Effect of Broccoli (Brassica oleracea) Tissue, Incorporated at Different Depths in a Soil Column, on Meloidogyne incognita

Brassicas have been used frequently for biofumigation, a pest-management strategy based on the release of biocidal volatiles during decomposition of soil-incorporated tissue. However, the role of such volatiles in control of plant-parasitic nematodes is unclear. The goal of this study was to determine the direct localized and indirect volatile effects of amending soil with broccoli tissue on root-knot nematode populations. Meloidogyne incognita-infested soil in 50-cm-long tubes was amended with broccoli tissue, which was mixed throughout the tube or concentrated in a 10-cm layer. After three weeks at 28°C, M. incognita populations in the amended tubes were 57 to 80% smaller than in non-amended tubes. Mixing broccoli throughout the tubes reduced M. incognita more than concentrating broccoli in a 10-cm layer. Amending a 10-cm layer reduced M. incognita in the non-amended layers of those tubes by 31 to 71%, probably due to a nematicidal effect of released volatiles. However, the localized direct effect was much stronger than the indirect effect of volatiles. The strong direct effect may have resulted from the release of non-volatile nematicidal compounds. Therefore, when using biofumigation with broccoli to control M. incognita, the tissue should be thoroughly and evenly mixed through the soil layer(s) where the target nematodes occur. Effects on saprophytic nematodes were the reverse. Amended soil layers had much greater numbers of saprophytic nematodes than non-amended layers, and there was no indirect effect of amendments on saprophytic nematodes in adjacent non-amended layers.     

Evaluation of soil biodesinfestation with crop and garden residues in the control of root-knot nematodes populations

Fresh crop and garden residues were applied both under laboratory conditions and in commercial greenhouse in order to asses their effect on soil nematodes populations and soil fertility. In the laboratory experiments, dosages of 5 to 20 g of cabbage residues, chicken manure, cabbage residues+chicken manure, grass+chicken manure, as well as leaves and stems of orange tree, pine tree, oleander, olive tree, palm tree and boxwood were mixed with 500 g soil having root-knot nematodes (Meloidogyne incognita) and soil moisture was adjusted at field capacity. A control treatment without residues was also included. The mixtures were kept into plastic bags, with four replications, and the bags were incubated for four weeks at 30 degrees C, when nematological and soil fertility analyses were carried out. In general, all these materials significantly (P < 0.05) reduced M. incognita populations and increased saprophagous nematodes, with slight effects on soil fertility except for the K increase with residues application. Tomato plants susceptible to M. incognita were planted in pots with 300 cm3 of the treated soils and kept for five weeks in a growth chamber (24 +/- 1 degrees C, 14 hours light), when root galling indices were evaluated. Most materials applied reduced root galling indices as regards to the control. In the greenhouse experiment, cabbage residues, cabbage residues+chicken manure, grass+chicken manure and grass+cabbage residues were applied to the soil and covered with a polyethylene sheet for 5 weeks. A cabbage residues:chicken manure treatment and a control (not-amended) treatment, without polyethylene, were also included. At the end of the experiment, the nematological analysis showed that all materials successfully controlled M. incognita populations, reaching 86-100% mortality with organic amendments vs. 6% for the control. After the greenhouse biodesinfestation experiment, a tomato crop was grown for one month, when root galling indices were determined. All materials significantly reduced this value from 4.75 in the control to 1.0-2.25 with the organic amendments, except for the cabbage residues+chicken manure treatment without polyethylene (index = 4.0). Our results show that fresh crop and garden residues successfully reduced M. incognita populations and root galling indices when applied with polyethylene covers, having good potential to be considered in integrated management programs.     

