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D. W. Dickson - One of the best experts on this subject based on the ideXlab platform.
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transfer and development of Pasteuria penetrans
Journal of Nematology, 2007Co-Authors: G M Kariuki, D. W. DicksonAbstract:Pasteuria penetrans isolate P-20 has been attributed as the cause of soil suppressiveness to peanut root-knot nematode in Florida. In this study, P. penetrans was transferred from a suppressive site to a new site and established by growing susceptible hosts to the peanut root-knot nematode during both summer and winter seasons. When two soil fumigants, 1,3-dichloropropene (1,3-D) and chloropicrin, were applied broadcast at the rate of 168 liters/ha and 263 kg/ha, respectively, the bacterium was not adversely affected by 1,3-D but was adversely affected by chloropicrin. In autumn 2005, after the harvest of the second peanut crop, the greatest number of J2 was recorded in the chloropicrin-treated plots, followed by the non-fumigated plots and 1,3-D-fumigated plots. The percentage J2 encumbered with endospores, endospores per J2 and percentage of P. penetrans-infected females were greatest in the non-fumigated plots, followed by 1,3-D- and chloropicrin-fumigated plots. This study demonstrates that P. penetrans can be transferred from a suppressive site to a new site and increased to suppressive densities against the peanut root-knot nematode.
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comparison of inoculation methods meloidogyne spp and different host plants for production of Pasteuria penetrans
Journal of Asia-pacific Entomology, 2005Co-Authors: D. W. Dickson, T. E. HewlettAbstract:Pasteuria penetrans is an effective biological control agent of root-knot nematode, but its practical use is limited by the lack of efficient methods for mass production of the endospores. Root-gall formation by Meloidogyne arenaria and/or M. javanica juveniles (J2s) attached with P. penetrans endospores was compared in plants receiving single vs. split inoculations and in different susceptible host plants. Number of endospores produced by M arenaria was compared among different host plants. Of six host plants tested, M. javanica produced the greatest number of galls on cucumber and M. arenaria produced the greatest number of galls on okra and tomato (P
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Distribution and Downward Movement of Pasteuria penetrans in Field Soil.
Journal of nematology, 2005Co-Authors: R. Cetintas, D. W. DicksonAbstract:Endospores of Pasteuria penetrans were evaluated for their vertical distribution in field soil and their downward movement through soil in the laboratory. In the field trial, the number of endospores attached to second-stage juveniles (J2) of Meloidogyne arenaria race 1 varied greatly in different soil depths. There were higher percentages of J2 with endospores attached in former weed fallow plots during the first 3 years of growing peanut than in former bahiagrass and rhizomal peanut plots (P = 0.05). In weed fallow plots a higher average number of endospores per J2 were maintained in all depths, upper three depths, and upper four depths in 1999, 2000, and 2001, respectively (P = 0.05). However, in 2002, there were no differences in the percentages of J2 with endospores attached and in the average of the numbers of endospores per J2 among the treatments (P 0.05). In laboratory trials, P. penetrans endospores were observed to move throughout the soil through the percolation of water. After one application of water, some endospores were detected 25 to 37.5 cm deep. Endospores were present at the greatest depth, 37.5 to 50 cm, after the third application of water. These results indicate that rain or water applications by irrigation are likely to move endospores to deeper levels of the soil, but the majority of endospores remain in the upper 0-to-30-cm depth.
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Microwave treatment of Pasteuria penetrans parasite preparation for selective elimination of undesired microorganisms
2004Co-Authors: R. K. Walia, T. E. Hewlett, D. W. DicksonAbstract:A Pasteuria penetrans spore laden parasite preparation, raised from peanut pod hulls in a field naturally infested with the bacterium and Meloidogyne arena ria (race 1), was exposed to microwave (MW) radiation to eliminate undesired microorganisms. MW radiation was given at medium, medium high or high levels for 1 or 2 min. Treatment of the parasite preparation at high radiation level for 2 min completely eliminated the undesirable fungal propagules, without significantly impeding the viability of P. penetrans endospores.
