2. Materials and methods
2.1. Fungus cultivation
P. indica ATCC (204458) was cultured in potato dextrose broth with constant shaking at 100 rpm at 30 °C. The mycelium was harvested 8 days after inoculation by filtration to remove liquid media.
2.2. Preparation of soil
Field soil was collected from an agricultural field with no soybean cyst nematode infestation at the Southern Outreach and Research Station in Waseca, Minnesota, USA. Soil was mixed with 30% sand and autoclaved at 121 °C for 60 min. Mycelium of P. indica at concentrations of 2.5% (w/w) and 5% (w/w) was thoroughly mixed with soil and placed into four 16-cm-diameter clay pots. A control treatment consisting of the autoclaved soil mixture with no P. indica amendment was similarly prepared. Eight soybean seeds were surface sterilized with 0.5% NaOCl for 3 min, rinsed three times in sterile water, and sown in each pot. One week after planting, seedlings were thinned to keep only five seedlings of approximately the same size and developmental stage per pot. The pots were arranged randomly and maintained in a greenhouse with a temperature ranging from 26 °C ± 4 °C with 16 h light/8 h dark. Pots and seedlings were watered daily.