Showing papers on "Meloidogyne incognita published in 2015"
TL;DR: Function-based metagenomic analysis indicated that the enriched bacterial populations in root gall harbored abundant genes related to degradation of plant polysaccharides, carbohydrate and protein metabolism, and biological nitrogen fixation.
Abstract: Endophytes are known to play important roles in plant's health and productivity. In this study, we investigated the root microbiome of tomato in association with infection by root knot nematodes. Our objectives were to observe the effects and response of the bacterial endophytes before nematode attacks and to reveal the functional attributes of microbes in plant health and nematode pathogenesis. Community analysis of root-associated microbiomes in healthy and nematode-infected tomatoes indicated that nematode infections were associated with variation and differentiation of the endophyte and rhizosphere bacterial populations in plant roots. The community of the resident endophytes in tomato root was significantly affected by nemato-pathogenesis. Remarkably, some bacterial groups in the nematode feeding structure, the root gall, were specifically enriched, suggesting an association with nematode pathogenesis. Function-based metagenomic analysis indicated that the enriched bacterial populations in root gall harbored abundant genes related to degradation of plant polysaccharides, carbohydrate and protein metabolism, and biological nitrogen fixation. Our data indicated that some of the previously assumed beneficial endophytes or bacterial associates with nematode might be involved in nematode infections of the tomato roots.
142 citations
Journal Article•
TL;DR: Though fluopyram is nematistatic, low concentrations of the fungicide were effective at reducing the ability of both nematode species to infect tomato roots.
Abstract: Fluopyram is a succinate dehydrogenase inhibitor (SDHI) fungicide that is being evaluated as a seed treatment and in-furrow spray at planting on row crops for management of fungal diseases and its effect on plant-parasitic nematodes. Currently, there are no data on nematode toxicity, nematode recovery, or effects on nematode infection for Meloidogyne incognita or Rotylenchulus reniformis after exposure to low concentrations of fluopyram. Nematode toxicity and recovery experiments were conducted in aqueous solutions of fluopyram, while root infection assays were conducted on tomato. Nematode paralysis was observed after 2 hr of exposure at 1.0 µg/ml fluopyram for both nematode species. Using an assay of nematode motility, 2-hr EC50 values of 5.18 and 12.99 µg/ml fluopyram were calculated for M. incognita and R. reniformis, respectively. Nematode recovery in motility was greater than 50% for M. incognita and R. reniformis 24 hr after nematodes were rinsed and removed from a 1-hr treatment of 5.18 and 12.99 µg/ml fluopyram, respectively. Nematode infection of tomato roots was reduced and inversely proportional to 1-hr treatments with water solutions of fluopyram at low concentrations, which ranged from 1.3 to 5.2 µg/ml for M. incognita and 3.3 to 13.0 µg/ml for R. reniformis. Though fluopyram is nematistatic, low concentrations of the fungicide were effective at reducing the ability of both nematode species to infect tomato roots.
103 citations
TL;DR: Relying on a single root-knot nematode management strategy is an outdated concept and different management options should be used in an integrated management context by considering the whole system of disease management.
Abstract: The encounter between Meloidogyne species and tomato is many centuries old. Meloidogyne species are known to cause high levels of economic loss worldwide in a multitude of agricultural crops, including tomato. This review was initiated to provide an overview of the damage potential of Meloidogyne spp. on cultivars of tomato ( Solanum lycopersicum ), and to compile the different studies done on the management of Meloidogyne spp. on tomato with particular emphasis on the Mi resistance gene. Numerous studies have been conducted to assess the damage potential of root-knot nematode on various tomato cultivars; its yield loss potential ranges from 25 to 100%. A range of management options from using synthetic nematicides to soilless cultures have been tried and are available for managing Meloidogyne spp. Resistant commercial cultivars and rootstocks carrying the Mi gene have been used successfully to manage Meloidogyne incognita , M. javanica and M. arenaria . However, virulent populations have been detected. Relying on a single root-knot nematode management strategy is an outdated concept and different management options should be used in an integrated management context by considering the whole system of disease management. In future management of Meloidogyne species, care must be taken in directly extrapolating the tolerance limit determined elsewhere, since it is affected by many factors such as the type of initial inoculum and physiological races of Meloidogyne spp., environmental conditions, types of cultivars and experimental approaches used.
102 citations
TL;DR: It is demonstrated that Mi-cpl-1 plays crucial role during plant-nematode interaction and plant-mediated downregulation of this gene elicits detrimental effect on M. incognita development, reinforcing the potential of RNAi technology for management of phytonematodes in crop plants.
Abstract: Root-knot nematodes (Meloidogyne incognita) cause substantial yield losses in vegetables worldwide, and are difficult to manage. Continuous withdrawal of environmentally-harmful nematicides from the global market warrants the need for novel nematode management strategies. Utility of host-delivered RNAi has been demonstrated in several plants (Arabidopsis, tobacco, and soybean) that exhibited resistance against root-knot and cyst nematodes. Herein, a M. incognita-specific protease gene, cathepsin L cysteine proteinase (Mi-cpl-1), was targeted to generate tomato transgenic lines to evaluate the genetically modified nematode resistance. In vitro knockdown of Mi-cpl-1 gene led to the reduced attraction and penetration of M. incognita in tomato, suggesting the involvement of Mi-cpl-1 in nematode parasitism. Transgenic expression of the RNAi construct of Mi-cpl-1 gene resulted in 60–80% reduction in infection and multiplication of M. incognita in tomato. Evidence for in vitro and in vivo silencing of Mi-cpl-1 was confirmed by expression analysis using quantitative PCR. Our study demonstrates that Mi-cpl-1 plays crucial role during plant-nematode interaction and plant-mediated downregulation of this gene elicits detrimental effect on M. incognita development, reinforcing the potential of RNAi technology for management of phytonematodes in crop plants.
