Quantitative effects of various tree species on tuber growth and pharmacological compositions of Gastrodia elata

Gastrodia elata is a myco-heterotrophic orchid that has been used in traditional medicine to treat number of human illnesses. It establishes symbiotic associations with compatible mycorrhizal fungi, such as Mycena species and Armillaria mellea , depending on its developmental stages. G. elata tubers contain two major pharmacological substances; gastrodin (GA) and ergothioneine (ERG). Here we investigated whether the use of different tree species could enhance the growth of G. elata tubers, or of the content of GA or ERG. A. mellea infected all 30 tree species but its infection levels varied among species. However, only 14 species stimulated the growth of G. elata immature tubers; Ulmus davidiana produced the biggest tubers (7.8 g FW) while Abies holophylla generated the least significant changes on the growth of tubers reaching their weights to 0.9 g. In contrast to the tuber growth, the infection levels of A. mellea in those trees were similar, indicating that the colonized levels of A. mellea on different tree hosts were not correlated with the yield of G. elata tubers. Interestingly, the weights of immature tubers developed on 14 tree species were negatively correlated with the levels of ERG, but not with those of GA. In conclusion, our study suggested that the use of U. davidiana instead of Quercus species, which has been used for traditional cultivation of G. elata , might enhance the yields of G. elata tubers, but reduce the ERG levels while maintaining the GA levels.