soil and then sterilized as follows: the samples were rinsed
with sterile distilled water 3 times; they were submerged in
75% ethanol for 1min and rinsed 5 times with sterile water,
followed by 0.1% HgCl2 for 1min; and lastly, they were rinsed
with sterile distilled water 5 more times. The sample surfaces
were dried with sterile blotting paper. The surface-sterilized
tubers were cut into 0.5 cm-long segments, and the center
of the sterilized leaves was cut into 10mm× 10mm pieces
with sterile blades. The tissues (4 segments or pieces per
plate) were placed on potato dextrose agar (PDA) medium
(containing more than 30gmL−1 streptomycin and ampicillin)
and incubated at 28 ◦C in the dark for 5–7 d. Three
replicate plates were used for each test. The colonies were
examined periodically, and the endophytic fungal hyphae that
emerged from the segments were transferred onto fresh PDA
medium. Transfers were not repeated until a pure culture was
obtained according to the colony morphology. To validate the
effect of surface disinfection, uncut tissues that were sterilized
according to the same steps were placed on PDA medium
and incubated under the same conditions as the control. In
addition, the last drift lotion from the surface-sterilization
process (1–2 drops) was added to the PDA culture medium
and coated evenly as another control. Finally, we examined
the effect of disinfection after checking whether colonies had
formed.