As a natural polysaccharide, chitosan (poly β-(1→4)
N-acetyl-D-glucosamine) represents a promising alternative
treatment for postharvest disease management due to its
antifungal activity and elicitation of defense response in
the plant host (Terry and Joyce 2004; Bautista-Baños et al.
2006). Previous reports have indicated that chitosan can
inhibit the growth of several postharvest fungal pathogens,
including Alternaria alternata (Reddy et al. 1997), Botrytis
cinerea (Chien and Chou 2006), Penicillium expansum (Liu
et al. 2007), Penicillium digitatum (Pacheco et al. 2008),
control at each day. In order to investigate whether chitosan
had inductive effects on carrot host, defense-related
enzymes of PPO and POD were detected. Generally, POD
activity increased gradually from 0 to 4 d of storage, and
chitosan treatment significantly induced this enzyme activity
(Fig. 6-A). PPO activity in control carrot dramatically
increased from 1 to 4 d, while that in chitosan treatment
had significantly higher activity at each day except 4th d
(Fig. 6-B).