Chemical treatment of cereal seed in relation to plant vigour and control of soil fungi

SUMMARY Treating oat seeds not contaminated with any known pathogen of this crop with an organo‐mercury preparation (Ceresan) increased seedling vigour only when they were grown in natural or simulated winter conditions with periods of frost. This beneficial effect on vigour was largely confined to seedlings and young plants. The fungicide protected the mesocotyls from contamination or invasion by certain soil‐borne fungi normally regarded as saprophytes. Cylindrocarpon radicicola and Fusarium sambucinum were closely associated with discoloured mesocotyls bearing lesions and reduced vigour of untreated plants. Protection from such fungi enabled mesocotyls to grow thicker, and, when seedlings were grown in unsterilised soil and exposed to frost, reduced the number with lesions or discolouration. Thus the ability of the saprophytic soil‐borne fungi to cause damage seems to be influenced by environmental conditions.