Overview of organic amendments for management of plant-parasitic nematodes, with case studies from Florida

Organic amendments have been widely used for management of plant-parasitic nematodes. Relatively rapid declines in nematode population levels may occur when decomposing materials release toxic compounds, while longer-term effects might include increases in nematode antagonists. Improved crop nutrition and plant growth following amendment use may lead to tolerance of plant-parasitic nematodes. Results depend on a great variety of factors such as material used, processing/composting of material, application rate, test arena, crop rotation and agronomic practices, soil type, climate, and other environmental factors. Reasons for variable performance and interpretation of results from amendment studies are discussed. Case studies of amendments for nematode management are reviewed from Florida, where composts and crop residues are the most frequently used amendments. Plant growth was often improved by amendment application, free-living nematodes (especially bacterivores) were often stimulated, but suppression of plant-parasitic nematodes was inconsistent. Amendments were generally not as effective as soil fumigation with methyl bromide for managing root-knot nematodes (Meloidogyne spp.), and often population levels or galling of root-knot nematodes in amended plots did not differ from those in non-amended control plots. While amendments may improve plant growth and stimulate soil food webs, additional study and testing are needed before they could be used reliably for management of plant-parasitic nematodes under Florida conditions.     

Effects of Chicken-excrement Amendments on Meloidogyne arenaria

The effects of chicken litter on Meloidogyne arenaria in tomato plants cv. Rutgers were determined in the greenhouse. Tomato seedlings were transplanted into a sandy soil amended with five rates of chicken litter and inoculated with 2,000 M. arenaria eggs. After 10 days, total numbers of nematodes in the roots decreased with increasing rates of chicken litter. After 46 days, egg numbers also decreased with increasing litter rates. In another experiment, soil was amended with two litter types, N-P-K fertilizer, and the two primary constituents of chicken litter (manure and pine-shaving bedding). After 10 days, numbers of nematodes in roots were smaller in chicken-excrement treatments as compared to nonexcrement treatments. At 46 days, there were fewer nematode eggs in chicken-excrement treatments compared to nonexcrement treatments. Egg numbers also were smaller for fertilizer and pine-shaving amendments as compared to nonamended controls. Chicken litter and manure amendments suppressed plant growth by 10 days after inoculation but enhanced root weights at 46 days after inoculation. Amendment of soil with chicken litter suppressed M. arenaria and may provide practical control of root-knot nematodes as part of an integrated management system.     

Potential of Leguminous Cover Crops in Management of a Mixed Population of Root-knot Nematodes (Meloidogyne spp.)

Root-knot nematode is an important pest in agricultural production worldwide. Crop rotation is the only management strategy in some production systems, especially for resource poor farmers in developing countries. A series of experiments was conducted in the laboratory with several leguminous cover crops to investigate their potential for managing a mixture of root-knot nematodes (Meloidogyne arenaria, M. incognita, M. javanica). The root-knot nematode mixture failed to multiply on Mucuna pruriens and Crotalaria spectabilis but on Dolichos lablab the population increased more than 2- fold when inoculated with 500 and 1,000 nematodes per plant. There was no root-galling on M. pruriens and C. spectabilis but the gall rating was noted on D. lablab. Greater mortality of juvenile root-knot nematodes occurred when exposed to eluants of roots and leaves of leguminous crops than those of tomato; 48.7% of juveniles died after 72 h exposure to root eluant of C. spectabilis. The leaf eluant of D. lablab was toxic to nematodes but the root eluant was not. Thus, different parts of a botanical contain different active ingredients or different concentrations of the same active ingredient. The numbers of root-knot nematode eggs that hatched in root exudates of M. pruriens and C. spectabilis were significantly lower (20% and 26%) than in distilled water, tomato and P. vulgaris root exudates (83%, 72% and 89%) respectively. Tomato lacks nematotoxic compounds found in M. pruriens and C. spectabilis. Three months after inoculating plants with 1,000 root-knot nematode juveniles the populations in pots with M. pruriens, C. spectabilis and C. retusa had been reduced by approximately 79%, 85% and 86% respectively; compared with an increase of 262% nematodes in pots with Phaseolus vulgaris. There was significant reduction of 90% nematodes in fallow pots with no growing plant. The results from this study demonstrate that some leguminous species contain compounds that either kill root-knot nematodes or interfere with hatching and affect their capacity to invade and develop within their roots. M. pruriens, C. spectabilis and C. retusa could be used with effect to decrease a mixed field populations of root-knot nematodes.     