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Biological Control Of Moloidogyne Incognita on Tomato and Banana with RhizOobacteria, Actinomycetes, and Pasteuria penetrans
Nematropica, 2000Co-Authors: E. I. Jonathan, K. R. Barker, F. F. Abdel-alim, T. C. Vrain, D. W. DicksonAbstract:Jonathan E. I., K. R. Barker, F. F. Abdel-Alim, T. C. Vrain, and D. W. Dickson. 2000. Biological control of Meloidogyne incognita on tomato and banana with rhizobacteria, actinomycetes, and Pasteuria penetrans . Nematropica 30:231-240. Glasshouse experiments were conducted to determine the efficacy of plant growth-promoting rhizobacteria, ( Bacillus cereus, B. subtilis, B. sphaericus, Agrobacterium radiobacter, Pseudomonas fluorescens, P. chlororaphis and Burkholderia cepacia ), uncharacterized actinomycetes (strains 29 and 45), and the nematode-parasitic bacterium Pasteuria penetrans (isolate 100) against Meloidogyne incognita race 1 on tomato and banana. All bacteria and actinomycetes enhanced the growth of both crops, and suppressed root-gall development on tomato as compared to control plants. Root-gall indices on tomato inoculated with M. incognita and bacteria ranged from 25 to 31% versus 94% for the nematode control. The bacteria also limited reproduction of M. incognita on bo
Keith G. Davies - One of the best experts on this subject based on the ideXlab platform.
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Exploring the endospore coat of Pasteuria penetrans, the bacterial hyperparasite of plant-parasitic nematodes, using Bacillus spp.
2016Co-Authors: Arohi Srivastava, Tim H Mauchline, Keith G. DaviesAbstract:Arohi Srivastava, Tim H. Mauchline, Keith Davies, ‘Exploring the endospore coat of Pasteuria penetrans, the bacterial hyperparasite of plant-parasitic nematodes, using Bacillus spp.’, poster presented at the 7th European Spores Conference, Royal Holloway University of London, UK, 18-20 April, 2016.
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the 16s rrna gene of Pasteuria penetrans provides an early diagnostic of infection of root knot nematodes meloidogyne spp
Nematology, 2012Co-Authors: Keith G. Davies, Tim H Mauchline, Uma RaoAbstract:The molecular interactions between hosts and parasites is an active area of research, and the parasitism of root-knot nematodes, obligate parasites of plants, by the hyper-parasitic bacterium Pasteuria penetrans offers a model by which to investigate aspects of innate immunity. Using a pouch system we were able to demonstrate by PCR, infection of Meloidogyne incognita 4 days prior to any microscopic observations of parasitism. The pouch system, although not strictly axenic, offered a relatively clean, flexible approach with a greatly reduced number of contaminating microbial species than in any soil-based system, whereby the early stages of nematode infection could be manipulated and controlled.
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Exploiting Genomics to Understand the Interactions Between Root-Knot Nematodes and Pasteuria penetrans
Biological Control of Plant-Parasitic Nematodes:, 2011Co-Authors: Jenn E. Schaff, Charles H Opperman, Tim H Mauchline, Keith G. DaviesAbstract:Caenorhabditis elegans was the first multicellular organism to have its genome sequenced and has proved useful in the investigations of innate immunity, the generic science that underpins the biology of host-pathogen interactions. This chapter explores the sequencing of plant-parasitic nematodes and microbial genomes and shows how this knowledge can help in understanding the biology of the interaction between Meloidogyne spp. and the bacterial nematode parasite Pasteuria penetrans. Three examples examine how genomic information can help in developing new approaches to the problems associated with using Pasteuria as a biological control agent: initially one focuses on the transportome and how genomics might help to understand the fastidious nature of Pasteuria growth in the nematode; secondly, comparative genomics is used to explore the phosphorylation pathway important in initiating sporulation; and, thirdly, comparative genomics is exploited to understand endospore attachment to the nematode cuticle where, in comparisons with other animal parasitic Bacillus spp., collagen-like fibres have been implicated. Finally the chapter suggests that genomics paves the way for the development of designer control agents but such an approach would not be without its critics.
