5.5. Assay of plasma membrane integrity
Mycelia from 2-d-old cultures of S. sclerotiorum grown in
PDB were collected, washed and dehydrated on filter paper.
The obtained mycelia were then transferred into conical
flasks (250 mL) containing 50 mL of sterile water (control)
or 1% chitosan (pH 5.0), and incubated at 180 r min–1 at
25°C for 20, 40 and 60 min. The mycelia were collected on
filter paper, and rinsed with 50 mmol L–1 sodium phosphate
buffer (pH 7.0) twice to remove residual medium. Fresh
mycelia were stained with 10 μg mL–1 propidium iodide
(PI) for 5 min at 30°C (Liu et al. 2007). Mycelia were
then collected and washed twice with the buffer to remove
residual dye. The mycelia were observed with a Zeiss
Axioskop 40 microscope (Carl Zeiss, Germany) equipped with an individual fluorescein rhodamine filter set (Zeiss No.
15: excitation BP 546/12 nm, emission LP 590 nm). Three
fields of view from each cover slip were chosen randomly,
and the experiment was repeated twice.