The Potential of Five Winter-grown Crops to Reduce Root-knot Nematode Damage and Increase Yield of Tomato

Broccoli (Brassica oleracea), carrot (Daucus carota), marigold (Tagetes patula), nematode-resistant tomato (Solanum lycopersicum), and strawberry (Fragaria ananassa) were grown for three years during the winter in a root-knot nematode (Meloidogyne incognita) infested field in Southern California. Each year in the spring, the tops of all crops were shredded and incorporated in the soil. Amendment with poultry litter was included as a sub-treatment. The soil was then covered with clear plastic for six weeks and M. incognita-susceptible tomato was grown during the summer season. Plastic tarping raised the average soil temperature at 13 cm depth by 7°C.The different winter-grown crops or the poultry litter did not affect M. incognita soil population levels. However, root galling on summer tomato was reduced by 36%, and tomato yields increased by 19% after incorporating broccoli compared to the fallow control. This crop also produced the highest amount of biomass of the five winter-grown crops. Over the three-year trial period, poultry litter increased tomato yields, but did not affect root galling caused by M. incognita. We conclude that cultivation followed by soil incorporation of broccoli reduced M. incognita damage to tomato. This effect is possibly due to delaying or preventing a portion of the nematodes to reach the host roots. We also observed that M. incognita populations did not increase under a host crop during the cool season when soil temperatures remained low (< 18°C).     

Evaluation of the resistance to two nematodes: Radopholus similis and Meloidogyne spp. in four banana genotypes in Morocco

Radopholus similis and Meloidogyne spp. are the main nematode parasites of banana plants grown under plastic shelters in Morocco. A test was made in pots to evaluate the resistance of four genotypes of banana to these nematodes. Infection by Meloidogyne spp. brought about an increase in root weight in all banana plants tested because of gall formation. The inoculation of R. similis produced a reduction in length and diameter of the pseudo-trunk as well as in root and aerial mass in all genotypes. Pisang jari buaya showed the significantly lowest number of Meloidogyne nematodes per 10 g of roots, whereas for R. similis, the significantly smallest numbers were obtained in Pisang berlin and Pisang jari buaya. Therefore, Pisang jari buaya was the only banana genotype studied to show some degree of resistance to both nematodes.     

Heterologous expression of the Mi-1.2 gene from tomato confers resistance against nematodes but not aphids in eggplant

The Mi-1.2 gene in tomato (Solanum lycopersicum) is a member of the nucleotide-binding leucine-rich repeat (NBLRR) class of plant resistance genes, and confers resistance against root-knot nematodes (Meloidogyne spp.), the potato aphid (Macrosiphum euphorbiae), and the sweet potato whitefly (Bemisia tabaci). Mi-1.2 mediates a rapid local defensive response at the site of infection, although the signaling and defensive pathways required for resistance are largely unknown. In this study, eggplant (S. melongena) was transformed with Mi-1.2 to determine whether this gene can function in a genetic background other than tomato. Eggplants that carried Mi-1.2 displayed resistance to the root-knot nematode Meloidogyne javanica but were fully susceptible to the potato aphid, whereas a susceptible tomato line transformed with the same transgene was resistant to nematodes and aphids. This study shows that Mi-1.2 can confer nematode resistance in another Solanaceous species. It also indicates that the requirements for Mi-mediated aphid and nematode resistance differ. Potentially, aphid resistance requires additional genes that are not conserved between tomato and eggplant.     

Influence of Volcanic Ash on Infectivity and Reproduction of Two Species of Meloidogyne

Mount St. Helens volcanic ash was incorporated into a loamy sand greenhouse soil mix to produce concentrations of 0, 0.5, 1.0, 2.0, 4.0, 8.0, 25, 50 and 100% ash. Chemical and physical properties of the various mixtures were determined. Three experiments were conducted in a greenhouse to determine if volcanic ash had any influence on root-knot nematode survival and infectivity. Tomato, Lycoperscion esculentum, seedlings cv. Columbia, susceptible to Meloidogyne hapla and M. chitwoodi were planted into pots of the soil-ash concentrations and infested with one of the two nematode species. Tomato seedlings were harvested 30, 50 and 60 days later and the roots examined for nematode infection and reproduction. Ash incorporation had no deliterious effect on root-knot nematodes in any of the experiments reported here. Nematode infection and reproduction on tomato were not affected at any ash concentration.     

