Academic journal article The American Midland Naturalist

Mycorrhizal Fungi and Cold-Assisted Symbiotic Germination of the Federally Threatened Eastern Prairie Fringed Orchid, Platanthera Leucophaea (Nuttall) Lindley

Academic journal article The American Midland Naturalist

Mycorrhizal Fungi and Cold-Assisted Symbiotic Germination of the Federally Threatened Eastern Prairie Fringed Orchid, Platanthera Leucophaea (Nuttall) Lindley

Article excerpt

ABSTRACT.-The 70% decline of the Federally threatened eastern prairie fringed orchid, Platanthera leucophaea (Nuttall) Lindley, has prompted concern for its recovery through artificial propagation. We describe a technique to germinate seeds and cultivate seedlings of P leucophaea in vitro using cold treatments (=stratification) and mycorrhizal fungi (=symbiotic seed germination). Five fungal isolates were recovered from mature P leucophaea plants in Illinois and Michigan and were identified as members of the anamorphic genus Ceratorhiza Moore. Stratified seeds inoculated with mycorrhizal fungi germinated within 25 d of sowing. Leaf-bearing seedlings were obtained by chilling young seedlings (protocorms) for 107 d. Our successful culture of leaf-bearing seedlings with a presumed mycotrophic capability may make it possible for this threatened orchid to be propagated in soil ex vitro, followed by reintroduction into suitable habitats.

INTRODUCTION

The Federally threatened eastern prairie fringed orchid, Platanthera leucophaea (Nuttall) Lindley, has declined by 70% across the United States mostly as a result of habitat conversion to agriculture (Bowles, 1983, 1999). Many of the remaining populations are small (50-100 plants), and it is feared that inbreeding depression may be contributing to P leucophaea's decline. Existing populations also remain vulnerable to habitat destruction, poaching and ineffective site management (Bowles, 1999), prompting concern for P leucophaea's recovery. To implement conservation of P leucophaea, reliable seed germination methods must be developed and the mycorrhizal symbionts identified. Unfortunately, little is known about the identity of orchid mycorrhizal fungi and few North American terrestrial orchid species have been successfully propagated from seed (Zettler, 1996).

Zelmer and Currah (1995) recovered Ceratorhiza pernacatena Zelmer and Currah from the mycorrhizas of Platanthera praeclara Sheviak and Bowles growing in a tallgrass prairie in Canada and speculated that the fungus could be specific to P praeclara or the P pr-aeclara-P leucophaea species pair. Leaf-bearing seedlings of P leucophaea have been obtained in one study (Stoutamire, 1996) on aseptic media containing an external carbon source (=asymbiotic germination; Stoutamire, 1974; Linden, 1980; Arditti et al., 1981) after seeds were pretreated with cold and moisture (=stratification); however, these seedlings did not survive soil transfer ex vitro (W. Stoutamire, pers. com.), possibly because they lacked the mycorrhizal symbiont. The use of fungi to propagate terrestrial orchids (eg., Platanthera) from seed (=symbiotic seed germination) has been employed as one technique to improve seedling establishment in soil (Clements and Ellyard, 1979; Clements et al., 1986; Anderson, 1991; Zettler and McInnis, 1992; Anderson, 1996), because it is assumed that seedlings are provided with a mycotrophic capability (Rasmussen, 1995). This would enable seedlings to use (digest) fungi as an energy source before initiating photosynthesis. For conservation purposes, planting symbiotically grown seedlings increases the likelihood that the critically important symbiotic partner is reintroduced into suitable habitats along with the seedlings (Zettler, 1997a).

In this article, we describe the mycorrhizal fungi recovered from mature Platanthera leucophaea root-like organs. We also provide a technique to germinate seeds and cultivate leaf- bearing seedlings of P. leucophaea in vitro, assisted by cold treatments and mycorrhizal fungi.

METHODS

Fungal isolation and characterization.-Mature (leaf-bearing) P leucophaea plants, along with intact soil were collected from Abbott Park, Lake Co., Illinois on 24 June 1998 and from Monroe Co., Michigan on 4 Oct. 1998. Plants were placed in plastic bags, sealed and transported to the laboratory immediately after collection. Root systems were detached for fungal isolations and the remaining above ground portion of the Abbott Park specimen was deposited as a voucher (LWZ #858) in the Illinois College Herbarium. …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.