Le Rheu, France
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Grenier E.,French National Institute for Agricultural Research | Fournet S.,French National Institute for Agricultural Research | Petit E.,French National Institute for Agricultural Research | Anthoine G.,Nematology Unit
Nematology | Year: 2010

The cyst nematode, Globodera pallida, is a major pest of potato, a plant native to South America. To investigate its phylogeography, an extensive sampling survey was conducted in 2002 in Peru and has laid the foundations of the ancient evolutionary history of this nematode species. We argue that the uplift of the Andes Mountains has triggered a variety of adaptive biotic radiations for Solanaceous plant-parasitic nematodes and has represented a key factor for the evolution and specialisation of Globodera species. We discuss the consequences of the wide genetic diversity observed in South American populations on the efficiency and durability of potato resistance and also the reliability of current molecular identification tools for quarantine purposes. Finally, we emphasise the need to get a more in-depth taxonomic characterisation of some of these nematode populations, and to conduct more extensive sampling in South America, especially south of Lake Titicaca, in order to understand fully potato cyst nematode evolution and their adaptation to their host plants. © 2010 Brill Academic Publishers.


Jansen-Girgan C.,North West University South Africa | Jansen-Girgan C.,Nematology Unit | Claassens S.,North West University South Africa | Fourie H.,North West University South Africa
Tropical Plant Pathology | Year: 2016

Eco-friendly control strategies, such as biological agents containing Bacillus firmus, are known to adversely impact the biology of Meloidogyne incognita and other nematode pests that damage agricultural crops. The efficacy of two isolated strains as well as one reference strain was evaluated for their effect on M. incognita second-stage juvenile (J2) motility. All three B. firmus strains successfully reduced J2 motility, with the reference strain being superior. Non-cultured cell-free products of the isolated strains inhibited J2 motility only between 3 and 7 % compared to the tap-water controls, respectively, and compared to up to 42 % by their cultured, cell-free water filtrate counterparts. The latter range was also recorded for the 100 % cultured, cell-free suspension concentration of the reference strain. The efficacy of cell suspensions of the two isolated strains were low (7-19 %) compared to the 100 % achieved by the reference strain. Although secondary compounds of the two isolated B. firmus strains may contribute towards disrupting the movement and host finding abilities of J2, they had no pronounced effects on J2 motility inhibition. © 2016, Sociedade Brasileira de Fitopatologia.


Oka Y.,Nematology Unit | Shuker S.,Nematology Unit | Tkachi N.,Nematology Unit
Pest Management Science | Year: 2016

BACKGROUND: Restrictions on soil fumigants are prompting the development of new compounds for controlling nematodes, other soilborne pathogens and weeds. We evaluated the nematicidal activity of five bromine compounds against Meloidogyne javanica in vitro, and tested the two most effective ones against Pratylenchus penetrans and Xiphinema index in vitro and in soil. RESULTS: Only allyl bromide and dibromo(nitro)methane showed nematicidal activity against M. javanica juveniles in vitro at <320mgL-1. Allyl bromide killed M. javanica and P. penetrans at 20mgL-1, and X. index at 10mgL-1, whereas 320mg dibromo(nitro)methane L-1 was required to kill P. penetrans. Allyl bromide also showed higher nematicidal activity than dibromo(nitro)methane against M. javanica and P. penetrans in soil. Allyl bromide at 40 and 20mgL-1 soil eliminated root galls and nematode eggs on tomato roots grown in M. javanica-inoculated loess and sandy soils respectively, showing higher nematicidal activity than 1,3-dichloropropene. No P. penetrans were recovered from soil treated with 80mg allyl bromide L-1 soil or 320mg dibromo(nitro)methane L-1 soil. CONCLUSION: Allyl bromide showed high nematicidal activity against all three nematode species, and nematicidal activity of dibromo(nitro)methane was discovered. These compounds could serve as new fumigation nematicides, pending further experiments. © 2015 Society of Chemical Industry.