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Phylogenetic Analysis of Pasteuria penetrans by Use of Multiple
2005Co-Authors: Lauren E. Charles, Keith G. Davies, David Mck. Bird, Brian R. Kerry, Ignazio Carbone, Mark Burke, Charles H OppermanAbstract:Pasteuria penetrans is a gram-positive, endospore-forming eubacterium that apparently is a member of the Bacillus-Clostridium clade. It is an obligate parasite of root knot nematodes (Meloidogyne spp.) and preferentially grows on the developing ovaries, inhibiting reproduction. Root knot nematodes are devastating root pests of economically important crop plants and are difficult to control. Consequently, P. penetrans has long been recognized as a potential biocontrol agent for root knot nematodes, but the fastidious life cycle and the obligate nature of parasitism have inhibited progress on mass culture and deployment. We are currently sequencing the genome of the Pasteuria bacterium and have performed amino acid level analyses of 33 bacterial species (including P. penetrans) using concatenation of 40 housekeeping genes, with and without insertions/deletions (indels) removed, and using each gene individually. By application of maximum-likelihood, maximum-parsimony, and Bayesian methods to the resulting data sets, P. penetrans was found to cluster tightly, with a high level of confidence, in the Bacillus class of the gram-positive, low-GC-content eubacteria. Strikingly, our analyses identified P. penetrans as ancestral to Bacillus spp. Additionally, all analyses revealed that P. penetrans is surprisingly more closely related to the saprophytic extremophile Bacillus haladurans and Bacillus subtilis than to the pathogenic species Bacillus anthracis and Bacillus cereus. Collectively, these findings strongly imply that P. penetrans is an ancient member of the Bacillus group. We suggest that P. penetrans may have evolved from an ancient symbiotic bacterial associate of nematodes, possibly as the root knot nematode evolved to be a highly specialized parasite of plants. Pasteuria penetrans is an endospore-forming, gram-positive, obligate parasitic bacterium of the root knot nematodes (RKN), Meloidogyne spp. RKN have a very broad host range, which includes more than 2,000 plant species, and most cultivated crops are attacked by at least one species of Meloidogyne (33); this causes economic losses of more than $50 billion per year. The problem in the subtropics and tropics is particularly severe, and many developing nations are seriously affected in terms of both food security and economics by RKN. Mature female RKN release hundreds of eggs into a proteinaceous matrix on the surface of the root. Following a first molt in the egg, a motile second-stage (J2) juvenile hatches in the soil and typically reinfects the same plant. The RKN J2 destructively penetrates the root, preferentially in the zone of elongation or at the site of lateral root emergence, and migrates intercellularly into the vascular cylinder, causing little or no injury. Once in the vascular cylinder, the nematode makes a commitment to establish a highly specialized feeding site, referred to as a giant cell. The relationship between an RKN and its host is both intimate and complex and involves dramatic changes both in the plant and in the nematode, leading to giant cell induction and gall formation. The Meloidogyne J2 stage is a nonfeeding, developmentally arrested, long-lived dispersal stage and can
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Pasteuria penetrans and P-nishizawae attachment to Meloidogyne chitwoodi, M-fallax and M-hapla
Nematology, 2004Co-Authors: Jane Wishart, Vivian C. Blok, Mark S. Phillips, Keith G. DaviesAbstract:This is the first report of endospores of Pasteuria penetrans and P. nishizawae isolates binding to juveniles of Meloidogyne chitwoodi and M. fallax. The patterns of endospore attachment to M. chitwoodi and M. fallax compared with the related M. hapla suggest that there are differences amongst these three temperate root-knot nematode species. Intraspecific variability in attachment of P. penetrans to juveniles of M. chitwoodi was demonstrated.
