ISHS Acta Horticulturae 747: VIII International Symposium on Protected Cultivation in Mild Winter Climates: Advances in Soil and Soilless Cultivation under Protected Environment
ASSESSING EFFICACY OF ULTRA-FILTRATION AND BIO-FILTRATION SYSTEMS USED IN SOILLESS PRODUCTION THROUGH MOLECULAR DETECTION OF PYTHIUM OLIGANDRUM AND BACILLUS SUBTILIS AS MODEL ORGANISMS |
| Authors: | L. Belbahri, G. Calmin, F. Lefort, G. Dennler, A. Wigger |
| Keywords: | recycled nutrient solution, real time PCR, rRNA sequencing |
| Abstract:
The majority of greenhouse crops are grown on artificial substrates in hydroponic systems. Re-circulating nutrient systems offer an advantageous alternative for controlling nutrient solutions leaching from greenhouses into the environment, which represents an environmental issue in greenhouse production areas. However, the potential for the rapid spread of root diseases, and other diseases, is the main hindrance to the general adoption of re-circulating nutrient systems by the greenhouse industry. In this study, the total bacterial, fungal and oomycete communities present in re-circulating nutrient solutions, were monitored using selective media and direct viable counts. Sequence analysis of 126 main representatives of these three communities showed for Eubacteria the presence of 11 genera of γ-Proteobacteria, 3 genera of Firmicutes, one genus of Actinobacteria and one genus of Flavobacteria. For the fungi, recovered strains belonged to Rhizopus and to Postia. Twenty strains belonged to the Stramenopile lineage, 19 of them to the genus Pythium (Oomycota) and one to the genus Splachnidium (Phaeophyceae). In addition, the efficacy of ultra-filtration and bio-filtration for eliminating oomycete and bacterial pathogens, artificially added in the re-circulating nutrient solution was assessed, by using a tangential ultrafiltration system, a slow sand filter and a rockwool granule filter. The oomycete Pythium oligandrum and the bacterium Bacillus subtilis were used as model organisms because of their easy culture, their lack of pathogenicity and their similarity with common oomycete and bacterial plant pathogens. Using real time PCR and species specific oligonucleotides showed that ultrafiltration is highly effective in removing P. oligandrum and B. subtilis. No P. oligandrum or B. subtilis were detected by real time PCR in filtrated nutrient solutions. Passage of nutrient solution through the slow sand filters also resulted in complete removal of P. oligandrum but was less effective for B. subtilis removal. | |
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