Oka Y.,Nematology Unit | Shuker S.,Nematology Unit | Tkachi N.,Nematology Unit
Pest Management Science | Year: 2012

Background: Fluensulfone, a new nematicide of the fluoroalkenyl group, has proved to be very effective in controlling root-knot nematodes, Meloidogyne spp., by soil application. The systemic activity of this compound against M. incognita on peppers via soil drenching and foliar spray was evaluated. Results: Root application of fluensulfone via soil drenching showed slight and no nematode control activity when applied 4 and 10 days, respectively, after inoculation. A single foliar spray of peppers with a fluensulfone solution at 3.0 g L -1 prior to inoculation reduced the galling index by 80% and the number of nematode eggs by 73-82% of controls. The reduction in these parameters by fluensulfone was much higher than that obtained with oxamyl or fenamiphos at the same concentration. This activity was also observed when the plants were sprayed 21 days before inoculation. A series of experiments suggested that foliar spray with fluensulfone prior to inoculation reduces nematode invasion. However, foliar spray after inoculation did not inhibit nematode development inside roots. Conclusion: Fluensulfone showed relatively high nematode control activity when sprayed on the foliage before inoculation. Fluensulfone may be used as a foliar application, in addition to soil application, for root-knot nematode control. © 2011 Society of Chemical Industry.


Oka Y.,Nematology Unit
Applied Soil Ecology | Year: 2010

Application of organic soil amendments is a traditional control method for plant-parasitic nematodes and it is considered a part of nematode-management programs. A variety of organic amendments, such as animal and green manures, compost, nematicidal plants and proteinous wastes, are used for this purpose, but nematode control efficacy is not always satisfactory. Elucidation of nematode-control mechanisms in amended soil may lead to improved efficacy or the development of more effective control techniques, although the effects of organic amendments on nematodes, microbial communities, plants and soil environments are very complex. Possible mechanisms involved in nematode suppression are: (1) release of pre-existing nematicidal compounds in soil amendments, (2) generation of nematicidal compounds, such as ammonia and fatty acids, during degradation, (3) enhancement and/or introduction of antagonistic microorganisms, (4) increase in plant tolerance and resistance, and (5) changes in soil physiology that are unsuitable for nematode behavior. Combinations of these mechanisms, rather than a single one, appear to produce nematode suppression in amended soils. © 2009 Elsevier B.V. All rights reserved.


Oka Y.,Nematology Unit | Shuker S.,Nematology Unit | Tkachi N.,Nematology Unit
Pest Management Science | Year: 2013

BACKGROUND: Fluensulfone, a fluoroalkenyl group nematicide, has proved to be very effective in controlling root-knot nematodes, Meloidogyne spp. The authors evaluated some soil environmental factors that might affect its nematicidal activity. RESULTS: Meloidogyne javanica juveniles exposed to fluensulfone lost their infectivity, even though they were rinsed in water when they were still active. Exposure of juveniles to fluensulfone at >1 mg L-1 for 48 h was very effective in reducing root galls. Peat as organic matter added to soil reduced nematicidal efficacy against M. javanica in pot experiments. Peat added to a soil column inhibited the downward movement of fluensulfone. The movement of fluensulfone was faster in sandy vs loess soil. Repeated soil application of fluensulfone did not reduce the nematicidal activity of fenamiphos or cadusafos, and repeated applications of these nematicides did not lower the nematicidal activity of a subsequent application of fluensulfone. CONCLUSION: Fluensulfone nematicidal activity and movement were affected by organic matter and clay content, probably via adsorption. Enhanced biodegradation or cross-biodegradation of fluensulfone by other compounds was not observed. Soil environment should be considered to obtain effective nematode control efficacy with a given compound. © 2013 Society of Chemical Industry.


Salame L.,Nematology Unit | Glazer I.,Nematology Unit | Miqaia N.,Institute of Plant Protection | Chkhubianishvili T.,Institute of Plant Protection
Phytoparasitica | Year: 2010

Entomopathogenic nematodes (EPNs) are known as effective biological agents against soil-dwelling stages of insect pests. In the present study new EPN populations from the Steinernematidae and Heterorhabditidae families were isolated at different locations in Israel. The newly isolated populations were subjected to a series of bioassays for beneficial traits, for selection of a superior isolate for biological control of insect pests. Nematode motility was measured in sand columns, with and without the susceptible insect Galleria mellonella. Infectivity was evaluated using an invasion rate assay, as well as a dose response assay in which LD50 values were calculated. Nematode tolerance to environmental stresses was examined in heat and desiccation tolerance assays. The reproductive potentials of the new isolates were assessed in cadavers of G. mellonella. All Steinernematid populations were identified as Steinernema feltiae and the Heterorhabditids as Heterorhabditis sp. Large variation between the various populations was recorded in all assays. In order to identify a superior isolate, each strain was scored as 1 if its performance did not differ significantly from the highest level recorded in the particular assay; -1 if its performance did not differ significantly from the lowest level; and 0 if its performance was between the highest and lowest levels or did not differ from either. The scores for the different traits were then summed for each population and the totals were compared. The best score (+4) was obtained for a S. feltiae population isolated in northern Israel. These results will be used for the utilization of the new population as a biological control agent. © Springer Science & Business Media B.V. 2009.


