Lectotypification of Agaricus brunnescens

Abstract

Agaricus brunnescens Peck sometimes is synonymized with A. bisporus ( J.E. Lange) Imbach, the cultivated button mushroom. However this relationship has not been accepted universally or unreservedly. For various reasons A. bisporus is the more commonly used name. This study demonstrated that A. brunnescens is based on a heterogeneous type, as suggested by elements of the type description, correspondence at NYS and a lack of consensus among studies of the type. DNA sequence analysis indicated that material corresponding to both A. bisporus and A. subrufescens Peck is present in the type as presently constituted. A lectotype corresponding to the concept of A. bisporus is chosen, and nomenclatural issues are discussed. A definitive history of A. brunnescens is attempted.

• cultivated mushroom
• lectotypification
• nomenclature

My thanks to John Haines, Lori Leonardi and NYS for access to Peck’s material and correspondence, loans of material, permission to reproduce Peck’s illustration of A. brunnescens, and hospitality, to Harry Thiers, who supported the initial evaluation of the material; to Bonnie Isaac, for facilitating the (second) loan from NYS; to Roy Halling, Donald Pfister, Geraldine Kaye and staff at FH for information on and access to the Wells and Palmer specimens, Burt’s correspondence and Bridgham’s painting and associated notes, and for their hospitality; to Christine Niezgoda and staff at F for loan of B-17943; to Daniel J. Royse, who invited David Malloch and myself to present our views in a 1986 symposium at Penn State; to Rytas Vilgalys, who long ago pointed out that I was “flogging a dead horse” (actually a pachyderm) in this matter; and to Rolf Singer, David Malloch, Luis Parra and especially Scott Redhead for stimulating discussions, data, encouragement, comments on this manuscript, and/or incentive to pursue this matter and to put both A. brunnescens and A. bisporus on a more sound footing.