*4.2. Symbiotic Cultures of A. roxburghii Plantlets*

In symbiotic cultures of plantlets, the substrate (humus soil: vermiculite: water = 3:1:1) was used. Each culture bottle (9 cm in diameter, 12.5 cm in height) containing 70 g substrate was sterilized at 101.33 kPa and a temperature of 121 ◦C for 180 min. Six plantlets, derived from asexual reproduction, were transferred into each culture bottle which was inoculated with 0.5 g of fungal solid substrates, while the culture bottles without fungal inoculum served as the control. The symbiotic cultures were placed in the growth room under a 12/12 h photoperiod at a temperature of 25 ± 1 ◦C and an illumination intensity of 1500 Lx. The samples (the whole plantlet) were collected once a month from the beginning of co-culture until the sixth month. Samples were immediately frozen in liquid nitrogen and stored at −80 ◦C for later analyses using LC-MS/MS, RNA-seq and qRT-PCR. Among them, the collected samples grown for six months were used for the metabolome and transcriptome analyses. All data were obtained based on three independent biological replicates.
