Ergosterol and Substitutes for the Ultraviolet Radiation Requirement for Conidia Formation In Stemphylium Solani

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Abstract
SUMMARY Stemphylium solani preconidiophores respond by subsequent pigmentation and conidia production to treatment with certain solvents and carriers alone or with added ergosterol. Treatment consisted of flooding 7-day-old cultures grown in the dark at 21 C on V-8 juice 1.5% agar with 4 ml of solution so that preconidiophores are wetted or soaked for 24 hr prior to deflooding and dark incubation for another 24 hr. Conidia were induced to form by 1–10% DMSO in 0.1 M KH2PO4 and by 2% ethanol. Ergosterol added to carriers or solvents increased conidial formation 2- to 5-fold over that in controls. The morphology and pigmentation of conidiophores and conidia were similar to those produced by ultraviolet radiation at appropriate doses. A possible explanation is that free ergosterol is involved in the conidial formation in S. solani.