Utilization of noxious weeds for the management of plant-parasitic nematodes infesting some vegetable crops: Einsatz von schädlichen unkräutern zur bekämpfung von pflanzenparasitären nematoden auf verschiedenen gëmusekulturen

Significant reduction was observed in the population of plant-parasitic nematodes, Meloidogyne incognita, Rotylenchulus reniformis and Tylenchorhynchus brassicae infesting eggplant and cauliflower when given root-dip treatment in the leaf extracts of Argemone maxicana and Solanum xanthocarpum at different concentrations and dip durations. The root-knot development and larval penetration of second stage juveniles of M. incognita were also inhibited, may be due to bare-root dip treatment in leaf extracts of both the weed plants. Leaf extracts of S. xanthocarpum caused more inhibition in root-knot development, nematode multiplication of reniform and stunt nematodes than that of A. maxicana. Plant growth improvement was noted which seems to be due to dip treatment and reduction in the population of parasitic nematodes. The efficacy of root-dip treatment with respect to improvement in plant growth of eggplant and cauliflower and reduction in root-knot development and nematode population, increased with increasing the concentration of leaf extracts and dip durations.     

The tomato Rme1 locus is required for Mi-1-mediated resistance to root-knot nematodes and the potato aphid

The tomato Mi-1 gene confers resistance against root-knot nematodes (Meloidogyne spp.) and a biotype of the potato aphid (Macrosiphum euphorbiae). Four mutagenized Mi-1/Mi-1 tomato populations were generated and screened for altered root-knot nematode resistance. Four independent mutants belonging to two phenotypic classes were isolated. One mutant was chosen for further analyzes; rme1 (for resistance to Meloidogyne) exhibited levels of infection comparable with those found on susceptible controls. Molecular and genetic data confirmed that rme1 has a single recessive mutation in a locus different from Mi-1. Cross-sections through galls formed by feeding nematodes on rme1 roots were identical to sections from galls of susceptible tomato roots. In addition to nematode susceptibility, infestation of rme1 plants with the potato aphid showed that this mutation also abolished aphid resistance. To determine whether Rme1 functions in a general disease-resistance pathway, the response against Fusarium oxysporum f.sp. lycopersici race 2, mediated by the I-2 resistance gene, was studied. Both rme1 and the wild type plants were equally resistant to the fungal pathogen. These results indicate that Rme1 does not play a general role in disease resistance but may be specific for Mi-1-mediated resistance.     

Interaction of vesicular arbuscular mycorrhiza with root knot nematodes in tomato

Summary The interaction between the VA mycorrhizal fungus,Glomus fasciculatus and the root-knot nematodes,Meloidogyne incognita andM. javanica, and their effects on the growth and phosphorus nutrition of tomato was studied in a red sandy loam soil of pH 6.0. Inoculation of tomato roots with root-knot nematodes enhanced infection and spore production byG. fasciculatus. Inoculation of tomato plants withG. fasciculatus significantly reduced the number and size of the root-knot galls produced byM. incognita andM. javanica. Inoculation withG. fasciculatus although improved plant growth and its total phosphorus content compared to the uninoculated plants, the difference were not statistically significant.     

Soil amendment with dried weed leaves as non-chemical approach for the management of Meloidogyne incognita infecting tomato

In pot trial, dried ground weed leaves of Cynodon dactylon, Datura stramonium, Eichhomia crassipes, Emex spinosus, Ricinus communis and Sisymbrium irio were mixed with soil at the rate of 1, 3, 5 and 10 g/kg soil and compared their nematicidal potential with carbofuran as a standard against the root-knot nematode, M. incognita infecting tomato. In addition, their effects on growth rate of tomato plants were also investigated. The results showed that M. incognita populations in the soil and root galling were significantly suppressed when the dried leaves of the tested weeds at all rates were allowed to decompose in the soil. All amendments exhibited varying degree of reduction compared to control. The highest reduction was noticeable with the plants grown in Sisymbrium irio amended soil followed by Datura stramonium and Emex spinosus. In addition, employing high rate of the tested weeds gave higher activity in suppressing the nematode both in the soil and in tomato roots than using low rate. The data also indicated that all amendments at low rates significantly increased growth indices of tomato over control treatment, except Cynodon dactylon and Emex spinosus which decreased it, particularly in the shoot system. On the other hand, their high rates showed phytotoxic effects. These weed species may offer considerable promise as soil amendments for control of root-knot nematode, M. incognita.     

