ACCUMULATION OF ANTIBACTERIAL SESQUITERPENOIDS IN BACTERIALLY INOCULATED GOSSYPIUM LEAVES AND COTYLEDONS

Two sesquiterpenoid naphthols, 2,7-dihydroxycadalene and 2-hydroxy-7-methoxycadalene, and their optically active oxidation products, lacinilene C and lacinilene C 7-methyl ether, have been isolated from cotton leaves and cotyledons after inoculation with incompatible bacteria. All four sesquiterpenoids accumulated to amounts one to two orders of magnitude higher in leaves and cotyledons infiltrated with incompatible bacteria than in those inoculated with compatible bacteria or sterile medium. In cotton plants inoculated withXanthomonas campestris pvmalvacearum in the field in August, sesquiterpenoid levels in incompatible leaves rose shortly before bacterial multiplication stopped, continued to rise for several days thereafter, and then fell. In leaves of a congenic compatible line, only the relatively insoluble, non-inhibitory 2-hydroxy-7-methoxycadalene accumulated to a level comparable to that in the incompatible line. However, all four sesquiterpenoids accumulated to moderate levels in unioculated leaves of both lines by 30 October. Water-solubilities and inhibitory activities towardX. campestris pvmalvacearum indicate that, with the exception of 2-hydroxy-7-methoxycadalene, these sesquiterpenoids can form aqueous solutions capable of inhibiting the bacterial pathogen. © 1990 Pergamon Press plc.