Formation of biphenyl and dibenzofuran phytoalexins in the transition zones of fire blight-infected stems of Malus domestica cv. 'Holsteiner Cox' and Pyrus communis cv. 'Conference'

► Fire blight-infected apple and pear shoots form biphenyls and dibenzofurans. ► The exclusive accumulation site is the transition zone of stems. ► Leaves are devoid of phytoalexins. ► 3,5-Dihydroxybiphenyl exhibits strong antibacterial activity against Erwinia amylovora.