The endophytic fungus Hyalodendriella sp. Ponipodef12 (GenBank accession number HQ731647) was isolated from the healthy stems of the 'Neva' hybrid of Populus deltoides Marsh × P. nigra L.. The fungus was cultured on PDA (potato 200 g/L, dextrose 20 g/L and agar 20 g/L) medium in Petri dishes at 25 °C for 10 days. For seed culture, two to three plugs of agar medium (0.5 × 0.5 cm) with fungal cultures were inoculated in each 250-mL Erlenmeyer flask containing 100 mL potato dextrose broth (PDB) medium, and incubated on a rotary shaker at 150 rpm and 25 °C for 5 days. For fermentation culture, about 50 mycelium pellets were inoculated in each 1,000-mL Erlenmeyer flask containing 300 mL PDB medium, and incubated on a rotary shaker at 150 rpm and 25 °C for 20 days.