New insights in Freesia leaf necrosis disease

Although freesia leaf necrosis disease (FLN) is known in freesia cultures for over forty years, the causal agent(s) is/are still under investigation. In plants with FLN symptoms a virus belonging to the genus Ophiovirus was found; this virus is now known as Freesia sneak virus (FreSV). The virus was mechanically inoculated to and artificially maintained in host plants and purified from these plants. An antiserum was raised and an ELISA-based detection method for FreSV was developed. Mechanical inoculation from indicator plants to freesia seedlings was never successful. Transmission of FreSV using resting spores from Olpidium brassicae was tested to establish whether FreSV is the cause of FLN. The detection of FreSV was evaluated in several surveys using freesias with symptoms (66 lots), without symptoms (98 lots) and by random testing (45 lots). More than 40 different cultivars were surveyed. FreSV was found associated with FLN symptoms, although not in all the freesia lots with FLN-like symptoms. In such lots often Freesia mosaic virus (FreMV) was present and in some lots neither FreSV nor FreMV could be detected. Implications of these findings will be discussed