Diaporthe perjuncta Does Not Cause Phomopsis Cane and Leaf Spot Disease of Grapevine in Australia

In Australia, Diaporthe perjuncta (formerly known as Phomopsis taxon 1) and Phomopsis viticola (Phomopsis taxon 2) have been associated with Phomopsis cane and leaf spot of grapevine. Although P. viticola causes distinct leaf spots, as well as lesions on shoots and canes, the pathogenicity of D. perjuncta is relatively unknown. The pathogenicity of D. perjuncta and P. viticola was studied in relation to symptom expression and bud loss. Only P. viticola caused brown-black, longitudinal, necrotic lesions on stem tissue and leaf spots characteristic of the disease, whereas both D. perjuncta and P. viticola induced bleaching of dormant canes. Inoculation of dormant buds with D. perjuncta did not cause bud death. D. perjuncta and P. viticola were reisolated from inoculated tissue and into pure culture. D. perjuncta colonized the epidermis and cortex of the grapevine shoot but not the vascular tissue. D. perjuncta appears to be an endophyte, rather than a pathogen of grapevine.