Species Meloidogyne Incognita Research Articles

Influence of medium modifications (optimization) on high nematicidal activity of the fermentation broth of Clostridium beijerinckii.

Introduction: The nematode species Meloidogyne incognita has been responsible for significant financial losses within the agricultural sector. Nematophagous bacteria, characterised by their extensive distribution and broad spectrum of hosts, exhibit remarkable efficacy as natural antagonists against nematodes. Sneb518 (Clostridium beijerinckii) fermentation broth displayed substantial biocontrol activity against M. incognita in previous research. Optimizing fermentation conditions is a fundamental technique for dramatically enhancing end product performance. There has been no such study conducted yet on enhancing the nematicidal activities of Sneb518 (Clostridium beijerinckii) fermentation using response surface methodology (RSM). Methods: The influence of strain Sneb518 fermentation media and conditions on nematicidal activity was examined using the three-factor technique and a Plackett-Burman design, and the interaction between various fermentation factors was examined using a Box-Behnken design. The present study employed response surface methodology (RSM) to examine and enhance the nematicidal activity of Sneb518 culture filtrates by identifying and optimising the influential components. Results: Glucose, peanut cake flour, and potassium chloride as carbon, nitrogen, and inorganic salts displayed considerably increased nematicidal potential in the present study. Furthermore, the corrected mortality of J2 ranged from 52.24% to 91.15% when utilizing the Box-Behnken design. These findings clearly support the application of RSM for medium optimization. Moreover, the outcomes of the validation experiment corresponded to the model predictions. Discussion: This research has enhanced the biocontrol ability of C. beijerinckii to control M. incognita and this research has led to the advancement of new biocontrol agents.

Chemical Composition and Nematicidal Properties of Sixteen Essential Oils-A Review.

Essential oils (EOs) can be a large source of new food-safe and healthy nematicidal products, due to their strong activity on crop pathogens and pests, including phytoparasitic nematodes, as well as to their low environmental persistence. This review summarizes the results from our 10-year studies on chemical features and nematicidal properties of 16 EOs with different botanical origins and compositions, i.e., the EOs from Artemisia herba-alba Asso (Asteraceae), Cinnamomum camphora (L.) J. Presl. and Cinnamomum verum J. Presl. (Lauraceae), Citrus aurantium L., Cinnamomum. sinensis L. Osbeck and Ruta graveolens L. (Rutaceae), Eucalyptus citriodora Hook, Eucalyptus globulus Labill. and Syzygium aromaticum (L.) Marry et Perry (Myrtaceae), Mentha piperita L., Monarda didyma L., Monarda. fistulosa L., Rosmarinus officinalis L. and Thymus satureioides Cosson (Lamiaceae), Pelargonium asperum Ehrh ex Willd (Geraniaceae) and Schinus molle L. (Anacardiaceae). All these EOs were chemically characterized and tested in vitro and/or in vivo for their activity against the phytoparasitic species Meloidogyne incognita Kofoid et White (Chitw.), Pratylenchus vulnus Allen et Jensen and Xiphinema index Thorne et Allen. Toxicity bioassays were conducted by exposing 2nd stage juveniles (J2) of M. incognita, mixed-age specimens of P. vulnus and adult females of X. index to 2–100 μg mL−1 concentrations of EOs or EO’s major constituents for 4–96 h and checking mortality effect after a further 24–72 h permanence in water. Egg hatchability bioassays consisted in exposing (24–48 h) M. incognita egg masses to 500–1000 mg mL−1 EO solutions followed by a 5-week hatching test in water. The in vivo experiments were undertaken in sandy soil strongly infested by M. incognita and treated with different doses of EOs, applied either in water solution or by fumigation. The effects of the treatments on nematode infestation on tomato and in soil were checked at the end of each experiment. Structure-activity relationships, as suggested by the different chemical compositions of tested EOs, were also highlighted. In agreement with literature data, our studies indicated that most of the tested EOs are highly suitable for the formulation of new safe nematicides, though still retarded by the lack of efficient stabilization processes and standardized EOs’ components and extraction techniques.

