Production of volatile alkyl sulphides by microbial degradation of synthetic alliin and alliin‐like compounds, in relation to germination of sclerotia of <i>Sclerotium cepivorum</i> Berk

Abstract

SUMMARY Onion distillands proved more stimulatory than distillates towards germination of sclerotia of Sclerotium cepivorum. Synthetic allylcysteine and n ‐propylcysteine and their sulphoxides stimulated germination of sclerotia when added to soil. Solutions of these compounds in the presence of unsterile soil produced gaseous alkyl mercaptans, sulphides and disulphides which were detected by gas‐liquid chromatography and which stimulated sclerotial germination when drawn through soil containing sclerotia. No volatile sulphides were detected above autoclaved solutions but the atmosphere over propyl and allylcysteines was slightly stimulatory although the corresponding autoclaved sulphoxides showed no such activity. The gases above all four solutions sterilized by membrane‐filtration were not stimulatory. Six common soil bacteria were shown to be capable of degrading the synthetic precursors, causing the evolution of appropriate volatile alkyl sulphides.