78 citations
TL;DR: Rucola can be considered as a promising companion plant in intercropping strategies for tomato growers to control root-knot nematodes and the nematicidal activity of fresh rucola used as soil amendant in a containerized culture of tomato decreased the nematode infection in a dose-response manner.
Abstract: Research on new pesticides based on plant extracts, aimed at the development of nontoxic formulates, has recently gained increased interest. This study investigated the use of the volatilome of rucola (Eruca sativa) as a powerful natural nematicidal agent against the root-knot nematode, Meloidogyne incognita. Analysis of the composition of the volatilome, using GC-MS-SPME, showed that the compound (Z)-3-hexenyl acetate was the most abundant, followed by (Z)-3-hexen-1-ol and erucin, with relative percentages of 22.7 ± 1.6, 15.9 ± 2.3, and 8.6 ± 1.3, respectively. Testing of the nematicidal activity of rucola volatile compounds revealed that erucin, pentyl isothiocyanate, hexyl isothiocyanate, (E)-2-hexenal, 2-ethylfuran, and methyl thiocyanate were the most active with EC50 values of 3.2 ± 1.7, 11.1 ± 5.0, 11.3 ± 2.6, 15.0 ± 3.3, 16.0 ± 5.0, and 18.1 ± 0.6 mg/L, respectively, after 24 h of incubation. Moreover, the nematicidal activity of fresh rucola used as soil amendant in a containerized culture of tom...
61 citations
TL;DR: Although the susceptible cultivar showed a more pronounced defense response to the infection, feeding sites were successfully established in its roots, and basal gene expression levels under normal conditions differed between the two cultivars, which may confer advantage to one of the genotypes toward resistance to nematodes.
Abstract: Nematodes are one of the major limiting factors in alfalfa production. Root-knot nematodes (RKN, Meloidogyne spp.) are widely distributed and economically important sedentary endoparasites of agricultural crops and they may inflict significant damage to alfalfa fields. As of today, no studies have been published on global gene expression profiling in alfalfa infected with RKN or any other plant parasitic nematode. Very little information is available about molecular mechanisms that contribute to pathogenesis and defense responses in alfalfa against these pests and specifically against RKN. In this work, we performed root transcriptome analysis of resistant (cv. Moapa 69) and susceptible (cv. Lahontan) alfalfa cultivars infected with RKN Meloidogyne incognita, widespread root-knot nematode species and a major pest worldwide. A total of 1,701,622,580 pair-end reads were generated on an Illumina Hi-Seq 2000 platform from the roots of both cultivars and assembled into 45,595 and 47,590 transcripts in cvs Moapa 69 and Lahontan, respectively. Bioinformatic analysis revealed a number of common and unique genes that were differentially expressed in susceptible and resistant lines as a result of nematode infection. Although the susceptible cultivar showed a more pronounced defense response to the infection, feeding sites were successfully established in its roots. Characteristically, basal gene expression levels under normal conditions differed between the two cultivars as well, which may confer advantage to one of the genotypes toward resistance to nematodes. Differentially expressed genes were subsequently assigned to known Gene Ontology categories to predict their functional roles and associated biological processes. Real-time PCR validated expression changes in genes arbitrarily selected for experimental confirmation. Candidate genes that contribute to protection against M. incognita in alfalfa were proposed and alfalfa-nematode interactions with respect to resistance are discussed.
60 citations
TL;DR: The results showed that B. firmus YBf-10 exhibits systemic nematicidal activity against Meloidogyne incognita, including lethal activity, inhibition of egg hatch and motility, and the systemic nematicsidal activity is likely attributed to the secondary metabolites produced by YBF-10.
Abstract: A strain of marine bacterium Bacillus firmus YBf-10 with nematicidal activity was originally isolated by our group. In the present study, the systemic nematicidal activity and biocontrol efficacy in pot experiment of B. firmus YBf-10 were investigated. Our results showed that YBf-10 exhibits systemic nematicidal activity against Meloidogyne incognita, including lethal activity, inhibition of egg hatch and motility. Pot experiment suggested that soil drenching with YBf-10 efficiently reduced damage of M. incognita to tomato plants, such as reduction of galls, egg masses on roots, and final nematode population in soil; and moreover, YBf-10 significantly promoted host plant growth. In addition, our results also indicated that the systemic nematicidal activity is likely attributed to the secondary metabolites produced by YBf-10. The obtained results of the current study confirmed that B. firmus YBf-10 is a promising nematicidal agent, and has great potential in plant-parasitic nematicidal management.
54 citations
TL;DR: Nematicidal assays in vivo showed that some of them exhibited good control efficacy against the cucumber root-knot nematode disease caused by Meloidogyne incognita, which indicated that 1,2,3-benzotriazin-4-one derivatives might be potential for novel promising nematicides.
Abstract: A series of novel 1,2,3-benzotriazin-4-one derivatives were synthesized by the reaction of 3-bromoalkyl-1,2,3-benzotriazin-4-ones with potassium salt of 2-cyanoimino-4-oxothiazolidine in the presence of potassium iodide. Nematicidal assays in vivo showed that some of them exhibited good control efficacy against the cucumber root-knot nematode disease caused by Meloidogyne incognita, up to 100% at the concentration of 10.0 mg L–1, which indicated that 1,2,3-benzotriazin-4-one derivatives might be potential for novel promising nematicides. The nematicidal activity was influenced by the combination of substituent type, substituted position, and linker length in the molecule. The inhibition rate data at the concentrations of 5.0 and 1.0 mg L–1 for the compounds with high inhibitory activities were also provided. When tested in vitro, none of them showed direct inhibition against M. incognita. The investigation of a significant difference between in vivo and in vitro data is in progress.