Expression of various odorant-response defective (odr) genes in the entomopathogenic nematode Heterorhabditis bacteriophora (Nematoda: Heterorhabditidae)

Entomopathogenic nematodes (EPNs) exhibit complex host-seeking behaviour in soil and utilise the insect- and plant-derived odorants to locate and infect their insect hosts. The odorant response defective (odr) genes were identified in Caenorhabditis elegans through a forward genetic screen for worms defective in odour sensing. It is hypothesised that odr genes could be involved in insect host recognition by the EPNs, but no information is available on these genes or their functions in EPNs. Here, we investigated and characterised odr genes in the EPN Heterorhabditis bacteriophora. Seven orthologs of C. elegans odr genes were identified by in-silico analysis in H. bacteriophora, of which four genes (Hb-odr-2, Hb-odr-3, Hb-odr-4 and Hb-odr-10) could be amplified and cloned from the cDNA. The developmental stage-specific expression in infective juvenile (IJ), fourth stage juvenile (J4) and adult stage of H. bacteriophora showed that Hb-odr-2, Hb-odr-3 and Hb-odr-10 were up-regulated only at the IJ stage, whereas Hb-odr-10 was significantly up-regulated in all the developmental stages. Exposure to insect hemolymph resulted in high transcript accumulation of Hb-odr-3 but did not affect the expression of other Hb-odr genes. The in-situ hybridisation assays showed that Hb-odr-2 mRNA expression was localised at the region of the nerve ring while that of Hb-odr-3 in the region of pharyngointestinal valve and anterior esophagous of the IJs. Our results extend the knowledge of C. elegans odr genes to the entomopathogenic nematode H. bacteriophora. To the best of our information, this is the second investigation on the characterisation of odr genes in a parasitic nematode after the plant-parasitic species Meloidogyne incognita.

Gene copy number variations as signatures of adaptive evolution in the parthenogenetic, plant-parasitic nematode Meloidogyne incognita.

Adaptation to changing environmental conditions represents a challenge to parthenogenetic organisms, and until now, how phenotypic variants are generated in clones in response to the selection pressure of their environment remains poorly known. The obligatory parthenogenetic root-knot nematode species Meloidogyne incognita has a worldwide distribution and is the most devastating plant-parasitic nematode. Despite its asexual reproduction, this species exhibits an unexpected capacity of adaptation to environmental constraints, for example, resistant hosts. Here, we used a genomewide comparative hybridization strategy to evaluate variations in gene copy numbers between genotypes of M.incognita resulting from two parallel experimental evolution assays on a susceptible vs. resistant host plant. We detected gene copy number variations (CNVs) associated with the ability of the nematodes to overcome resistance of the host plant, and this genetic variation may reflect an adaptive response to host resistance in this parthenogenetic species. The CNV distribution throughout the nematode genome is not random and suggests the occurrence of genomic regions more prone to undergo duplications and losses in response to the selection pressure of the host resistance. Furthermore, our analysis revealed an outstanding level of gene loss events in nematode genotypes that have overcome the resistance. Overall, our results support the view that gene loss could be a common class of adaptive genetic mechanism in response to a challenging new biotic environment in clonal animals.

A Novel Root-Knot Nematode Resistance QTL on Chromosome Vu01 in Cowpea.

The root-knot nematode (RKN) species Meloidogyne incognita and M. javanica cause substantial root system damage and suppress yield of susceptible cowpea cultivars. The narrow-based genetic resistance conferred by the Rk gene, present in some commercial cultivars, is not effective against Rk-virulent populations found in several cowpea production areas. The dynamics of virulence within RKN populations require a broadening of the genetic base of resistance in elite cowpea cultivars. As part of this goal, F and F populations from the cross CB46-Null (susceptible) x FN-2-9-04 (resistant) were phenotyped for M. javanica induced root-galling (RG) and egg-mass production (EM) in controlled growth chamber and greenhouse infection assays. In addition, F families of the same cross were phenotyped for RG on field sites infested with Rk-avirulent M. incognita and M. javanica. The response of F to RG and EM indicated that resistance to RKN in FN-2-9-04 is partially dominant, as supported by the degree of dominance in the F and F populations. Two QTL associated with both RG and EM resistance were detected on chromosomes Vu01 and Vu04. The QTL on Vu01 was most effective against aggressive M. javanica, whereas both QTL were effective against avirulent M. incognita. Allelism tests with CB46 x FN-2-9-04 progeny indicated that these parents share the same RKN resistance locus on Vu04, but the strong, broad-based resistance in FN-2-9-04 is conferred by the additive effect of the novel resistance QTL on Vu01. This novel resistance in FN-2-9-04 is an important resource for broadening RKN resistance in elite cowpea cultivars.

