Showing papers on "Meloidogyne incognita published in 2010"
TL;DR: A member of plant growth-promoting rhizobacteria, Bacillus megaterium YMF3.25, was demonstrated to be an efficient biocontrol agent (BCA) against root-knot nematode Meloidogyne incognita and could significantly inhibit the hatch of eggs and reduce infection of the nematodes through production of nematicidal volatiles.
Abstract: A member of plant growth-promoting rhizobacteria, Bacillus megaterium YMF3.25, was demonstrated to be an efficient biocontrol agent (BCA) against root-knot nematode Meloidogyne incognita. Results from three-compartmented Petri dish tests and a pot experiment indicated that the bacterial culture could significantly inhibit the hatch of eggs and reduce infection of the nematode through production of nematicidal volatiles. After analysis by gas chromatograph/mass spectrometer and confirmation with commercial pure compounds, the nematicidal volatiles produced by the bacterium were characterised to include mainly the benzeneacetaldehyde, 2-nonanone, decanal, 2-undecanone and dimethyl disulphide, which were active against to both juveniles and eggs at the concentration of 0.5 mmol. Six compounds (phenyl ethanone, nonane, phenol, 3,5-dimethoxy-toluene, 2,3-dimethyl- butanedinitrile and 1-ethenyl-4-methoxy- benzene) with nematicidal activityies of 30%–63% also contributed to nematicidal efficacy of the bacterium.
151 citations
TL;DR: The results suggest that the selected monoterpenoids, and essential oils with high concentration of these compounds, are potential nematicides against Meloidogyne.
Abstract: Nematicidal activity of 22 monoterpenoids were evaluated in vitro and in pot experiments. Twenty of the twenty-two monoterpenoids significantly reduced hatching, and 11 reduced J2 mobility of the root-knot nematode Meloidogyne incognita at a concentration of 250 mg/liter. In general, compounds with hydroxyl and carbonyl groups exhibited higher nematicidal activity than other terpenoids. Borneol, carveol, citral, geraniol, and alpha-terpineol showed the highest nematicidal activity among the in vitro tested monoterpenoids. These compounds exhibited a dose dependent effect, and drastically reduced eggs hatching and J2 viability at low concentrations. These monoterpenoids, at 100 and 250 mg/kg concentration, diminished root galling of tomato plants in pot experiments. The results suggest that the selected monoterpenoids, and essential oils with high concentration of these compounds, are potential nematicides against Meloidogyne.
120 citations
TL;DR: The target is to find the antagonist for control nematode, and secondary infection agents and stimulate plant growth by evaluating antagonist effect on plant pathogenic fungi collected from nematodes-infected plant, plant growth hormone and siderophore production.
Abstract: Root-knot nematodes are serious pathogens that severe damage to major crops. They damage plant root system that caused significant yield losses. Moreover, the predisposition of nematode-infected plants is secondary infection from fungal plant pathogen that additional adverse effects on plant growth. Our target is to find the antagonist for control nematode, and secondary infection agents and stimulate plant growth. Twenty-three plant-parasitic nematode infested soils were taken from some provinces in the northern and center of Thailand and actinomycetes and fungi were isolated. Eighty-three isolates belong to actinomycete and 67 isolates were fungi. The predominant actinomycete taxa was Streptomyces (97.6%). The predominant fungal taxa were Penicillium (37.3%) and Fusarium (32.8%). All actinomycete and fungal isolates were subjected for primary screening in vitro for their effects on egg hatching and juvenile mortality of Meloidogyne incognita. Secondary screening was evaluated for antagonist effect on plant pathogenic fungi collected from nematode-infected plant, plant growth hormone (indole-3-acetic acid; IAA) and siderophore production. From primary screening, 7 actinomycete and 10 fungal isolates reduced egg hatching and kill juveniles of M. incognita after 7 days incubation. In secondary screening, 10 nematophagous microbes produced IAA and 9 isolates produced hydroxamate siderophore. Streptomyces sp. CMU-MH021 was selected as a potential biocontrol agent. It reduced egg hatching rate to 33.1% and increased juvenile mortality rate to 82% as contrasted to the control of 79.6 and 3.6%, respectively. This strain had high activity to against tested fungi and high ability on IAA (28.5 μg ml−1) and siderophore (26.0 μg ml−1) production.
89 citations
TL;DR: Four bottle gourd (Lagenaria siceraria) cultivars and five wild watermelon germplasm lines derived from C. lanatus var.
Abstract: Four bottle gourd (Lagenaria siceraria) cultivars, one squash (Cucurbita moschata × C maxima) hybrid, five wild watermelon (Citrullus lanatus var citroides) germplasm lines, and one comme
88 citations
Journal Article•
TL;DR: In 2006-2008, a survey was conducted in 16 major vegetable production areas of the Punjab with the purpose of determining the incidence and distribution of Meloidogyne incognita and its reproduction on vegetable crop genotypes in nematode infested fields and in the green house.
