ISSR fingerprinting for the assessment of the bindweed biocontrol agent Stagonospora convolvuli LA39 after field release

Aims: To develop a molecular identification method based on ISSR fingerprints to monitor the fungal leaf pathogen Stagonospora convolvuli LA39 used to biologically control bindweeds after a field release. Methods and Results: The developed method proved to be suitable to clearly distinguish LA39 from resident Stagonospora spp. and was applied in two field experiments. First, the environmental persistence of LA39 was assessed in an overwintering experiment. LA39 could be re-isolated from infected bindweed 1 year after field application, but with very low frequency of occurrence. Secondly, LA39 was applied in an area with natural bindweed infestation and re-isolated from infected bindweed. The dispersal of LA39 during one season was poor (4-5 m). Conclusion: ISSR fingerprinting has been shown to be a valuable tool to monitor the environmental fate of S. convolvuli in the field. It is concluded that an LA39-based mycoherbicide will have minimal environmental impact caused by the restricted mobility, poor proliferation and poor persistence over seasons of LA39. Significance and Impact of the study: Studies about the dispersal and survival of biocontrol agents after field release as well as the development of methods needed for this purpose are indispensable for a comprehensive risk assessment for biocontrol agents.