Investigations on crop developments and microbial suppressiveness of Pythium aphanidermatum after different disinfection treatments of the circulating nutrient solution

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Abstract

In this study results are presented of investigations on the development of a cucumber crop in a closed rockwool system and on the potential change in microbial suppressiveness due to different disinfection methods after inoculating part of the plants with the fungal pathogen Pythium aphanidermatum. Two trials were executed at which the core treatments were disinfection (UV, slow filtration and no disinfection as control), while additional treatments were priming half of the systems before planting either with an 'old' nutrient solution from a former cucumber crop (spring trial) or an actinomycetes suspension (autumn trial). Crop developments (yield, disease and root development) and composition of the microflora were recorded. Non-inoculated plants showed that disinfection is needed either with UV or slow (sand) filtration to avoid spread of the pathogen; yield and root development was better and disease symptoms were less compared to the control. The hypothesis that passive disinfection might realise a more suppressive environment against Pythium aphanidermatum could not be proved, since inoculated plants showed a similar yield, disease and root development after the different disinfection treatments. Priming the nutrient solution with an 'old' solution did not show significant differences in the composition of the microflora either by plate-counts or by PCR-DGGE. However, the addition of actinomycetes before planting resulted a 100 to 1000 fold increase of the actinomycetes population in the cropping system up to the end of the trial. In the spring trial, differences within the microflora as a result of the disinfection treatments were only detected for pseudomonads. In the autumn trial, differences in numbers of pseudomonads, actinomycetes and fungi were significant in the treated nutrient solution, but not in the drain. With PCR-DGGE, differences in the bacterial profile were detected in autumn in both the drain and treated solution; i.e. less bands (corresponding to certain bacterial species) occurred in the UV treatment compared to slow filtration and control
Original languageEnglish
Pages (from-to)563-570
JournalActa Horticulturae
Volume644
DOIs
Publication statusPublished - 2004

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