Abstract: In 2006-2008, a survey was conducted in 16 major vegetable production areas of the Punjab with the purpose of determining the incidence and distribution of Meloidogyne incognita and its reproduction on vegetable crop genotypes in nematode infested fields and in the green house. Two root knot nematode species. M. incognita and M. javanica, were identified from 260 samples. Meloidogyne incognita was the predominantly found species and was detected in 13.6% of all the fields surveyed. In the field, the average nematode incidence was 41.5% and ranged from 5.4% in fields planted with mustard to 94.4% in fields planted with okra. The root gall severity averaged 5.5 on scale of 0 to 9. Seventeen vegetable genotypes were evaluated for resistance to gall formation and reproduction by M. incognita. Resistance was identified only in cauliflower, mustard, and radish. The most susceptible genotypes were bitter gourd, carrot, cucumber, eggplant, lettuce, okra, pea, pumpkin, sponge gourd and watermelon meanwhile; three plant species cabbage, chilies, and coriander provided an intermediate host response. Some plant genotypes appeared to be hypersensitive as they exhibited heavy root galling but suppressed nematode reproduction. These included members of family Cucurbitaceae.
87 citations
TL;DR: Soil-drenching with SA and MetSA were the only treatments that caused a long-lasting induction of plant defences as they inhibited the infestation by the second generation of the nematode.
65 citations
TL;DR: The results suggested that the aurovertin-type metabolites produced by P. chlamydosporia might be one of the pathogenic factors involved in the suppression of nematodes.
Abstract: Chemical investigation of one fungal strain P. chlamydosporia YMF 1.00613 isolated from root knots of tobacco infected by Meloidogyne incognita led to the isolation and identification of four aurovertin-type metabolites, which include a new compound, aurovertin I (A1), and three known metabolites, aurovertins E, F and D (A2-A4). Their structures were established by spectroscopic studies such as 1D- and 2D-NMR and MS analysis. Aurovertin I (A1) is the first natural product with an aurovertin skeleton with one less carbon. Compounds A3 and A4 showed the toxicity to the worms of the free-living nematode Panagrellus redivevus with the LC(50) values 88.6 and 41.7 microg/mL at 48 h, respectively. All four aurovertins did not show obvious inhibitory effects on egg hatch of root knot nematode Meloidogyne incognita. The results suggested that the aurovertin-type metabolites produced by P. chlamydosporia might be one of the pathogenic factors involved in the suppression of nematodes.
63 citations
TL;DR: Overexpression of CeCPI in transgenic tomato has inhibitory functions not only in the early RKN infection stage but also in the production of offspring, which may result from intervention in sex determination.
Abstract: Plant-parasitic nematodes are a major pest of many plant species and cause global economic loss. A phytocystatin gene, Colocasia esculenta cysteine proteinase inhibitor (CeCPI), isolated from a local taro Kaosiang No. 1, and driven by a CaMV35S promoter was delivered into CLN2468D, a heat-tolerant cultivar of tomato (Solanum lycopersicum). When infected with Meloidogyne
incognita, one of root-knot nematode (RKN) species, transgenic T1 lines overexpressing CeCPI suppressed gall formation as evidenced by a pronounced reduction in gall numbers. In comparison with wild-type plants, a much lower proportion of female nematodes without growth retardation was observed in transgenic plants. A decrease of RKN egg mass in transgenic plants indicated seriously impaired fecundity. Overexpression of CeCPI in transgenic tomato has inhibitory functions not only in the early RKN infection stage but also in the production of offspring, which may result from intervention in sex determination.
58 citations
TL;DR: It is shown, to the knowledge for the first time, that combining expression of these dsRNAs by crossing appropriate Arabidopsis thaliana lines resulted in an additive effect that further reduced nematode numbers and developmental capacity.
52 citations
TL;DR: Contrasted patterns of microsatellite abundance and diversity were characterized in five nematode genomes, even in the case of two closely related Meloidogyne species.
Abstract: Background
Microsatellites are the most popular source of molecular markers for studying population genetic variation in eukaryotes. However, few data are currently available about their genomic distribution and abundance across the phylum Nematoda. The recent completion of the genomes of several nematode species, including Meloidogyne incognita, a major agricultural pest worldwide, now opens the way for a comparative survey and analysis of microsatellites in these organisms.
51 citations
TL;DR: Among five plant essential oils, application of a rate of 50 mu L plant(-1) of thyme or garlic in tomato production areas could give the best results in root nematode control and be an alternative to the current control methods.
