Identification in Australia of the quarantine pathogen of sunflower Phoma macdonaldii (Teleomorph : Leptosphaeria lindquistii)

Isolations from black stem lesions of sunflower growing in south-eastern Queensland yielded fungi putatively identified as species of Phoma. Pathogenicity assays showed that these isolates were capable of killing sunflower plants under glasshouse conditions. The isolates were compared with authentic cultures of Phoma macdonaldii and other isolates of Phoma taken from sunflower from around the world. Random amplified polymorphic DNA analysis showed that all the Australian isolates examined were very similar to the holotype culture of Phoma macdonaldii from Canada. Sequencing of the internal transcribed spacer regions also revealed the relatedness of the Australian isolates to the holotype. This is the first official record of P. macdonaldii in Australia.