Juvenile Nematodes Research Articles

Studying the Symbiotic Bacterium Xenorhabdus nematophila in Individual, Living Steinernema carpocapsae Nematodes Using Microfluidic Systems.

Animal-microbe symbioses are ubiquitous in nature and scientifically important in diverse areas, including ecology, medicine, and agriculture. Steinernema nematodes and Xenorhabdus bacteria compose an established, successful model system for investigating microbial pathogenesis and mutualism. The bacterium Xenorhabdus nematophila is a species-specific mutualist of insect-infecting Steinernema carpocapsae nematodes. The bacterium colonizes a specialized intestinal pocket within the infective stage of the nematode, which transports the bacteria between insects that are killed and consumed by the pair for reproduction. Current understanding of the interaction between the infective-stage nematode and its bacterial colonizers is based largely on population-level, snapshot time point studies on these organisms. This limitation arises because investigating temporal dynamics of the bacterium within the nematode is impeded by the difficulty of isolating and maintaining individual living nematodes and tracking colonizing bacterial cells over time. To overcome this challenge, we developed a microfluidic system that enables us to spatially isolate and microscopically observe individual, living Steinernema nematodes and monitor the growth and development of the associated X.nematophila bacterial communities-starting from a single cell or a few cells-over weeks. Our data demonstrate, to our knowledge, the first direct, temporal, in vivo visual analysis of a symbiosis system and the application of this system to reveal continuous dynamics of the symbiont population in the living host animal. IMPORTANCE This paper describes an experimental system for directly investigating population dynamics of a symbiotic bacterium, Xenorhabdus nematophila, in its host-the infective stage of the entomopathogenic nematode Steinernema carpocapsae. Tracking individual and groups of bacteria in individual host nematodes over days and weeks yielded insight into dynamic growth and topology changes of symbiotic bacterial populations within infective juvenile nematodes. Our approach for studying symbioses between bacteria and nematodes provides a system to investigate long-term host-microbe interactions in individual nematodes and extrapolate the lessons learned to other bacterium-animal interactions.

ROS and Cell Death in Tomato Roots Infected by Meloidogyne Incognita.

Phytoparasitic nematodes are plant pests causing serious problems to a broad range of hosts, and Meloidogyne species are widely recognized as the most damaging among the root knot nematode groups. During the incompatible interaction between avirulent pathogens and resistant tomato cultivars, juvenile nematode invasions provoke a defense cascade, culminating in hypersensitive responses. Methods to detect the key molecules involved in oxidative metabolism of the infected tomato roots are described here.

Determination of infection dynamics of root-knot nematode juveniles after tobacco seedling transplantation in laboratory and field

Determination of infection dynamics of root-knot nematode juveniles after tobacco seedling transplantation in laboratory and field

Cytotoxic, larvicidal, nematicidal, and antifeedant activities of piperidin-connected 2-thioxoimidazolidin-4-one derivatives.

The objective of this study was to investigate brine shrimp cytotoxicity, larvicidal, nematicidal, and antifeedant activities of novel piperidin-connected 2-thioxo-imidazolidin-4-one derivatives. The activities of target compounds were compared with some naturally occurring (−)-pinidinol, hydantocidin, and positive controls. Target compounds were synthesized via cyclocondensation method. The compounds were synthesized and then characterized by infrared spectroscopy, 1H NMR, 13C NMR, mass spectral, and elemental analyses. Brine shrimp cytotoxicity assay was investigated using freshly hatched, free-swimming nauplii of Artemiasalina. Larvicidal screening was performed against urban mosquito larvae (Culex quinquefasciatus). Nematicidal activity was evaluated using juvenile nematodes of Meloidogyne javanica. Regarding antifeedant activity, marine-acclimated Oreochromis mossambicus fingerlings were used. Compounds 3a-c (piperidin-connected 2-thioxoimidazolidin-4-one) were found to be lethal to the second instar larvae of mosquito, which produced LD50 values of 1.37, 6.66, 6.51 μg/mL, compared to compounds (−) pinidinol and hyantocidin LD50 values of 18.28 and 22.11 μg/mL respectively. Compound 3a-c was found to kill 100% of fish fingerlings within 6 h at 20 µg/mL, with LD50 values of 1.54, 1.79, 1.52 µg/mL, compared to compounds (−) pinidinol and hyantocidin with LD50 values of 10.21 and 21.05 μg/mL respectively. Compound 3c with LD50 value of 1.57 μg/mL demonstrated high nematicidal activity compared to compound 3a, 3b, (−) Pinidinol and Hyantocidin LD50 values of 6.45, 2.42, 14.25, 26.30 μg/mL respectively. Therefore, the 2-thioxoimidazolidin-4-one with piperidin ring showed high potential cytotoxic, larvicidal, nematicidal, and antifeedent activities.