The fluoroalkenyl fluensulfone, known to have strong nematicidal activity against Meloidogyne spp. (root-knot nematodes), was evaluated in vitro and in soil against the migratory nematodes Bursaphelenchus xylophilus, Aphelenchoides besseyi, Aphelenchoides fragariae, Ditylenchus dipsaci, Pratylenchus penetrans, Pratylenchus thornei and Xiphinema index. RESULTS: B. xylophilus and D. dipsaci were not immobilised by 48 h in vitro exposure to up to 16 mg L-1 of fluensulfone. A. besseyi and A. fragariae were affected by 8 mg L-1, the highest concentration used for these nematodes. More than 60% of P. penetrans and P. thornei were immobilised by 4 mg L-1 of fluensulfone; however, exposure of P. penetrans to the compound prior to inoculation did not affect their root penetration ability. The immobilisation rate of X. index was increased by 48 h exposure to even 1.0 mg L-1 of fluensulfone. Incorporation of over 2 mg L-1 of fluensulfone into the soil reduced populations of P. penetrans and P. thornei before and after planting lettuce and chickpea respectively. The efficacy of fluensulfone against the tested nematodes was the same or higher than that of fenamiphos in most cases. CONCLUSION: A. besseyi, A. fragariae, B. xylophilus and D. dipsaci were tolerant to fluensulfone and fenamiphos. P. penetrans, P. thornei and X. index were affected by fluensulfone, but nematicidal activity was much lower than that reported for root-knot nematodes. © 2014 Society of Chemical Industry.


PubMed | Nematology Unit
Type: Journal Article | Journal: Pest management science | Year: 2016

Restrictions on soil fumigants are prompting the development of new compounds for controlling nematodes, other soilborne pathogens and weeds. We evaluated the nematicidal activity of five bromine compounds against Meloidogyne javanica in vitro, and tested the two most effective ones against Pratylenchus penetrans and Xiphinema index in vitro and in soil.Only allyl bromide and dibromo(nitro)methane showed nematicidal activity against M. javanica juveniles in vitro at <320mgL(-1) . Allyl bromide killed M. javanica and P. penetrans at 20mgL(-1), and X. index at 10mgL(-1), whereas 320mg dibromo(nitro)methane L(-1) was required to kill P. penetrans. Allyl bromide also showed higher nematicidal activity than dibromo(nitro)methane against M. javanica and P. penetrans in soil. Allyl bromide at 40 and 20mgL(-1) soil eliminated root galls and nematode eggs on tomato roots grown in M. javanica-inoculated loess and sandy soils respectively, showing higher nematicidal activity than 1,3-dichloropropene. No P. penetrans were recovered from soil treated with 80mg allyl bromide L(-1) soil or 320mg dibromo(nitro)methane L(-1) soil.Allyl bromide showed high nematicidal activity against all three nematode species, and nematicidal activity of dibromo(nitro)methane was discovered. These compounds could serve as new fumigation nematicides, pending further experiments.


Different strategies have been employed for selective isolation of Streptomycetes from 20 marine samples varied in their biological nature. The recovery of Streptomycetes isolates (112) was influenced preferentially by different strategies; sediment samples were the best source of potential candidate Streptomycetes. All isolates exhibited antimicrobial activities with variable spectrum; the most promising isolates (31) were phenotypically characterized and identified as Streptomyces sp.; these isolates exhibited variable capacity for secretion of numerous hydrolytic enzymes such as catalase, protease, amylase, lipase, lecithinase, asparaginase, chitinase and pectinase. All the strains resisted both penicillin and streptomycin, 29 were sensitive to neomycin; the majority of strains (25) showed multiple antibiotic resistance index greater than 0.2; 23, 22 and 13 degraded the shrimp shell, chicken feather and corn cob, respectively, producing bioactive substance(s) which indicates their diversity and their ecological role in the marine ecosystem. At least 28 strains exhibited nematicidal activity in vitro and in vivo against root-knot nematode and supported plant growth. In vitro, the assessed Streptomyces species exhibited the ability to produce gibberellic acid, indole acetic acid, abscisic acid, kinetin and benzyladenine. Except for indole acetic acid, this is the first report concerning the ability of marine Streptomyces to produce such phytohormones and the use of shrimp shell waste as a mono component medium for production of phytohormones. The study is efficacious in selecting effective biodiverse strains of marine Streptomyces that may work under diverse agro-ecological conditions as a useful element in plant nutrition and as biocontrol agents involved in integrated management programs.

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