Assessment of Predacity and Efficacy of Arthrobotrys dactyloides for Biological Control of Root Knot Disease of Tomato

Five isolates of Arthrobotrys dactyloides were isolated from different locations of India and their in vitro predacity was tested against Meloidogyne incognita (J₂), Tylenchorhynchus brassicae and Hoplolaimus indicus. All isolates of A. dactyloides captured and killed M. incognita and T. brassicae but not H. indicus. The isolates also differed in their predacity of the first two nematode species. The application of mass culture of A. dactyloides in soil infested with 2000 juveniles of M. incognita per ‘kg’ before planting of tomato seedlings reduced the number of root knots by 5.6–45.6%, of females by 44.7–72.9%, of egg masses by 44.5–51.3% and of juveniles by 37.9–81.8% and increased the plant growth in a pot experiment. The effect of this fungus as biocontrol agent was enhanced when its mass culture was applied with cow dung manure, which reduced the number of root knots by 61.7–66.6%, of females by 80.6–94.7%, of egg masses by 80.3–89.6% and of juveniles by 68.1–88.0%.     

Suitability of crops,fruit trees/plants to plant parasitic nematodes

Fifteen economically important plant species were tested for their suitability to commonly occurring plant parasitic nematodes viz, Hoplolaimus indicus, Helicotylenchus indicus, Tylenchus filiformis, Rotylenchulus reniformis, Tylenchorhynchus brassicae, Pratylenchus zeae and Meloidogyne incognita. The plants reacted differently to different nematodes. Moreover, eight fruit trees/plants were also tested for their suitability to nematodes.     

Nematophagous Fungi Associated with Root Galls of Rice Caused by Meloidogyne graminicola and its Control by Arthrobotrys dactyloides and Dactylaria brochopaga

Root galls of rice caused by Meloidogyne graminicola were examined for natural colonization by nematophagous fungi from four fields with different nematode infestations. Old galls from severely infested fields had a higher frequency of Monacrosporium eudermatum and Stylopaga hadra than young galls. The frequency of Arthrobotrys oligospora, Arthrobotrys dactyloides, Dactylaria brochopaga and Monacrosporium gephyropagum was lower. A greater proportion (%) of root galls were colonized by nematophagous fungi in those fields in which rice roots had a greater root gall index. This indicated that disease severity supported the colonization of galls by nematophagous fungi. In vitro predacity tests of four fungi showed that A. dactyloides was most effective in capturing and killing J₂ of Mel. graminicola followed by D. brochopaga and Mon. eudermatum. Application of inocula of A. dactyloides and D. brochopaga in soil infested with Mel. graminicola, respectively, reduced the number of root galls by 86% and of females by 94%, and eggs and juveniles by 94%. The application of these fungi to soil increased plant growth: shoot length by 42.7% and 39.8%, root length by 45.5% and 48.9%, fresh weight of shoot by 59.9% and 56.7% and fresh weight of root by 20.3% and 25.1%, respectively, compared to these parameters for plants grown in nematode‐infested soil.     

Variability in Indian Isolates of Arthrobotrys dactyloides Drechsler: A Nematode-Trapping Fungus

Five isolates of Arthrobotrys dactyloides (A, B, C, D, and E) were isolated from different locations of India. Their variability in relation to morphology, radial growth, and nematode capturing or trap-forming ability was observed. All of the five isolates produced two-celled slender conidia, whereas wider two- and three-celled conidia were produced by isolates A, C, D, and E only. The wider two- and three-celled conidia were not observed in cultures of isolate B. The isolate B produced macroconidia as well as microconidia. The microconidia were produced on separate conidiophores of smaller size. Macroconidia and microconidia were never produced on the same conidiophore, but the two types of conidiophores were produced on same or different hyphae. Similar to macroconidia, the microconidia also produced constricting rings of smaller size in presence of Meloidogyne graminicola. The constricting rings formed on microconidia did not capture second-stage juveniles of M. graminicola because of their smaller size. Among all the isolates, isolate B showed slow growth and higher nematode-capturing ability or trap-forming ability.     

