Production, in vitro, de périthèces du Nectria ditissima, agent du chancre du hêtre (Fagus sylvatica). II. Effets de la composition carbone–azote du milieu nutritif et influence de la lumière

Abstract

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.