Attachment tests of Pasteuria penetrans to the cuticle of plant and animal parasitic nematodes, free living nematodes and srf mutants of Caenorhabditis elegans.

Populations of Pasteuria penetrans isolated from root-knot nematodes (Meloidogyne spp.) and cyst nematodes (Heterodera spp.) were tested for their ability to adhere to a limited selection of sheathed and ex-sheathed animal parasitic nematodes, free living nematodes, including Caenorhabditis elegans wild type and several srf mutants, and plant parasitic nematodes. The attachment of spores of Pasteuria was restricted and no spores were observed adhering to any of the animal parasitic nematodes either with or without their sheath or to any of the free living nematodes including C. elegans and the srf mutants. All spore attachment was restricted to plant parasitic nematodes; however, spores isolated from cyst nematodes showed the ability to adhere to other genera of plant parasitic nematodes which was not the case with spores isolated from root-knot nematodes. The results are discussed in relationship to cuticular heterogeneity.     

Integrated management of root-knot nematode, Meloidogyne incognita infestation in tomato and grapevine

An integrated approach with the obligate bacterial parasite, Pasteuria penetrans and nematicides was assessed for the management of the root-knot nematode, Meloidogyne incognita infestation in tomato and grapevine. Seedlings of tomato cv. Co3 were transplanted into pots filled with sterilized soil and inoculated with nematodes (5000 juveniles/pot). The root powder of P. penetrans at 10 mg/pot was applied alone and in combination with carbofuran at 6 mg/pot. Application of P. penetrans along with carbofuran recorded lowest nematode infestation (107 nematodes/200 g soil) compared to control (325 nematodes/200 g soil). The rate of parasitization was 83.1% in the carbofuran and P. penetrans combination treatment as against 61.0% in the P. penetrans treatment only. The plant growth was also higher in the combination treatment compared to all other treatments. A field trial was carried out to assess the efficacy of P. penetrans and nematicides viz., carbofuran and phorate in the management of root-knot nematode, M. incognita infestation of grapevine cv. Muscat Hamburg. A nematode and P. penetrans infested grapevine field was selected and treatments either with carbofuran or phorate at 1 g a.i/vine was given. The observations were recorded at monthly interval. The results showed that the soil nematode population was reduced in nematicide treated plots. Suppression of nematodes was higher under phorate (117 nematodes/200 g soil) than under carbofuran (126.7 nematodes/200 g soil) treatment. The number of juveniles parasitized was also influenced by nematicides and spore load carried/juvenile with phorate being superior and the increase being 17.0 and 29.0% respectively over the control. The results of these experiment confirmed the compatibility of P. penetrans with nematicides and its biological control potential against the root-knot nematode.     

Influence of Six Varieties of Cynodon on Four Meloidogyne spp.

Two years of giant star grass, Cynodon nlemluensis var. nlemfuensis, in a field plot markedly reduced the incidence of the root-knot nematodes. Tomato planted following the grass showed very little or no root galling and the yield was thrice that of tomato planted on an adjacent field plot previously cropped to tomato. Replicated greenhouse experiments indicated that six varieties of Cynodon were resistant to root-knot nematode but it took up to 6 months of grass growth to appreciably lower the nematode population. The nematodes were eliminated from the soil by all the six grass varieties after 18 months.     

Morphological and molecular characteristics of a new species of Pasteuria parasitic on Meloidogyne ardenensis

A species of the hyper-parasitic bacterium Pasteuria was isolated from the root-knot nematode Meloidogyne ardenensis infecting the roots of ash (Fraxinus excelsior). It is morphologically different from some other Pasteuria pathogens of nematodes in that the spores lack a basal ring on the ventral side of the spore and have a unique clumping nature. Transmission electron microscopy (TEM) showed that the clumps of spores are not random aggregates but result from the disintegration of the suicide cells of the thalli. Sporulation within each vegetative mycelium was shown to be asynchronous. In addition to the novel morphological features 16S rRNA sequence analysis showed this to be a new species of Pasteuria which we have called P. hartismeri. Spores of P. hartismeri attach to juveniles of root-knot nematodes infecting a wide range of plants such as mint (Meloidogyne hapla), rye grass (unidentified Meloidogyne sp.) and potato (Meloidogyne fallax).     