Volatile Substances Produced by Fusarium oxysporum from Coffee Rhizosphere and Other Microbes affect Meloidogyne incognita and Arthrobotrys conoides

Microorganisms produce volatile organic compounds (VOCs) which mediate interactions with other organisms and may be the basis for the development of new methods to control plant-parasitic nematodes that damage coffee plants. In the present work, 35 fungal isolates were isolated from coffee plant rhizosphere, Meloidogyne exigua eggs and egg masses. Most of the fungal isolates belonged to the genus Fusarium and presented in vitro antagonism classified as mutual exclusion and parasitism against the nematode-predator fungus Arthrobotrys conoides (isolated from coffee roots). These results and the stronger activity of VOCs against this fungus by 12 endophytic bacteria may account for the failure of A. conoides to reduce plant-parasitic nematodes in coffee fields. VOCs from 13 fungal isolates caused more than 40% immobility to Meloidogyne incognita second stage juveniles (J₂), and those of three isolates (two Fusarium oxysporum isolates and an F. solani isolate) also led to 88-96% J₂ mortality. M. incognita J₂ infectivity decreased as a function of increased exposure time to F. oxysporum isolate 21 VOCs. Gas chromatography-mass spectrometry (GC-MS) analysis lead to the detection of 38 VOCs produced by F. oxysporum is. 21 culture. Only five were present in amounts above 1% of the total: dioctyl disulfide (it may also be 2-propyldecan-1-ol or 1-(2-hydroxyethoxy) tridecane); caryophyllene; 4-methyl-2,6-di-tert-butylphenol; and acoradiene. One of them was not identified. Volatiles toxic to nematodes make a difference among interacting microorganisms in coffee rhizosphere defining an additional attribute of a biocontrol agent against plant-parasitic nematodes.     

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

Abstract

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

Possible utilization of weeds for the management of plant parasitic nematodes infesting some vegetable crops

Leaf extracts of noxious weeds such as Solanum xanthocarpum and Argemone maxicana were used as bare-root dip treatment for the management of three important plant-parasitic nematodes, Meloidogyne incognita, Rotylenchulus reniformis and Tylenchorhynchus brassicae infesting tomato (Lycopersicon esculantum ) and chilli (Capsicum annuum) plants. Significant reduction was observed in the root-knot development caused by M. incognita, multiplication of nematode populations of R. reniformis and T. brassicae on both the test plants. Larval penetration of second stage juveniles of M. incognita was also inhibited at various concentrations of leaf extracts and dip durations. Leaf extract of S. xanthocarpum caused relatively more inhibition in root-knot development in case of root-knot nematode, nematode multiplication of reniform and stunt nematodes than that of A. maxicana. Because of dip treatment in leaf extracts of Argemone maxicana and Solanum xanthocarpum, the plants show better growth and at the same time the populations of nematodes such as M. incognita, R. reniformis and T. brassicae significantly decreased, which naturally improved plant growth. The efficacy of root-dip treatment with respect to improvement in plant weight and reduction in root-knot development and nematode populations, increased with increasing the concentration of leaf extracts and dip durations.     

Genetic characterization of <Emphasis Type="Italic">Meloidogyne incognita</Emphasis> isolates from Turkey using sequence-related amplified polymorphism (SRAP)

Southern root knot nematode Meloidogyne incognita is the most widespread-species, causing serious yield losses in protected vegetables fields in the West Mediterranean region of Turkey. The knowledge of genetic variation within M. incognita is required for disease management and improvement of resistant varieties by breeding programs. In the present study, the isolates were classified into different groups based on sequence-related amplified polymorphism (SRAP) fingerprints. To our knowledge, this is the first study carried out on the characterization of M. incognita isolates using SRAP. The schematic diagram by tested primers to differentiate of M. incognita isolates was formed in discrimination of nematodes as an effective molecular tool since it is cost effective and easiness. Data presents a genetic variation on root-knot nematode species. These selected SRAP markers can be used to follow genetic structure and differentiation on M. incognita isolates in a certain region.     