48 citations
TL;DR: The biocontrol efficacy of Trichoderma longibrachiatum, a fungal species native to China, against M. incognita is determined and it can be considered to be a promising bio-control agentagainst M.incognita with a high efficacy.
45 citations
TL;DR: 7H08 was found to activate the expression of reporter genes in both yeast and plant systems, the first report of a plant-parasitic nematode effector with transcriptional activation activity.
Abstract: Root-knot nematodes are sedentary biotrophic endoparasites that maintain a complex interaction with their host plants. Nematode effector proteins are synthesized in the oesophageal glands of nematodes and secreted into plant tissue through a needle-like stylet. Effectors characterized to date have been shown to mediate processes essential for nematode pathogenesis. To gain an insight into their site of action and putative function, the subcellular localization of 13 previously isolated Meloidogyne incognita effectors was determined. Translational fusions were created between effectors and EGFP-GUS (enhanced green fluorescent protein-β-glucuronidase) reporter genes, which were transiently expressed in tobacco leaf cells. The majority of effectors localized to the cytoplasm, with one effector, 7H08, imported into the nuclei of plant cells. Deletion analysis revealed that the nuclear localization of 7H08 was mediated by two novel independent nuclear localization domains. As a result of the nuclear localization of the effector, 7H08 was tested for the ability to activate gene transcription. 7H08 was found to activate the expression of reporter genes in both yeast and plant systems. This is the first report of a plant-parasitic nematode effector with transcriptional activation activity.
44 citations
TL;DR: Light is shed on the transcriptional changes that accompany plant infection by P. penetrans, and will aid in identifying potential gene targets for selection and use to design effective control strategies against root lesion nematodes.
Abstract: The root lesion nematode Pratylenchus penetrans is considered one of the most economically important species within the genus. Host range studies have shown that nearly 400 plant species can be parasitized by this species. To obtain insight into the transcriptome of this migratory plant-parasitic nematode, we used Illumina mRNA sequencing analysis of a mixed population, as well as nematode reads detected in infected soybean roots 3 and 7 days after nematode infection. Over 140 million paired end reads were obtained for this species, and de novo assembly resulted in a total of 23,715 transcripts. Homology searches showed significant hit matches to 58% of the total number of transcripts using different protein and EST databases. In general, the transcriptome of P. penetrans follows common features reported for other root lesion nematode species. We also explored the efficacy of RNAi, delivered from the host, as a strategy to control P. penetrans, by targeted knock-down of selected nematode genes. Different comparisons were performed to identify putative nematode genes with a role in parasitism, resulting in the identification of transcripts with similarities to other nematode parasitism genes. Focusing on the predicted nematode secreted proteins found in this transcriptome, we observed specific members to be up-regulated at the early time points of infection. In the present study, we observed an enrichment of predicted secreted proteins along the early time points of parasitism by this species, with a significant number being pioneer candidate genes. A representative set of genes examined using RT-PCR confirms their expression during the host infection. The expression patterns of the different candidate genes raise the possibility that they might be involved in critical steps of P. penetrans parasitism. This analysis sheds light on the transcriptional changes that accompany plant infection by P. penetrans, and will aid in identifying potential gene targets for selection and use to design effective control strategies against root lesion nematodes.
TL;DR: This protocol provides progress toward a standardized strategy for identification of RKN species from small, preserved samples and a rational starting point for classifying species present in regions where previous knowledge has been limited.
Abstract: The asexual root-knot nematodes (RKNs) (Meloidogyne spp) exemplified by Meloidogyne incognita are widespread and damaging pests in tropical and subtropical regions worldwide Comparison of amplification products of two adjacent polymorphic regions of the mitochondrial genome using DNA extracts of characterized RKN strains, including 15 different species, indicate that several species are derived from the same or closely related female lineages Nevertheless, M javanica, M enterolobii, M incognita, and other key species could each be assigned unique mitochondrial haplotypes based on polymerase chain reaction fragment size and restriction cleavage patterns M arenaria isolates did not group as a single haplotype, consistent with other reports of diversity within this species To test the utility of this assay, we characterized ethanol-preserved samples from 103 single-species isolates from four countries in sub-Saharan Africa (Benin, Nigeria, Kenya, and Tanzania) Mitochondrial haplotypes corr
TL;DR: The results confirmed that emamectin benzoate has enormous potential for the control of M. incognita in tomato production in China and resulted in increased tomato yields.
Abstract: Southern root-knot nematode (Meloidogyne incognita) is an obligate, sedentary endoparasite of more than 3000 plant species, that causes heavy economic losses and limit the development of protected agriculture of China. As a biological pesticide, emamectin benzoate has effectively prevented lepidopteran pests; however, its efficacy to control M. incognita remains unknown. The purpose of the present study was to test soil application of emamectin benzoate for management of M. incognita in laboratory, greenhouse and field trials. Laboratory results showed that emamectin benzoate exhibited high toxicity to M. incognita, with LC50 and LC90 values 3.59 and 18.20 mg L(-1), respectively. In greenhouse tests, emamectin benzoate soil application offered good efficacy against M. incognita while maintaining excellent plant growth. In field trials, emamectin benzoate provided control efficacy against M. incognita and resulted in increased tomato yields. Compared with the untreated control, there was a 36.5% to 81.3% yield increase obtained from all treatments and the highest yield was received from the highest rate of emamectin benzoate. The results confirmed that emamectin benzoate has enormous potential for the control of M. incognita in tomato production in China.
