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Florian M W Grundler - One of the best experts on this subject based on the ideXlab platform.

  • The Plant Sesquiterpene Nootkatone Efficiently Reduces Heterodera schachtii Parasitism by Activating Plant Defense.
    International journal of molecular sciences, 2020
    Co-Authors: Samer S. Habash, Florian M W Grundler, Philipp P. Könen, Anita Loeschcke, Matthias Wüst, Karl-erich Jaeger, Thomas Drepper, A. Sylvia S. Schleker
    Abstract:

    Plant parasitic nematodes, including the beet cyst nematode Heterodera schachtii, constitute a devastating problem for crops worldwide. The limited availability of sustainable management options illustrates the need for new eco-friendly control means. Plant metabolites represent an invaluable source of active compounds for the discovery of such novel antagonistic agents. Here, we evaluated the impact of eight plant terpenoids on the H. schachtii parasitism of Arabidopsis thaliana. None of the metabolites affected the plant development (5 or 10 ppm). Nootkatone decreased the number of adult nematodes on A. thaliana to 50%, with the female nematodes being smaller compared to the control. In contrast, three other terpenoids increased the parasitism and/or female size. We discovered that nootkatone considerably decreased the number of nematodes that penetrated A. thaliana roots, but neither affected the nematode viability or attraction to plant roots, nor triggered the production of plant reactive oxygen species or changed the plant's sesquiterpene profile. However, we demonstrated that nootkatone led to a significant upregulation of defense-related genes involved in salicylic and jasmonic acid pathways. Our results indicate that nootkatone is a promising candidate to be developed into a novel plant protection agent acting as a stimulator of plant immunity against parasitic nematodes.

  • Heterodera schachtii glutathione peroxidase hsgpx is a parasitism protein
    Journal of Plant Diseases and Protection, 2020
    Co-Authors: Florian M W Grundler, Samer S. Habash, Isao Aharen, Cynthia Gleason, Masaki Inada, Abdelnaser Elashry
    Abstract:

    The beet cyst nematode (Heterodera schachtii) is a specialized obligate biotroph that is considered a major threat to sugar beet production. After infection, H. schachtii induce massive physiological and molecular changes to plant cells and create sophisticated syncytial feeding sites. Nematode secretions called effectors govern all of these changes. Here, we identify one of these effectors, H. schachtii glutathione peroxidase (HsGPx), and provide evidence that HsGPx is involved in parasitism. In situ hybridization showed that HsGPx is specifically localized within esophageal glands of pre-parasitic second-stage juveniles (J2). We also showed that HsGPx is upregulated in the post-parasitic stages. Knocking down HsGPx in nematodes by host-induced gene silencing hampers nematode development and leads to smaller nematode size and smaller associated feeding sites in Arabidopsis. Therefore, HsGPx plays an important role in the interaction between the nematode and plant.

  • arabidopsis hipp27 is a host susceptibility gene for the beet cyst nematode Heterodera schachtii
    Molecular Plant Pathology, 2018
    Co-Authors: Zoran S. Radakovic, Elizabeth Escobar, Divykriti Chopra, Ana Claudia Silva, Miroslaw Sobczak, Muhammad Shahzad Anjam, Florian M W Grundler, Carolina Escobar, Javier Cabrera, Shahid Siddique
    Abstract:

    : Sedentary plant-parasitic cyst nematodes are obligate biotrophs that infect the roots of their host plant. Their parasitism is based on the modification of root cells to form a hypermetabolic syncytium from which the nematodes draw their nutrients. The aim of this study was to identify nematode susceptibility genes in Arabidopsis thaliana and to characterize their roles in supporting the parasitism of Heterodera schachtii. By selecting genes that were most strongly upregulated in response to cyst nematode infection, we identified HIPP27 (HEAVY METAL-ASSOCIATED ISOPRENYLATED PLANT PROTEIN 27) as a host susceptibility factor required for beet cyst nematode infection and development. Detailed expression analysis revealed that HIPP27 is a cytoplasmic protein and that HIPP27 is strongly expressed in leaves, young roots and nematode-induced syncytia. Loss-of-function Arabidopsis hipp27 mutants exhibited severely reduced susceptibility to H. schachtii and abnormal starch accumulation in syncytial and peridermal plastids. Our results suggest that HIPP27 is a susceptibility gene in Arabidopsis whose loss of function reduces plant susceptibility to cyst nematode infection without increasing the susceptibility to other pathogens or negatively affecting the plant phenotype.

