- Selcuk Journal of Agriculture and Food Sciences
- Vol: 18 Issue: 34
- Roles of Phenolics in Plant Diseases Resistance
Roles of Phenolics in Plant Diseases Resistance
Authors : Nuh Boyraz, Barış Sürel
Pages : 56-69
View : 9 | Download : 22
Publication Date : 2004-12-25
Article Type : Research Article
Abstract :A wide range of substances possessing an aromatic ring bearing a hydroxyl substituent are called phenolic substances. Carbohydrates are the precursors of phenolics, which show antifungal, antibacterial, and antiviral activities. At high concent-rations they inhibit spore germination and growth of fungi. Toxicity of phenolics varies depending upon their structure and, in general, o-dihydroxy phenolics are higly toxic. Some phenolics inhibit the production of fungal enzymes and inactivate the enzymes produced by the pathogens. Phenolics may suppress toxin production by the pathogens or detoxify the toxins produced by them. Specific phenolics such as catechol, protocatechuic acid, chlorogenic acid, umbelliferone, scopoletin, catechin, gallocatec-hin, isoquercetin, methoxyhydroquinone, avenacin, arbutin, hordatine, sitosterol, phloridzin glucoside, tomatine, tuliposide, methoxymellein, falcarinol, and anthocyanins have been observed to be involved in specific resistant interactions. Oxidized phenolics are more toxic than the phenolics and the oxidation is carried out by polyphenol oxidase or peroxidase. Hence, inc-reased activity of these enzymes has been shown to be related to disease resistance. Many attempts have been made to control the diseases by altering the phenol metabolism of plants, but some attempts ha-ve resulted in success. Since phenolics are phytotoxic also, foliar aplication at high concentration is not possible. Applications of phenols in irrigation water has given encouraging results. Spraying of ethylene or gibberillic acid or sugars, or application of potassium has increased the synthesis of phenolics and induced resistance.Keywords : Dayanıklılık, fenolikler, hastalık