ARS | Publication request: IDENTIFICATION AND SYNTHESIS OF TRINORCADALENE PHYTOALEXINS FORMED BY HIBISCUS CANNABINUS

Submitted to: Phytochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 24, 1998
Publication Date: N/A

Interpretive Summary: The kenaf plant, which is in the same plant family as cotton, is highly resistant to fungal wilt diseases that affect cotton. We undertook a study to determine the biochemical reasons for this resistance. Kenaf produced two major antibiotics in response to infection by the pathogen Verticillium dahliae. These two antibiotics were identified and their toxicity to cotton wilt pathogens were determined. One compound, o-hibiscanone, was 8 times more toxic than any antibiotic produced by the cotton plant, even though it apparently is produced from the same precursors as cotton antibiotics. Cloning and transfer of 1 or 2 genes from kenaf to cotton may allow synthesis of the more potent antibiotic and, thus, increase disease resistance.

Technical Abstract: Two trinorcadalene phytoalexins, hibiscanal (2,8-dihydroxy-4, 7-dimethoxy-6-methyl-1-naphthaldehyde) and o-hibiscanone (3,8-dimethyl-1,2-naphthoquinone), were isolated and identified from stem stele of kenaf (Hibiscus cannabinus) inoculated with the fungal pathogen Verticillium dahliae. o-Hibiscanone also was synthesized. The ED50 values of hibiscanal and o-hibiscanone against V. dahliae were 25.83 and 1.18 ug/ml, respectively. o-Hibiscanone is more toxic to V. dahliae than desoxyhemigossypol, the most toxic phytoalexin known in cotton (Gossypium species), or mansonone C (3,8-dimethyl-5-isopropyl-1,2-naphthoquinone) which has been isolated from other malvaceous species. The implications of these findings for the genetic engineering of cotton phytoalexins is discussed.