Induced resistance of cucumbers to Fusarium wilt disease by synthesized N-acetylchitooligosaccharide analogues

Abstract

Induced resistance of cucumbers to Fusarium wilt disease by three synthesized oligosaccharides: β-1,3-N-acetyl-glucosamine disaccharide, β-1,3-N-acetyl-glucosamine trisaccharide and Lewisa trisaccharide was investigated. In radicle phase, after the roots were soaked with β-1, 3-N-acetyl-glucosamine disaccharide and β-1, 3-N-acetyl-glucosamine trisaccharide solution, the cucumbers showed resistance to the wilt disease with relative induced efficiencies of 21.9 and 22.3, respectively; the effective induced concentration of β-1,3-Nacetyl-glucosamine oligosaccharides was at least 5 μg·mL-1. In cucumber seedling phase, the plants treated with β-1,3-N-acetyl-glucosamine disaccharide and β-1,3-N-acetyl-glucosamine trisaccharide solution by foliar spraying also showed resistance to the wilt disease with relative induced efficiencies of 28.5 and 23.5, respectively; the effective induced concentration of β-1,3-N-acetyl-glucosamine oligosaccharides was at least 10 μg·mL-1. However, in both growth phases, after the plants were treated with Lewisa trisaccharide by the same way mentioned above, they showed no resistance to the wilt disease. The cucumber resistant differences of N-acetylchitooligosaccharide analogues (β-1, 3-N-acetyl-glucosamine disaccharide and β-1, 3-N-acetyl -glucosamine trisaccharide) and Lewisa trisaccharide may be caused by the differences of the sugar residues, the substituents on the reducing terminal residue or (and) the oligosaccharide backbone structures.

Keywords

• cucumber <italic>Fusarium</italic> wilt disease
• induced resistance
• β-1,3-N-acetyl-glucosamine disaccharide
• β-1,3-N-acetyl-glucosamine trisaccharide
• Lewis^a trisaccharide