Symbiotic seed germination has become one of the research hotspots in orchid conservation. It involves isolation, identification, and culture of effective symbiotic fungi that promote seed germination and / or reintroduction of threatened orchid species. However, few studies involved other ecological factors, such as humidity, pH, and species of substance.
Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) used seeds of Papilionanthe teres, a locally endangered and medicinally valuable epiphytic orchid in Xihsuangbanna, to attract germination-enhancing fungi on its four host plants. They placed orchid seed packets near the roots of adult P. teres plants to locate, isolate, and identify naturally occurring fungi capable of stimulating seed germination under natural conditions. They also wanted to test the effects of the fungi on seed germination and protocorm development of P. teres.
They assessed the impacts of four epiphytic host substrates, Averrhoa carambola, Lagerstroemia villosa, Callistemon rigidus, and Butea monosperma, on symbiotic seed germination and protocorm development of P. teres. By the in situ seed baiting technique, they detected a highly compatible mycorrhizal fungus (Epa-01 strain, Epulorhiza sp.) which enhanced seed germination by more than 80 % and promoted protocorm development to reach stage 5 (with two leaves).
. Seeds cocultured with the Epa-01 strain and oat meal agar medium significantly outperformed in germination and growth speed, which indicated that symbiotic seed germination was an effective method for P. teres seedling production. Ex situ and ex vitro symbiotic seed germination indicated that the distribution preference of P. teres for its host trees was possibly and partly related to the abundance and vitality of the Epa-01 strain on the host plants. Choosing A. carambola and L. villosa as epiphytic host plants of P. teres  may contribute to improving in situ seed germination and seedling development, and enhancing the success rate of its reintroduction.
The results suggest that in situ seed baiting may be used to effectively capture germination-enhancing fungi in epiphytic orchids, and testing the effects of bark substrate types on seed germination and protocorm development contributed to selecting appropriate host plants for its reintroduction into natural habitats.
  The study entitled “Highly compatible Epa-01 strain promotes seed germination and protocorm development of Papilionanthe teres (Orchidaceae)” has been published in Plant Cell, Tissue and Organ Culture (PCTOC).

Contact
GAO Jiangyun Ph.D Principal investigator
Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan 666303, China
E-mail: gjy@xtbg.org.cn