Chitosan, Antifungal Product against Fusarium oxysporum f. sp. albedinis and Elicitor of Defence Reactions in Date Palm Roots

Abstract

The effect of chitosan on the growth and morphology of Fusarium oxysporum f. sp. albedinis (Foa), the
causal agent of Bayoud disease, and its ability to elicit a defence reaction against this fungus in date palm roots were
investigated. Chitosan at 1 mg ml-1 reduced the growth of Foa on potato dextrose agar medium by an average of 75%,
while mycelial growth was totally inhibited in a liquid medium. When added to a solid medium, chitosan caused
morphological changes in Foa mycelium. In addition, when injected into roots at three concentrations (0.1, 0.5 and 1
mg ml-1), chitosan elicited peroxidase (PO) and polyphenoloxidase (PPO) activity and, particularly at the concentration
of 1 mg ml-1, increased the level of phenolic compounds. Concerning phenolics, chitosan led to an accumulation of
non-constitutive hydroxycinnamic acid derivatives, known to be of great importance in date palm resistance to Bayoud.
The accumulation of hydroxycinnamic acid derivatives was greater in cv. BSTN than in cv. JHL. Chitosan could be
used to protect date palm against this vascular disease.