Variation in Septocyta ruborum and its potential for biological control of European blackberry

Abstract

The fungus Septocyta ruborum causes a destructive necrosis of floricanes in blackberry (Rubus fruticosus) in Europe and is a potential candidate for biological control in Australia. Over 100 accessions of S. ruborum from Europe were analysed for variation in pathogenicity and virulence. Virulence varied among accessions within R. fruticosus 'species'. Accessions screened for genetic diversity using (internal transcribed spacer (ITS) sequencing and RAPD (random amplification of polymorphic DNA) yielded identical ITS sequences, but three of 120 RAPD primers showed high levels of polymorphism. Accessions clustered into five main groups, but these were not related exclusively to virulence or geography. Some accessions from northern Europe and one accession from Hungary clustered apart from the main group. The large amount of polymorphism in both virulence and genetics suggests that S. ruborum reproduces sexually or that it has subdivided into many races. The large genetic variation offers considerable potential for selection of host-specific forms, an advantage in biological control