CONTROLE BIOLÓGICO DE NEMATOIDES UTILIZANDO MINHOCAS

The objective of this study was to evaluate the efficacy of using Lumbricus rubellus to control Meloidogyne incognita in Lactuca sativa roots. The experiment was carried out at the Laboratory of Soil Microbiology from the university Universidade do Oeste Paulista. We evaluated the worm species Lumbricus rubellus together with nematodes of the species Meloidogyne incognita and used fertilization with organic manure (cow and bird). For testing, we used Lactuca sativa, and the study was done using soil for growing vegetables in three-litter pots inside a greenhouse where relative humidity and temperature were monitored. After 45 days, the pots were removed and analysed. Analysis showed that, in comparison to the other situations analysed, the combination of bird manure with the worms resulted in a lower count of nematodes in the roots and better development of the plants. Therefore, there is a possibility these worms are effective in the biological control of nematodes.

Transcriptome analysis of root-knot nematode (Meloidogyne incognita)-resistant and susceptible sweetpotato cultivars.

Transcriptome analysis was performed on the roots of susceptible and resistant sweetpotato cultivars infected with the major root-knot nematode species Meloidogyne incognita. In addition, we identified a transcription factor-mediated defense signaling pathway that might function in sweetpotato-nematode interactions. Root-knot nematodes (RKNs, Meloidogyne spp.) are important sedentary endoparasites of many agricultural crop plants that significantly reduce production in field-grown sweetpotato. To date, no studies involving gene expression profiling in sweetpotato during RKN infection have been reported. Therefore, in the present study, transcriptome analysis was performed on the roots of susceptible (cv. Yulmi) and resistant (cv. Juhwangmi) sweetpotato cultivars infected with the widespread, major RKN species Meloidogyne incognita. Using the Illumina HiSeq 2000 platform, we generated 455,295,628 pair-end reads from the fibrous roots of both cultivars, which were assembled into 74,733 transcripts. A number of common and unique genes were differentially expressed in susceptible vs. resistant cultivars as a result of RKN infection. We assigned the differentially expressed genes into gene ontology categories and used MapMan annotation to predict their functional roles and associated biological processes. The candidate genes including hormonal signaling-related transcription factors and pathogenesis-related genes that could contribute to protection against RKN infection in sweetpotato roots were identified and sweetpotato-nematode interactions involved in resistance are discussed.

Nematicidal activity of essential oils from aromatic plants of Morocco

Essential oils (EOs) from Moroccan ecotypes of Artemisia herba-alba, Citrus sinensis, Rosmarinus officinalis and Thymus satureioides and their main components were comparatively evaluated for their in vitro activity against the phytonematode species Meloidogyne incognita, Pratylenchus vulnus and Xiphinema index. Suppressiveness of drench or fumigation soil treatment with the four EOs was also investigated against M. incognita on tomato in potting mixes. The in vitro nematicidal activity of the main constituents of the four EOs was also determined. More than 94 % mortality of M. incognita juveniles occurred after a 24-h exposure to a 15 μg ml−1 solution of A. herba-alba EO. A 100 % mortality of X. index females was observed at all exposure times and concentrations of all EOs except that from C. sinensis. Mortality of P. vulnus peaked at 75 % only after a 96-h permanence in the 15 μg ml−1 solution of R. officinalis EO. The in vitro activity of EOs’ main components was never as high as that of the whole EOs, suggesting a synergistic action of the EO multicomponent mixture. Soil treatments with the four EOs generally resulted in a significant reduction of root-knot nematode infestation on tomato, though in an aggregate comparison of data the A. herba-alba EO was more active than the other three EOs, and fumigation treatments were more effective than application in water solution. The high nematicidal activity of most of the tested EOs and their large availability make them a potential source of new nematicide formulations.

IPR AFRODITE - new oat cultivar with nematode resistance

The oat cultivar IPR Afrodite, resulting from a cross between CFT 2 and the inbred line ER 88144-1, is high-yielding, has grain quality traits that are relevant for food processing and industry, and is resistant to the root-knot nematode species Meloidogyne incognita, M. javanica, M. paranaensis and M. enterolobii.

Comparison of two short DNA barcoding loci (COI and COII) and two longer ribosomal DNA genes (SSU & LSU rRNA) for specimen identification among quarantine root-knot nematodes (Meloidogyne spp.) and their close relatives