Abstract: This research was conducted to evaluate the nematicidal activity of five plant essential oils (rosemary, thyme, mint, garlic and sesame) against Southern root-knot nematode, Meloidogyne incognita race 2. Trial was designed as randomized complete block design with three nematode inoculums densities (0, 1000 and 2000 J2 plant(-1)) and three essential oil volumes (0, 50 and 150 plant mu L(-1)) replicated six times. There were no significant differences between nematode inoculums density and essential oil volumes used. However, all oil treatments suppressed nematode populations and resulted an increase in root mass tissue. Compared with control groups, among the essential oils, thyme (2.82+/-0.47%) and garlic (5.53+/-1.68%) treatments reduced root galling significantly and produced the lowest percent of galls on the plants whereas, rosemary, mint and sesame treatments were less effective in reducing root-galling. Compared with control groups thyme (2.46+/-0.17) and garlic (2.50+/-0.22) yielded also the lowest egg masses. Among five plant essential oils, application of a rate of 50 mu L plant(-1) of thyme or garlic in tomato production areas could give the best results in root nematode control and be an alternative to the current control methods. However, more studies need to be conducted in the field and greenhouse conditions to see the possible differences because nematodes and essential oils could be influenced by different experimental conditions.
TL;DR: Pulverised lyophilised (dehydrated) Melia azedarach (Meliaceae) fruits (PMF) fruits were tested in a dose-response pot experiment against juveniles (J2) of the root-knot nematode Meloidogyne incognita and revealed a dose and time dependent response effect, after exposure to MME, but not to MO.
Abstract: Pulverised lyophilised (dehydrated) Melia azedarach (Meliaceae) fruits (PMF) were tested in a dose-response pot experiment against juveniles (J2) of the root-knot nematode Meloidogyne incognita. Successively, with different extraction procedures, a polar (melia methanol extract, MME) and a nonpolar (melia oil, MO) fragments were obtained and their effects were tested on nematode motility and development, in dose and time response bioassays and pot experiments. An EC 50 value was calculated for all experiments. A dose―response effect was found in pot bioassays using PMF and, after an incubation period of 24 and 48 h, the EC 50 values were calculated at 0.41% and 0.34% w/w, respectively. Motility bioassays revealed a dose and time dependent response effect, after exposure to MME, but not to MO. Doses of MME higher than 0.08% were nematicidal, whereas lower ones were nematostatic (the loss of motility as a result of the presence of the substance was reversible). In a pot experiment, MME doses higher than 2.5% w/w caused 100% nematode control with EC 50 value of 0.916% w/w.
Journal Article•
TL;DR: The study revealed that the culture filtrates of endophytic bacterial isolates viz., EB3, EB16, EB18 and EB19 significantly reduced the number of adult females, egg masses, eggs/ eggmass, root and soil infestation of M. incognita.
Abstract: A random survey was conducted to obtain endophytic bacterial isolates in different agroecosystems comprising of ten districts in Tamil Nadu. Nineteen endophytic bacterial isolates were obtained from surface-sterilized roots of different crops. Study on the morphological, phenotypic and biochemical characterization of endophytic bacteria revealed that eight isolates viz., EB1 to EB8 belong to the group of Pseudomonas sp., ten isolates viz., EB9 to EB18 belong to the group of Bacillus sp. and isolate EB19 belongs to Methylobacterium sp. On seed bacterization with nineteen endophytic bacterial isolates, four isolates viz., EB3, EB16, EB18 and EB19 significantly enhanced the germination percentage, shoot and root length and vigour index of bhendi seedlings by roll towel technique and pot culture studies. Eight endophytic bacterial isolates were screened for their nematicidal action against Meloidogye incognita under pot culture conditions. The study revealed that the culture filtrates of endophytic bacterial isolates viz., EB3, EB16, EB18 and EB19 significantly reduced the number of adult females, egg masses, eggs/ eggmass, root and soil infestation of M. incognita. The lowest root gall index (1.00) was registered both in EB16 and EB18 isolates and it was followed by EB19 and EB3 (1.33) compared to untreated control (4.67).
Journal Article•
TL;DR: Abo-Elyousr, Kamal A., Zakaullah Khan, Magd El-Morsi Award, and Montaser Fawzy Abedel-Moneim as mentioned in this paper evaluated plant extracts and Pseudomonas spp. for control of root-knot nematode, Meloidogyne incognita on tomato.
