No abstract

No abstract

Colonies ofReticulitermes flavipes andR. santonensis were collected from the southeastern United States (Georgia) and the southwest of France (Charente-maritime). Defensive compounds and cuticular hydrocarbons were identified by gas chromatography-mass spectrometry and quantified by gas chromatography using an internal standard for each caste and all colonies. These analyses show that although the cuticular hydrocarbons ofR. santonensis in Europe andR. flavipes in Georgia are identical, their relative proportions are different. However, the defensive compounds synthesized by their soldiers are different. A strong chemical polymorphism between sympatric colonies ofR. flavipes in the SW United States was detected in terms of both the hydrocarbons of the workers and soldiers and in the defensive secretions of the soldiers. The six defensive secretion phenotypes are based on the presence or absence of terpenes whereas the cuticular hydrocarbon phenotypes are based on significant differences in the proportions of the various components. A multivariate analysis (analysis of principal components) clearly permitted discrimination of four phenotypes (three inR. flavipes and one inR. santonensis) without intermediates. The hydrocarbons responsible for these variations were identified, and it was shown that the variations are neither seasonal nor geographic. The phenotypes of the cuticular hydrocarbons (workers and soldiers) and defensive compounds are linked in each colony, forming in three groups inR. flavipes Georgia, one subdivided into four subgroups according to the defensive secretion phenotypes. The role of these polymorphisms is discussed and ethological tests indicate that the chemical polymorphism do not determine aggressive behavior. The taxonomic significance of these results is considered and two hypothesis are formulated: (1) We only detected a strong genetic polymorphism in one unique species, and we believe thatR. santonensis was introduced into Europe in the last century from oneR. flavipes colony. (2) Chemical variability characterizes the sibling species that can be grouped into the same subspeciesR. flavipes. Unknown mechanisms of reproductive isolation separate them.

A gel filtration chromatography method was developed for the isolation and concentration of the high molecular weight polynuclear aromatic hydrocarbons (PAH) contained in the most biologically active fraction of cigarette smoke condensate (CSC). The unusually complex mixture of large PAH found in CSC necessitated the use of preparative gas chromatography followed by high-pressure liquid chromatography to achieve separation and identification. Mass spectral, ultra-violet absorption, and chromatographic retention data were needed for the comprehensive identification of the large molecular weight PAH components of CSC. The majority of the more than 200 isolated compounds were identified. Compounds newly identified in CSC included 3,4-dimethylenepyrene, 3,4-trimethylenepyrene, cyclopenta(c,-d)pyrene, 4,5-methylenetriphenylene, benzo[b]perylene, and several dibenzofluoranthenes.

Leaves of Tobacco Introduction TI-165 were found to be resistant to tobacco budworm [Heliothis virescens (F.)] attack. HPLC profiles of leaf extracts showed that TI-165 had relatively high levels of two components (A and B) that were absent in susceptible varieties. Compounds A and B were isolated from TI-165 by a combination of preparative C18, silicic acid column, and centrifugal thin-layer chromatography. They were identified as diterpene glycosides:  compound A, 16-hydroxygeranyllinalyl-3-O-[α-l-rhamnopyranosyl(1→4)]-β-d-glucopyranoside-16-O-[α-l-rhamnopyranosyl(1→6)]-β-d-glucopyranoside; compound B, 16-hydroxygeranyllinalyl-3-O-[α-l-rhamnopyranosyl(1→4)]-β-d-glucopyranoside-16-O-[α-l-rhamnopyranosyl(1→6)]-[α-l-rhamnopyranosyl(1→4)]-β-d-glucopyranoside (hydroxygeranyllinalool glycosides). Budworm bioassays with whole tobacco leaves and purified mixtures of A and B showed significant correlation 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. Keywords: Nicotiana; Heliothis virescens (F.); antibiosis; 16-hydroxygeranyllinalool glycosides; diterpene glycosides