<Emphasis Type="Italic">Catenaria anguillulae</Emphasis> Sorokin: a Natural Biocontrol Agent of <Emphasis Type="Italic">Meloidogyne graminicola</Emphasis> Causing Root Knot Disease of Rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Summary Catenaria anguillulae parasitized and killed the eggs and second stage juveniles (J₂) of Meloidogyne graminicola under natural conditions. The percentage of infection in eggs was higher than J₂ of M.␣graminicola, which ranged between 0–50.3% and 0–18.9% in 2004 and 0–46.6% and 0–21.7% in 2005, respectively. The higher parasitism of eggs and J₂ was recorded from those fields in which plants were severely infected with M. graminicola. The degree of parasitism of eggs and J₂ by C. anguillulae varied with severity of root knot disease. The fields with a higher root gall index recorded a higher percentage of infection in eggs and J₂ of M. graminicola. In general, old galls when teased and incubated, recorded higher parasitism of eggs and juveniles than young galls.     

Effects of Monoclonal Antibodies,Cationized Ferritin,and Other Organic Molecules on Adhesion of Pasteuria penetrans Endospores to Meloidogyne incognita

The incidence of adhesion of Pasteuria penetrans endospores to Meloidogyne incognita second-stage juveniles (J2) was studied after pretreatment of the latter with monoclonal antibodies (MAb), cationized ferritin, and other organic molecules in replicated trials. Monoclonal antibodies developed to a cuticular epitope of M. incognita second-stage juveniles gave significant reductions in attachment of P. penetrans endospores to treated nematodes. MAb bound to the entire length of J2 except for the area of the lateral field, where binding was restricted to the incisures. Since reductions in attachment with MAb treatment were modest, it is uncertain if these results implicated a specific surface protein as a factor that interacted in binding of the endospore to the nematode cuticle. Endospore attachment was decreased following treatment of the nematode with the detergents sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB). Endospore attachment to live nematodes was significantly greater than attachment to dead nematodes. Attachment rates of three P. penetrans isolates to M. incognita race 3 varied between isolates. The effects of neuraminidase, pronase, pepsin, trypsin, lipase, and Na periodate on endospore attachment were inconsistent. The cationic dye alcian blue, which binds sulfate and carboxyl groups on acidic glycans, had no consistent effect on endospore attachment. The incidence of endospore attachment was significantly lower but modest, at best, for nematodes that were treated with cationized ferritin alone or cationized ferritin following monoclonal antibody. The lack of consistency or extreme reduction in most experiments suggests that attachment of P. penetrans spores to M. incognita is not specified by only one physico-chemical factor, but may involve a combination of at least two physico-chemical factors (including surface charge and movement of the J2). This points to a need for analysis of combined or factorial treatment effects.     

Comparison of Reproduction by Meloidogyne graminicola and M. incognita on Trifolium Species

The reproductive potential of Meloidogyne graminicola was compared with that of M. incognita on Trifolium species in greenhouse studies. Twenty-five Trifolium plant introductions, cultivars, or populations representing 23 species were evaluated for nematode reproduction and root galling 45 days after inoculation with 3,000 eggs of M. graminicola or M. incognita. Root galling and egg production by the two root-knot nematode species was similar on most of the Trifolium species. In a separate study, the effect of initial population densities (Pi) of M. graminicola and M. incognita on the growth of white clover (T. repens) was determined. Reproductive and pathogenic capabilities of M. graminicola and M. incognita on Trifolium spp. were similar. Pi levels of both root-knot nematode species as low as 125 eggs per 10-cm-d pots severely galled white clover plants after 90 days. Meloidogyne graminicola has the potential to be a major pest of Trifolium species in the southeastern United States.     

Effect of inter-cropping bell-pepper with ginger on plant parasitic nematode populations and crop yields

During 1994 studies were undertaken to improve ginger (Zingiber officinale Roscoe) yield against the nematodes Pratylenchus penetrans, Meloidogyne incognita, Helicotylenchus dihystera and Tylenchorhynchus mashhoodi in Himachal Pradesh (HP) (India) by inter-cropping bell-pepper (Capsicum annum L) in eight different sequences (treatments). Inter-cropping of “one rhizome of ginger x one plant of bell-pepper” gave the highest ginger yield (600 g per rhizome). This treatment was completely free from P. penetrans and M. incognita. All treatments with bell-pepper plants equal to or higher in number to that of ginger rhizomes had higher ginger yields than treatments with ginger alone or with fewer bell-pepper plants. In the former, populations of P. penetrans and M. incognita were lower than in the latter treatments. The yield of ginger varied irrespective of population densities of H. dihystera and T. mashhoodi, indicating that P. penetrans and M. incognita are the major nematode problems of ginger in HP. Bell-pepper was a non-host to P. penetrans and non-preferred host to M. incognita. This helped to improve ginger yields by making the rhizosphere unfavourable for the development and multiplication of the major ginger nematode pests.     