TL;DR: The methanol extract of the aerial part of Triumfetta grandidens (Tiliaceae) was highly active against Meloidogyne incognita, with second-stage juveniles (J2s) mortality of 100% at 500 μg/mL at 48 h post-exposure.
Abstract: The methanol extract of the aerial part of Triumfetta grandidens (Tiliaceae) was highly active against Meloidogyne incognita, with second-stage juveniles (J2s) mortality of 100% at 500 μg/mL at 48 h post-exposure. Two 4-quinolone alkaloids, waltherione E (1), a new alkaloid, and waltherione A (2), were isolated and identified as nematicidal compounds through bioassay-guided fractionation and instrumental analysis. The nematicidal activities of the isolated compounds against M. incognita were evaluated on the basis of mortality and effect on egg hatching. Compounds 1 and 2 exhibited high mortalities against J2s of M. incognita, with EC50 values of 0.09 and 0.27 μg/mL at 48 h, respectively. Compounds 1 and 2 also exhibited a considerable inhibitory effect on egg hatching, which inhibited 91.9 and 87.4% of egg hatching, respectively, after 7 days of exposure at a concentration of 1.25 μg/mL. The biological activities of the two 4-quinolone alkaloids were comparable to those of abamectin. In addition, pot experiments using the crude extract of the aerial part of T. grandidens showed that it completely suppressed the formation of gall on roots of plants at a concentration of 1000 μg/mL. These results suggest that T. grandidens and its bioactive 4-quinolone alkaloids can be used as a potent botanical nematicide in organic agriculture.
TL;DR: Examination of the use of F. parviflora, in green house and field experiments, as a green manure against Meloidogyne incognita on tomato suggests that the plant could be used alone or as part of an Integrated Pest Management strategy as a novel management tool for M. incognita.
TL;DR: In conclusion, gfp-transformation did not change the nematicidal activity of A. implicatum and is a tool to examine the mode of plant endophytism and opportunistic egg parasitism of GFP-tagged A.implicatum.
Abstract: Acremonium implicatum is an endophytic fungus with biocontrol potential against Meloidogyne incognita based on its opportunistic egg-parasitic, hatching inhibition, and toxic properties. To understand its mode of plant endophytism and opportunistic egg parasitism, GFP-tagged A. implicatum was constructed by PEG-mediated protoplast transformation. By laser scanning confocal microscopy (LSCM), we evaluated the endophytism and opportunistic egg parasitism of a stable gfp transformant (Acr-1). Acr-1 could colonize epidermal tissue, cortical tissue, and xylem of roots and form a mutualistic symbiosis with tomato host plants. LSCM of Acr-1 infecting M. incognita eggs revealed that hyphae penetrated the shell and grew inside eggs to form trophic hyphae. A large number of hyphae enveloped parasitized eggs. In addition, the egg shell integrity was destroyed by fungal penetration. The percentage of egg parasitism was 33.8 %. There were no marked differences between the wild type and mutant in nematode second-stage juvenile mortality and egg hatching and in fungal control efficiency in a pot experiment. In conclusion, gfp-transformation did not change the nematicidal activity of A. implicatum and is a tool to examine the mode of plant endophytism and opportunistic egg parasitism of A. implicatum.
TL;DR: Although the free-living nematode structure was negatively influenced by all treatments, B. carinata DMS proved the best compromise between efficiency to control M. incognita and environmental impact, confirming the interesting potential of biofumigant DSM amendments as alternatives to chemical fumigants for a more environment-friendly control of some soil-borne diseases.
Journal Article•
TL;DR: Positive results were achieved for control of M. incognita on tomato and cucumber and M. arenaria on snapdragon with commercial formulations of the biocontrol agent Pasteuria penetrans.
Abstract: Meloidogyne incognita and Meloidogyne arenaria are important parasitic nematodes of vegetable and ornamental crops. Microplot and greenhouse experiments were conducted to test commercial formulations of the biocontrol agent Pasteuria penetrans for control of M. incognita on tomato and cucumber and M. arenaria on snapdragon. Three methods of application for P. penetrans were assessed including seed, transplant, and post-plant treatments. Efficacy in controlling galling and reproduction of the two root-knot nematode species was evaluated. Seed treatment application was assessed only for M. incognita on cucumber. Pasteuria treatment rates of a granular transplant formulation ranged from 1.5 × 105 endospores/cm3 to 3 × 105 endospores/cm3 of transplant mix applied at seeding. Additional applications of 1.5 × 105 endospores/cm3 of soil were applied as a liquid formulation to soil post-transplant for both greenhouse and microplot trials. In greenhouse cucumber trials, all Pasteuria treatments were equivalent to steamed soil for reducing M. incognita populations in roots and soil, and reducing nematode reproduction and galling. In cucumber microplot trials there were no differences among treatments for M. incognita populations in roots or soil, eggs/g root, or root condition ratings. Nematode reproduction on cucumber was low with Telone II and with the seed treatment plus post-plant application of Pasteuria, which had the lowest nematode reproduction. However, galling for all Pasteuria treatments was higher than galling with Telone II. Root-knot nematode control with Pasteuria in greenhouse and microplot trials varied on tomato and snapdragon. Positive results were achieved for control of M. incognita with the seed treatment application on cucumber.
TL;DR: This research is the first study to report that C. pustulatus is a suitable rootstock with simultaneous resistance to root-knot nematode and Fusarium wilt for cucumber, melon, and watermelon, and these rootstocks are thus promising for low-input sustainable horticulture.