Control of Root-knot Nematodes on Tomato in Stone Wool Substrate with Biological Nematicides

The efficacy of four biological nematicides on root-galling, root-knot nematode (Meloidogyne incognita) reproduction, and shoot weight of tomato (Solanum lycopersicum) grown in stone wool substrate or in pots with sandy soil was compared to an oxamyl treatment and a non-treated control. In stone wool grown tomato, Avid® (a.i. abamectin) was highly effective when applied as a drench at time of nematode inoculation. It strongly reduced root-galling and nematode reproduction, and prevented a reduction in tomato shoot weight. However, applying the product one week before, or two weeks after nematode inoculation was largely ineffective. This shows that Avid® has short-lived, non-systemic activity. The effects of Avid® on nematode symptoms and reproduction on soil-grown tomato were only very minor, probably due to the known strong adsorption of the active ingredient abamectin to soil particles. The neem derived product Ornazin® strongly reduced tomato root-galling and nematode reproduction only in stone wool and only when applied as a drench one week prior to nematode inoculation, suggesting a local systemic activity or modification of the root system, rendering them less suitable host for the nematodes. This application however also had some phytotoxic effect, reducing tomato shoot weights. The other two products, Nema-Q™ and DiTera®, did not result in strong or consistent effects on nematode symptoms or reproduction.     

Efficacy of dried seed powder of some plant species as soil amendment against Meloidogyne incognita (Tylenchida: Meloidogynidae) on tomato

The nematicidal activity of dried ground seeds of Ammi majus, Matricaria chamomilla, Ricinus communis, Brassica alba, B. oleracea, Peganum harmala, Solanum nigrum, Raphanus sativus and Eucalyptus sp. was assessed against the root-knot nematode, Meloidogyne incognita, infecting tomato in a glasshouse. The powdered seeds of the tested plants were incorporated into the soil at the rate of 5 g/kg and their nematicidal activity was compared with that of the synthetic nematicide carbofuran at the rate of 0.01 g a.i./kg. The effects of the treatments on the growth of tomato were also examined. The populations of M. incognita in the soil and root galling of tomato were significantly suppressed by the powdered seeds of all the plant species tested, with the greatest reduction occurring in soil amended with M. chamomilla, followed by soil treated with powdered seeds of A. majus, S. nigrum, R. communis and Eucalyptus sp. The efficacy of B. oleracea, B. alba, M. chamomilla and R. communis in reducing the number of J₂ in the soil was similar to that of carbofuran. All amendments, except powdered seeds of M. chamomilla and A. majus significantly increased shoot length compared to the untreated inoculated plants. Shoot weight was significantly increased in soil amended with powdered seeds of B. oleracea, B. alba, R. communis, P. harmala and S. nigrum, but not in soil amended with the other seed powders when compared with untreated inoculated soil. Significant increases in root length occurred in pots amended with seed powder of B. alba, R. communis and Eucalyptus and in root weight for P. harmala. None of the tested dried seeds was phytotoxic to tomato plants at the applied rate.     

Observations on the suppression of root-knot nematode (Meloidogyne arenaria) on tomato by incorporation of cyanobacterial powder (Oscillatoria chlorina) into potting field soil

Experiments were carried out to investigate the nematicidal potential of a cyanobacterium, Oscillatoria chlorina, against the root-knot nematode, Meloidogyne arenaria on tomato plants grown in pots filled with 500 cm3 of field soil infested with 12-s stage juveniles (J2)/cm3 soil. Incorporation of freeze-dried cyanobacterial powder into potted field soil at the rate of 0.2%, 0.4%, 0.6%, 0.8% and 1.0% (w/w) 5 days prior to tomato planting, reduced root galling, final population of M. arenaria and increased vegetative growth of tomato plants and root-mass production, compared with untreated control (P > or = 0.05). The beneficial effect of adding cyanobacterial powder into infested potted field soil increased exponentially with concentration up to 0.8%. Root galling and nematode population decreased by 68.9% and 97.6%, respectively at the highest dose (1%) of cyanobacterial powder compared with the untreated control. Addition of cyanobacterial powder into infested potted field soil at 5 days before planting was the most effective followed by 2 days before and at the time of tomato planting. We conclude that application rate and timing are important factors in the control of root-knot nematodes with O. chlorina.