Thierry Mateille - One of the best experts on this subject based on the ideXlab platform.
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spatial distribution of the nematode biocontrol agent Pasteuria penetrans as influenced by its soil habitat
Soil Biology & Biochemistry, 2009Co-Authors: Thierry Mateille, S Fould, K R Dabire, Mamadou Thiam Diop, Saliou NdiayeAbstract:Root-knot nematodes belonging to the Meloidogyne genus are ubiquitous plant-parasitic pests, especially on vegetables. The Pasteuria penetrans bacterium is an obligate parasite of nematodes, parasitizing most of the Meloidogyne species. Spatial distributions of Meloidogyne javanica populations infested or not by P. penetrans and of bacterial populations were studied in a vegetable plot naturally infested by these organisms. It was observed that distributions of M. javanica populations, of populations infested by P. penetrans, and of free bacteria populations were not overlapped. Soil factors involved were investigated. Soil texture and water flow in porosity are concerned, as they directly influence the level of the pool of bacteria and then the chances of both organisms to meet. The soil solution has a direct effect on the attachment of the bacterium on the nematode cuticle.
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relationships between abiotic soil factors and epidemiology of the biocontrol bacterium Pasteuria penetrans in a root knot nematode meloidogyne javanica infested field
Biological Control, 2007Co-Authors: Roch K Dabire, S Ndiaye, D Mounport, Thierry MateilleAbstract:Abstract The epidemiology of Pasteuria penetrans, parasite of Meloidogyne javanica, was studied in a field cultivated with an African egg-plant (Solanum aethiopicum) in Senegal. Abiotic and biological parameters were analyzed from 100 soil samples. Soil physical characteristics were studied with principal component analysis (PCA). Similarity between the parameters according to biotic and abiotic variables was established by hierarchical classification and corroborated by Discrimin analysis (AFD). The coarser fractions (>200 μm) were positively correlated to intensive irrigation, whereas finest fractions (
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New developments in the estimation of spores of Pasteuria penetrans
Biology and Fertility of Soils, 2001Co-Authors: K R Dabire, Jean-luc Chotte, Joel Fardoux, Thierry MateilleAbstract:New developments in the estimation of free spores of Pasteuria penetrans , a hyperparasite of plant-parasitic nematodes, including Meloidogyne spp., have been tested in contrasted textured soils. They were dedicated to improving the recovery of spores. Different methods of increasing energy of aggregate dispersion were compared in their efficiency in recovering spores inoculated in a sandy clay soil and a clay soil. The dispersion of the soils by the less energetic method (method A) allowed only 50% and 20% of the spore inoculum to be recovered from the sandy clay soil and clay soil, respectively. For these soils, 76% and 81% of the particle-size fraction (0–20 µm) isolated by this method were still aggregated in coarser structures. With increasing energy (methods B and C), these coarse aggregates disappeared entirely in both soils. At the same time, the recovery of spores increased sharply, representing about 87% and 75% of the inoculum of the sandy clay soil and clay soil, respectively. Therefore, at most 25% of the pool of spores remained undetectable. The formation of artificial aggregates during the enumeration procedure could not be advocated to explain this result, since the dispersion of the fraction collected for the enumeration did not improve spore recovery.