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

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

Mycorrhizas reduce tomato root penetration by false root-knot nematode Nacobbus aberrans

Arbuscular mycorrhizal fungi (AMF) are considered as a possible alternative for the biological control of plant-parasitic nematodes. The false root-knot nematode Nacobbus aberrans is an endoparasite that induces the formation of galls in plant roots and causes severe damage to crops of economic importance. The purpose of the study was to evaluate the effect of the individual and combined application of two AMF species (Rhizophagus intraradices and Funneliformis mosseae) on the tomato root penetration of N. aberrans second-stage juveniles (J2). Forty-five days after the application of AMF, 300 J2 were inoculated per plant. Tomato roots were analyzed after 4, 8 and 12days in order to quantify the nematodes that had invaded them. Plants inoculated with AMF presented a lower number of juveniles within the roots compared with non-mycorrhizal plants. No significant differences were observed between the individual and combined application of AMF regarding the number of nematode juveniles. The use of R. intraradices and F. mosseae (both individually and combined) reduced the entry of nematodes in tomato roots. The antagonistic effect of AMF on the invasion of N. aberrans J2 is reported for the first time.

Sequestration and activation of plant toxins protect the western corn rootworm from enemies at multiple trophic levels.

Highly adapted herbivores can phenocopy two-component systems by stabilizing, sequestering and reactivating plant toxins. However, whether these traits protect herbivores against their enemies is poorly understood. We demonstrate that the western corn rootworm Diabrotica virgifera virgifera, the most damaging maize pest on the planet, specifically accumulates the root-derived benzoxazinoid glucosides HDMBOA-Glc and MBOA-Glc. MBOA-Glc is produced by D. virgifera through stabilization of the benzoxazinoid breakdown product MBOA by N-glycosylation. The larvae can hydrolyze HDMBOA-Glc, but not MBOA-Glc, to produce toxic MBOA upon predator attack. Accumulation of benzoxazinoids renders D. virgifera highly resistant to nematodes which inject and feed on entomopathogenic symbiotic bacteria. While HDMBOA-Glc and MBOA reduce the growth and infectivity of both the nematodes and the bacteria, MBOA-Glc repels infective juvenile nematodes. Our results illustrate how herbivores combine stabilized and reactivated plant toxins to defend themselves against a deadly symbiosis between the third and the fourth trophic level enemies.

FMRFamide-like peptides expand the behavioral repertoire of a densely connected nervous system

Animals, including humans, can adapt to environmental stress through phenotypic plasticity. The free-living nematode Caenorhabditis elegans can adapt to harsh environments by undergoing a whole-animal change, involving exiting reproductive development and entering the stress-resistant dauer larval stage. The dauer is a dispersal stage with dauer-specific behaviors for finding and stowing onto carrier animals, but how dauers acquire these behaviors, despite having a physically limited nervous system of 302 neurons, is poorly understood. We compared dauer and reproductive development using whole-animal RNA sequencing at fine time points and at sufficient depth to measure transcriptional changes within single cells. We detected 8,042 genes differentially expressed during dauer and reproductive development and observed striking up-regulation of neuropeptide genes during dauer entry. We knocked down neuropeptide processing using sbt-1 mutants and demonstrate that neuropeptide signaling promotes the decision to enter dauer rather than reproductive development. We also demonstrate that during dauer neuropeptides modulate the dauer-specific nictation behavior (carrier animal-hitchhiking) and are necessary for switching from repulsion to CO2 (a carrier animal cue) in nondauers to CO2 attraction in dauers. We tested individual neuropeptides using CRISPR knockouts and existing strains and demonstrate that the combined effects of flp-10 and flp-17 mimic the effects of sbt-1 on nictation and CO2 attraction. Through meta-analysis, we discovered similar up-regulation of neuropeptides in the dauer-like infective juveniles of diverse parasitic nematodes, suggesting the antiparasitic target potential of SBT-1. Our findings reveal that, under stress, increased neuropeptide signaling in C. elegans enhances their decision-making accuracy and expands their behavioral repertoire.

