Phytoalexin - Role of Natural Phenols in The Plant Defense Against Fungal Pathogens

Role of Natural Phenols in The Plant Defense Against Fungal Pathogens

Natural phenols play a role in the plant defense against fungal pathogens.

In Vitis vinifera grape, trans-resveratrol is a phytoalexin produced against the growth of fungal pathogens such as Botrytis cinerea and delta-viniferin is another grapevine phytoalexin produced following fungal infection by Plasmopara viticola. Pinosylvin is a pre-infectious stilbenoid toxin (i.e. synthesized prior to infection), contrary to phytoalexins which are synthesized during infection. It is present in the heartwood of Pinaceae. It is a fungitoxin protecting the wood from fungal infection.

Sakuranetin is a flavanone, a type of flavonoid. It can be found in Polymnia fruticosa and rice, where it acts as a phytoalexin against spore germination of Pyricularia oryzae. In Sorghum, the SbF3'H2 gene, encoding a flavonoid 3'-hydroxylase, seems to be expressed in pathogen-specific 3-deoxyanthocyanidin phytoalexins synthesis, for example in Sorghum-Colletotrichum interactions.

6-Methoxymellein is a dihydroisocoumarin and a phytoalexin induced in carrot slices by UV-C, that allows resistance to Botrytis cinerea and other microorganisms.

Danielone is a phytoalexin found in the papaya fruit. This compound showed high antifungal activity against Colletotrichum gloesporioides, a pathogenic fungus of papaya.

Stilbenes are produced in in Eucalyptus sideroxylon in case of pathogens attacks. Such compounds can be implied in the hypersensitive response of plants. High levels of polyphenols in some woods can explain their natural preservation against rot.

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