|White Jr, Robert|
|Jackson, David - Mike|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/1997
Publication Date: N/A
Citation: N/A Interpretive Summary: The leaves of a Tobacco Introduction (TI) TI165 were found to be resistant to tobacco budworm (Heliothis virescens) attack. Two compounds were found in TI-165 that correlated with budworm resistance and were absent in susceptible varieties. Isolation and identification of the compounds showed that they were hydroxygeranyllinalool glycosides. Budworms fed diets containing the isolated compounds did not grow, proving that these compounds are the resistance factor in TI-165. Other resistant tobacco varieties were shown to contain the same compounds. A number of wild Nicotiana species were shown to contain similar compounds. Breeding studies to produce agronomically acceptable tobacco with high levels of the compounds to yield resistant varieties are currently in progress. The findings also have potential for the introduction of these types of compounds into other crops attacked by H. virescens.
Technical Abstract: The leaves of Tobacco Introduction TI-165 were found to be resistant to tobacco budworm (Heliothis virescens (F.)) attack. HPLC profiles of methanolic leaf extracts showed that TI-165 had relatively high levels of two components (designated A and B) that were absent in susceptible varieties. Compounds A and B were isolated from TI-165 by a combination of preparative C-18, silicic acid column-, and centrifugal thin-layer chromatography. Analysis of A and B by NMR and FAB/MS showed that they are hydroxygeranyllinalool glycosides. Budworm bioassays with whole tobacco leaves and purified mixtures of A and B, incorporated into laboratory diets, showed significant correlation factors of r=-0.83 and r=-0.92, respectively, between larval weights and levels of A and B. HPLC analyses of freeze-dried leaves of 68 Nicotiana species indicated that 26 species had high levels of diterpene glycosides identical to or related to A and B. Incorporation of A and B into tobacco breeding lines or other budworm susceptible crops should provide H. virescens resistance.