Tapping the potential of vegetable Amaranth genotype to trap the root knot nematode pest

Abstract Nine genotypes of Amaranthus tricolor L. and one genotype of Amaranthus cruentus L. were evaluated for susceptibility to root knot nematode, shoot and root traits in a nematode infested plot. A significantly higher proportion of parasitism (1.0) was recorded in four of the plant genotypes. All 10 amaranth genotypes failed to develop root galls by nematodes when cultivated after a fallow crop of African marigold. Three highly susceptible genotypes and one tolerant genotype were further screened in containers filled with sterile soil. The sterile soil was inoculated with the known amount of inoculums of two populations of root knot nematode (Meloidogyne incognita Kofoid and White) in the treatments. Two populations of nematodes were native to Old Goa and Varanasi of Goa and Uttar Pradesh states of India respectively. Plants in the un-inoculated control were maintained with sterile soil only. Staining the root samples with acid fuchsin was carried to confirm the presence of egg mass and juvenile nematodes in roots. One genotype of A. tricolor, IgAtR-60 (IC0598184) recorded the high degree of nematode parasitism when intercropped in arecanut garden. The genotype also had least reduction in root and shoot traits but remained highly susceptible to inoculation with both Old Goa and Varanasi populations of M. incognita. IgAtR-60 (IC-0598184) holds promise in nematode sick plots as trap-catch intercrop after confirmatory investigations.

English

Nematodes are obligatory parasites that compromise agricultural production worldwide. The use of alternative methods to replace the chemical pesticides in the control of this pest is increasingly growing, due to its pollution to the environment. In order to evaluate the biocidal effect of plant extracts, combinations of extracts of Neem (Azadirachta indica), croton (Croton campestris) and manioc (Manihot esculenta) were used in the control of root knot nematode, Meloidogyne incognita in tomato plants. The extracts were obtained from dried leaves and exposed to cold extraction with ethanol, under reduced pressure, with the aid of rotaevaporador. The application of the treatments took place 72 h after inoculation of suspension with 4,000 eggs/juveniles in the region of the root. Extracts from croton and cassava promoted plant height in the order of 26.75 and 34.50%, respectively; while neem extract inhibited the numbers of nematode juveniles in the root (51.34%), croton (50.85%), and manioc (41.31%). As for juveniles in the soil, only 47.33% was reduced in cassava. However, the mix of the extracts potentiated the effects on improvement of growth parameters and reduction of nematode parasitism. Key words: Alternative control, Meloidogyne incognita, Solanum lycopersicum.

Eretmochelys imbricata shells present a dynamic substrate for a facilitative epibiont relationship between macrofauna richness and nematode diversity, structure and function

Although nematodes are the most abundant metazoans in marine environments and present an important biological and ecological model organism to assess marine ecosystem processes and functions, there are in fact very few studies that use nematodes to investigate ecological communities and relationships on “mobile” ecosystems. Arguably one of the most mobile or dynamic marine ecosystems is a sea turtle carapace, hosting tens to hundreds or even thousands of epibiotic organisms; and as the turtle breeds, feeds and migrates, provides an ecosystem that is continuously exposed to changes and potential colonizers. In this study we investigated the nematode communities associated with 19 Hawksbill sea turtle carapaces (Eretmochelys imbricata), and compared nematode structural (composition, richness and diversity) and functional (trophic types and gender/life stages) community parameters with those of other comparable epibiotic substrates (macrophytes, natural and artificial hard substrates) to see whether turtle carapaces are hotspots of nematode diversity and function among substrates suitable for epifauna. We also addressed potential epibiotic macrofauna-nematode interactions by looking at the relationships between macrofauna richness and nematode richness, diversity and community composition. Results suggest that the macrofauna play a bioconstructing role, creating several microenvironments, and thereby enhancing the richness and diversity of the associated nematode assemblages. This was supported by a direct and positive relationship between macrofauna and nematode richness, and implies a genera enrichment process across size classes and phyla. All heterotrophic nematode feeding guilds were recovered from the carapaces, with dominance of predators/omnivores and epistrate feeders. Nematode juveniles dominated in terms of abundance, and a female/male ratio of 1.11 was observed. Nematode richness and diversity were higher than found on other substrates, but feeding guild, gender and life stage structure did not differ compared to nematode communities from all other epibiotic substrates. As a result, we argue that turtle carapaces can be seen as hotspots for nematode biodiversity compared to other epibiotic substrates, but this is not reflected in the function of the nematode community. This study is the first to investigate in detail sea turtle carapace nematode communities, their richness, diversity, trophic and life cycle structure, and potential interactions with their co-epibionts, the macrofauna.

