Further evidence of Ceratobasidium D.P. Rogers (Basidiomycota) serving as the ubiquitous fungal associate of Platanthera leucophaea (Orchidaceae) in the North American tallgrass prairie

Abstract

Background: In the United States and Canada, ca. one-half of native orchid species are now threatened with extinction. A number of these species are restricted to tallgrass prairies of central North America, such as the Eastern Prairie Fringed Orchid, Platanthera leucophaea (Nutt.) Lindl.-a U.S. Federally threatened species.

Results: We provide new records of fungi recovered from roots of P. leucophaea and five other orchid species inhabiting prairie sites in Illinois and neighboring states during a 10-year period (2008-2017). A total of 39 fungal endophytes were isolated from Cypripedium candidum (1), Platanthera lacera (1), P. leucophaea (32), P. peramoena (3), Spiranthes lacera (1), and S. magnicamporum (1), 31 (79%) of which were assignable to Ceratobasidium and the remainder to Tulasnella. These fungi were acquired from 16 different sites, 13 of which are new records including two new state records (Iowa, Wisconsin). Molecular analysis revealed that some Ceratobasidium strains were virtually identical despite being geographically isolated by > 300 km.

Conclusions: This study, encompassing a decade of work, confirms that Platanthera leucophaea is a mycorrhizal specialist with heavy reliance on Ceratobasidium with the tallgrass prairie ecosystem of North America. Our isolation of Ceratobasidium from P. leucophaea spanning additional sites suggests that the association is widespread. Such information should provide conservationists and land managers with more confidence in developing protocols that facilitate the long-term conservation of this prairie orchid.

Keywords: Conservation; Endophytes; Mycorrhizal fungi; Specificity; Tulasnella.

Fig. 1

The U.S. Federally-listed (threatened) Eastern Prairie Fringed Orchid, Platanthera leucophaea (Nutt.) Lindl. (Photo courtesy of Dr. Timothy J. Bell)

Fig. 2

Locations in the Midwestern United States where Ceratobasidium fungi were isolated from roots and/or protocorms of Platanthera leucophaea as of 2017. The shaded areas reflect the orchid’s historic distribution (Bowles 1983). Solid dots indicate locations where Ceratobasidium (=Ceratorhiza) was recovered from P. leucophaea prior to the present study. The two solid dots from lower region of Illinois (Christian and Macoupin Co.) were locations where protocorms of P. leucophaea were acquired from seed packets (see Zettler and Piskin 2011). Pink dots with numbers represent sites where Ceratobasidium was acquired from P. leucophaea in the present study: 1 = Lake Co., IL; 2 = Dupage Co., IL; 3 = Kenosha Co., WI; 4 = Tuscola Co., MI; 5 = McHenry Co., IL; 6 = Jackson Co., IA; 7 = Cook Co., IL; 8 = Will Co., IL; 9 = Kane Co., IL; 10 = Lee Co., IL. Pink dots lacking a number reflect tallgrass prairie sites where Ceratobasidium was isolated from orchids other than P. leucophaea (i.e., Platanthera lacera, P. peramoena, Spiranthes magnicamporum, S. vernalis)