Production of botryosphaeria species conidia using grapevine green shoots

Abstract

Methods for producing large numbers of conidia were developed to allow investigation of the pathogenicity of five Botryosphaeria species (B. lutea, B. australis, B. obtusa, B. parva and B. stevensii), previously isolated from symptomatic grapevines. Pycnidium formation of all five species was low on five mycological media tested. Further, any pycnidia produced on the media contained few conidia. An alternative method was developed, whereby grapevine green shoots were infected with Botryosphaeria species, the lesions air dried and then induced to sporulate under moist conditions. Botryosphaeria australis, B, lutea and B. stevensii produced abundant pycnidia oozing conidia within 36 h. The air dried stem pieces could still produce pycnidia that oozed conidia after 3 months of storage at room temperature. Botryosphaeria parva produced few pycnidia that did not release any conidia. Botryosphaeria obtusa lesions were small and restricted to the inoculation point, with only a few pycnidia and conidia being produced.