Abstract: Abo-Elyousr, Kamal A., Zakaullah Khan, Magd El-Morsi Award, and Montaser Fawzy Abedel-Moneim. 2010. Evaluation of plant extracts and Pseudomonas spp. for control of root-knot nematode, Meloidogyne incognita on tomato. Nematropica 40:289-299. Fresh leaf extracts of Azadirachta indica (neem), Allium sativum (garlic) and Tagetes erecta (African marigold) and bacterial suspensions of Pseudomonas fluorescens and P. aeruginosa were tested against Meloidogyne incognita on tomato under in vitro, pots and field conditions. All treatments immobilized juveniles (J2); with the highest effect caused by neem leaves extract and the lowest by P. aeruginosa after 24 h and 48 h of exposures. In soil all treatments significantly reduced root galling, nematode population, and enhanced plant growth and yield, with bacterial treatments being the most effective. Nematode populations were reduced greater by nematicide (Vydate 10 G) treatment but the greatest increase in yield (67%) was obtained with P. fluorescens; the treatment reduced root galling by 68-70% and 48% in pot and field experiments, respectively. Among the plant species, garlic demonstrated best control reducing root galls by 57% in pots under greenhouse and 33% in field conditions and increasing fruits yield by 47%. Abo-Elyousr, Kamal A., Zakaullah Khan, Magd El-Morsi Award and Montaser Fawzy Abedel-Moneim. 2010. Evaluacion de extractos de plantas y de Pseudomonas spp. para el control de Meloidogyne incognita en tomate. Nematropica 40:289-299. Se probaron extractos frescos de hojas de Azadirachta indica (nim), Allium sativum (ajo) y Tagetes erecta (clavelon africano) y suspensions bacteriales de Pseudomonas fluorescens y P. aeruginosa para el control de Meloidogyne incognita en tomate in vitro, en macetas y en campo. Todos los tratamientos inmovilizaron los juveniles (J2); observandose el mayor efecto con el extracto de hojas de nim y el menor con el extracto de P. aeruginosa despues de 24 y 48 h de exposicion. En el suelo, todos los tratamientos redujeron significativamente el agallamiento y la densidad de poblacion del nematodo, y aumentaron el crecimiento y rendimiento de la planta, siendo los tratamientos bacteriales los mas efectivos. La mayor reduccion en las poblaciones del nematodo se observo con el tratamiento con nematicida (Vydate 10 G), pero el mayor aumento en rendimiento (67%) se obtuvo con P. fluorescens; cuyo tratamiento redujo el agallamiento en 68-70% y 48% en macetas y campo, respectivamente. Entre los tratamientos vegetales, el ajo demostro el major control de agallamiento, con una reduccion del 57% en macetas y 33% en campo, y un aumento del rendimiento del 47%.
TL;DR: Soil application of the neem-based formulations would be applicable for the control of both leaf-sucking and soil pests, and soil treatment with Neemaplus greatly improved the growth of cucumber plants in nematode-infested pots.
Abstract: Toxicity of the plant-derived natural pesticide azadirachtin and two types of commercial neem (Azadirachta indica A. Juss)-based formulations, Neema (liquid type) and Neema-plus (pellet type), were evaluated based on the mortality rate and developmental inhibition of the sweetpotato whitefly (Bemisia tabaci) and root-knot nematode (Meloidogyne incognita). In a laboratory assay, when B. tabaci adults were fed leaves containing 5 or 10 ppm of azadirachtin solutions, the rates of female oviposition, subsequent egg hatch, and adult eclosion were significantly reduced to 23.1, 53.2, and 26.6% of the control, respectively. At a tomato greenhouse, the rates of adult colonization, oviposition and egg hatch were reduced to 78.2, 47.0, and 71.2% by Neema foliar spray and 31.3, 34.1, and 66.8% by soil treatment with Neema-plus relative to the control, respectively. When isolated soil nematodes were exposed to various concentrations of azadirachtin, Neema, and Neema-plus, the immobility of juvenile nematodes showed no change at 2 h after treatment, whereas a reduction of 36.3% was observed at day 1 with 10 ppm of azadirachtin. Nevertheless, the effects of neem formulations were faster and much higher than those of azadirachtin. At a cucumber greenhouse, soil treatments with neem formulations significantly reduced the numbers of soil nematodes and plant root-knots; the reduction with Neema was 12.1 and 9.0%, and with Neema-plus 26.4 and 24.6% of the control, respectively. Furthermore, soil treatment with Neemaplus greatly improved the growth of cucumber plants in nematode-infested pots. These results showed that azadirachtin and neem-based formulations were highly effective on the developmental inhibition of both whiteflies and root-knot nematodes. Thus, soil application of the neem-based formulations would be applicable for the control of both leaf-sucking and soil pests.
TL;DR: This is the first report of populations of RKN virulent to the Mi-1 gene in Turkey and shows that seven populations of M. incognita and six populations of J. javanica were able to overcome the resistance controlled by the Mi -1 gene.
Abstract: Root-knot nematodes (Meloidogyne spp.; RKN) are one of the most important pathogens of vegetables in Turkey. Assessing the existing virulent RKN populations is of importance for pathogen mapping in the west Mediterranean region of Turkey. Therefore, 95 populations of RKN were collected from different protected vegetable-growing locations in the region. Pure cultures were obtained and identified by means of species-specific primers. Virulence of the populations against the Mi-1 gene conferring resistance to Meloidogyne incognita, M. javanica and M. arenaria was determined according to their egg masses and gall rating on resistant and susceptible tomato varieties. Results showed that seven populations of M. incognita and six populations of M. javanica were able to overcome the resistance controlled by the Mi-1 gene. The frequency of virulent populations of M. incognita and M. javanica collected from different protected-grown vegetables was 11.7% and 21.4%, respectively. To our knowledge, this is the first report of populations of RKN virulent to the Mi-1 gene in Turkey.
