Production of ethylene by sweet potato roots infected by black rot fungus

概要

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Ethylene production by sweet potato roots infected by the black rot fungus, Ceratocystis fimbriata, increased strikingly after infection. The fungus grown on potato extract containing 1% sucrose or steamed sweet potato produced no ethylene. Thus, ethylene was proven to be produced from the host tissue affected by fungus invasion. The ethylene production seemed to be stimulated by carbon dioxide. Oxygen was essential for production, but excess oxygen, probably over 80%, was found to be inhibitory. Apparent fungus growth on sweet potato was reduced under a high tension of oxygen, but this was not a cause of reduced ethylene production in excess oxygen. When tissue plugs of infected sweet potato which were actively producing ethylene were sliced into thin discs, ethylene production was abolished with the exception that the first 1mm discs at the 1st and 2nd day stages produced a significant amount of ethylene. Similarly, plugs which were removed from fungus-invaded parts did not produce an appreciable amount of ethylene. The production of ethylene was observed only by tissue plugs which consisted of both fungus invaded and non-invaded parts. Infected sweet potato tissue produced ethylene at a rate comparable to that in apples and may provide a good system for the study of ethylene biosynthesis.