*4.1. Plant and Mycorrhizal Fungus Materials*

Tissue culture plantlets of *A. roxburghii* were about 3 month-old and 2–3 cm in height from Yongan city, Fujian province, China. The mycorrhizal fungus AR2 (NCBI accession No: MN068847) was previously isolated in our laboratory and deposited at the microbiological center of the Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China. Before symbiotic cultures, the fungal strain was inoculated on the potato dextrose agar medium (PDA: potato 200 g·L−1, glucose 20 g·L−1, agar 12 g·L−1, pH 5.2) in darkness at a temperature of 25 <sup>±</sup> <sup>1</sup> ◦C for 5 days. Two pieces (0.5 cm3) of the fungal inoculum were inoculated on solid matrix medium (sawdust: wheat bran: water = 3:1:1.5, *v*/*v*/*v*; 101.33 kPa and 121 ◦C for 180 min) in darkness at a temperature of 25 ± 1 ◦C for 15 days. After that, the fungal solid substrates were obtained for subsequent symbiotic culture.