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Immunological quantification of the nematode parasitic bacterium Pasteuria penetrans in soil
FEMS Microbiology Ecology, 2001Co-Authors: S Fould, Keith G. Davies, A.l. Dieng, Philippe Normand, Thierry MateilleAbstract:Currently, the abundance of Pasteuria penetrans in soils, an unculturable bacterial parasite of root-knot nematodes (Meloidogyne spp.), is estimated by the percentage of nematode juveniles infected with bacteria and the number of spores attached to their cuticle. Indirect immunofluorescence led to detection of free spores directly in soil suspensions using UV light and polyclonal antibodies raised against two P. penetrans populations (ORS-21414-Sen and PP1). Three extraction methods were compared in order to improve spore recovery. A gentle shaking/sieving method recovered more than 90% of the spores inoculated in soils and was more efficient and simple than aqueous two-phase partitioning and polyethylene glycol extractions. All the spores inoculated in sandy or sandy–clay soils were detected with immunofluorescence microscopy. The quantification of the spores was improved using an ELISA technique that showed a good correlation between optical density and spore concentration in inoculated soils. Specific antibodies provide a suitable method to quantify P. penetrans and may be used to follow the evolution of the real pool of bacteria either in native suppressive soils or in inoculated ones.
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beneficial effects of enterobacter cloacae and pseudomonas mendocina for biocontrol of meloidogyne incognita with the endospore forming bacterium Pasteuria penetrans
Nematology, 1999Co-Authors: M Amadou, Robin Duponnois, Thierry MateilleAbstract:Two rhizosphere bacteria, Enterobacter cloacae and Pseudomonas mendocina, were isolated from the rhizosphere of tomato plants growing in a soil heavily infested with both root-knot nematodes and the parasitoid endospore-forming bacterium Pasteuria penetrans. Bacteria E. cloacae and P. mendocina stimulated plant growth, inhibited the reproduction of the root knot nematode Meloidogyne incognita, and increased the attachment of the endospores of P. penetrans on the nematodes in vitro. E. cloacae significantly increased the reproduction of P. penetrans in plant roots. Consequently, the introduction of such bacteria in soils, or cultural practices aimed to increase the activity of native strains of these bacteria, could greatly contribute to the efficiency of nematode biocontrol with P. penetrans. Stimulation de l'activite antagoniste de Pasteuria penetrans envers Meloidogyne incognita par Enterobacter cloacae et Pseudomonas mendocina - Deux bacteries rhizospheriques, Enterobacter cloacae et Pseudomonas mendocina, ont ete isolees a partir de la rhizosphere de plants de tomate preleves dans un sol tres infeste par des nematodes a galles et l'actinomycete Pasteuria penetrans. Les deux souches bacteriennes ont stimule la croissance de la plante, inhibe le developpement du nematode Meloidogyne incognita et augmente in vitro l'attachement des spores de P. penetrans sur la cuticule des nematodes. E. cloacae a significativement stimule la multiplication de P. penetrans dans les racines. En consequence, l'utilisation de telles bacteries pourrait ameliorer de maniere importante l'efficacite de P. penetrans contre les nematodes du genre Meloidogyne.
Z X Chen - One of the best experts on this subject based on the ideXlab platform.
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Review of Pasteuria penetrans: Biology, Ecology, and Biological Control Potential
Journal of nematology, 1998Co-Authors: Z X Chen, D. W. DicksonAbstract:Pasteuria penetrans is a mycelial, endospore-forming, bacterial parasite that has shown great potential as a biological control agent of root-knot nematodes. Considerable progress has been made during the last 10 years in understanding its biology and importance as an agent capable of effectively suppressing root-knot nematodes in field soil. The objective of this review is to summarize the current knowledge of the biology, ecology, and biological control potential of P. penetrans and other Pasteuria members. Pasteuria spp. are distributed worldwide and have been reported from 323 nematode species belonging to 116 genera of free-living, predatory, plant-parasitic, and entomopathogenic nematodes. Artificial cultivation of P. penetrans has met with limited success; large-scale production of endospores depends on in vivo cultivation. Temperature affects endospore attachment, germination, pathogenesis, and completion of the life cycle in the nematode pseudocoelom. The biological control potential of Pasteuria spp. have been demonstrated on 20 crops; host nematodes include Belonolaimus longicaudatus, Heterodera spp., Meloidogyne spp., and Xiphinema diversicaudatum. Pasteuria penetrans plays an important role in some suppressive soils. The efficacy of the bacterium as a biological control agent has been examined. Approximately 100,000 endospores/g of soil provided immediate control of the peanut root-knot nematode, whereas 1,000 and 5,000 endospores/g of soil each amplified in the host nematode and became suppressive after 3 years.
