Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Abstract Only
Publication Acceptance Date: 1/12/2002
Publication Date: 4/2/2002
Citation: PUCKHABER, L., STIPANOVIC, R.D., DOWD, M.K., HOWELL, C.R. TOXICITY OF (+)- AND (-)-GOSSYPOL TO RHIZOCTONIA SOLANI. PROCEEDINGS OF BELTWIDE COTTON CONFERENCES. CD-ROM. MEMPHIS, TN: NATIONAL COTTON COUNCIL. 2002.
Technical Abstract: Gossypol occurs as two stable enantiomers due to restricted rotation around the carbon-carbon binaphthyl bond. The biological activities of the enantiomers have consistently been shown to differ in a wide range of bioassays. In almost all bioassays, the (-)- enantiomer has been the more biologically active. Howell and co-workers have shown that the biocontrol agent Trichoderma virens induces in cotton seedling roots the biosynthesis of terpenoids, including desoxyhemigossypol, hemigossypol and gossypol. This induction appears to be an essential component in the biocontrol of the seedling pathogen Rhizoctonia solani. Of the induced terpenoids, gossypol is the most abundant with concentrations 10-20 times that of hemigossypol or desoxyhemigossypol. The ratio of the (+)- enantiomer to the (-)-enantiomer in cotton seedling roots and their toxicities to R. solani, however, had not been investigated. Our study found that the ratio of enantiomers in seedling roots is unequal, with the (+)-enantiomer present at concentrations two to three times that of the (-)-enantiomer. We also determined that the toxicities to R. solani of racemic gossypol, and the (+)- and (-)-enantiomers of gossypol were found to be 13.00 +/- 0.53; 12.38+/-0.75; and 12.59+/-1.13, microgram ml-1, respectively.