Assay of mycelial growth of S. sclerotiorum
S. sclerotiorum was isolated from infected carrot and
maintained on potato dextrose agar (PDA) (Beijing
Borunlaite Sciense & Technology Co., Ltd., China). The
effect of chitosan on mycelial growth was assayed according
to Yao and Tian (2005). Mycelial disks (5 mm in diameter)
from 10-d-old cultures, grown at 25°C, were placed in the
centre of Petri dishes (90 mm in diameter) containing 20 mL
of PDA supplemented with 1% chitosan. The concentration
of chitosan was selected based on preliminary experiments
conducted at pH 5.0. PDA without chitosan served as a
control. Mycelial growth was determined by measuring
colony diameter at daily intervals for 5 d.