Abstract: Southern root-knot nematode causes dramatic galling on the roots of cucurbitaceous plants such as cucumber, melon, and watermelon. Even low nematode levels can cause high yield losses. Control of root-knot nematode is usually based on soil fumigation with toxic methyl bromide. However, since methyl bromide is now banned, growers are looking for alternative pest control. A potential solution is to graft susceptible scions onto nematode-resistant rootstocks. Here, we selected a Meloidogyne incognita-resistant rootstock suitable for cucumber, melon, and watermelon scions. First, we screened the resistance against nematode and Fusarium. Then, we tested a wild Cucumis species, Cucumis pustulatus, as a possible rootstock for cucumber, melon, and watermelon scions. We measured the survival rate, plant growth, yield, and fruit quality of grafted plants. Fifty-three accessions from 16 species were studied. Five accessions exhibited high resistance to southern root-knot nematode, and 12 accessions exhibited resistance to Fusarium wilt. This research is the first study to report that C. pustulatus is a suitable rootstock with simultaneous resistance to root-knot nematode and Fusarium wilt for cucumber, melon, and watermelon. C. pustulatus rootstocks are thus promising for low-input sustainable horticulture. They should benefit to home gardeners, especially to those in areas highly infested with southern root-knot nematode.
TL;DR: Soil fumigation with EOs of E. globulus and P. asperum significantly reduced nematode multiplication and gall formation on tomato roots at all the tested rates, whereas the EOsof E. citriodora, M. piperita and R. graveolens were more suppressive at levels greater than 50 µL kg−1 soil.
Abstract: The effectiveness of soil fumigation with 50, 100 and 200 µL kg−1 soil of essential oils (EOs) from the plant species Eucalyptus citriodora, Eucalyptus globulus, Mentha piperita, Pelargonium asperum and Ruta graveolens was assessed against the root-knot nematode Meloidogyne incognita on potted tomato. Plant growth parameters and number of galls, nematode eggs and juveniles on tomato roots were evaluated after two months of maintenance of the treated plants at 25°C in greenhouse. EOs of E. globulus and P. asperum significantly reduced nematode multiplication and gall formation on tomato roots at all the tested rates, whereas the EOs of E. citriodora, M. piperita and R. graveolens were more suppressive at levels greater than 50 µL kg−1 soil. Biofumigation with EOs of E. globulus and P. asperum resulted also in the largest increase of tomato plant top and root biomass. The five samples of EOs had a different chemical composition as determined by GC and GC-MS. Structure–activity relationship based on the main constituents of the tested EOs and their nematicidal effect on M. incognita is discussed.
TL;DR: This study provides useful information to employ PI 567516C in soybean breeding in order to develop new cultivars with resistance to multiple nematodes, and reveals that there might be Peking-type Rhg1 in PI 56 7516C.
Abstract: Soybean cyst nematode (SCN, Heterodera glycine Ichinohe), southern root-knot nematode [SRKN, Meloidogyne incognita (Kofoid and White) Chitwood] and reniform nematode (RN, Rotylenchulus reniformis Linford and Oliveira) are three important plant–parasitic pests in soybean. Previous study showed that plant introduction (PI) 567516C harbored novel quantitative trait loci (QTL) conferring SCN resistance to soybean. However, QTL underlying resistance to SRKN and RN in PI 567516C remain unknown. The objectives of this study were to identify QTL for resistance to SRKN and RN in PI 567516C. Two hundred and forty-seven F6:9 recombinant inbred lines, derived from a cross between cultivar Magellan and PI 567516C, were evaluated for resistance to SRKN and RN. Two hundred and thirty-eight simple sequence repeats and 687 single nucleotide polymorphism markers were used to construct a genetic linkage map. Three significant QTL associated with resistance to SRKN were mapped on chromosomes (Chrs.) 10, 13 and 17. Two significant QTL associated with resistance to RN were detected on Chrs. 11 and 18. Whole-genome resequencing revealed that there might be Peking-type Rhg1 in PI 567516C. Our study provides useful information to employ PI 567516C in soybean breeding in order to develop new cultivars with resistance to multiple nematodes.
TL;DR: Nineteen DAB species were demonstrated to be antagonists against the M. incognita-P.
Abstract: BACKGROUND
The use of dually antagonistic bacteria (DAB) as alternatives to chemicals for biological control of disease complexes has received little attention. In this study targeting the Meloidogyne incognita–Phytophthora nicotianae complex, DAB from the tobacco rhizosphere were identified and screened against the diseases caused by one or both pathogens in tobacco.
RESULTS
From 450 soil tobacco rhizosphere samples, 26 DAB were identified and had in vitro nematicidal and antifungal efficacies of 37.2–100% and 32.9–73.4% respectively. These DAB were classified into 19 species of 11 genera. In pot experiments, Streptomyces flavofungini SNA26, Pseudomonas putida SNB53 and Serratia marcescens subsp. sakuensis SNB54 effectively suppressed black shank (control effect 72.0–80.2%), root knot (70.0–81.7) and the disease complex (58.7–68.5%) caused by P. nicotianae, M. incognita and both pathogens in tobacco respectively.
CONCLUSION
Nineteen DAB species were demonstrated to be antagonists against the M. incognita–P. nicotianae complex. Because S. flavofungini SNA26, P. putida SNB53 and S. marcescens subsp. sakuensis SNB54 significantly suppressed the infection of M. incognita and P. nicotianae in tobacco, these species have potential for development as biocontrol agents against the diseases and complex caused by these two pathogens. © 2014 Society of Chemical Industry
TL;DR: The interaction between Meloidogyne incognita and Rhizoctonia solani in a root rot disease complex of green beans was examined in a greenhouse pot experiment and Nematode reproduction was adversely affected by the presence of the fungus except by the synchronized inoculation.
TL;DR: This is the first comprehensive report of bacterial flora associated with the RKN identified by pyrosequencing‐based analysis, and provides valuable information for understanding nematode–microbiota interactions and may be helpful in the development of novel nematodes‐control strategies.
