<scp> <i>Botrytis cinerea</i> </scp> : Woody Trunk Endophytes That Interact With Botryosphaeriaceae Members of the Grapevine Trunk Disease Complex and Modulate Disease Expression

ABSTRACT In a previous study of fungal endophytes associated with grapevine trunk disease (GTD) in New Zealand vineyards, Botrytis cinerea was recovered from the inner trunk tissues of vines that were symptomatic or asymptomatic for GTD. The effect of B. cinerea , considered an endophytic latent pathogen, on colonisation and symptom development by the grapevine trunk pathogens Neofusicoccum parvum and Diplodia seriata was investigated. B. cinerea isolates recovered from both GTD symptomatic and asymptomatic grapevine trunks, and isolates from infected berries, were pathogenic on green shoots and berries. In planta interactions between B. cinerea and N. parvum or D. seriata were evaluated on detached green Sauvignon Blanc shoots and woody stems of 2‐year‐old potted Sauvignon Blanc vines. Lesion length and colonisation of the shoots by the pathogens was determined by reisolation, 2 and 12 weeks post‐inoculation for detached and attached shoots, respectively. D. seriata did not produce lesions but was shown to endophytically colonise, being recovered from inoculated shoots. Reisolation of D. seriata was unaffected by co‐inoculation with B. cinerea in both detached and attached shoots. For N. parvum , co‐inoculation with B. cinerea did not affect lesion lengths in detached shoots. In contrast, in attached shoots co‐inoculation by B. cinerea inhibited N. parvum lesion development. This was hypothesised to be due to contrasting infection mechanisms by the two Botryosphaeriaceae species and alteration in the host response between detached and attached tissues. The findings indicate that B. cinerea is involved in the GTD complex and affects symptom expression.