Effects of cultivating orchid Gastrodia elata with the introduced Armillaria in a local ecosystem

To characterize the potential effects of an introduced fungus in a local ecosystem, an experiment was performed in an abandoned farmland, where a traditional Chinese medicinal plant, Gastrodia elata had been continuously cultivated using the introduced Armillaria M2 and it had not been grown for the last 6 years. In this case, a newly introduced Armillaria strain M1 was used to cultivate orchid G. elata again. Inoculating strain M1 showed an infection rate of 95.56% on G. elata, much higher than that of without, 22.2%. Molecular evidence showed that all Armillaria re-isolated from G. elata in the farmland were genetically identical to the introduced ones. It suggested that the introduced Armillaria completely blocked the infection of natural ones on G. elata. Such an effect could persist several years even after stopping cultivation of G. elata. A total of 53 strains of Armillaria were obtained from a variety of isolation sources. Analysis of their intergenic spacer (IGS) sequences revealed that diverse and novel species of Armillaria existed in local forest. They are valuable resources for cultivating G. elata in future. Regarding ecological risk, utilization of the introduced Armillaria is not recommendable for local farmers. Key words: Gastrodia elata, Armillaria, the introduced microbe, orchid, ecological risk.