Interactive effect of root-knot nematode,Meloidogyne incognita and root-rot fungus,Rhizoctonia solani,on okra [Abelmoschus esculentus L.]

The individual, concomitant and sequential inoculation of second stage juveniles (at 2000 J₂/kg soil) of Meloidogyne incognita and Rhizoctonia solani (at 2 g mycelial mat/kg soil) showed significant reduction in plant growth parameters viz. plant length, fresh weight and dry weight as compared to control. The greatest reduction in plant growth parameters was recorded in the plants simultaneously inoculated with M. incognita and R. solani followed by sequential and individual inoculation. In sequential inoculation, plant inoculated with M. incognita 15 days prior to R. solani shows more reduction in comparison to plant inoculated with R. solani 15 days prior to M. incognita. Moreover, the multiplication of nematode and number of galls/root system were significantly reduced in concomitant and sequential inoculation as compared to individual inoculation, whereas the intensity of root-rot/root system caused by R. solani was increased in the presence of root-knot nematode M. incognita as compared to when R. solani was inoculated individually.     

Occurrence,Parasitism, and Pathogenicity of Nematodes Associated with Sycamore (Platanus occidentalis L.)

Ten species of stylet-bearing nematodes were recovered in a survey of sycamore (Platanus occidentalis L. ) stands in Georgia. Helicotylenchus, Xiphinema, and Criconemoides were the genera found most frequently. Populations of Hoplolaimus galeatus, Scutellonema brachyurum, Helicotylenchus dihystera and H. pseudorobustus increased on greenhouse-grown sycamore, but Trichodorus christiei, Xiphinema americanum, Meloidogyne hapla, M. arenaria and M. incognita did not. Hoplolaimus galeatus and S. brachyurum are semi-endoparasites; H. dihystera and H. pseudorobustus are migratory endoparasites. Hoplolaimus galeatus caused extensive root necrosis and marked decrease of fresh weights of seedling roots and tops. Helicotylenchus dihystera and S. brachyurum produced only qualitatively different sparse and unhealthy root growth. Helicotylenchus pseudorobustus caused only a reduction in root surface area.     

Separation and purification of a keratinase as pesticide against root-knot nematodes

A new alkaline keratinase, which could kill Meloidogyne incognita (a root-knot nematode) was separated and purified from Bacillus sp. 50-3 in this study. The solid ammonium sulfate was selected to precipitate the enzyme and its proper adding mass was also determined. After solid ammonium sulfate precipitation and liquid chromatography on DEAE-Sephadex-A50 column, there was 17.7-fold purification with a yield of 46.5%, as determined by azokeratin as substrate. The purification effect was determined through SDS-PAGE and the molecular weight of the enzyme was found to be 27,423 Da by the MALDI-TOF-MS. When the second-stage juveniles of Meloidogyne incognita were exposed to 50 μg/ml of keratinase solution, 98.5% of Meloidogyne incognita mortality rates were obtained compared to control after 24 h. Its simple purification step and high yield from the cheap medium affords this keratinase great biotechnological potential, especially in controlling root-knot nematodes such as Meloidogyne incognita. To the best of our knowledge, this study is the first report that uses keratinase as a pesticide.     

Pathogenic potential of root-knot nematode Meloidogyne incognita and root-rot fungus Fusarium solani on chilli (Capsicum annuum L.)

