Induction of mycorrhiza‐like structures and defence reactions in dual cultures of spruce callus and ectomycorrhizal fungi

Abstract

summaryHeterotrophic spruce (Picea abies [L.] Karst.) callus cells were grown in dual culture with ectomycorrhizal fungi (Amanita muscaria [L.] Pers., Lactarius deterrimus Gröger, Hebeloma crustuliniforme [Bull.] Quél., Suillus variegatus [Sw.: Fr.] O.K.) or with the pathogenic fungus Heterobasidion annosum [Fr.] Bref. Spruce cells stimulated growth of the mycorrhizal fungi, whereas growth of the pathogenic fungus was not affected. Two of the mycorrhizal fungi, 5. variegatus and L. deterrimus, caused hypersensitive reactions in spruce cells. In contact with the surface of the plant cells the mycorrhizal fungi developed densely interwoven lobed, hand‐ and fan‐shaped structures. They resembled morphological features occurring in the hyphal mantle and Hartig net of ectomycorrhizas. The ectomycorrhizal fungi did not show altered branching patterns when growing on cellophane sheets. These results demonstrate that callus cells of the host P. abies are able to stimulate fungal growth and to induce ectomycorrhizal fungi to form mycorrhiza‐like structures which normally are only generated in the presence of host roots.