Assessing the environmental biosafety of phage-based biocontrol applications

Over the past decades, phage biocontrol as a means of treating bacterial plant diseases has regained keen interest. Indeed, pioneering trials have shown this is a promising strategy to treat different diseases. However, just like other plant protection products, the biosafety of bacteriophages needs to be validated and reported before registration on the European market is possible. In this regard, the EU has provided data requirements for viral biocontrol in EU Regulations 283/2013 and 284/2013. However, the guidelines on how to determine important characteristics with regard to phage biosafety, remain scarce. Based on the current data requirements and literature, we developed a pipeline based on taxonomic analysis using PCR-based 16S rRNA gene amplicon sequencing. As an illustration of the power of this approach, we show that FoX2 and FoX4, capable of infecting and killing Xanthomonas campestris pv. campestris, appear not to affect non-target species and hence, are environmentally safe.