Root-knot nematodes (Meloidogyne spp.) are important pests of numerous crops worldwide. Some members of this genus have a quarantine status, and accurate species identification is required to prevent further spreading. DNA barcoding is a method for organism identification in non-complex DNA backgrounds based on informative motifs in short DNA stretches (≈600 bp). As part of the EU 7th Framework project QBOL, 15 Meloidogyne species were chosen to compare the resolutions offered by two typical DNA barcoding loci, COI and COII, with the distinguishing signals produced by two ribosomal DNA genes (small and large subunit rDNA; SSU ≈ 1,700 and LSU ≈ 3,400 bp). None of the four markers distinguished between the tropical species Meloidogyne incognita, M. javanica and M. arenaria. Taking P ID (Liberal) values ≥0.93 as a measure for species delimitation, the four mtDNA and rDNA markers performed well for the tropical Meloidogyne species complex, M. enterolobii, M. hapla, and M. maritima. Within cluster III A (Holterman et al. Phytopathology, 99, 227–235, 2009), SSU rDNA did not offer resolution at species level. Both mtDNA loci COI and COII did, whereas for LSU rDNA a longer fragment (≥700 bp) is required. The high level of mitochondrial heteroplasmy recently reported for M. chitwoodi (Humphreys-Pereira and Elling Nematology, 15, 315–327, 2013) was not found in the populations under investigation, suggesting this could be a regional phenomenon. For identification of RKNs, we suggest the combined use of SSU rDNA with one of three other markers presented here.

Survey of Root-Knot Nematodes Infecting Vegetables in Northern Nigeria

Systematic surveys of root-knot nematodes were conducted in three states (Jos, Kaduna and Katsina) of Northern Nigeria. Infected root samples of vegetables were collected in polythene bags and brought to the laboratory. Root galls were dissected for mature females and perineal patterns were prepared from each sample. Species of root-knot nematodes were identified on the basis of perineal patterns. Two species Meloidogyne incognita and M. javanica were found to be associated with vegetables crops. M. incognita was present on all the vegetables, while M. javanica was present on few vegetables. Frequency of M. incognita was greater than M. javanica. Overall, incidence of disease was found 49.3% and intensity (gall index/egg mass index) was ranged from 2–4/0–4 with variation on different vegetables.

Genome-wide survey and analysis of microsatellites in nematodes, with a focus on the plant-parasitic species Meloidogyne incognita

BackgroundMicrosatellites 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.ResultsUsing MsatFinder, the total numbers of 1-6 bp perfect microsatellites detected in the complete genomes of five nematode species (Brugia malayi, Caenorhabditis elegans, M. hapla, M. incognita, Pristionchus pacificus) ranged from 2,842 to 61,547, and covered from 0.09 to 1.20% of the nematode genomes. Under our search criteria, the most common repeat motifs for each length class varied according to the different nematode species considered, with no obvious relation to the AT-richness of their genomes. Overall, (AT)n, (AG)n and (CT)n were the three most frequent dinucleotide microsatellite motifs found in the five genomes considered. Except for two motifs in P. pacificus, all the most frequent trinucleotide motifs were AT-rich, with (AAT)n and (ATT)n being the only common to the five nematode species. A particular attention was paid to the microsatellite content of the plant-parasitic species M. incognita. In this species, a repertoire of 4,880 microsatellite loci was identified, from which 2,183 appeared suitable to design markers for population genetic studies. Interestingly, 1,094 microsatellites were identified in 801 predicted protein-coding regions, 99% of them being trinucleotides. When compared against the InterPro domain database, 497 of these CDS were successfully annotated, and further assigned to Gene Ontology terms.ConclusionsContrasted patterns of microsatellite abundance and diversity were characterized in five nematode genomes, even in the case of two closely related Meloidogyne species. 2,245 di- to hexanucleotide loci were identified in the genome of M. incognita, providing adequate material for the future development of a wide range of microsatellite markers in this major plant parasite.

Inter- and intra-specific cuticle variation between amphimictic and parthenogenetic species of root-knot nematode ( Meloidogyne spp.) as revealed by a bacterial parasite ( Pasteuria penetrans)

Specific host–parasite interactions exist between species and strains of plant parasitic root-knot nematodes and the Gram-positive bacterial hyperparasite Pasteuria penetrans. This bacterium produces endospores that adhere to the cuticle of migrating juveniles, germinate and colonise the developing female within roots. Endospore attachment of P. penetrans populations to second-stage juveniles of the root-knot nematode species Meloidogyne incognita and Meloidogyne hapla showed there were interactive differences between bacterial populations and nematode species. Infected females of M. incognita produced a few progeny which were used to establish two nematode lines from single infective juveniles encumbered with either three or 26 endospores. Single juvenile descent lines of each nematode species were produced to test whether cuticle variation was greater within M. hapla lines that reproduce by facultative meiotic parthenogenesis than within lines of M. incognita, which reproduces by obligate parthenogenesis. Assays revealed variability between broods of individual females derived from single second-stage juvenile descent lines of both M. incognita and M. hapla suggesting that progeny derived from a single individual can differ in spore adhesion in both sexual and asexual nematode species. These results suggest that special mechanisms that produced these functional differences in the cuticle surface may have evolved in both sexually and asexually reproducing nematodes as a strategy to circumvent infection by this specialised hyperparasite.