  • effects of exogenous amino acid applications on the plant parasitic nematode Heterodera schachtii
    Nematology, 2018
    Co-Authors: Roman Christopher Blumel, Daniel F Fischer, Florian M W Grundler
    Abstract:

    Amino acid (AA) applications have been reported to affect plant-parasitic nematodes. Here, we analysed the effects of methionine (Met), lysine (Lys), threonine (Thr), isoleucine (Ile), homoserine (Hom) and tryptophan (Trp) on the sedentary plant-parasitic nematode, Heterodera schachtii , under in vitro conditions. No AA showed direct effects on the activity of infective second-stage juveniles (J2) of H. schachtii . Soaking J2 in Lys for 24 h increased the number of developing females and reduced the number of males. Thr treatments reduced the total number of nematodes developing in the host plant. The strongest effects were observed when AA were added to the nutrient medium in a monoxenic Arabidopsis thaliana culture. Ile, Met or Thr clearly reduced the number of female nematodes developing in the host plant. These AA are direct metabolic derivatives of Hom. Direct effects on pre-infective J2 can be differentiated from effects that may involve the host plant.

  • arabidopsis hipp27 is a host susceptibility gene for the beet cyst nematode Heterodera schachtii
    bioRxiv, 2017
    Co-Authors: Zoran S. Radakovic, Elizabeth Escobar, Divykriti Chopra, Ana Claudia Silva, Miroslaw Sobczak, Muhammad Shahzad Anjam, Florian M W Grundler, Carolina Escobar, Javier Cabrera, Shahid Siddique
    Abstract:

    Sedentary plant-parasitic cyst nematodes are obligate biotrophs that infect the roots of their host plant. Their parasitism is based on modification of infected root cells to form a hypermetabolic syncytium from which the nematodes draw their nutrients. The aim of this study was to identify nematode susceptibility genes in Arabidopsis thaliana and to characterize their roles in supporting the parasitism of Heterodera schachtii. By selecting genes that were most strongly upregulated in response to cyst nematode infection, we identified HIPP27 (HEAVY METAL-ASSOCIATED ISOPRENYLATED PLANT PROTEIN 27) as a host susceptibility factor required for beet cyst nematode infection and development. Detailed expression analysis revealed that HIPP27 is a cytoplasmic protein and that HIPP27 is strongly expressed in leaves, young roots and nematode-induced syncytia. Loss-of-function Arabidopsis hipp27 mutants exhibited severely reduced susceptibility to Heterodera schachtii and abnormal starch accumulation in syncytial and peridermal plastids. Our results suggest that HIPP27 is a susceptibility gene in Arabidopsis whose loss-of-function reduces plant susceptibility to cyst nematode infection without increasing susceptibility to other pathogens or negatively affecting plant phenotype.

G Gheysen - One of the best experts on this subject based on the ideXlab platform.

  • Detection of putative secreted proteins in the plant-parasitic nematode Heterodera schachtii
    Parasitology Research, 2006
    Co-Authors: Bartel Vanholme, Makedonka Mitreva, Wim Criekinge, Marc Logghe, David Bird, James P. Mccarter, G Gheysen
    Abstract:

    The beet cyst nematode Heterodera schachtii is an important pathogen worldwide, but its molecular characterization has been limited to studying individual genes of interest. We undertook a high-throughput genomic approach and drastically increased the number of available sequences for this parasite. A total of 2,662 expressed sequence tags were grouped into 1,212 clusters representing a nonredundant catalog of H. schachtii genes. Implementing a bioinformatic workflow, we identified 50 sequences coding for candidate secreted proteins. All of these contain a putative signal peptide required for entry into the secretory pathway and lack any transmembrane domain. Included are previously postulated cell-wall-degrading enzymes and other parasitism-related genes. Moreover, we provide the first report of an arabinogalactan endo-1,4-β-galactosidase enzyme (EC 3.2.1.89) in animals. As sequence data increase at a rapid rate, developing high-throughput genomic screening is a necessity. The in silico approach described here is an effective way to identify putative secreted proteins and prioritize candidates for further studies.

