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United States Department of Agriculture

Agricultural Research Service

Title: Identification and Synthesis of a Kenaf Phytoalexin Highly Active Against Fungal Wilt Pathogens

item Stipanovic, Robert
item Puckhaber, Lorraine - TEXAS A&M UNIVERSITY
item Bell, Alois

Submitted to: American Chemical Society Abstracts
Publication Type: Book / Chapter
Publication Acceptance Date: July 31, 1997
Publication Date: N/A

Interpretive Summary: Fusarium and Verticillium wilts caused losses to cotton production estimated to be in excess of $120M in the U.S. Kenaf is highly resistant to these pathogens, but the mechanism of this resistance is unknown. Since kenaf and cotton are in the same plant Family, an investigation into the mechanism of resistance with a few to the possible transfer of this resistance into cotton was deemed appropriate. We found these kenaf, when infected with Verticillium dahliae, produces an antifungal compound, 3,8-dimethyl-1,2-naphthoquinone, which is more active than similar compounds produced in cotton. Production of this compound may be instrumental in protecting kenaf from these pathogens.

Technical Abstract: A new potent phytoalexin has been isolated from kenaf (Hibiscus cannabinus) and identified as 3,8-dimethyl-1,2-naphthoquinone, which we call o-hibiscanone. o-hibiscanone had ED50 values of 0.5 ug/ml and 1.1 ug/ml against conidia of Verticillium dahliae and Fusarium oxysporum f. sp. vasinfectum, respectively. In comparison, desoxyhemigossypol, the most potent phytoalexin in cotton xylem tissue, had ED50 values of 5.2 ug/ml and 8.8 ug/ml, respectively. V. dahliae detoxifies o-hibiscanone by converting it to the benign hydroquinone. Mansanone C, a phytoalexin from elm which differs from o-hibiscanone in that the latter lacks the isopropyl group of the former, was less than one-half as toxic to V. dahliae. o-Hibiscanone is believed to be derived from delta-cadinene [2,3,4,6,7,8-hexahydro-1,6-dimethyl-4-(1- methylethyl)naphthalene]. A biosynthetic pathway to account for the loss of the isopropyl group is proposed.

Last Modified: 4/22/2015