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Applied and Environmental Microbiology, July 2009, p. 4790-4800, Vol. 75, No. 14
0099-2240/09/$08.00+0     doi:10.1128/AEM.02643-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Influence of Pythium oligandrum Biocontrol on Fungal and Oomycete Population Dynamics in the Rhizosphere{triangledown}

Jessica Vallance,1,2,4 Gaétan Le Floch,1,2 Franck Déniel,1,2 Georges Barbier,1,2 C. André Lévesque,3 and Patrice Rey2,4*

Université Européenne de Bretagne, France,{dagger},{dagger} Université de Brest, EA3882 Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, IFR148 ScInBioS, ESMISAB, Technopôle Brest-Iroise, 29280 Plouzané, France,2 Agriculture and Agri-Food Canada, Eastern Cereal and Oilseed Research Centre, 960 Carling Avenue, Ottawa, Ontario K1A 0C6, Canada,3 UMR Santé Végétale 1065, INRA, ENITA de Bordeaux, Université de Bordeaux, 33175 Gradignan, France4

Received 18 November 2008/ Accepted 7 May 2009

Fungal and oomycete populations and their dynamics were investigated following the introduction of the biocontrol agent Pythium oligandrum into the rhizosphere of tomato plants grown in soilless culture. Three strains of P. oligandrum were selected on the basis of their ability to form oospores (resting structures) and to produce tryptamine (an auxin-like compound) and oligandrin (a glycoprotein elicitor). Real-time PCR and plate counting demonstrated the persistence of large amounts of the antagonistic oomycete in the rhizosphere throughout the cropping season (April to September). Inter-simple-sequence-repeat analysis of the P. oligandrum strains collected from root samples at the end of the cropping season showed that among the three strains used for inoculation, the one producing the smallest amount of oospores was detected at 90%. Single-strand conformational polymorphism analysis revealed increases in the number of members and the complexity of the fungal community over time. There were no significant differences between the microbial ecosystems inoculated with P. oligandrum and those that were not treated, except for a reduction of Pythium dissotocum (ubiquitous tomato root minor pathogen) populations in inoculated systems during the last 3 months of culture. These findings raise interesting issues concerning the use of P. oligandrum strains producing elicitor and auxin molecules for plant protection and the development of biocontrol.

* Corresponding author. Mailing address: ENITA de Bordeaux, UMR Santé Végétale 1065 INRA/ENITAB, Institut des Sciences de la Vigne et du Vin, 1 cours du Général de Gaulle, 33175 Gradignan CS 40201, France. Phone: 33 (0)5 57 35 07 60. Fax: 33 (0)5 57 35 07 59. E-mail: p-rey{at}enitab.fr

{triangledown} Published ahead of print on 15 May 2009.

http://www.ueb.eu.

Applied and Environmental Microbiology, July 2009, p. 4790-4800, Vol. 75, No. 14
0099-2240/09/$08.00+0     doi:10.1128/AEM.02643-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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