TL;DR: In vitro experiments carried out in vitro to determine the efficacy of indigenous fungi isolated from egg masses of root-knot nematode, Meloidogyne incognita on egg parasitism, egg hatching, mobility and mortality against root-Knot nem atode, A. strictum and A. terreus showed good biocontrol potential.
Abstract: The present study was carried out in vitro to determine the efficacy of indigenous fungi isolated from egg masses of root-knot nematode, Meloidogyne incognita on egg parasitism, egg hatching, mobility and mortality against root-knot nematode, M. incognita. The tested fungi were Acremonium strictum, Aspergillus terreus, A. nidulans, A. niger, Chetomium aubense, Chladosporium oxysporum, Fusarium chlamydosporium, F. dimarum, F. oxysporum, F. solani, Paecilomyces lilacinus, Pochonia chlamydosporia, Trichoderma viride and T. harzianum. All tested fungi showed varied effects against the nematodes. Culture filtrates of A. strictum was very effective against the nematode in regards to egg parasitism (53%), egg hatching inhibition (86%) and mortality (68%) compared to controls. A. strictum was found to have an advantage over P. lilacinus, P. chlamydosporia, T. viride and T. harzianum in that it caused greater mortality of the second stage juveniles (J2). A. terreus did not show egg parasitism but was foun...
Journal Article•
TL;DR: The establishment of mycorrhiza prior to the nematode infection contributed for the reduction of symptoms severity and reproduction of M. incognita in disinfested soil.
Abstract: The effects of inoculation of sweet passion fruit plants with the arbuscular mycorrhizal (AM) fungus Scutellospora heterogama on the symptoms produced by Meloidogyne incognita race 1 and its reproduction were evaluated in two greenhouse experiments. In the 1st, the M. incognita (5000 eggs/plant) and S. heterogama (200 spores/plant) inoculations were simultaneous; in the 2nd, the nematodes were inoculated 120 days after the fungal inoculation. In both the experiments, 220 days after AM fungal inoculation, plant growth was stimulated by the fungus. In disinfested soil, control seedlings (without S. heterogama) were intolerant to parasitism of M. incognita, while the growth of mycorrhized seedlings was not affected. Sporulation of S. heterogama was negatively affected by the nematodes that did not impair the colonization. M. incognita did not affect mycorrhizal seedling growth. The establishment of mycorrhiza prior to the nematode infection contributed for the reduction of symptoms severity and reproduction of M. incognita in disinfested soil.
TL;DR: To enhance the virulence of Paecilomyces lilacinus against Meloidogyne incognita eggs, a serine protease was overexpressed in P. lilacine 9410 and the relative parasitizing rates of the transformants against M. incognitas eggs increased by about 20% in both conidial suspension and mycelium treatment groups.
Abstract: To enhance the virulence of Paecilomyces lilacinus against Meloidogyne incognita eggs, a serine protease was overexpressed in P. lilacinus 9410 (PL9410). The cDNA of a mature serine protease gene was cloned from PL9410 and integrated into the genomes of PL9410 transformants through Agrobacterium tumefaciens-mediated transformation. Our results confirmed that the serine protease gene was overexpressed at the transcriptional level, and that the serine protease activities were enhanced in the transformants when compared to the parent strain. The bioassay results indicated that the relative parasitizing rates of the transformants against M. incognita eggs increased by about 20% in both conidial suspension and mycelium treatment groups.
TL;DR: A novel pathogenesis-related class 10 (PR-10) protein with papain inhibitory activity, named CpPRI, was purified from Crotalaria pallida roots and demonstrated nematostatic and nematicide effects on this parasite in bioassays.
Abstract: A novel pathogenesis-related class 10 (PR-10) protein with papain inhibitory activity, named CpPRI, was purified from Crotalaria pallida roots by ammonium sulfate precipitation followed by three reverse-phase high-performance liquid chromatographies (HPLCs). CpPRI is made up of a single polypeptide chain with a Mr of 15 kDa, as determined by sodium dodecyl sulfate−polyacrylamide gel electrophoresis (SDS−PAGE). This protein exhibited a Ki value of 1.8 × 10−9 M and operates via a noncompetitive inhibition mechanism. The alignment of the N-terminal amino acid sequence of CpPRI with other proteins revealed its identity with PR-10 proteins. CpPRI acts against digestive proteinase from root-knot nematode Meloidogyne incognita and demonstrated nematostatic and nematicide effects on this parasite in bioassays. In a localization study, fluorescein-5-isothiocyanate (FITC)−CpPRI was observed to internalize and diffuse over the entire J2 body after 6 h of incubation. This fact could explain the natural tolerance of t...
TL;DR: The results suggest that CO2 enrichment may not only increase plant C : N ratio but can disrupt the allocation of plant resources between growth and defence in some genetically modified plants and thereby reduce their resistance to nematodes.
