Induction of morphogenesis, branching and conidiogenesis in Fomes annosus

Abstract

In Foynes annosus the addition of 1,-threonine induces specifically branching and septum formation in the leading hyphae of the mycelium. The formation of conidia is stimulated by the combination of light and dark phases and starvation. IntroductionThe basic concept of biological and biochemical control of pathogenic organisms is to find means to manipulate the metabolism of the parasite in a way which will be detrimental for it without adverse effects for the host. This concept, however, requires a very detailed knowledge of the metabolism of the pathogen. With this concept in mind, such differentiations in the pathogen are especially attractive, which lead to dormant stages. These morphogenetic stages are known to arrest the organisms in its metabolism, a feature which is very attractive in view of possible means of control.The most prominent differentiation in Fomes annosus when cultivated in the laboratory is the production of conidiophores (SCURFIELD and DA COSTA 1969;COOK 1977), the asexual form of propagation in this organism. Although conidiation and conidiospores have been exploited as indicators for physiological variabilities among different isolates of Fomes annosus (COURTOIS 1972 a, b) studies on the physiology of this morphogenesis are still lacking. In this communication we will report on a method of induction of conidiation in rather high yields in the absence of net growth and nutrients.Another, rather simple morphogenetic change in fungi is branching, the induction of formation of growth points in the hyphae. KRITZMAN et al. (1976) have reported that in Scleroderris rolfsii, a Basidiomycete which is pathogen against subtropical annuals like tomatoes or melons, branching can be induced by the addition of some nutrients hke lactose or threonine. Since such changes in the growth pattern of the hyphae may be of general interest, we extended these studies on Fomes annosus, too. Materials and methods Strain and growth conditions: Fomes annosus. Strain I'215 (ATCC 18222) w.is used in all experiments.Stoek cultures were kept on malt extraet agar and experimental cultures were grown on liquid modified Dekhuijzen medium (glucose, aspartate, thiamine, and salts) as described previously (HUTTERMANN and VoLGER 1973). Transfer of the liquid cultures was done according to the procedure given by Z ' WECK etal. (1978). Microscopic detection of branching: For analyzing the morphogenetic effects of the various chemicals, the fungus was grown on 2 % agar plates containing the defined medium and the additions. To facilitate the isobtion of the leading hyphae, the agar plate was covered with sterile eellophane before inoculation. After growth of the fungus on it, the front of the mycelium was cut with a blade and the cellophane disc was inspected under a Zeiss-phase contrast microscope, drawn and photographed.Induction of morphogenesis, branching and conidiogenesis in F. annosus 171 V'sualization of the growth points with calcofluor white H2R and Wheat-germ lectin fluorescin isoth' cvanate: For the detection of the ...