Phenotype and Cellular Response of Wheat Lines Carrying Cre Genes to Heterodera avenae Pathotype Ha91.

The cereal cyst nematode (CCN, Heterodera avenae), a major limiting factor for wheat production worldwide, is widespread in most wheat-growing regions in China. Accordingly, screening and characterization of resistant (R) wheat sources against H. avenae are very important. In this study, we screened 51 wheat lines, collected from the International Wheat and Maize Improvement Center (CIMMYT), carrying various Cre genes (Cre1, Cre2, Cre3, Cre5, Cre7, Cre8, CreR, and Pt). From that screen, we identified one immune (M) cultivar (with no adult females produced) and five resistant cultivars (with fewer than five females) to H. avenae pathotype Ha91. The Cre3 gene conferred the most effective resistance against H. avenae pathotype Ha91 in both field and greenhouse assays. Conversely, the Cre1 and CreR genes conferred the poorest effective resistance. Using Pluronic F-127 gel and a staining assay, juvenile nematodes invading wheat roots were observed, and nematode development was analyzed. Compared with R and M roots, those of the susceptible (S) wheat cultivar Wenmai19 were more attractive to H. avenae second-stage juveniles (J2s). We observed the retardation of nematode development in R cultivars and tiny white female cysts protruding from the R cultivar VP1620. Nematodes in M roots either disintegrated or remained J2s or third-stage juveniles (J3s) and failed to complete their life cycle. Molting was also suppressed or delayed in R and M genotypes. For both S and R cultivars, syncytia were characterized by cell wall perforations and dense cytoplasm in hypertrophied syncytium component cells. Syncytial size increased gradually with nematode development in S cultivars. Moreover, an incompatibility reaction occurred in M wheat roots: the syncytium was disorganized, exhibiting disintegration and condensed nuclei. These sources of genetic resistance against CCN can potentially be planted in severely infested fields to reduce economic loss or can be used for introgression in breeding.

Expression of PR genes in tomato tissues infected by nematode Meloidogyne incognita (Kofoid et White, 1919) Chitwood, 1949.

The dynamics of expression of PR1 and PR6 genes, which are involved in the defense response of plants infected with the root-knot nematode Meloidogyne incognita, was studied in the "tomato-root-knot nematode" parasitic system. The invasion of the resistant plants was accompanied by an increased accumulation of transcripts of PR genes, which reflects their fast response to the penetration of nematode juveniles with subsequent development of an adequate defense response. In the susceptible plants, changes in the PR1 and PR6 gene activity induced by the nematode invasion were insignificant, which may be one of the causes of the disease. An exogenous salicylic acid treatment of the susceptible plants increased the PR1 and PR6 genes activity and led to the development of resistance of these plants to nematode invasion.

Microaspiration of Solanum tuberosum root cells at early stages of infection by Globodera pallida

BackgroundSedentary endoparasitic cyst nematodes form a feeding structure in plant roots, called a syncytium. Syncytium formation involves extensive transcriptional modifications, which leads to cell modifications such as increased cytoplasmic streaming, enlarged nuclei, increased numbers of organelles, and replacement of a central vacuole by many small vacuoles. When whole root RNA is isolated and analyzed, transcript changes manifested in the infected plant cells are overshadowed by gene expression from cells of the entire root system. Use of microaspiration allows isolation of the content of nematode infected cells from a heterogeneous cell population. However, one challenge with this method is identifying the nematode infected cells under the microscope at early stages of infection. This problem was addressed by staining nematode juveniles with a fluorescent dye prior to infection so that the infected cells could be located and microaspirated.ResultsIn the present study, we used the fluorescent vital stain PKH26 coupled with a micro-rhizosphere chamber to locate the infected nematode Globodera pallida in Solanum tuberosum root cells. This enabled microaspiration of nematode-infected root cells during the early stages of parasitism. To study the transcriptional events occurring in these cells, an RNA isolation method from microaspirated samples was optimized, and subsequently the RNA was purified using magnetic beads. With this method, we obtained an RNA quality number of 7.8. For transcriptome studies, cDNA was synthesized from the isolated RNA and assessed by successfully amplifying several pathogenesis related protein coding genes.ConclusionThe use of PKH26 stained nematode juveniles enabled early detection of nematode infected cells for microaspiration. To investigate transcriptional changes in low yielding RNA samples, bead-based RNA extraction procedures minimized RNA degradation and provided high quality RNA. This protocol provides a robust procedure to analyze gene expression in nematode-infected cells.