Damaging threshold levels of root-knot nematode Meloidogyne incognita and root-rot fungus Fusarium solani on plant growth parameters, viz., plant length, fresh and dry weight of chilli were determined by conducting their pathogenicity trials in pot experiments. The results revealed a significant reduction in the plant growth parameters at and above the inoculum level of about 1000?J₂ per plant of M. incognita and the highest reduction was recorded at 8000?J₂ per plant. Significant reduction in plant growth parameters was recorded at 1.00?g mycelial mat of F. solani per plant, while the highest reduction was observed at 8.00?g mycelial mat per plant. The damaging threshold level was 1000?J₂ per plant of M. incognita and 1.00?g mycelial mat of F. solani.     

Relative efficacy of different cropping sequences integrated with ploughing for the management of plant parasitic nematodes: Relative wirksamkeit verschiedener beim pflügen integrierter fruchtfolgen zur bekämpfung von pflanzenparasitären nematoden

The relative efficacy of 25 different cropping sequences was tested at the end of the experiment. It appears that for Hoplolaimus indicus sequence number 16, 20, 8 and 10 gave high reduction in rate of reproduction, for Helicotylenchus indicus sequence No. 6, 11, 17 and 3, for Rotylenchulus reniformis sequence No. 2, 8, 13 and 14, for Tylenchorhynchus brassicae sequence No. 6, 24, 3 and 13, for Meloidogyne incognita larvae sequence No. 1, 2, 4 and 24, for Pratylenchus coffeae sequence No. 1, 2, 3 and 5; for Tylenchus filiformis sequence No. 2, 3, 4 and 5.     

Comprehensive report on the prevalence of root-knot nematodes in the Poonch division of Azad Jammu and Kashmir,Pakistan

The present study documents the root-knot nematodes (RKN) fauna of the Poonch division in Azad Jammu and Kashmir infecting vegetables. An overall prevalence of 40% of RKN was recorded. Of the four districts investigated, maximum prevalence was recorded in district Poonch with 59%, followed by Sudhnuti with 58%. The lowest prevalence of RKN was found in districts Bagh (29%) and Haveli (33%). Out of 15 vegetables investigated, RKN was found on five crops. The highest prevalence of 37.8% was recorded on okra, followed by 31.3% on cucumber and 17.5% on tomato. RKN was less prevalent on eggplant (8.3%) and beans (7.7%). Three RKN species, that is Meloidogyne incognita, Meloidogyne javanica and Meloidogyne arenaria, were found infecting the hosts. M. javanica was found to be the most prevalent followed by M. incognita and M. arenaria. This trend was found in all the districts. Overall prevalence of M. javanica as sole population was 9% and that of M. incognita was 2%. Meloidogyne arenaria was not found in any of the fields as sole population. The prevalence of M. incognita with M. javanica or M. arenaria as mixed populations was 8% and 5%, respectively, and that of M. javanica with M. arenaria was 4%. Similarly, all the three species prevailed as mixed populations in 12% of the fields in the division. The severity of RKN infections, measured as galling index, was found to be variable within each infected field (GI 2–9). Identification of RKN species was based on the morphology of perineal patterns and confirmed by molecular SCAR and CO1 makers based identification. In conclusion, RKN were distributed in the Poonch division and M. javanica was predominant. Cucumber, okra, tomato and eggplant were severely attacked by these nematodes warranting the adoption of stringent control strategies for their management.     

Effects of culture filtrates from the nematophagous fungus Verticillium leptobactrum on viability of the root-knot nematode Meloidogyne incognita

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.     

Nematodes Parasitic on Forest Trees: III. Reproduction on Selected Hardwoods

The host-parasite relationships of 13 species of plant parasitic nematodes and five species of hardwoods native to the southeastern United States were tested on greenhouse-grown tree seedlings for 6-10 months. Criteria for parasitism were completion o f life cycle and population increase of nematodes. Belonolaimus longicaudatus, Helicotylenchus dihystera, Scutellonema brachyurum and Tylenchorhynchus claytoni parasitized and reproduced on three or more of the species tested. Hoplolaimus galeatus and Pratylenchus brachyurus parasitized two species, Trichodorus christiei and Criconemoides xenoplax parasitized only red maple. Meloidogyne javanica/Liriodendron tulipifera combination was the only positive root-knot nematode/hardwood host-parasite relationship. Hemicycliophora silvestris, Meloidogyne arenaria, M. incognita, and M. hapla were not parasites of the tree species tested.