Abstract: The root knot nematode (RKN), Meloidogyne incognita, belongs to the most damaging plant pathogens worldwide, and is able to infect almost all cultivated plants, like tomato. Recent research supports the hypothesis that bacteria often associated with plant-parasitic nematodes, function as nematode parasites, symbionts, or commensal organisms etc. In this study, we explored the bacterial consortia associated with M. incognita at different developmental stages, including egg mass, adult female and second-stage juvenile using the pyrosequencing approach. The results showed that Proteobacteria, with a proportion of 71-84%, is the most abundant phylum associated with M. incognita in infected tomato roots, followed by Actinobacteria, Bacteroidetes, Firmicutes etc. Egg mass, female and second-stage juvenile of M. incognita harbored a core microbiome with minor difference in communities and diversities. Several bacteria genera identified in M. incognita are recognized cellulosic microorganisms, pathogenic bacteria, nitrogen-fixing bacteria and antagonists to M. incognita. Some genera previously identified in other plant-parasitic nematodes were also found in tomato RKNs. The potential biological control microorganisms, including the known bacterial pathogens and nematode antagonists, such as Actinomycetes and Pseudomonas, showed the largest diversity and proportion in egg mass, and dramatically decreased in second-stage juvenile and female of M. incognita. This is the first comprehensive report of bacterial flora associated with the RKN identified by pyrosequencing-based analysis. The results provide valuable information for understanding nematode-microbiota interactions and may be helpful in the development of novel nematode-control strategies.
TL;DR: In this article, the RNA interference approach was applied, using fragments of M. incognita genes that encode for two essential molecules, heat-shock protein 90 (HSP90) and isocitrate lyase (ICL).
Abstract: Crop losses caused by nematode infections are estimated to be valued at USD 157 billion per year. Meloidogyne incognita, a root-knot nematode (RKN), is considered to be one of the most important plant pathogens due to its worldwide distribution and the austere damage it can cause to a large variety of agronomically important crops. RNA interference (RNAi), a gene silencing process, has proven to be a valuable biotechnology alternative method for RKN control. In this study, the RNAi approach was applied, using fragments of M. incognita genes that encode for two essential molecules, heat-shock protein 90 (HSP90) and isocitrate lyase (ICL). Plant-mediated RNAi of these genes led to a significant level of resistance against M. incognita in the transgenic Nicotiana tabacum plants. Bioassays of plants expressing HSP90 dsRNA demonstrated a delay in gall formation and up to 46% reduction in eggs compared with wild-type plants. A reduction in the level of HSP90 transcripts was observed in recovered eggs from plants expressing dsRNA, indicating that gene silencing persisted and was passed along to first progeny. The ICL knock-down had no clear effect on gall formation but resulted in up to 77% reduction in egg oviposition compared with wild-type plants. Our data suggest that both genes may be involved in RKN development and reproduction. Thus, in this paper, we describe essential candidate genes that could be applied to generate genetically modified crops, using the RNAi strategy to control RKN parasitism.
TL;DR: It is important that lessons learned through extensive research on soybean-nematode interactions in South Africa be shared with researchers and industries in other countries as they might experience or expect similar problems and/or challenges.
Abstract: The area planted to soybean in South Africa has increased by 54% since the 2009 growing season, mainly as a result of the increasing demand for protein-rich food and fodder sources. Moreover, the introduction of advanced technology, namely the availability of genetically modified herbicide tolerant soybean cultivars also contributed towards increased soybean production. The omnipresence of plant-parasitic nematodes in local agricultural soils, however, poses a threat to the sustainable expansion and production of soybean and other rotation crops. Meloidogyne incognita and M. javanica are the predominant nematode pests in local soybean production areas and those where other grain-, legume- and/or vegetable crops are grown. The lack of registered nematicides for soybean locally, crop production systems that are conducive to nematode pest build-ups as well as the limited availability of genetic host plant resistance to root-knot nematode pests, complicate their management. Research aimed at various aspects related to soybean-nematode research, namely, audits of nematode assemblages associated with the crop, identification of genetic host plant resistance in soybean germplasm to M. incognita and M. javanica, the use of molecular markers that are linked to such genetic resistance traits as well as agronomic performance of pre-released cultivars that can be valuable to producers and the industry are accentuated in this review. Evaluation of synthetically-derived as well as biological-control agents are also discussed as complementary management tactics. It is important that lessons learned through extensive research on soybean-nematode interactions in South Africa be shared with researchers and industries in other countries as they might experience or expect similar problems and/or challenges.
TL;DR: It is demonstrated that Arabidopsis can be used as a model system for studying plant–nematode–endophyte tripartite interactions; thus, opening new possibilities for further characterizing the molecular mechanisms behind these interactions.
Abstract: The research demonstrated that Arabidopsis can be used as a model system for studying plant–nematode–endophyte tripartite interactions; thus, opening new possibilities for further characterizing the molecular mechanisms behind these interactions.
Arabidopsis has been established as an important model system for studying plant biology and plant–microbe interactions. We show that this plant can also be used for studying the tripartite interactions among plants, the root-knot nematode Meloidogyne incognita and a beneficial endophytic isolate of Fusarium oxysporum, strain Fo162. In various plant species, Fo162 can systemically reduce M. incognita infection development and fecundity. Here it is shown that Fo162 can also colonize A. thaliana roots without causing disease symptoms, thus behaving as a typical endophyte. As observed for other plants, this endophyte could not migrate from the roots into the shoots and leaves. Direct inoculation of the leaves also did not result in colonization of the plant. A significant increase in plant fresh weight, root length and average root diameter was observed, suggesting the promotion of plant growth by the endophyte. The inoculation of A. thaliana with F. oxysporum strain Fo162 also resulted in a significant reduction in the number of M. incognita juveniles infecting the roots and ultimately the number of galls produced. This was also observed in a split-root experiment, in which the endophyte and nematode were spatially separated. The usefulness of Arabidopsis opens new possibilities for further dissecting complex tripartite interactions at the molecular and biochemical level.