Abstract: Interactions between the root-knot nematode Meloidogyne incognita and three isogenic tomato (Lycopersicon esculentum) genotypes were examined when plants were grown under ambient (370 ppm) and elevated (750 ppm) CO2. We tested the hypothesis that, defence-recessive genotypes tend to allocate 'extra' carbon (relative to nitrogen) to growth under elevated CO2, whereas defence-dominated genotypes allocate extra carbon to defence, and thereby increases the defence against nematodes. For all three genotypes, elevated CO2 increased height, biomass, and root and leaf total non-structural carbohydrates (TNC):N ratio, and decreased amino acids and proteins in leaves. The activity of anti-oxidant enzymes (superoxide dismutase and catalase) was enhanced by nematode infection in defence-recessive genotypes. Furthermore, elevated CO2 and nematode infection did not qualitatively change the volatile organic compounds (VOC) emitted from plants. Elevated CO2 increased the VOC emission rate only for defence-dominated genotypes that were not infected with nematodes. Elevated CO2 increased the number of nematode-induced galls on defence-dominated genotypes but not on wild-types or defence-recessive genotypes roots. Our results suggest that CO2 enrichment may not only increase plant C : N ratio but can disrupt the allocation of plant resources between growth and defence in some genetically modified plants and thereby reduce their resistance to nematodes.
TL;DR: The results clearly show that, in addition to Crotalaria, certain other PA-producing plant species have the potential to be used in sustainable nematode management, especially true for management of sedentary endoparasitic nematodes species.
Abstract: 1,2-dehydropyrrolizidine ester alkaloids (pyrrolizidine alkaloids; PAs) are a class of secondary plant metabolites found in hundreds of plant species. In vitro, PAs are known to affect plant-parasitic nematodes. Thus, PA-producing plants might be used in nematode management. So far, however, Crotalaria is the only PA-producing plant that has been used for nematode control. Consequently, we reviewed the literature on other PA plants and their effects on nematodes. This included the analysis of in vitro experiments with PA plant extracts, host tests with PA plants, as well as experiments in which PA-producing plants were used as different types of soil amendments (mulch, in situ mulching, extracts). Our results clearly show that, in addition to Crotalaria, certain other PA-producing plant species have the potential to be used in sustainable nematode management. This is especially true for management of sedentary endoparasitic nematode species. Promising applications include the use of PA plant extracts and mulches, as well as the use of PA plants for in situ mulching.
Journal Article•
TL;DR: Trichoderma harzianum and Trichodermas viride were tested for their capacity to reduce the incidence and pathogenicity of the root-knot nematode Meloidogyne incognita on tomato as discussed by the authors.
Abstract: Trichoderma harzianum and Trichoderma viride were tested for their capacity to reduce the incidence and
pathogenicity of the root-knot nematode Meloidogyne incognita on tomato. In vitro studies demonstrated that all
tested isolates were effective in causing second-stage juvenile (J2) mortality compared with the control.
However, a slight increase in J2 mortality coincided with the use of Trichoderma harzianum (Th3) when
compared to the other Trichoderma isolates. Trichoderma slightly reduced nematode damage to tomato in vivo.
Treatment of the soil with the biocontrol agents slightly improved nematode control when applied one week
before transplanting, but not at transplanting time. The Trichoderma isolates could not be re-isolated from the
endorhiza, but were successfully re-isolated from the rhizosphere 45 days after fungal inoculation. Only slight
increases in plant growth could be measured. The mutualistic endophyte F. oxysporum162, used as positive
control, was significantly more effective in root-knot nematode biocontrol than the Trichoderma isolates.
TL;DR: Filtrates of three isolates of the nematophagous fungus Verticillium leptobactrum were evaluated for their nematicidal activity against the root-knot nematode Meloidogyne incognita, showing inhibited egg hatching and suggested the production of chitin-degrading enzymes or other active compounds.
Abstract: Filtrates of three isolates of the nematophagous fungus Verticillium leptobactrum were evaluated for their nematicidal activity against the root-knot nematode Meloidogyne incognita. The filtrates inhibited egg hatching, with maximum toxicity observed for isolate HR21 at 50% (v:v) dilution, after 7 days exposure. Filtrates also inactivated second-stage juveniles (J2) at 10-50% dilutions. A scanning electron microscopy study of treated eggs showed severe alterations caused by the filtrate of isolate HR43 on M. incognita eggs, which appeared collapsed and not viable, suggesting the production of chitin-degrading enzymes or other active compounds.
TL;DR: Investigation of the effect of soil temperature on root-knot nematode resistance conferred by two genes of tomato, using some commercial tomato cultivars, rootstocks, and PI lines found significant differences in the galling index among heat-stable sources and plants containing the Mi-1.2 gene.