  • production of auxin and related compounds by the plant parasitic nematodes Heterodera schachtii and meloidogyne incognita
    Communications in agricultural and applied biological sciences, 2005
    Co-Authors: De Meutter J, Tom Tytgat, G Gheysen, Els Prinsen, Van Onckelen H
    Abstract:

    Mass spectrometric analysis revealed the presence of auxin, mainly in conjugated form, in secretions of Heterodera schachtii and Meloidogyne incognita, with or without treatment with DMT or resorcinol. M. incognita showed the highest production rates, though treatment of M. incognita with resorcinol had a negative effect on auxin production. Analysis of auxin precursor molecules in lysates of H. schachtii, M. incognita and Caenorhabditis elegans suggested that auxin is most probably a degradation product of tryptophan and that auxin may be synthesized via several intermediates, including indole-3-acetamide which is an intermediate of a pathway so far only characterized in bacteria. Furthermore, high levels of anthranilate, a degradation product of tryptophan in animals, but possibly also a precursor for auxin were detected.

  • identification of cytokinins produced by the plant parasitic nematodes Heterodera schachtii and meloidogyne incognita
    Molecular Plant Pathology, 2003
    Co-Authors: Jan De Meutter, Tom Tytgat, G Gheysen, Erwin Witters, G Gheysen, Henri Van Onckelen
    Abstract:

    SUMMARY The presence of different types of cytokinins was analysed in exudates and lysates of stage-2 juveniles of Heterodera schachtii and Meloidogyne incognita and in mixed stages of Caenorhabditis elegans. For all species, cytokinins were detected in lysates and exudates in which benzyladenine and zeatin-type cytokinins were the most prominent forms. The production of cytokinins by Meloidogyne was much higher than by Heterodera, and the detected levels were in a range which interfered with the physiological activities of the host plant. The presence of 5-methoxy-N,N-dimethyltryptamine hydrogen oxalate did not affect hormone production by H. schachtii, whereas resorcinol slightly stimulated hormone production by M. incognita. The exuded cytokinins may play a role in feeding site induction, more particularly in cell cycle activation and in establishing the feeding site as a nutrient sink.

  • an improved method for whole mount in situ hybridization of Heterodera schachtii juveniles
    Parasitology Research, 2002
    Co-Authors: Bartel Vanholme, Jan De Meutter, Tom Tytgat, G Gheysen, Isabelle Vanhoutte
    Abstract:

    An optimized protocol is presented to visualize gene expression in the sedentary beet cyst nematode, Heterodera schachtii, by whole-mount in situ hybridization. Two different probes were used for genes with known expression pattern in other nematodes. Vacuum infiltration of the fixative significantly increased its efficiency and resulted in a nicely preserved morphology. Additional modifications were introduced to simplify and standardize the process.

  • development and pharyngeal gland activities of Heterodera schachtii infecting arabidopsis thaliana roots
    Nematology, 2002
    Co-Authors: Tom Tytgat, Bartel Vanholme, Jan De Meutter, G Gheysen, Myriam Claeys, Liesbeth Verreijdt, August Coomans
    Abstract:

    As plant-nematode research continues to use the model host plant Arabidopsis thaliana more and more, we made a detailed life cycle study of Heterodera schachtii on this host, and investigated pharyngeal gland activities at the most crucial steps during the establishment of the parasitic interaction. In our experimental set up, in most cases induction of syncytia occurred during day 2, and the second moult during day 6. In pre-parasitic juveniles, both subventral glands contained numerous secretory granules, which gradually disappeared during intracellular migration of the juvenile through the roots. At the same time, both glands decreased in size and, after induction of the feeding cell, new kinds of secretory granules could be observed in the cytoplasm. During migration and induction of the feeding cell, the dorsal pharyngeal gland continuously increased in size. Secretory granules were already present in the dorsal gland of pre-parasitic juveniles, and a continuous synthesis of these granules was observed thereafter. Once the syncytium was induced, however, different types of secretory granules were formed.

Müller J. - One of the best experts on this subject based on the ideXlab platform.