TL;DR: Developing several RKN-resistant Citrullus lanatus var.
Abstract: Southern root-knot nematodes (Meloidogyne incognita) are an important reemerging pest of watermelon in the United States and worldwide. The re-emergence of root-knot nematodes (RKNs) in watermelon and other cucurbits is largely the result of the intensive cultivation of vegetable crops on limited agricultural lands coupled with the loss of methyl bromide for pre-plant soil fumigation, which has been the primary method for control of RKNs and many soilborne diseases of cucurbits and other vegetable crops for several decades. One alternative for managing RKN in watermelon is the use of resistant rootstocks for grafted watermelon. We have developed several RKN-resistant Citrullus lanatus var. citroides lines (designated RKVL for Root-Knot Vegetable Laboratory), which have shown promise as rootstocks for grafted watermelon. In 2011 and 2012, we demonstrated that F1 hybrids derived from our selected RKVL lines exhibited resistance to RKN that was equal to or greater than that of the parental RKVL lines when grown in fields highly infested with M. incognita. In 2011, although significant differences were not observed among rootstocks, the F1 hybrids produced slightly higher yields compared with the selected parental lines. Among the selected parental lines, RKVL 318 produced high yields in both years. In 2011, three of four RKVL parental lines and all four of their F1 hybrids produced greater (P < 0.05) fruit yields than self-grafted ‘Tri-X 313’, ‘Emphasis’ bottle gourd, and ‘Strong Tosa’ squash hybrid. In 2012, three RKVL F1 hybrid lines produced higher yields than the selected parents. Overall, these F1 hybrids were vigorous and should provide useful genetic material for selection and development of robust RKN-resistant C. lanatus var. citroides rootstock lines. As a result of intensive cultivation of vegetable crops on limited land resources, soilborne diseases and pests of vegetable crops have significantly increased in recent years, particularly after the removal of the soil fumigant methyl bromide from the market in accordance with the Montreal Protocol on Substances that Deplete the Ozone Layer and the U.S. Clean Air Act (U.S. Environmental Protection Agency, 2012). Presently, there are no alternative fumigants that are as effective as methyl bromide in controlling major soilborne diseases and plant-parasitic nematodes, and it is projected that the phase-out of this pre-plant soil fumigant will result in annual yield losses of at least 15% to 20% for watermelon in Georgia and Florida, two of the largest watermelon-producing states in the United States (Lynch and Carpenter, 1999). The practice of grafting vegetables on diseaseor pest-resistant rootstocks as a tool for reducing damage by soilborne diseases and pests has been expanding worldwide. To reduce soilborne disease pressure, Cucurbita rootstocks have been used for grafted watermelon in Asia and the Mediterranean region (Yetisir et al., 2003). However, these rootstocks are highly susceptible to RKNs (Thies et al., 2010). The USDA, ARS maintains 134 U.S. PIs of the wild-type watermelon Citrullus lanatus var. citroides collected in Africa, which is considered the possible center of origin of watermelon (Jarret et al., 1997). In previous studies, we identified a considerable number of C. lanatus var. citroides PIs that show resistance to RKNs (Thies and Levi, 2003, 2007). Several of these resistant PIs were selected and self-pollinated in three successive generations to obtain pure line selections. These lines (which we have designated RKVL) have proved to be vigorous rootstocks, producing significantly higher watermelon yield than the commercially available cucurbit rootstocks in fields infested with RKNs (Thies et al., 2010). F1 hybrid rootstocks have proved useful in different crops, including the Cucurbita maxima · C. moschata hybrid rootstock used for grafting melon, cucumber, and watermelons. Most of the watermelons grown in the Mediterranean basin are grafted on F1 hybrids of Cucurbita rootstocks (Yetisir et al., 2003). The wide genetic diversity that exists among the C. lanatus var. citroides accessions might be useful for generating heterotic F1 hybrid rootstocks, resistant to RKNs, and possibly to other soilborne diseases of watermelon (Levi et al., 2012). Our overall goal is to develop heterotic F1 hybrid lines of RKVL that produce higher yields and have increased disease and pest resistances (Thies et al., 2012). In this study, we examined the responses of our selected RKVL lines and their F1 hybrids as rootstocks for grafted watermelon in fields infested with RKNs. Materials and Methods Expt. 1: Charleston, SC, 2011. The experiment was conducted in an M. incognitainfested field at the U.S. Vegetable Laboratory in Charleston, SC. Seeds of watermelon scion ‘Tri-X 313’ plants and rootstock plants were sown in 72 cell trays (TLC Polyform, Inc., Minneapolis, MN) on 19 May 2011. Ten days later, ‘Tri-X 313’ watermelon scions were grafted on to each of the rootstocks using the single cotyledon method (Hassell, 2007). On 15 June 2011, grafted plants were transplanted into single-row plots on raised white plastic mulch beds on 6.1-m centers. The experimental design was a randomized complete block with six replications and each plot consisted of a single row of six watermelon plants with plants spaced 0.9 m apart. Four elite rootstock lines (designated RKVL) of C. lanatus var. citroides and four F1 hybrids of these lines (developed at the U.S. Vegetable Laboratory, USDA, ARS in Charleston, SC) were selected for use in the experiment. Commercial rootstocks also included in the study were ‘Emphasis’ Lagenaria siceraria, ‘Ojakkyo’ C. lanatus var. citroides, ‘Strong Tosa’ Cucurbita maxima · Cucurbita moschata hybrid, and