Resistance to toxin-mediated fungal infection: role of lignins, isoflavones, other seed phenolics, sugars, and boron in the mechanism of resistance to charcoal rot disease in soybean

摘要

Soybean seed is a major food source for human nutrition and livestock feed. Soybean seed contains protein and amino acids, oil and fatty acids, sugars (sucrose, raffinose, and stachyose), minerals (Bellaloui et al., 2009; Bellaloui et al., 2010a; Bellaloui et al., 2011), and secondary natural metabolites such as phenolics, including phenolic acid, lignin, and isoflavones (Sakthivelu et al., 2008). Phenolics are a class of natural chemical compounds containing of a hydroxyl group (-OH) bonded to an aromatic hydrocarbon group. They possess an aromatic ring, bearing one (phenol) or more (polyphenol) hydroxyl substituents, including functional derivatives such as esters, methyl ethers, and glycosides (Harborne, 1989). Phenolics are synthesized through the shikimate-phenylpropanoids-flavonoids pathways, producing monomeric and polymeric phenolics and polyphenols (Lattanzio et al., 2006; Knaggs, 2001). Phenolics are classified based on the number of carbon. For example, C6 (simple phenol, benzo-quinones), C6-C1 (phenolic acid), C6-C3-C6 (flavonoids,isoflavonoids), (C6)n, (C6-C3-C6)n (lignins) (Aoki et al., 2000; Whiting, 2001). Phenolic compounds are essential for growth, reproduction, and protection of plants against bio tic (fungus, bacteria, virus, and insect infection) or abiotic stresses such as drought and temperature. From a human nutrition perspective, phenolics have natural antioxidant properties which may protect against degenerative diseases such as coronary heart disease, osteoporosis, stroke, and cancers (Messina et al., 1994; Potter et al., 1998; Sakthivelu et al., 2008; Wikipedia, 2011).