  • Grünbrache mit resistentem Ölrettich zur Bekämpfung des Rübennematoden (Heterodera schachtii)
    Nachrichtenblatt des Deutschen Pflanzenschutzdienstes, 2018
    Co-Authors: Müller J.
    Abstract:

    Ölrettich- und Senfsorten mit Resistenz gegen Rübennematoden (Heterodera schachtii) wurden bisher auschließlicb als Zwischenfrüchte mit Saat nach Wintergetreide angebaut, und Anforderungen an ihre Resistenz sind auf diesen Einsatz - festgelegt. In einem dreijährigen Freilandversuch wurde geprüft, wie die Resistenz bei ganzjähriger Kultur unter den Bedingungen der Grünbrache zu bewerten ist. Dabei zeigte sich, daß bei einer geringen anfänglichen Populationsdichte von nur 250 Eiern und Larven pro 100 g Boden unter der resistenten Ölrettichsorte 'Nemex' noch ein Populationsabbau eintrat. Die wirtsspezifische Verseuchungsdichte lag unterhalb von 50 Eiern und Larven pro 100 g Boden, während sie bei der anfälligen Sorte 'Siletina' mehr als 2000 erreichte. In Zuckerrüben/Getreide-Fruchtfolgen, in denen es Probleme mit Rübennematoden gibt, kann in einem Grünbrachejahr mit resistentem Ölrettich eine effektive Bekämpfung von Heterodera schachtii erreicht werden. „Grünbrache" with resistant oil radish for the control of sugarbeet nematode (Heterodera schachtii)Until now oil radish and mustard vaneties resistant to sugarbeet nematode (Heterodera schachtii) were only grown as green manure crops sown after winter cereals, and requirements to resistance are related to this purpose. In a three years field trial we testea resistance under conditions of all the year round „Grünbrache". lt was shown that even at a low initial population density of only 250 eggs per 100 g of soil a population decrease was obtained with the resistant oil radish variety 'Nemex'. An equilibrium density of less than 50 eggs per 100 g of soil was found, whereas it was above 2000 with the susceptible variety 'Siletina'. In sugarbeet/cereal-rotations with nematode problems, a year with resistant oil radish as „Grünbrache" can give effective control of Heterodera schachtii

  • Ein verbessertes Extraktionsverfahren für Heterodera schachtii
    Nachrichtenblatt des Deutschen Pflanzenschutzdienstes, 2018
    Co-Authors: Müller J.
    Abstract:

    Zysten von Heterodera schachtii können aus Boden mit Hilfe verschiedener Verfahren extrahiert werden, von denen das Schlämmverfahren nach F'ENWICK in Europa die größte Verbreitung gefunden hat. Es erlaubt keine vollständige Trennung von Zysten und Boden, was ein Aussuchen der Zysten per Hand erforderlich macht. Dieser Arbeitsgang ist zeitraubend und kann zu Fehlern führen. - Die hier beschriebene Methode kombiniert einen Siebgang mit anschließender Zentrifugation in einer Zuckerlösung. Die Zysten können dabei soweit von Bodenpartikeln getrennt werden, daß sie sich anschließend direkt in einem Zystenzertrümmerer weiter verarbeiten lassen. Die Verseuchung ,wird als Zahl der Eier und Larven pro Bodeneinheit angegeben, auf die nur bedingt aussagekräftige Zystenzahl wird verzichtet. Im Vergleich zu den Schlämmverfahren nach FENWICK oder SEINHORST erzielte die Methode gleich gute oder bessere Ergebnisse, wobei das manuelle Aussuchen der Zysten nicht erforderlich ist. An improved method for the extraction of Heterodera schachtii For the extraction of Heterodera schachtii cysts from soil several methods are used, among which the FENWICK-can is most widely applied in Europe. lt does not separate cysts and soil completely, the cysts must be picked out by hand from remaining soil particles. This is time-consuming and may involve errors. - The described new method combines sieving and the centrifugal-flotation technique. lt allows the extraction of cysts almost free from soil particles. The cysts can then be homogenized in a cyst-squashing device. The infestation level is determined by the number of eggs and larvae per soil unit. Cyst counts are omitted as they give little information. The efficiency of the method is superior to the FENWICK- or SEINHORST-can for the extraction of old cysts. Handpicking of cysts is not necessary

  • Über die jährliche Generationszahl von Heterodera schachtii unter Feldbedingungen an Zuckerrüben
    Nachrichtenblatt des Deutschen Pflanzenschutzdienstes, 2018
    Co-Authors: Müller J.
    Abstract:

    In den Jahren 1977 und 1978 wurde unter Feldbedingungen untersucht, wieviele Entwicklungszyklen Heterodera schachtii in einer Vegetationsperiode an Zuckerrüben durchlaufen kann. Eine annähernd synchrone Entwicklung wurde durch Infektion der Rüben mit ausschließlich dem zweiten Larvenstadium des Nematoden erreicht. Der weitere Versuchsablauf ermöglichte eine sichere Trennung der einzelnen Generationen. In beiden Versuchsjahren konnte H. schachtii drei Entwicklungszyklen abschließen. Wegen der schnellen Generationsfolge dürfte H. schachtii mit chemischen Mitteln schwieriger zu bekämpfen sein als andere zystenbildende Arten, deren Entwicklung einer Diapause unterworfen ist. On the number of generations of Heterodera schachtii produced in a year under field conditions on sugar beet In 1977 and 1978 the number of generations of Heterodera schachtii produced in one season was investigated using sugar beet grown under field conditions. An almost synchronous development was achieved by infesting sugar beet only with second stage larvae of the nematode. During the experiment if was possible to separate the consecutive generations exactly. In both years H. schachtii completed its life-cycle three times. Therefore, controlling sugar beet cyst nematode populations by chemicals is less effective than it is in other cyst forming species, which - due to a diapause - produce only one generation in a year

  • Untersuchungen zur Verschleppung von Rübennematoden (Heterodera schachtii) mit Zuckerrübensaatgut
    Nachrichtenblatt des Deutschen Pflanzenschutzdienstes, 2018
    Co-Authors: Müller J.
    Abstract:

    Für Länder, in denen Heterodera schachtii bisher nicht nachgewiesen wurde, spielt die Frage der Verschleppung mit Saatgut eine besondere Rolle. Es wurde deshalb untersucht, ob eine Kontamination von Zuckerrübensaatgut vorkommt, und welche Gegenmaßnahmen gegebenenfalls getroffen werden können. Methodische Untersuchungen zeigten, daß ein schwacher Nematodenbesatz nur bei Berücksichtigung einer großen Saatgutmenge nachweisbar ist. Als am besten geeignet erwies sich ein kombiniertes Sieb-Zentrifugier-Verfahren. Damit war es möglich, H. schachtii in einer maschinell geernteten, ungereinigten Saatgutpartie nachzuweisen. Mit Hilfe der für die Saatgutaufbereitung üblichen Reinigungsverfahren läßt sich die Kontamination mit Rübennematoden um über 80 % verringern. Durch anschließendes Polieren der Samen körner, welches im allgemeinen der Pillierung vorangeht, wird das Restrisiko unter Praxisbedingungen bedeutungslos. Zusätzliche Sicherheit bietet eine Heißwasserbehandlung des Saatgutes für 20 min bei 57 °C, die in Kombination mit der mechanischen Reinigung auch extrem hohen Anforderungen gerecht wird.Investigatlons on the dissemination of sugar beet nematode (Heterodera schachtii) with sugar beet seedDissemination of Heterodera schachtii with seed is most important for countries not yet infested with this nematode. Therefore, we investigated if spread with sugar beet seed can occur and how it can be prevented. Detection of slight contaminations is only possible with appropriate methods and from high quantities of seed. A combined sieving-centrifugation method proved to be most suitable. Using this procedure, it was possible to detect H. schachtii in a mechanically harvested, but not yet cleaned seed Jot. More than 80 % of nematode contamination can be removed by standard industrial cleaning methods. The following rubbing and grading, which usually precedes pelleting, can eliminate any further risk. Additional security is achieved with a hot water treatment for 20 min at 57 °C, which will fulfil even extremely high requirements

  • Der Einfluß resistenter ölrettichlinien auf die Abundanzdynamik von Heterodera schachtii Schmidt
    Nachrichtenblatt des Deutschen Pflanzenschutzdienstes, 2018
    Co-Authors: Steudel W., Müller J.
    Abstract:

    In Topfversuchen in Klimakammern, im Gewächshaus und im Freiland sowie in mehreren Feldversuchen wurde der Einfluß resistenter Zuchtlinien des Ölrettichs (Raphanus sativus) auf die Schlüpfaktivität und die Abundanzdynamik von Heterodera schachtii untersucht. Die Populationsentwicklung wurde auf die Ausgangsverseuchung bezogen; Raps und anfälliger Ölrettich dienten als Vergleichspflanzen. Das Ausmaß der Resistenz der Ölrettichlinien hing von Versuchsdauer, Temperatur und Lichtverhältnissen ab. Zusätzlich wurden die Ergebnisse durch die Parasitierung der Nematodenpopulation mit Pilzen beeinflußt.Der größte Teil der Pflanzen war resistent, jedoch entwickelten sich insbesondere bei längerer Versuchsdauer an einzelnen Pflanzen zahlreiche neue Zysten. Diese genetische Inhomogenität kann unter extremen Bedingungen zu einer schwachen Vermehrung des Schädlings führen. In Feldversuchen, angelegt nach Wintergerste und Anfang November ausgewertet, nahm die Population von H. schachtii unter resistentem Ölrettich signifikant ab. The influence of resistant oil radish breeding lines on the population dynamics of Heterodera schachtii Schmidt Oil radish (Raphanus sativus) breeding lines were tested for resistance to Heterodera schachtii in pot experiments as weil as in field trials. Nematode multiplication was compared with that on rape and on susceptible varieties and related to the initial infestation level. Resistance varied with temperature, light, and duration of the experiment. Fungal parasitism in the nematode population influenced the results. The majority of the test plants proved to be resistant. Occasionally, however, on single plants numerous new cysts developed. Inhomogeneity of the seed resulted under certain conditions in a Pr : P; ratio > 1. Beet cyst nematode populations decreased significantly, when resistant oil radish lines were grown as green manure crops in field trials

J. O. Becker - One of the best experts on this subject based on the ideXlab platform.

  • effect of Heterodera schachtii female age on susceptibility to three fungal hyperparasites in the genus hyalorbilia
    Journal of Nematology, 2020
    Co-Authors: Smith J Becker, James Borneman, J. O. Becker
    Abstract:

    Three closely related nematophagous fungi in the genus Hyalorbilia were compared for their ability to parasitize females and eggs of Heterodera schachtii at different developmental stages. DoUCR50, StM, and ARF were originally isolated from Heterodera schachtii, Meloidogyne incognita, and Heterodera glycines, respectively. Phylogenetic analysis and pairwise sequence analysis showed that DoUCR50 and StM are more closely related to each other than they are to ARF. DoUCR50 parasitism suppressed 100% of the J2 hatch from 3-week-old H. schachtii females and 75% of the hatch from 4-week-old females. Eggs within 5-week-old females were resistant to parasitism, and hatch of J2 was unaffected by exposure to DoUCR50. StM and ARF did not reduce the hatch of J2 from H. schachtii females of any age. Eggs removed from females and spread onto water agar cultures of the fungi were mostly resistant to parasitism. DoUCR50 parasitized only 16% of such eggs from 3-week-old females. Extracellular hydrolytic enzyme production by the three fungal strains grown on PDA or parasitized H. schachtii females was evaluated using API ZYM (bioMerieux) test strips. All three fungi produced extracellular hydrolytic enzymes when grown on PDA or H. schachtii females. Trypsin-like protease activity was uniquely detected in DoUCR50 grown on PDA and H. schachtii females, with the highest activity associated with the fungus grown on parasitized females.

  • Impact of soil suppressiveness on various population densities of Heterodera schachtii
    Annals of Applied Biology, 2001
    Co-Authors: A Westphal, J. O. Becker
    Abstract:

    Summary Infectivity of second-stage juvenile (J2) populations of Heterodera schachtii was assayed with radish.The numbers of J2 in three-day-old seedlings were proportional to the numbers of J2 in two differently textured soils.In a microplot trial with a known H.schachtii-supprcssivc soil, half of the plots contained untreated suppressive soil, the other half contained the same soil, but methyl iodide-fumigated and therefore conducive.Both soils were infested with cysts introducing the equivalents of 0, 30, 60 or 120 H.schachtii eggs g-1 soil, kept moist for 2 months, and then planted to Swiss chard.The numbers of J2 in radish roots were proportional to the numbers of H.schachtii eggs introduced into the microplots, at a low level of detection in suppressive soil and at a high level in conducive soil.Growth of Swiss chard was not different at increasing infestation levels in suppressive soil, but growth was reduced in conducive soil proportionally to increasing nematode infestation level.

