Agron. Sustain. Dev. 26 (2006) 185-193
DOI: 10.1051/agro:2006015

A dynamic biofilter to remove pathogens during tomato soilless culture

Franck Déniel, David Renault, Yves Tirilly, Georges Barbier and Patrice Rey

Laboratoire de Biodiversité et Écologie Microbienne (EA3882), ESMISAB, Université de Bretagne Occidentale-Brest, Technopôle Brest-Iroise, 29280 Brest, France

(Accepted 29 June 2006; published online 29 September 2006)

Abstract - In tomato soilless culture, slow filtration is used to control the development of diseases caused by pathogenic microorganisms. We report a three-year monitoring study of the use of a "shier biofilter", which is a dynamic filtration system where the water and the filtering media, pozzolana particles, are maintained in constant motion by an air pump. We found that this biofilter removed more fungi than bacteria under tomato production conditions. The rate of efficacy against pathogenic fungi was genus-dependent. Indeed, against Pythium spp., more than 99% of thalli were eliminated over the 3-year survey. But, against Fusarium oxysporum, efficacy fell within 92.7 and 99.3%. Regarding the total cultured-bacteria microflora, despite a high elimination rate of 91.2-98.9% the effluent solution was colonized by large populations, from 6.6 10² to 1.4 10⁴ colony-forming units/mL. The biofilter efficiency was found to be mainly related to the biological activity of the bacterial biofilm on the pozzolana particles. The high rate of Pythium spp. elimination by the dynamic biofilter was correlated with the low colonization of roots by these pathogens. Necrotic symptoms were only observed in September, i.e. at the end of the cultural season. By limiting the dissemination of pathogens and eliminating the root-fungi dynamic, filtration proved to be a helpful technique. It, however, preserved most of the bacteria driven to plants by the nutrient solution, which led us to discuss their potentially beneficial effect on roots.

Key words: Pythium spp. / Fusarium oxysporum / Bacillus / Pseudomonas / disinfection / root disease / recirculation

Corresponding author: Patrice Rey patrice.rey@univ-brest.fr

© INRA, EDP Sciences 2006