Morphology and possible mycobiont (Suillus pictus) of a tuberculate ectomycorrhiza on Pinus strobus

Abstract

Suillus pictus was consistently associated with tuberculate ectomycorrhizae (tubercles) on Pinus strobus in North Carolina. Histological, cultural, and chemical reaction studies were used to examine this association. Tubercles were examined by light and scanning electron microscopy. Clamp connections, a reduced to absent tannin layer, and appressed mantle hyphae were observed. Naturally occurring rhizomorphs of Suillus pictus and tubercles have a similar morphology consisting of an outer pseudoparenchymatous sheath, large vessel-like cells, and a prosenchymatous layer between the sheath and the vessel-like cells. Similar macroscopic chemical color reactions to 10% FeSO4, 15% KOH, concentrated NH4OH, concentrated H2SO4, and Melzer's reagents were observed on rhizomorphs of S. pictus and tubercles, surface of tubercles, and stipes of S. pictus. Chemical color reactions and growth characteristics of S. pictus and the tubercle mycobiont were similar on different agar media.