Doses of bokashi in the control of Meloidogyne javanica in lettuce

Root-knot nematodes are among the major yield-limiting factors on vegetables, and the use of organic matter can be a viable method for controlling the parasite. Thus, the present study aimed to assess the use of doses of bokashi and reapplication of the compost in the control of Meloidogyne javanica in lettuce. Tomato seedlings were transplanted into plant pots containing 2 liters of autoclaved soil and were inoculated with 2000 eggs and eventual juveniles of the nematode. After 60 days of cultivation, the aerial part was discarded and lettuce seedlings were transplanted, and different doses of bokashi treatments were applied, as follows: 0, 5, 10 and 20 g, at two periods: only at planting and at planting + reapplication after 15 days. Forty-five (45) days after transplant, vegetative (dry and fresh weight of aerial part) and nematode (galls and nematodes g -1 of root) parameters were evaluated. In general, the period of application of bokashi did not increase the plant growth and nematode control. However, the doses had direct effects, with increase in vegetative growth observed in the application of about 14 g plant -1 , and nematode control following doses between 13 and 14 g plant -1 .

Diversity and biocontrol potential of bacterial consortia associated to root-knot nematodes

The bacteria associated to egg masses and second stage juveniles (J2) of root-knot nematodes (Meloidogyne spp.) were studied using three different soils from naturally infested farms in Apulia (Italy). The species were isolated and identified with 16S rRNA sequencing or characterized with metabolic profiles. They included members of genera Pseudomonas and Bacillus, together with Lysinibacillus sphaericus and an unclassified Chryseobacterium sp. To identify potential biocontrol agents, a greenhouse assay was carried out with isolates of B. cereus, B. licheniformis, L. sphaericus, P. fluorescens and P. brassicacearum. The bacteria were introduced in soil on tomato seedlings before inoculation with juveniles of Meloidogyne incognita, and significantly reduced the nematode densities after two reproductive cycles. However, plants and root weights were not affected by treatments. In a second assay with higher bacterial inocula, B. licheniformis and P. fluorescens significantly reduced the J2 galling on tomato roots, at 21dpi. The potential of rhizosphere bacteria in management of root knot nematodes is discussed.

Parasites of the Plateau Brown Frog,Rana kukunorisNikolsky, 1918 (Anura: Ranidae) from the Northeast of the Qing-Tibetan Plateau, with the Description of a New Species ofIsospora(Apicomplexa: Eimeriidae)

Fifty-six plateau brown frogs, Rana kukunoris Nikolsky, 1918, were collected from June to August 2014, and examined for parasites. Our goal was to survey the parasite species and its prevalence and mean intensity from the plateau brown frog in the Northeast of Qing-Tibetan plateau. Thirty-three of 56 (59%) frogs examined were infected with 1 or more parasites, including 19 (34%) with Dolichosaccus ranae Wang, 1980; 11 (20%) with Nematotaenia dispar (Goeze 1782) Luhe, 1899; 53 (95%) with Aplentana leesi Hristovski and Riggo, 1975; 3 (5%) with Rhabdias sp.; and 8 (14%) with unidentified juvenile nematodes. In addition, 4 (7%) frogs were found to harbor a previously unreported isosporan, which we describe herein. Sporulated oocysts of the new isosporan were ellipsoidal, 14.2 × 10.2 (12–16 × 8–12) μm, with a smooth, thin wall, and a shape index of 1.4 (1.1–1.8). No micropyle or oocyst residuum were present, but the oocysts contained one polar granule composed of 1–2 globules stuck together. Sporocysts were ovoidal, 8.7 × 7.2 (8–10 × 6–9) μm, with a shape index of 1.2 (1.0–1.4), and lacked Stieda, sub-Stieda, and para-Stieda bodies; they possessed a large sporocyst residuum consisting of an aggregate of granules bounded by a limiting membrane. Sporozoites were sausage-shaped, with one end slightly pointed and arranged head-to-tail around the sporocyst residuum; refractile bodies and nuclei were not discernible. These parasite species were recovered from R. kukunoris in China and all represent new host and distribution records.

