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Keywords:

C3/19/047#55510266

Abstract:

The last decades, rhizogenic agrobacteria are increasingly causing Hairy Root Disease (HRD) in several hydroponic crops, including tomato, cucumber, eggplant, and recently also bell pepper[1,2]. It is known that the rhizosphere, which is a complex ecosystem consisting of microbes in the interface between growth medium and plant roots, can affect plant productivity and health[3]. However, the bacterial community dynamics in hydroponic systems has been very poorly studied. Until now, it is not known if the presence or absence of key bacterial players in tomato hydroponics has an impact on the incidence of HRD. In this study, high-throughput amplicon sequencing of partial ribosomal RNA (rRNA) genes was used to characterize bacterial communities in rockwool samples obtained from healthy or HRD-infested tomato, during an entire growing season. The alpha diversity in rockwool increased significantly throughout the season. Interestingly, samples obtained from healthy greenhouses presented a significantly lower alpha diversity than those from HRD-infested greenhouses. Beta diversity analysis showed that bacterial community composition also differed throughout the growing season. As expected, amplicon Sequence Variants (ASVs) identified as rhizogenic Agrobacterium biovar 1 were more abundant in infested greenhouses. Conversely, ASVs identified as Paenibacillus spp., a genus that includes previously identified as biocontrol organisms of rhizogenic agrobacteria[4], were more abundant in healthy greenhouses. Furthermore, this study allowed to identify indicator organisms associated with a higher or lower risk of HRD incidence. Altogether, this study greatly contributes to the knowledge of bacterial communities in rockwool hydroponic systems, particularly with respect to the incidence of HRD. References [1] L. Bosmans, R. Moerkens, L. Wittemans, R. De Mot, H. Rediers, B. Lievens, Plant Pathology 2017, 66, 1043–1053. [2] P. Vargas, S. Van Kerkckhove, B. Van Calenberge, L. Bosmans, B. Lievens, H. Rediers, Plant Disease 2019, 104, 968. [3] C. Brunel, R. Pouteau, W. Dawson, M. Pester, K. S. Ramirez, M. van Kleunen, Trends in Plant Science 2020, 25, 1017–1029. [4] L. Bosmans, I. De Bruijn, S. Gerards, R. Moerkens, L. Van Looveren, L. Wittemans, B. Van Calenberge, A. Paeleman, S. Van Kerckhove, R. De Mot, J. Rozenski, H. Rediers, J. M. Raaijmakers, B. Lievens, Frontiers in Microbiology 2017, 8, DOI 10.3389/fmicb.2017.00447.