Biology of the gourmet and medicinal mushroom Agaricus subrufescens, development of its cultivation and of new products of therapeutic interest or for disease prevention. – AgaSub

Agaricus blazei Murrill, known as Himematsutake in Japan, is an edible mushroom distributed across America. The pharmacological effects of A. blazei, such as antitumor and antihypertensive effects and its potential in prevention of carcinogenesis processes are of particular interest. The development of A. blazei cultivars with superior properties such as high fruiting body productivity, disease resistance, and proved human health benefits will be very important for promoting commercial production. Based on various studies, some health promoting effects are being claimed for this mushroom, but several studies stress toxicological risks. In Japan, A. blazei is cultivated by a procedure based on the method of Agaricus bisporus (the so-called champignon de Paris). Both are saprophytic fungi acting as secondary decomposers in forest litters. Wastes used as their cultivation support can be viewed as valorised products, at least in term of providing new economic opportunities for using these wastes with positive environmental consequences. There is, however, little information available about the development of A. blazei cultivars and optimisation of cultures. Therefore, many of the spawn cultures used in A. blazei cultivation may be derived from a few numbers of Brazilian wild strains with a subtropical habitat, and a very low genetic variability is observed in the set of cultivated strains. It seems to be a tetrasporic species, but its life cycle is not well known. A recent publication and our own preliminary studies tend to synonymise various almond-flavoured Agaricus spp including the cultivated strains of A. blazei under the common name: Agaricus subrufescens. These rare Agaricus spp are probably present in various continents and specimens were recently collected in France, Spain, and Mexico. They seem to be lesser dependant on high temperatures for their cultivation than the cultivated A. blazei. In this context, fundamental genetic research on A. subrufescens and a non controversial clarification of the species complex become obviously important. If A. subrufescens from Europe and other origins are recognized by careful comparative DNA analyses and interfertility tests as the same species than the commercial strains of A. blazei, the abundant literature on pharmacological effects could be used for claiming health promoting effects of this new strains, and one could expect improving their properties and production processes through the use of this new biodiversity and breeding. However the toxicological risks will have to be checked and specific pharmaceutical properties will have to be confirmed and explained. This project aims to developing the cultivation of A. subrufescens and to using this fungus as nutraceutical food or source of bio products and substances of interest in diseases prevention or treatment. Moreover, the cultivation of this fungus will valorize agricultural by-products by using lignocellulose materials waste as cultivation substrate. To do so, knowledge on the biology of this fungus needs to be improved. This research project will thus focus on three main axes: (i) taxonomy of both A. subrufescens and A. blazei, their life cycles and analysis of intraspecies biodiversity (ii) the culture parameters and mechanisms inducing fruiting and responsible for fruit body development, (iii) the nature and composition of the metabolites produced by this species and their toxicological or pharmacological effects. The scientific programme is on based these three sets of subject area working on the same biological objects. For each subject area, technical competences in mycology, biochemistry and molecular biology are used. Two successive phases for researches are planed: 1- Determination of the species concept by comparison of the genetics and biology a commercial A. blazei and a European isolate of A. subrufescens, for the 3 sets of disciplines; - Research of biologically active metabolites, in the two isolates and comparison with A. bisporus. 2- Evaluation of the genetic and phenotypic biodiversity, and impact of variations in environmental factors during cultivation. Utilization for improving productivity and quality of the products. The deliverables are: 1- Scientific data presented in international publications on: Life cycle of A. subrufescens. Phylogeny and intra-specific biodiversity. Lignocellulose degradation and enzyme production, toxicological risks and pharmacological effects of mushrooms and fractions. 2- Material for further developments: Biological resources. Methods for breeding programs. Data base on metabolites or fractions with valuable biological activities and/or purified product(s). 3- Implementation of industrial developments: Sustainable agricultural production. Added value products for human health and environment.