Phytochemical Screening and Nematicidal Activity of Cinnamon and Ginger Extracts Against Root-knot Nematode (Meloidogyne incognita) Infecting Tomato

The purpose of this work was to assess the nematicidal and antioxidantactivities of different extracting solvents from cinnamon (Cinnamomum zeylanicum)and ginger (Zingiber officinale) against Meloidogyne incognita infecting tomato.Three solvents namely n-hexane, ethyl acetate and methanol were used.Phytochemical analysis of such extracts revealed the presence of morecomponents in ethyl acetate and methanolic extracts than n-hexane extract of eithercinnamon or ginger. The highest amount of total phenolics and flavonoids weredetected in ethyl acetate extract of both ginger and cinnamon reaching 105.6; 93.6mg gallic acid /g and 54.2; 45.1 mg quercetin/ g dry weight, respectively.Additionally, ethyl acetate and methanolic extracts of ginger exhibited the highestantioxidant activity (DPPH free radicals) reaching 90.0 and 89.1%, respectively. Theefficacy of cinnamon and ginger using three solvents at two concentrations (50 and10ul) on juveniles mortality of Meloidogyne incognita was studied in vitro. Ethylacetate extracts gave better results than did methanol or hexane extracts. Gingerextracts gave promising results after 72hr of exposure compared to cinnamon ones.Hence, among ginger extracts the maximum mortality in nematode juveniles wasachieved with ethyl acetate (68.0 %) followed by methanol (42.0%) and hexaneextracts (30%) @ the concentration of 50μl after 72 hours of exposure. Ginger ethylacetate (300 ppm) proved to be the best for enhancing total plant fresh weight withpercentage of increase over control amounted to 196.0 %. Population densities,root galling and number of egg masses were significantly suppressed with suchtested extracts. Leaves of tomato were assayed for NPK, total cholorophyll,proteins, and phenols. Activities of polyphenol oxidase (PPO), peroxide oxidase(PO) were also evaluated in roots of tomato infected with M. incognita. PO activitywas much greater in ginger ethyl acetate at lower concentration (100 ppm).Conversely, PPO activity was increased in cinnamon ethyl acetate (100 ppm).Thepresent study revealed high potential antioxidants and nematicidal properties inboth cinnamon and ginger. The biological activities of these plants might beattributed to the various kind of secondary metabolites.

Nematicidal Activity of the Essential Oil of Three Varieties of Tagetes minuta from Argentina

Essential oils composition of three Tagetes minuta varieties and a wild population (WP) from Argentina and their in vitro and in vivo nematicidal activity against root-knot nematode, Meloidogynejavanica, are described. All T. minuta EOs tested were very active against nematode juveniles (J2), but the strongest nematicidal effects were exhibited by the TmV3 variety oil, characterized by a high content of (E)-ocimenone. High nematode egg hatching suppression (> 90%) was induced by TmV3 EO after five days of incubation. In vivo tests on tomato seedlings showed a significant reduction of infection rate of M javanica J2 treated with TmV3 and WP oils at sub lethal dose. Therefore, EOs from chemically stable new varieties of T. minuta could be environmentally friendly nematicidal agents.

Bioefficacy of different bioagents against root-knot nematode, Meloidogyne incognita infesting bottle gourd under laboratory conditions

The bioefficacy of different bioagents viz., Paecilomyces lilacinus (2x10 6 cfu/g), Pseudomonas fluorescens (1x10 9 cfu/g), Trichoderma viride (2x10 6 cfu/g), Phule Trichoderma plus (2x10 6 cfu/g) and Pochonia chlamydosporium (2x106 cfu/g) against second stage juveniles of root-knot nematode infesting bottle gourd crop was studied under laboratory conditions. In this bioassay Paecilomyces lilacinus fungus caused higher rate of juvenile mortality at 1.00 per cent concentration was found to be promising in laboratory bioassay studies and recorded 80.00 per cent mortality of second stage juveniles of root-knot nematode. This was followed by 76.67 per cent mortality of second stage juveniles of root-knot nematode by Pseudomonas fluorescens at 1.00 per cent concentration after 72 hrs treatment of respective bioagents. The fungi Phule Trichoderma plus, Trichoderma viride recorded 70.00, 66.67 per cent juvenile mortality, while as in case of fungi Pochonia chlamydosporium 53.33 per cent juvenile mortality was observed after 72 hrs treatment of respective bioagents at 1.00 per cent concentrations.