INTERACTIONS BETWEEN CALLUS-CULTURES OF EUROPEAN BEECH, INDIGENOUS ASCOMYCETES AND DERIVED FUNGAL EXTRACTS

Ascomycete fungi from the Xylariaceae and Diatrypaceae responded in th ree distinct ways when grown in dual culture with callus material of b eech (Fagus sylvatica L.). Growth of the putative weak pathogens Bisco gniauxia nummularia (Bull.) 0. Kuntze and Eutypa spinosa (Pers.) Tul. & C. Tul. was stimulated whilst the saprotrophs Ustulina deusta (Hoffm .) Lind. and Xylaria polymorpha (Pers.) Grev. were unaffected by the p resence of callus. Sapwood-colonizing fungi displayed a range of respo nses, with Diatrype stigma (Hoffm.) Fr. being unaffected, Diatrype dis ciformis (Hoffm.) Fr. stimulated, and Hypoxylon fragiforme (Pers.: Fr. ) Kickx and 'Hypoxylon purpureum' inhibited by the presence of callus. Changes in morphology were evident in many of the fungi during intera ctions, with yeast-like forms being produced by those members of the X ylariaceae which have been recognized as endophytes. Reciprocally, hig h concentrations of cell free extracts of some of the Xylariaceous fun gi resulted in necrosis or inhibition of callus growth, while at sub-l ethal concentrations marked stimulation of growth was evident. The imp ortance of these results with respect to pathogenicity testing and elu cidation of the biology of tree-fungus interactions is discussed.