The implementation of RhizoTalk was broken down in five work packages (WPs), three of which were entirely result-oriented. WP1 was devoted to the identification of communication systems in AZ78 and the characterization of its response to main soil bacterial communication signals. WP2 was devoted to the identification of soil bacterial strains producing signals relevant for AZ78 and the characterization of bipartite interactions between those and AZ78. The third WP (WP3) was instead dedicated to the development and validation of biocontrol formulations of AZ78 in consortium with other bacterial species. WP4 and WP5 addressed dissemination and outreach activities, as well as issues related to career development and project management, and consequently lasted during the entire duration of the project.
A transcriptome approach to biopesticide development
The presence of genes involved in cell-cell signalling systems in the genome of AZ78 was determined by genome mining, and production of quorum-sensing signals by AZ78 was evaluated using reporter strains. Next, a functional analysis of bacterial signalling compounds was performed in vitro. Firstly, at a microbiological level, by evaluating the effect of main QS signals on AZ78 biocontrol activity, and secondly, at a molecular level by evaluating the transcriptome response of AZ78 to QS molecules by RNA-Seq. Our findings showed that AZ78 perceive and produce different kinds of QS signals. Moreover, it allowed for the identification of important genes modulated by QS signals, shedding a light on the molecular mechanisms involved in AZ78 establishment in the soil.
Bacterial formulations as biopesticides against soil borne pathogens
A collection of bacterial isolates deriving from copper contaminated soils was screened for pathogen inhibition in binary combinations with AZ78. Each strain was tested for potential enhancement of AZ78 biocontrol activity and tolerance to desiccation and UV light. Strains were taxonomically identified using 16S rDNA PCR and characterised for their plant growth promoting traits and their ability to produce QS signals. Strains enhancing AZ78 biocontrol activity and resistance to environmental stresses were designated as helper bacterial strains (HBS) and were further formulated together with AZ78. AZ78 and HBS were blended, supplemented with additives and incorporated to inorganic carriers to produce water dispersible granules. A total of 16 formulations consisting of AZ78 and HBS were developed and characterized. Shelf life was monitored under different storage conditions and best performing formulations were validated under greenhouse conditions.
Results derived from RhizoTalk have been disseminated in conferences and seminars. Moreover, RhizoTalk have given rise to a book chapter, and 3 peer-reviewed publications will be soon available. Additionally, RhizoTalk has taken part in events addressed to the public like the European Researchers' Night.
