Gavilea australis is a terrestrial orchid endemic from insular south Argentina and Chile. Meeting aspects of mycorrhizal fungi identity and compatibility in this orchid species is essential for propagation and conservation purposes. These knowledge represent also a first approach to elucidate the mycorrhizal specificity of this species. In order to evaluate both the mycorrhizal compatibility and the symbiotic seed germination of G. australis, we isolated and identified its root endophytic fungal strains as well as those from two sympatric species: Gavilea lutea and Codonorchis lessonii. In addition, we tested two other strains isolated from allopatric terrestrial orchid species from central Argentina. All fungal strains formed coilings and pelotons inside protocorms and promoted, at varying degrees, seed germination, and protocorm development until seedlings had two to three leaves. These results suggest a low mycorrhizal specificity of G. australis and contribute to a better knowledge of the biology of this orchid as well as of other sympatric Patagonian orchid species, all of them currently under serious risk of extinction.
Aa achalensis is an endangered terrestrial orchid endemic from Argentina. In vitro symbiotic seed germination was evaluated for its propagation. Five different fungal strains were isolated from this species: two Rhizoctonia-like related to Thanatephorus cucumeris and three ascomicetaceous fungi belonging to Phialophora graminicola and one to an uncultured Pezizaceae. All five isolates promoted seed germination being one T. cucumeris strain the most effective. After 16 weeks of growth, 30% of A. achalensis protocorms developed until seedlings with two/four leaves in this treatment. These findings open an opportunity to the knowledge and preservation of this species.
Tuberization in many terrestrial orchids represents the most important physiological process for reproduction and survival. An in vitro controlled and reproducible tuberization and plant regeneration system was designed for Habenaria bractescens. Multinodal segments were incubated on Murashige and Skoog (MS) medium supplemented with different concentrations of N 6 -benzylaminopurine (BAP) and sucrose. After 45 days, the explants developed root tubers in vitro in 8 of the 12 media assayed. MS medium with 87.6 mM sucrose plus 4.4 lM BAP was one of the most effective for stimulating root tubers. Plants derived from in vitro root tubers were successfully transferred to the greenhouse without any acclimatization. The morphology and anatomy of the regenerated underground organs were examined to find identifying and distinguishing features. The protocol to regenerate root tubers of H. bractescens will be useful to study the basic aspects and control of tuberization and to carry out restoration programs.
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