosphere colonization pattern. However, colonization was highest in brinjal rhizosphere and lowest in the mungbean rhizosphere. A slight host genotype effect on the biocontrol performance of the bacterial inoculants was also detected at cultivar level. When five soya bean cultivars were compared, biocontrol bacteria exhibited best suppression of the root‐knot nematode in cv. Ajmeri. Antibiotic overproducing strain CHA0/pME3424 substantially reduced fresh shoot weights of the soya bean cultivars Centuray 84 and NARC‐I while strain CHA89 enhanced shoot weights of the cultivars Ajmeri, William‐82 and NARC‐II. Wild type strain CHA0 had no significant impact on fresh shoot weights of any of the soya bean cultivars. Strain CHA0/pME3424 reduced fresh weights of root of Century 84, NARC‐I and NARC‐II while strain CHA89 increased root weights. Bacterial rhizosphere colonization was highest in variety NARC‐I and lowest in variety Ajmeri. Plant age had a significant impact on the biocontrol performance of bacterial inoculants against nematodes. The biocontrol effect of all bacterial strains was more prominent during early growth stage (7 days after nematode inoculation). A strong negative correlation between bacterial rhizosphere colonization and nematode invasion in soya bean roots was observed.     

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.