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Conference paper - Peer-reviewed, 2019

Implications on the root microbial community in the presence of Pythium ultimum in soilless cultivation systems

Rosberg, Anna Karin; Wohanka, Walter; Hultberg, Malin; Alsanius, Beatrix


The main problem associated with closed hydroponic growing systems is the increased risk of root pathogen dispersal. Organic nutrients released by plant roots differ between plant species and are dependent on plant age and on biotic and abiotic factors affecting plant growth. Damage by necrotrophic pathogens has been shown to alter the composition of rhizodeposits and consequently the rhizosphere microbiota. In this study, high-throughput pyrosequencing was used to make a comprehensive analysis of bacterial communities associated with the roots of non-inoculated and Pythium ultimum-inoculated tomato plants at three different plant physiological stages. Plate counts were used for quantification purposes. The results showed that the presence of P. ultimum changed the microbial communities in the plant rhizoplane. These changes were most evident in the fruit-bearing plant stage, where a clear difference was seen between the treatments in terms of dominant bacterial phyla, which changed from Proteobacteria in the control to Bacteroidetes in the P. ultimuminoculated treatment. Numbers of total bacteria and fluorescent pseudomonads were significantly higher in the rhizoplane and in the nutrient solution of the P. ultimuminoculated treatment at the fruit-bearing plant stage. Hence inoculation with P. ultimum altered the composition of root-associated microbial communities on the roots of hydroponically grown tomato.


bacteria; closed systems; greenhouse; high-throughput sequencing; root microorganisms

Published in

Acta Horticulturae
2019, Volume: 1266, pages: 215-222
Title: Proceedings of the international symposium on growing media, soilless cultivation, and compost utilization in horticulture
ISBN: 9789462612631, eISBN: 978-94-62612-63-1
Publisher: ISHS


International symposium on growing media, soilless cultivation, and compost utilization in horticulture, 170820-170825, Portland, Oregon, USA