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Estimating Incidence of Attachment of Pasteuria penetrans Endospores to Meloidogyne spp. with Tally Thresholds.
Journal of Nematology, 1997Co-Authors: Z X Chen, D. W. DicksonAbstract:Pasteuria penetrans has .been identified as an important biological control agent of root-knot nematodes. In this study the use of tally thresholds was evaluated for estimating P. penetrans endospore attachment to second-stage juveniles (J2) of Meloidogyne spp. A tally threshold (T) is defined as the maximum number of individuals in a sample unit that may be treated as absent based on binomial sampling. Three different data sets that originated from centrifugal bioassay, incubation bioassay, and field experiments were investigated. The data sets each contained 70, 33, and 111 estimates of the mean number of endospores attached per J2 (m), respectively. Empirical relationships between m and proportions of J2 with =T endospores attached (P[subT]) were developed using parameters from the linear regression of ln(m) on P[subT] (0 P[subT] 1): ln(m) = a + b P[subT], T was set to 0, 1, 2, 3, 4, 5, 8, and 10 endospores/J2. The results indicated that the variances of linear equations tended to decrease with increasing Tvalues for all three data sets. T values of 0, 1, 8, and 10 endospores/J2 for centrifugal bioassay and incubation bioassay, and of 0, 1, 2, and 3 endospores/J2 for field experiments were associated with an r² of = 0.8. These T values were robust for estimating m from P[subT], reducing the variability as well as the time and effort spent in estimating the mean number of endospores attached per J2. Key words: bacterium, biological control, endospore, Meloidogyne spp., nematode, Pasteuria penetrans, root-knot nematode, sampling, tally threshold.
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Effect of Ammonium Nitrate and Time of Harvest on Mass Production of Pasteuria penetrans
Nematropica, 1997Co-Authors: Z X Chen, D. W. DicksonAbstract:Pasteuria penetrans, a biological control agent for root-knot nematodes, has great potential for development as a bionematicide. Previous studies have shown that high nitrogen levels affect the development of root-knot nematodes. The objectives of this study were to determine the effects of various levels of ammonium nitrate and of harvest time on development of P. penetrans. Five levels of ammonium nitrate (0.0, 0.2, 0.4, 0.8, 1.6 g/pot) and five different harvest times (37, 44, 51, 58, 65 days after inoculation) were tested separately with six replicates each for both experiments. Ammonium nitrate adversely affected the development of both M. arenaria race 1 and P. penetrans. A quadratic relationship was established between the number of females per root system and the nitrogen levels. Number of endospores per root system and number of endospores per female were negatively correlated with the nitrogen levels and decreased 1.1 million and 0.013 million, respectively, per 0.1 g ammon
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Minimal Growth Temperature of Pasteuria penetrans.
Journal of nematology, 1997Co-Authors: Z X Chen, D. W. DicksonAbstract:Pasteuria penetrans is an obligate, mycelial, and endospore-forming bacterial parasite of Meloidogyne spp. with promise for the management of root-knot nematodes. Our objective was to use regression analysis of developmental time (days) to various temperatures to determine the minimal temperature for growth and development of P. penetrans in Meloidogyne spp. The data set for regression originated from a previously published report. The data fit well to hyperbolic equations. For various developmental stages of P. penetrans, the minimal growth temperature ranged from 16.7 degrees C to 17.8 degrees C and averaged 17.2 degrees C.
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Ultrastructure, Morphology, and Sporogenesis of Pasteuria penetrans.