Abstract: Rootstocks have been effective against many soil-borne pathogens in protected tomato production. Rootstocks with heat-stable root-knot nematode resistance may prolong the production season since the root-knot nematode resistance gene Mi-1.2 irreversibly breaks down at soil temperatures above 28°C. The objective of this study was to investigate the effect of soil temperature on root-knot nematode resistance conferred by two genes of tomato, using some commercial tomato cultivars, rootstocks, and PI lines. The response of these genes against Meloidogyne incognita race 2 was studied in two commonly used rootstock cv. Beaufort and Vigomax, in tomato cultivars Astona RN F1 and Simita F1, and in Solanum lycopersicum L. accessions PI126443 and PI270435, known to possess heat-stable nematode resistance, at 24°C and 32°C under controlled conditions. Each plant was inoculated with 1000 M. incognita race 2 second-stage juveniles (J2s) and its response was evaluated 8 weeks post inoculation. The presence of the Mi-1.2 gene was determined with molecular markers. Astona RN F1, Vigomax, Beaufort, PI126443 and PI 270435 which carried the Mi-1.2 gene were resistant to Meloidogyne incognita race 2 at 24°C. The egg masses and J2s were significantly fewer in these lines than in the susceptible Simita F1 at 24°C, and there were no significant differences among resistant plants. In contrast, there were significant differences in the galling index among heat-stable sources and plants containing the Mi-1.2 gene. Simita F1, Astona RN F1 and the rootstocks had a susceptible reaction to M. incognita race 2 at 32°C, but PI 126443 and PI 270435 were resistant. However, at this temperature there were significant differences in the number of juveniles in the soil, the egg mass and the galling index between the heat-stable and the heat-unstable plants. Rootstocks have been effective against many soil-borne pathogens in protected tomato production. Rootstocks with heat-stable root-knot nematode resistance may prolong the production season since the rootknot nematode resistance gene Mi-1.2 irreversibly breaks down at soil temperatures above 28°C. The objective of this study was to investigate the effect of soil temperature on root-knot nematode resistance conferred by two genes of tomato, using some commercial tomato cultivars, rootstocks, and PI lines. The response of these genes against Meloidogyne incognita race 2 was studied in two commonly used rootstock cv. Beaufort and Vigomax, in tomato cultivars Astona RN F1 and Simita F1, and in Solanum lycopersicum L. accessions PI126443 and PI270435, known to possess heat-stable nematode resistance, at 24°C and 32°C under controlled conditions. Each plant was inoculated with 1000 M. incognita race 2 second-stage juveniles (J2s) and its response was evaluated 8 weeks post inoculation. The presence of the Mi-1.2 gene was determined with molecular markers. Astona RN F1, Vigomax, Beaufort, PI126443 and PI 270435 which carried the Mi-1.2 gene were resistant to Meloidogyne incognita race 2 at 24°C. The egg masses and J2s were significantly fewer in these lines than in the susceptible Simita F1 at 24°C, and there were no significant differences among resistant plants. In contrast, there were significant differences in the galling index among heat-stable sources and plants containing the Mi-1.2 gene. Simita F1, Astona RN F1 and the rootstocks had a susceptible reaction to M. incognita race 2 at 32°C, but PI 126443 and PI 270435 were resistant. However, at this temperature there were significant differences in the number of juveniles in the soil, the egg mass and the galling index between the heat-stable and the heat-unstable plants. Rootstocks have been effective against many soil-borne pathogens in protected tomato production. Rootstocks with heat-stable root-knot nematode resistance may prolong the production season since the rootknot nematode resistance gene Mi-1.2 irreversibly breaks down at soil temperatures above 28°C. The objective of this study was to investigate the effect of soil temperature on root-knot nematode resistance conferred by two genes of tomato, using some commercial tomato cultivars, rootstocks, and PI lines. The response of these genes against Meloidogyne incognita race 2 was studied in two commonly used rootstock cv. Beaufort and Vigomax, in tomato cultivars Astona RN F1 and Simita F1, and in Solanum lycopersicum L. accessions PI126443 and PI270435, known to possess heat-stable nematode resistance, at 24°C and 32°C under controlled conditions. Each plant was inoculated with 1000 M. incognita race 2 second-stage juveniles (J2s) and its response was evaluated 8 weeks post inoculation. The presence of the Mi-1.2 gene was determined with molecular markers. Astona RN F1, Vigomax, Beaufort, PI126443 and PI 270435 which carried the Mi-1.2 gene were resistant to Meloidogyne incognita race 2 at 24°C. The egg masses and J2s were significantly fewer in these lines than in the susceptible Simita F1 at 24°C, and there were no significant differences among resistant plants. In contrast, there were significant differences in the galling index among heat-stable sources and plants containing the Mi-1.2 gene. Simita F1, Astona RN F1 and the rootstocks had a susceptible reaction to M. incognita race 2 at 32°C, but PI 126443 and PI 270435 were resistant. However, at this temperature there were significant differences in the number of juveniles in the soil, the egg mass and the galling index between the heat-stable and the heat-unstable plants.
TL;DR: Higher mortality percentages of nematodes were recorded by bacterial cultures than their comparative cultural filtrates and NFB7, PSB2 and KSB2 isolates showed the highest protease, gelatinase and chitinase activities which were thought responsible for their nematicidal effect.