  • Transfer of Biological Soil Suppressiveness Against Heterodera schachtii.
    Phytopathology®, 2000
    Co-Authors: A Westphal, J. O. Becker
    Abstract:

    Heterodera schachtii-suppressive soil at a rate of either 1 or 10% (dry wt/wt) transferred suppressiveness against the beet cyst nematode to fumigated field plots when mixed into the upper 10-cm soil layer. Soil suppressiveness was established after 1 month of moist fallow and 77 days of Swiss chard cropping in the 10% transfer treatment and after 230 days in the 1% transfer treatment. The number of infective second-stage juveniles (J2) of H. schachtii, monitored initially at 150 degree-day intervals and later at 300 degree-day intervals, indicated the status of suppressiveness in the different treatments during the cropping period. In a greenhouse experiment, amending fumigated field soil with 0.1, 1.0, or 10% suppressive soil, suppressed multiplication of H. schachtii when soils were infested with an additional 5,000 J2. In a second greenhouse experiment, a fumigated sandy loam amended with 10 or 25% suppressive soil and a fumigated loam amended with 25% suppressive soil had significantly fewer eggs per cyst than the nonamended fumigated treatments when 1,000 J2 were added.

  • biological suppression and natural population decline of Heterodera schachtii in a california field
    Phytopathology, 1999
    Co-Authors: A Westphal, J. O. Becker
    Abstract:

    ABSTRACT Soil suppressiveness to Heterodera schachtii was demonstrated in a field at the research station of the University of California, Riverside. In two field trials planted to Swiss chard (Beta vulgaris), introduced H. schachtii multiplied 2.7 and 1.7 times more in preplant metam sodium-fumigated plots than in nontreated plots in 1994 and 1995, respectively. In greenhouse experiments, preplant treatments with metam sodium, methyl bromide, methyl iodide, formaldehyde, and aerated steam reduced suppressiveness of soil against H. schachtii to undetectable levels. H. schachtii multiplied significantly less in nontreated soil than in treated soil on Swiss chard. At harvest, the number of infective second-stage juveniles in suppressive soil was close to the lowest detection level, whereas high numbers were encountered in soils initially treated. In a crop rotation trial with host crops of H. schachtii, introduced H. schachtii populations were monitored for five cropping periods over 30 months in initially ...

  • evaluation of biocontrol activity of rhizobacteria from beta vulgaris against Heterodera schachtii
    Journal of Nematology, 1999
    Co-Authors: P W Neipp, J. O. Becker
    Abstract:

    One hundred fifty rhizobacteria isolated from roots of Swiss chard grown in a soil suppressive to the sugar beet cyst nematode, Heterodera schachtii, were tested for their influence on the nematode's ability to hatch and infect roots. Two screening systems were used that focused on the ability of bacteria to inhibit either nematode hatching or root infection. Most of the bacterial strains reduced hatching in vitro compared to the control, while with 5% of the strains there were 0% hatch. Seven percent of all strains significantly reduced second-stage juvenile (J2) infection of mustard roots raised in soil-less growth pouches. Eighteen strains from four genera (Bacillus, Pseudomonas, Variovorax, and Arthrobacter) were selected for greenhouse trials. In the greenhouse trials four bacterial strains, including two strains of Bacillus megaterium, reduced nematode infection of sugar beet when eggs were used as inoculum. Seven bacterial strains reduced nematode infection of sugar beet in one of two trials when plants were inoculated with J2. Most of the effective strains were Bacillus spp., primarily B. megaterium. Colonization of sugar beets roots by two B. megaterium strains was found to be stable over 30 days in the greenhouse.

A Westphal - One of the best experts on this subject based on the ideXlab platform.

