CULTURAL STUDIES OF SEXUAL REPRODUCTION OF CERATOCYSTIS FAGACEARUM

Abstract

The optimum KH2PO4 concentration for perithecium production by Ceratocystis fagacearum in a semi-synthetic agar medium was 7.4 × 10−1 M. A great reduction in the number of perithecia occurred at 0.1 M and none were formed at 0.2 M concentration. The optimum pH was 5.2 and no perithecia formed at pH 7.0. Either exogenous thiamine or its pyrimidine moiety is absolutely essential for perithecium formation. Pyridoxine, inositol and biotin were not required for growth or reproduction. Receptivity of 14-day-old cultures remained high for longer periods when stored at 12 °C than at 3 °C or 21 °C. Of the 17 isolates studied, 14 produced sterile perithecia before conidia were applied experimentally. Attempts to fertilize these were unsuccessful. Perithecia which did not extrude ascospores formed on colonies following application of conidia. In such perithecia, opened ostiolar hyphae did not necessarily indicate sterility. Neither abrasion of colonies, nor brushing with sterile distilled water or with a filtrate of sonic-disrupted condia, increased sterile perithecium production. However, brushing the colonies with an extract of germinated conidia did increase their formation.