Abstract: Representative soil samples were collected from soil apart and the rhizosphere of different plant varieties grown in five Egyptian Governorates. The presence of plant parasitic nematodes (PPN) and free living nematodes (FLN) in the collected samples were estimated. In addition, one hundred and 65 bacterial cultures which well known as biofertilizers (some are able to fix nitrogen and the others solubilize either phosphate or potassium) were isolated. The isolated bacteria were screened depending on their rate of growth. Thirty-five cultures of fast growing nitrogen fixing bacteria (NFB), phosphate solubilizing bacteria (PSB) and potassium solubilizing bacteria (KSB) and their cultural filtrates were tested in vitro as biocontrol agents against the second stage juvenile (J2s) of the Meloidogyne incognita. In general, higher mortality percentages of nematodes were recorded by bacterial cultures than their comparative cultural filtrates. The highest mortality percentages were recorded by cultures of NFB7, PSB2 and KSB2 (100% at dilution 1/10), while it was 99.3, 99 and 97.8% at dilution 1/100, respectively. NFB7 exhibited a high nitrogen fixation rate (4.2 μmole N2/mL/h), while PSB2 and KSB2 effectively solubilized phosphate and potassium comparing with the control treatments (1.94 fold of available phosphate and 2.0 fold of available potassium, respectively). NFB7, PSB2 and KSB2 isolates showed the highest protease, gelatinase and chitinase activities which were thought responsible for their nematicidal effect. The three bacterial isolates were identified as Paenibacillus polymyxa, Bacillus megaterium and Bacillus circulans, respectively.
TL;DR: The HR-like phenotype observed in the ‘UFV 408-28’—M.
Abstract: Root-knot nematodes (RKN) are obligate parasite species of the genus Meloidogyne that cause great losses in Arabica coffee (Coffea arabica L.) plantations. Identification of resistant genotypes would facilitate the improvement of coffee varieties aiming at an environmental friendly and costless nematode control. In this work, the C. arabica genotype ‘UFV 408-28’ was found to be resistant to the most destructive RKN species M. incognita. Pathogenicity assays indicated that the highly aggressive populations of M. incognita races 1, 2 and 3 were not able to successfully reproduce on ‘UFV 408-28’ roots and displayed a low gall index (GI = 2). An average reduction of 87% reduction of the M. incognita population was observed on ‘UFV 408-28’ when compared to the susceptible cultivar ‘IAC 15’. By contrast, ‘UFV 408-28’ was susceptible to the related species M. exigua and M. paranaensis (GI = 5 and 4, respectively). Histological observations performed on sections of UFV408-28 roots infected with M. incognita race 1 showed that nematode infection could be blocked right after penetration or during migration and establishment stages, at 6 days, 7 days and 8 days after infection (DAI). Fluorescence and bright field microscopy observations showed that root cells surrounding the nematodes exhibited HR-like features such as accumulation of phenolic compounds and a necrotic cell aspect. In the susceptible ‘IAC 15’ roots, 6 DAI, feeding sites contained giant cells with a dense cytoplasm. Necrotic cells were never observed throughout the entire infection cycle. The HR-like phenotype observed in the ‘UFV 408-28’—M. incognita interaction suggests that the coffee resistance may be mediated by a R-gene based immunity system and may therefore provide new insights for understanding the molecular basis of RKN resistance in perennial crops.
Journal Article•
TL;DR: Low to moderate concentrations of these indigenous botanicals are effective in reducing the pathogenicity of the root-knot nematode and is accompanied by a yield increase in cowpea.
Abstract: Water extracts of Ocimum gratissimum, Azadirachta indica, Vernonia amygdalina and Moringa oleifera were evaluated for their effect on pathogenicity of Meloidogyne incognita race 2 and on the growth and yield of cowpea. Eggs and juveniles of M. incognita were exposed to water extracts from leaves of these indigenous plants for ten days in a completely randomized design with four replicates. Data on egg hatch inhibition and juvenile mortality were taken daily. Three cowpea cultivars were inoculated with M. incognita and later drenched with the botanical extracts at 10,000 mg/kg and 20,000 mg/kg in pots. The experiment was laid out in a randomized complete block design with five replications. Data collected were number of leaves, plant height, grain yield at harvest; nematode population in soil and roots, and the reproductive factor of the nematodes. Egg hatch inhibition ranged from 40% - 63.7% in the extracts compared to the control with 0%. Juvenile mortality in extracts was from 82% - 93.8% compared to the control with 25%. Grain yield of plants treated with V. amygdalina at 10,000 mg/kg and 20,000 mg/kg; and 20,000 mg/kg of A. indica, O. gratissimum and M. oleifera were significantly higher than in the untreated plants. These plants also had nematode reproductive factors comparable to the uninoculated control. This study therefore shows that low to moderate concentrations of these indigenous botanicals are effective in reducing the pathogenicity of the root-knot nematode and is accompanied by a yield increase in cowpea.