Phytopathology, 1997Co-Authors: Z X Chen, D. W. Dickson, L. G. Freitas, James F. PrestonAbstract:ABSTRACT Pasteuria penetrans is a bacterial parasite of root-knot nematodes that shows great potential as a biocontrol agent. Scanning and transmission electron microscopy were used to study the ultrastructure, morphology, and sporogenesis of four isolates of P. penetrans. The effects of different Meloidogyne spp. and tobacco cultivars on sporangium size and morphology of endospores attached to the cuticle of second-stage juveniles (J2) of root-knot nematodes also were investigated. The P. penetrans isolates and their origins were P-20 from M. arenaria race 1 in Levy County, FL; P-100 from Meloidogyne sp. in Pasco County, FL; B-4 from Pratylenchus scribneri in Seminole County, FL; and P-120 from Meloidogyne spp. in Alachua County, FL. Sporangia of the four isolates were identical morphologically and similar in their dimensions, ranging from 2.39 to 3.42 μm in diameter and from 1.38 to 2.38 μm in height. Different Meloidogyne spp. and tobacco cultivars had no effect on sporangium size. Endospores attached ...
T. E. Hewlett - One of the best experts on this subject based on the ideXlab platform.
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comparison of inoculation methods meloidogyne spp and different host plants for production of Pasteuria penetrans
Journal of Asia-pacific Entomology, 2005Co-Authors: D. W. Dickson, T. E. HewlettAbstract:Pasteuria penetrans is an effective biological control agent of root-knot nematode, but its practical use is limited by the lack of efficient methods for mass production of the endospores. Root-gall formation by Meloidogyne arenaria and/or M. javanica juveniles (J2s) attached with P. penetrans endospores was compared in plants receiving single vs. split inoculations and in different susceptible host plants. Number of endospores produced by M arenaria was compared among different host plants. Of six host plants tested, M. javanica produced the greatest number of galls on cucumber and M. arenaria produced the greatest number of galls on okra and tomato (P
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Microwave treatment of Pasteuria penetrans parasite preparation for selective elimination of undesired microorganisms
2004Co-Authors: R. K. Walia, T. E. Hewlett, D. W. DicksonAbstract:A Pasteuria penetrans spore laden parasite preparation, raised from peanut pod hulls in a field naturally infested with the bacterium and Meloidogyne arena ria (race 1), was exposed to microwave (MW) radiation to eliminate undesired microorganisms. MW radiation was given at medium, medium high or high levels for 1 or 2 min. Treatment of the parasite preparation at high radiation level for 2 min completely eliminated the undesirable fungal propagules, without significantly impeding the viability of P. penetrans endospores.
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Phylogenetic Analysis of Pasteuria penetrans by 16S rRNA Gene Cloning and Sequencing
Journal of nematology, 1999Co-Authors: Joseph M. Anderson, D. W. Dickson, T. E. Hewlett, James F. Preston, N. H. Williams, James E. MaruniakAbstract:Pasteuria penetrans is an endospore-forming bacterial parasite of Meloidogyne spp. This organism is among the most promising agents for the biological control of root-knot nematodes. In order to establish the phylogenetic position of this species relative to other endospore-forming bacteria, the 16S ribosomal genes from two isolates of P. penetrans, P-20, which preferentially infects M. arenaria race 1, and P-100, which preferentially infects M. incognita and M. javanica, were PCR-amplified from a purified endospore extraction. Universal primers for the 16S rRNA gene were used to amplify DNA which was cloned, and a nucleotide sequence was obtained for 92% of the gene (1,390 base pairs) encoding the 16S rDNA from each isolate. Comparison of both isolates showed identical sequences that were compared to 16S rDNA sequences of 30 other endospore-forming bacteria obtained from GenBank. Parsimony analyses indicated that P. penetrans is a species within a clade that includes Alicyclobacillus acidocaldarius, A. cycloheptanicus, Sulfobacillus sp., Bacillus tusciae, B. schlegelii, and P. ramosa. Its closest neighbor is P. ramosa, a parasite of Daphnia spp. (water fleas). This study provided a genomic basis for the relationship of species assigned to the genus Pasteuria, and for comparison of species that are parasites of different phytopathogenic nematodes.
