The S. luteus and T. virens on the MMN agar medium and PDA agar medium were cut with a sterile puncher (U = 10 mm). Suspension cultures of S. luteus and T.
virens were obtained by transferring the mycelium inoculum to liquid MMN and PD liquid medium (MMN and PDA medium without agar), respectively. Then, threeweek-old (S. luteus) and five-day-old (T. virens) suspension cultures maintained in the dark at 27 C under agitation (120 r/min) were used to inoculate the P. sylvestris var. mongolica seedlings. The seeds of P. sylvestris var. mongolica were surface sterilized with potassium permanganate (0.5 %, v/v) for 30 min, then washed three times with sterile distilled water. They were then germinated on sterile moistened gauze at 25 C for 5 days. After germination, the seedlings were separately transferred to plastic pots (20–30 seeds per pot) filled with a sterile culture medium, vermiculite/soil/sand (1:2:1, v/v/v) mixture which was sterilized in a high-temperature autoclave for 2 h under 121 C. The basic soil parameters are shown in Table 1. The pots were kept under greenhouse conditions (day/night thermal regime of 23/9 ± 2 C and 14 h light/10 h dark photoperiod) for 1 month, and the seedlings were then inoculated with the fungi.