  • Components of soil suppressiveness against Heterodera schachtii
    Soil Biology and Biochemistry, 2001
    Co-Authors: A Westphal, J. Ole Becker
    Abstract:

    Heterodera schachtii populations were introduced into nematode-suppressive and conducive field plots and were monitored for 2550 degree-days (DD). At 1200 DD, H. schachtii population densities significantly increased in conducive versus suppressive plots, up to 14-fold at termination of the trial. In greenhouse experiments with the same soil, H. schachtii female population densities were similar in suppressive and conducive soil in the first nematode generation, but remained low in the suppressive soil compared to significant increase in conducive soil in the second generation. At termination of the experiment, ca. one third of the cysts, but no females from suppressive soil were infested with fungi, whereas fungal-infested females and cysts were rarely found in conducive soil. The most common fungi isolated from infested cysts were Fusarium oxysporum, Fusarium sp. nov., and Dactylella oviparasitica. Paecilomyces lilacinus and some nonidentified fungi occurred less frequently. Suppressiveness was transferred at a rate of one cyst from suppressive soil amended to 110 g of H. schachtii-infested conducive soil. Heat treatment of suppressive soil for 30 min at 558C eliminated H. schachtii suppressiveness and reduced F. oxysporum populations to the detection level. q 2001 Elsevier Science Ltd. All rights reserved.

  • Impact of soil suppressiveness on various population densities of Heterodera schachtii
    Annals of Applied Biology, 2001
    Co-Authors: A Westphal, J. O. Becker
    Abstract:

    Summary Infectivity of second-stage juvenile (J2) populations of Heterodera schachtii was assayed with radish.The numbers of J2 in three-day-old seedlings were proportional to the numbers of J2 in two differently textured soils.In a microplot trial with a known H.schachtii-supprcssivc soil, half of the plots contained untreated suppressive soil, the other half contained the same soil, but methyl iodide-fumigated and therefore conducive.Both soils were infested with cysts introducing the equivalents of 0, 30, 60 or 120 H.schachtii eggs g-1 soil, kept moist for 2 months, and then planted to Swiss chard.The numbers of J2 in radish roots were proportional to the numbers of H.schachtii eggs introduced into the microplots, at a low level of detection in suppressive soil and at a high level in conducive soil.Growth of Swiss chard was not different at increasing infestation levels in suppressive soil, but growth was reduced in conducive soil proportionally to increasing nematode infestation level.

  • Transfer of Biological Soil Suppressiveness Against Heterodera schachtii.
    Phytopathology®, 2000
    Co-Authors: A Westphal, J. O. Becker
    Abstract:

    Heterodera schachtii-suppressive soil at a rate of either 1 or 10% (dry wt/wt) transferred suppressiveness against the beet cyst nematode to fumigated field plots when mixed into the upper 10-cm soil layer. Soil suppressiveness was established after 1 month of moist fallow and 77 days of Swiss chard cropping in the 10% transfer treatment and after 230 days in the 1% transfer treatment. The number of infective second-stage juveniles (J2) of H. schachtii, monitored initially at 150 degree-day intervals and later at 300 degree-day intervals, indicated the status of suppressiveness in the different treatments during the cropping period. In a greenhouse experiment, amending fumigated field soil with 0.1, 1.0, or 10% suppressive soil, suppressed multiplication of H. schachtii when soils were infested with an additional 5,000 J2. In a second greenhouse experiment, a fumigated sandy loam amended with 10 or 25% suppressive soil and a fumigated loam amended with 25% suppressive soil had significantly fewer eggs per cyst than the nonamended fumigated treatments when 1,000 J2 were added.

  • biological suppression and natural population decline of Heterodera schachtii in a california field
    Phytopathology, 1999
    Co-Authors: A Westphal, J. O. Becker
    Abstract:

    ABSTRACT Soil suppressiveness to Heterodera schachtii was demonstrated in a field at the research station of the University of California, Riverside. In two field trials planted to Swiss chard (Beta vulgaris), introduced H. schachtii multiplied 2.7 and 1.7 times more in preplant metam sodium-fumigated plots than in nontreated plots in 1994 and 1995, respectively. In greenhouse experiments, preplant treatments with metam sodium, methyl bromide, methyl iodide, formaldehyde, and aerated steam reduced suppressiveness of soil against H. schachtii to undetectable levels. H. schachtii multiplied significantly less in nontreated soil than in treated soil on Swiss chard. At harvest, the number of infective second-stage juveniles in suppressive soil was close to the lowest detection level, whereas high numbers were encountered in soils initially treated. In a crop rotation trial with host crops of H. schachtii, introduced H. schachtii populations were monitored for five cropping periods over 30 months in initially ...