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Suppression Mechanisms of Meloidogyne arenaria Race 1 by Pasteuria penetrans.
Journal of nematology, 1997Co-Authors: Z X Chen, R. Mcsorley, D. W. Dickson, D J Mitchell, T. E. HewlettAbstract:The biological control of Meloidogyne arenaria on peanut (Arachis hypogaea) by Pasteuria penetrans was evaluated using a six x six factorial experiment in field microplots over 2 years. The main factors were six inoculum levels of second-stage juveniles (J2) of M. arenaria race 1 (0, 40, 200, 1,000, 5,000, and 25,000 J2/microplot, except that the highest level was 20,000 J2/microplot in 1995) and six infestation levels of P. penetrans as percentages of J2 with endospores attached (0, 20, 40, 60, 80, and 100%). The results were similar in 1994 and 1995. Numbers of eggs per root system, J2 per 100 cm³ soil at harvest, root galls, and pod galls increased with increasing nematode inoculum levels and decreased with increasing P. penetrans infestation levels (P = 0.05), except that there was no effect of P. penetrans infestation levels on J2 per 100 cm³ soil in 1994 (P 0.05). There were no statistical interaction effects between the inoculum levels of J2 and the infestation levels of P. penetrans (P 0.05). When the infestation level was increased by 10%, the number of eggs per root system, root galls, and pod galls decreased 7.8% to 9.4%, 7.0% to 8.5%, and 8.0% to 8.7% in 1994 and 1995, respectively, whereas J2 per 100 cm³ soil decreased 8.8% in 1995 (P = 0.05). The initial infestation level of P. penetrans contributed 81% to 95% of the total suppression of pod galls, whereas the infection of J2 of the subsequent generations contributed only 5% to 19% suppression of pod galls. The major suppressive mechanism of M. arenaria race 1 by P. penetrans on peanut is the initial endospore infestation of J2 at planting. Key words: Arachis hypogaea, bacterium, biological control, endospore, Meloidogyne arenaria, Pasteuria penetrans, peanut, root-knot nematode.
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suppression of meloidogyne arenaria race 1 by soil application of endospores of Pasteuria penetrans
Journal of Nematology, 1996Co-Authors: Z X Chen, R. Mcsorley, D. W. Dickson, D J Mitchell, T. E. HewlettAbstract:The potential of Pasteuria penetrans for suppressing Meloidogyne arenaria race 1 on peanut (Arachis hypogaea) was tested over a 2-year period in a field microplot experiment. Endospores of P. penetrans were mass-produced on M. arenaria race 1 infecting tomato plants. Endospores were inoculated in the first year only at rates of 0, 1,000, 3,000, 10,000, and 100,000 endospores/g of soil, respectively, into the top 20 cm of microplots that were previously infested with M. arenaria race 1. One peanut seedling was planted in each microplot. In the first year, root gall indices and pod galls per microplot were significantly reduced by 60% and 95% for 100,000 endospores/g of soil, and 20% and 65% for 10,000 endospores/g of soil, respectively. Final densities of second-stage juveniles (J2) in soil were not significantly different among the treatments. The number of endospores attached to J2 and percentage of J2 with attached endospores significantly increased with increasing endospore inoculation levels. Pasteuria penetrans significantly reduced the densities of J2 that overwintered. In the second year, root and pod gall indices, respectively, were significantly reduced by 81% and 90% for 100,000 endospores/g of soil, and by 61% and 82% of 10,000 endospores/g of soil. Pod yields were significantly increased by 94% for 100,000 and by 57% for 10,000 endospores/g of soil, respectively. The effect of P. penetrans on final densities of J2 in soil was not significant. Regression analyses verified the role of P. penetrans in the suppression of M. arenaria. The minimum number of endospores required for significantly suppressing M. arenaria race 1 on peanut was 10,000 endospores/g of soil.