Approximately half of all native orchids in North America, North of Mexico, are threatened with extinction. All orchids produce small dust-like seeds and require the presence of a specific fungus to germinate in nature. However, the characterization of the mycorrhizal partner for a species can be difficult, due to differences in habitat and some orchids ability to germinate with a wider set of fungi. Currently, identification of the appropriate mycorrhizal fungus and the collection and storage of seeds, are viewed as crucial elements to ensure the conservation of these orchids. Additionally, the long-term storage of seeds can vary depending on the species and storage method. Recently, there has been increased interest in growing seedlings in-vitro and re-introducing them back in the field to increase population sizes. Platanthera and Spiranthes are the two largest genera of orchids in North America. Many of the species in both genera are listed as either threatened or endangered at the federal and state level. The goal of this study three-fold: First, we investigated whether a fungus obtained from S. lacera at one location, could germinate the seed of S. cernua from another location; Second, we wanted to determine if four-year-old seed from S. vernalis was still viable; Third, we wanted to know if the fungus associated with two local forms of P. dilatata (small and large flowered) differs across five habitats they occupy in South-East Alaska.
Fungal isolation from S. lacera and P. dilatata was performed by excising the lateral roots of juvenile-adult orchids and manually removing growing pelotons. Identification of pure fungal cultures was achieved by amplification of the nuclear ITS region and Sanger sequencing at the University of Illinois Core Sequencing Facility (UIUC). Seeds were obtained from S. cernua in the fall of 2018 were processed, dried, and stored prior to symbiotic germination experiments.
In total, 11 fungal cultures were obtained from S. lacera. Three were identified as Tulasnella spp., with the remaining eight identified as Ceratobasidium spp. Symbiotic germination trials using S. cernua seed demonstrated the ability of a Tulasnella spp., obtained from S. lacera, to germinate seed. Germination experiments were also performed using S. vernalis seed showed they were still viable after four years in storage. Because S. cernua was able to germinate with fungus obtained from another site, the idea of introducing seedlings to the site where S. lacera occurs is supported. In addition, the seedlings of S. vernalis can be re-introduced to increase the population size of this endangered orchid. Nine fungal isolates were obtained from P. dilatata that occurred across four habitat types. We found Ceratobasidium was only isolated from the small local form of P. dilatata, while we were only able to isolate Tulasnella or Epulorhiza from the remaining habitats. Comparisons of the sequence similarity between Tulasnella isolates suggests the isolates differed not only between sites, but in some cases also differed in orchids obtained from the same site.
|Commitee:||Brunkow, Paul, Fowler, Thomas|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 81/12(E), Masters Abstracts International|
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