Mycorrhizal compatibility and symbiotic reproduction of Gavilea australis, an endangered terrestrial orchid from south Patagonia

Abstract

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.

Using In Situ Symbiotic Seed Germination to Restore Over-collected Medicinal Orchids in Southwest China

“…Interestingly, Sebastian et al (2014) used five fungal strains from the corresponding host of Aa achalensis to promote seed germination and found that seed germination depended on the strains used. Varying results have also been shown in Gavilea australis where percentage seed germination varied depending on the origin of the mycorrhizal fungi isolated from the host (roots or protocorm) or conspecific vs. heterospecific species (Fracchia et al, 2014). Based on our results, as well as those of previous studies, it seems likely that advanced restoration-friendly techniques should include the screening of compatible mycorrhizal fungi (as in Luo et al, 2003) from corresponding host protocorms to promote in situ seed germination.…”

Quantitative evaluation of protocorm growth and fungal colonization in Bletilla striata (Orchidaceae) reveals less-productive symbiosis with a non-native symbiotic fungus

“…The specificity between orchids and mycorrhizal fungi has been the subject of controversy for a long time [ 37 ]. Green terrestrial orchids likely exhibit low fungal specificity at the germination stage [ 38 , 39 ]. By contrast, Warcup and other researchers have reported that at least genus-level specificity of symbiotic fungi might exist [ 7 , 40 , 41 ].…”

Mycorrhizal fungi associated with Codonorchis lessonii (Brongn.) Lindl., a terrestrial orchid from Chile

“…Phylogenetic analyses showed that three different fungal strains belonging to Ceratobasidiaceae and one to Tulasnellaceae associate with C. lessonii. Fracchia et al (2014) identified Tulasnella calospora associated with the roots of an Argentinian population of C. lessonii. Similar associations with different Ceratobasidium and Tulasnella taxa had also been reported for other endemic Chilean orchids such as Gavilea araucana (Duran et al 2007), Bipinnula fimbriata (Steinfort et al 2010), Chloraea collicensis and C. gavilu (Pereira et al 2014, Herrera et al 2017, and C. cuneata (Atala et al 2015).…”

“…However, this is not the case for South American terrestrial orchids, particularly temperate species, where studies are relatively scarce and have focused on a few genera like Bipinnula and Chloraea (Pereira et al 2014, 2015. Recently, Fracchia et al (2014) isolated a Tullasnella species from Codonorchis lessonii in Argentina and tested it in the symbiotic germination of Gavilea australis. Understanding the fungal association in orchids is of great importance, as fungal availability in the environment may play a key role in orchid distribution and diversity (Brundrett 2007, McCormick et al 2012, Otero et al 2002.…”