Species of the Botryosphaeriaceae Are Associated With Blackcurrant Dieback in New Zealand

ABSTRACT Dieback of blackcurrants ( Ribes nigrum ) is an increasing problem worldwide with several pathogens including the Botryosphaeriaceae species, Neofusicoccum ribis , reported as being associated with dieback. To identify the species of Botryosphaeriaceae associated with blackcurrant dieback in New Zealand, isolations were carried out from plant samples with dieback symptoms collected from blackcurrant orchards in the main growing areas in the South Island of New Zealand. For one site, symptomatic grapevines in an adjacent vineyard were also sampled as they are known hosts of these species. The pathogenicity of representative isolates from each of the species recovered was determined on detached blackcurrant shoots. Of the 242 symptomatic plant materials collected, 29% were infected by Botryosphaeriaceae. Species of Botryosphaeriaceae were recovered from plant samples from all four orchards sampled. Of the 70 Botryosphaeriaceae isolates recovered from blackcurrant, Diplodia seriata (43 isolates) and D. mutila (17 isolates) were the most prevalent species, with Neofusicoccum australe (6 isolates), N. cryptoaustrale (3 isolates) and one isolate of D. sapinea also recovered. D. seriata , D. mutila , N. australe and N. cryptoaustrale were also recovered from symptomatic grapevine tissues sampled from the adjacent vineyard and all but N. cryptoaustrale were found in the blackcurrant crop adjacent to this vineyard. All species were pathogenic on detached green shoots, with N. australe and N. cryptoaustrale the most pathogenic, producing the longest lesions compared with D. seriata and D. mutila . This is the first study on the incidence and pathogenicity of species of the Botryosphaeriaceae infecting blackcurrant plants in New Zealand.