Genetic variations of ectomycorrhizal fungi: extramatrical phase of Pisolithus sp.

Abstract

The ability of 28 monokaryons and 78 reconstituted dikaryons of Pisolithus sp. from South Africa to form mycelial strands in association with Pinus pinaster was tested under aseptic and non-aseptic conditions. All monokaryotic and some dikaryotic cultures failed to form mycelial strands either on agar medium or in growth pouches. The remaining dikaryotic cultures showed wide genetic variation in the development of mycelial strands and in the extension of their extramatrical phase. The exploration of the surrounding environment by the extramatrical phase from synthesized Pinus pinaster – dikaryotic cultures of the Pisolithus sp. depended largely upon the type of medium used, being more extensive in soil than on nutrient agar medium. Microscopic observation showed that mycelial strands were formed by aggregations of hyphae. Large central hyphae with disorganized cytoplasm were observed in some strands. The results are discussed in relation to nutrient and water absorption. Key words: Pisolithus sp., Pinus pinaster, genetic, extramatrical phase, mycelial strands.