Comprehensive transcriptome profiling in tomato reveals a role for glycosyltransferase in Mi-mediated nematode resistance.

Root-knot nematode (RKN; Meloidogyne spp.) is a major crop pathogen worldwide. Effective resistance exists for a few plant species, including that conditioned by Mi in tomato (Solanum lycopersicum). We interrogated the root transcriptome of the resistant (Mi+) and susceptible (Mi-) cultivars 'Motelle' and 'Moneymaker,' respectively, during a time-course infection by the Mi-susceptible RKN species Meloidogyne incognita and the Mi-resistant species Meloidogyne hapla. In the absence of RKN infection, only a single significantly regulated gene, encoding a glycosyltransferase, was detected. However, RKN infection influenced the expression of broad suites of genes; more than half of the probes on the array identified differential gene regulation between infected and uninfected root tissue at some stage of RKN infection. We discovered 217 genes regulated during the time of RKN infection corresponding to establishment of feeding sites, and 58 genes that exhibited differential regulation in resistant roots compared to uninfected roots, including the glycosyltransferase. Using virus-induced gene silencing to silence the expression of this gene restored susceptibility to M. incognita in 'Motelle,' indicating that this gene is necessary for resistance to RKN. Collectively, our data provide a picture of global gene expression changes in roots during compatible and incompatible associations with RKN, and point to candidates for further investigation.

Selection and parasite evolution: a reproductive fitness cost associated with virulence in the parthenogenetic nematode Meloidogyne incognita

Selection in plant parasites for virulence on resistant hosts and the resulting effects on parasite fitness may be considered as a driving force in host-parasite coevolution. In the present study, we tested the hypothesis that a fitness cost may be associated with nematode virulence, using the interaction between the parthenogenetic species Meloidogyne incognita and tomato as a model system. The reproductive parameters of near-isogenic lines of the nematode, selected for avirulence or virulence against the tomato Mi resistance gene, were analysed and combined into a reproductive index that was taken as a measure of fitness. The lower fitness of the virulent lines on the susceptible tomato cultivar showed for the first time that a measurable fitness cost is associated with unnecessary virulence in the nematode. Although parthenogenesis should theoretically lead to little genetic variability, such cost may impose a direct constraint on the coevolution between the plant and the nematode populations, and suggests an adaptive significance of trade-offs between selected characters and fitness-related traits. These results indicate that, although plant resistance can be broken, it might prove durable in some conditions if the virulent nematodes are counterselected in susceptible plants, which could have important consequences for the management of resistant cultivars in the field.

Elimination of nematodes from ginger (Zingiber officinaleRoscoe) by tissue culture

The rootknot nematode species Meloidogyne incognita and M. javanica pose a serious threat to the cultivation of ginger in South Africa. Tissue culture was investigated as a method of obtaining prop...

Influência da adubação e da fumigação do solo, na incidência de nematôides em tubérculos de batatinha

Dentre as causas que podem levar ao fracasso a cultura da batatinha (Solanum tuberosum L.) no Brasil, sobressaem as devidas aos nematóides causadores de galhas ou pipoca Meloidogyne incognita (Kofoide & White, 1919) Chitwood, 1949. Os tubérculos, quando atacados, tornam-se impróprios ao plantio e ao consumo apodrecendo rapidamente. Em vista dêsse fato vêm sendo realizadas, no Instituto Agronômico de Campinas, experiências visando ao combate àquela praga. Os resultados obtidos ultimamente, quando se procurou constatar a influência sôbre a redução da infestação exercida pelas adubações e pelas fumigações do solo com dibrometo de etileno, forneceram os seguintes esclarecimentos: a adubação não exerceu nenhuma influência sôbre o aumento ou diminuição das infestações dos tubérculos pelos nematóides; o dibrometo de etileno mostrou-se eficiente na redução da infestação, na dose de 276 litros por hectare, não devendo, todavia, ser aplicado no terreno no ato do plantio da batatinha mas sim com antecedência de oito ou mais dias; o melhor espaçamento entre aplicações foi o de 20x20 cm; a produção de tubérculos aumentou satisfatoriamente com a fumigação, principalmente quando o nematocida foi aplicado duas vezes no mesmo terreno, isto é, antes de cada uma das culturas ("da sêca" e "das águas").