Screening of Agaricus bisporus (Lange, Imbach) Strains and the Casing Variables for Quality Mushroom Production in Spain

Production and quality parameters of three commercial strains of cultivated mushroom Agaricus bisporus (Lange, Imbach) were evaluated. A correlation matrix was made between the main parameters. Blancochamp BL-40, a smooth white hybrid, generally produced the greatest number of mushrooms and provided the highest yield, and its firm mushrooms showed high protein, dry matter, and soluble solid content. Pla. 8.9, a midrange hybrid type, produced mushrooms with a high protein, soluble solid, and ash content. The third strain assayed was Gurelan 45, which produced large, firm off-white mushroom crops. A correlation matrix was made between the main parameters. In regard to the other parameters considered, no strain stood out from the others. The Rioja-type casing produced the greatest number of mushrooms, although these were smaller and harvested earlier than those produced in other casing mixtures. Soil without additives produced the largest mushrooms, which also had a higher dry matter content, were firmer, and contained more soluble solids. The other casing materials, binary mixtures of soil with sphagnum or black peat, produced mushrooms of intermediate values. The correlation matrix showed that the higher the number of mushrooms, the greater the overall yield, the smaller the size, and the earlier the first flush. It was also observed that a higher content in dry matter was correlated with firmer texture, greater contents in soluble solid and protein, and lower pH and ash content. Fungi have been viewed with scepticism, reserve, and prejudice since primitive times (Tseng and Luong, 1984). They were being consumed in ancient China 3000 years ago and were even considered a source of immortality in ancient Egypt. The Greeks and Romans knew them for their delicious aroma and taste, but it was not until the 18th century in France that the first serious attempts were made to grow mushrooms [Agaricus bisporus (Lange) Imbach] commercially. A technique for a short method of composting and the use of synthetic composts was introduced at the beginning of the last century (Tseng and Luong, 1984). At present, mushrooms are cultivated in 80 countries of the world with a production of 6.3 MT in 1997, of which 31.7% corresponded to A. bisporus (Courvoisier, 1999). The European Union with 45.7% of world production (mainly Holland and France), North America (24.9%), and Asia (20.7%) are the main production regions (ANICC, 1995). At present, four clearly differentiated commercial mushroom strains exist on the market: 1) pure white strains, characterized by their white and relatively small fruit bodies without scales; 2) off-white strains with large white mushrooms with often dark scales on the cap; 3) hybrid strains, the most widely cultivated and resulting from a cross between the previously mentioned strains, which produce high yields and good quality; and 4) brown strains with a brownish to palecolored cap (Fritsche and Sonnenberg, 1988). However, the actual cap characteristics of these strains regarding size, shape, and color are strongly influenced by environmental and cultivation conditions (Tschierpe, 1983). The production and quality parameters of most interest are: number, size, earliness, freshness, color, shape, firmness, aroma, freedom from debris, the degree of maturity and development stage, and visual defects (Burton, 1989; Burton et al., 1995; Carey and O’Connor, 1991; Pardo, 1999). Any change in one or more of these factors may affect acceptability by the consumer. Like with most horticultural products, mushrooms have a limited storage life (1 to 3 d at 18 C) and that quality is affected by cultivation techniques, the strain, handling, and storage conditions (Burton, 1989). In mushroom cultivation, the casing material plays a very important role because it conditions the stage of fructification. The casing has several functions because, among others, it: 1) constitutes the physical medium that supports the sporophores; 2) maintains an adequate degree of moisture; 3) provides a suitable medium for stimulatory bacteria; 4) protects the compost surface from drying out; 5) provides the mycelium with an aerated environment, facilitating gas exchange; and 6) provides an environment with a low osmotic value (Bazerque and Laborde, 1975; Visscher, 1988; Wuest and Beyer, 1996). The most widely used casing is, without doubt, sphagnum peat because of its high waterretaining capacity and excellent structural characteristics (Yeo and Hayes, 1979). Different types of soil have also been widely used with good results, the main properties needed being a good structure and a minimum of 5% organic matter (Edwards, 1974; Hayes, 1978; Pizer and Leaver, 1947). Such mineral materials are usually combined with different organic substrates, mainly peat, which act as structural and water-holding correctors. In Spain, there are two main mushroomgrowing areas (Castilla-La Mancha and La Rioja-Navarra), which are responsible for almost all the mushrooms grown and each area tends to use its own casing materials. In Castilla-La Mancha, growers use soils of different origins to which peat is added, and in La Rioja-Navarra, a fine lime gravel combined with brown peat is used. During the present study, we have evaluated the production (number, yield, unitary weight, and earliness) and quality (color, dry matter, texture, protein and soluble solids content, ash, and pH) of three commercial mushroom strains (Pla 8.9, Blancochamp BL-40, and Gurelan 45) grown in four casings (soil, soil + sphagnum peat, soil + black peat, and the casing usually used in La Rioja). A correlation matrix has been presented among the principal production and quality parameters. Our aim is the agronomic evaluation of different casing layers used in mushroom cultivation. Materials and Methods Mushroom cultivation and experimental design. The experiment was carried out in the Centro de Investigación, Experimentación y Servicios del Champiñón (Quintanar del Rey, Cuenca, Spain) using an Ibercex experimental walk-in growth chamber (ASL, S.A., San Fernando de Henares, Madrid, Spain) provided Received for publication 9 Sept. 2009. Accepted for publication 19 Nov. 2009. We thank the Consejerı́a de Agricultura de CastillaLa Mancha, the Diputación Provincial de Cuenca and Recomsa, S.C.L., for enabling us to carry out the present work as part of their agreement for agricultural investigation and experimentation (project 160/45-CH). To whom reprint requests should be addressed; e-mail [email protected]. HORTSCIENCE VOL. 45(2) FEBRUARY 2010 231 CROP PRODUCTION