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Ascocarp production in Nectria ditissima Tul. was found to occur on a wide range of C and N substrates. However, all the organic acids, certain amino acids and ammonium salts tested prevented perithecial formation. Optimal production of ascocarps was observed with carbohydrates like lactose, dextrins, or maltose, with single N (isoleucine, phenylalanine, γ amino butyric acid) or mixed N sources (alanine, asparagine, glutamic acid). A C/N ratio ranging between 10 and 30 favoured perithecial production with an optimum when the C concentration was from 4 to 5 g/L or the N concentration from 150 to 250 mg/L. In liquid cultures at pH 5.5 and at 18 °C, N. ditissima developed perithecia only in the presence of light although light requirements were very low. Short duration of light (1 h/day) with a low intensity (10 μW∙cm−2) illumination was sufficient to trigger many ascocarps. Maximum sexual differentiation was induced at wavelengths 330, 380, 430, 480, and 500 nm. |