self-grafted and non-grafted seedless watermelon ‘Tri-X 313’ C. lanatus var. lanatus. Fruits were harvested and fruit weights recorded six times from 8 Aug. through 31 Received for publication 1 Oct. 2013. Accepted for publication 11 Nov. 2013. Mention of a trademark name or proprietary product does not constitute a warranty or guarantee by the U.S. Department of Agriculture nor does it imply exclusion of other products that may also be suitable. To whom reprint requests should be addressed; e-mail Judy.Thies@comcast.net. HORTSCIENCE VOL. 50(1) JANUARY 2015 9 Aug. On 2 Sept., shoots of all plants were clipped and roots were lifted from soil and washed. Root systems of each plant were stained using the method of Thies et al. (2002) and evaluated for severity of galling and egg mass production. Percentages of root system galled or covered in egg masses were recorded for each plant. Root systems from each plot were bulked, weighed, cut into 1to 2-cm pieces, and eggs were extracted using 1.0% NaOCl (Hussey and Barker, 1973). Eggs were counted using a stereomicroscope. Eggs per gram fresh root were log (x + 1) transformed for analysis of variance (ANOVA) to normalize data. Analysis of variance was conducted using the GLM procedure of SAS Version 9.1 for Windows (SAS Institute Inc., Cary, NC) and means were separated using Fisher’s protected least significant difference (LSD). Expt. 2: Charleston, SC, 2012. The experiment was conducted in Charleston, SC, at the same field site as in 2011 and experimental methods were the same as those previously described for the 2011 experiment. Seeds of watermelon scion ‘Tri-X 313’ plants and rootstock plants were sown on 22 Mar. 2012. ‘Tri-X 313’ watermelon scions were grafted on to each of the rootstocks 10 d later. Plots were laid out as in 2011 and grafted plants were transplanted into the field on 1 June. The experimental design was a randomized complete block design with six replicates. Fruits were harvested and fruit weights recorded eight times from 2 Aug. through 23 Aug. On 29 Aug., shoots of all plants were clipped and roots were lifted from soil and washed. Percentages of root galling and egg masses present on the roots and percentages of root systems with fibrous roots were recorded. Eggs of M. incognita were extracted from roots and counted as described for the 2011 experiment. Eggs per gram fresh root were log (x + 1) transformed for ANOVA to normalize the data. Data were analyzed using the GLM procedure of SAS and means were separated by Fisher’s protected LSD. Results and Discussion The first objective of these studies, conducted in both 2011 and 2012, was to examine whether F1 hybrids derived from our selected RKN-resistant RKVL lines (Thies et al., 2010, 2012) exhibited resistance in fields highly infested with this soilborne pest. In 2011, there were no significant differences among the selected parental RKVL lines and their F1 hybrids for the percentages of root systems with galls and egg masses present (Table 1). Percentages of root systems with galls and egg masses ranged from 4.9 to 12.4 and 0.9 to 3.6, respectively, for the selected parental RKVL lines. In comparison, the four F1 hybrid RKVL lines had percentages of root systems galled ranging from 9.8 to 14.8 and percentages of root systems with egg masses ranging from 3.3 to 6.6. Root systems of ‘Tri-X 313’ non-grafted and ‘Tri-X 313’ self-grafted had 14.6% and 11.0%, respectively, and 2.7% and 2.6% egg mass production. All RKVL lines and their F1 hybrids had significantly lower (P < 0.05) percentages of root galling and egg mass production than the squash hybrid rootstock ‘Strong Tosa’ (92.0% and 86.3%, respectively) and the bottle gourd rootstock ‘Emphasis’ (78.2% and 51.4%, respectively) (Table 1; Fig. 1). All but one of each of the RKVL parental lines and their F1 hybrids (RKVL 317 and RKVL 318 · 301) had significantly lower numbers (P < 0.05) of eggs per gram fresh root (range five to 24) than ‘Tri-X 313’ non-grafted (41) and ‘Tri-X 313’ self-grafted (34). F1 hybrids had lower (P < 0.05) numbers of eggs per gram fresh root than the commercial rootstocks ‘Emphasis’ bottle gourd (1114) and ‘Strong Tosa’ squash hybrid (2653) (Table 1)
TL;DR: Nematicidal P. chlamydosporia strains obtained from the nematode worms tended to yield a total yellow pigment aurovertin production exceeding the inhibitory concentration shown in nematicidal bioassays, which advance the understanding of the roles of aurovertsin production in the interactions between nematodes and the pathogen fungus.
Abstract: Nematophagous fungi are globally distributed soil fungi and well-known natural predators of soil-dwelling nematodes. Pochonia chlamydosporia can be found in diverse nematode-suppressive soils as a parasite of nematode eggs and is one of the most studied potential biological control agents of nematodes. However, little is known about the functions of small molecules in the process of infection of nematodes by this parasitic fungus or about small-molecule-mediated interactions between the pathogenic fungus and its host. Our recent study demonstrated that a P. chlamydosporia strain isolated from root knots of tobacco infected by the root-knot nematode Meloidogyne incognita produced a class of yellow pigment metabolite aurovertins, which induced the death of the free-living nematode Panagrellus redivevus. Here we report that nematicidal P. chlamydosporia strains obtained from the nematode worms tended to yield a total yellow pigment aurovertin production exceeding the inhibitory concentration shown in nematic...
TL;DR: A dual gene overexpression system was used to transform tomato in order to provide protection from all growth stages of RKN, demonstrating that transgenic plants had inhibitory effects on RKN that were superior to plants transformed with a single gene.