Tobacco cuticular components

Cuticular diterpenes-duvanes and labdanes. Cutler have found that the cuticular diterpenes of green tobacco have both allelopathic and insect-deterrent effects (38). Present in the cuticle are duvane and/or labdane diterpenes (Figure 3) The levels of these specific cuticular components are believed to be responsible for the observed resistance of some types of tobacco to green peach aphids Myzus persicae (Sulzer), tobacco budworm Heliothis virescens (F.), and tobacco hornworm Manduca sexta (L.) (39). 

Figure 6 Sucrose ester mixtures isolated from the cuticular components of tobacco TI 165 (Refer to Table V for details).

Figure 7. Effects of sucrose ester mixtures isolated from the cuticular components of tobacco TI 16 5 on the growth of etiolated wheat (X aestivum L. cv Vakeland) coleoptiles. Significant inhibition (P<0.01) below solid line. Control broken line. (Refer to Figure 6 for details).

D. M. Jackson, G.R. Gwynn, J.F. Chaplin, and M.G. Stephenson Quantitation of major cuticular components from green leaf of different tobacco types J. Agr. Food Chem. 32 (1984) 566-570. 

In this report, we will discuss investigations of the cuticular components from Nicotiana species and their effects on tobacco homworm and tobacco budworm moth oviposition. The response of tobacco budworm moths to specific cuticular isolates from a Nicotiana species also will be discussed. 

TABLE V. Ovipositional Response of Tobacco Budworm Moths to Cuticular Components from Nicotiana spp. Applied to Nonpreferred TI 1112 (Entry A) in Paired Choice Tests with TI 1112 Sprayed with Solvent Blank (Entry B). 

Severson RF, Jackson DM, Johnson AW, Sisson VA, Stephenson MG (1991) Ovipositional behaviour of tobacco budworm and tobacco hornworm. Effects of cuticular components from Nicotiana species. ACS Sympos Ser vol 449, American Chemical Society, Washington, DC, pp 264-277... 

The cuticular component extracts were analyzed by capillary gas chromatography using a slightly modified method of Severson et al. (75). An internal standard (92.5 iig of tricosanol) was added to the vial containing the cuticular extract and the sample was mixed. About a 0.75 cm equivalent of the sample from tobaccos with secreting trichomes or 1.5 cm from tobaccos with... 

Cuticular extracts used for the isolation of components were obtained from different N. tabacum genotypes that were grown in blocks of 100 plants. Cuticular components were extracted from plant tops using methylene chloride as previously described (75). The extracts from the following tobaccos were used to isolate specific components using the methodology reported by Severson et al.(76) a- and B-4,8,13-duvatriene-l,3-diols (DVT-diols) (97+% by GC, 3 1 a-diol to B-diol) from NC 2326 a- and B-4,8,13-duvatrien-l-ols (DVT-ols) (98+% by GC, 9 1 a-ol to B-ol) from PD 1097 a sucrose ester fraction (SE, 6-O-acetyl-2,3,4-tri-0-acyl-sucrose) (97+%by GC) from PD 1097 labda-12,14-dien-8a-ol (cw-abienol) (98+% as monohydrate, mp 67 C) from NET and labda-13-ene-8a,15-diol(labdenediol) (99+%, mp 126-128 C) from PD 964. 

Table I compares the relative field plot aphid ratings with the composition and levels of the trichome-produced cuticular components. The aphid susceptible cultivars NC 2326 (flue-cured) and KY 14 (burley) produced similar levels of DVT-diols. The DVT-diols are the major cuticular components of flue-cured and burley tobacco types (72). The aphid-resistant lines either have nonsecreting trichomes, and very low levels of cuticular components, or glanded trichomes which produce heavy exudates consisting of DVT-ols, and or dj-abienol and labdenediol and or SE (see 72, 74, 18 for structures). The TI 1112 and breeding...

Table I. Average Levels of Cuticular Components (1990-1991) and Average Infestation Ratings for the Tobacco Aphid (1990-1992) in Field Plots at Oxford, NC and Tifton, GA...

Tobacco entry Relative aphid rating Cuticular Components (/ig/cm SE... 

The differences in hydrocarbon patterns in surface waxes and in the components of interior tissue are illustrated by analysis of pupae of Manduca (tobacco hornworm). n-Alkanes only comprised ca 3% of the hydrocarbon fraction of the cuticular wax, the balance being unsaturated compounds. In contrast, internal tissues (fat bodies, muscle, gut) contained the same carbon spectrum (C21 to C41) as in the wax but now branched alkanes made up the bulk of the hydrocarbon fraction ca 80%), followed by n-alkanes (9%) with the residue being unsaturated compounds The proportion of n-alkanes in the hydrocarbon fraction from cuticular wax of a Bombyx silkworm fell from 95 to 35% on passage from the larval to the pupal stage " and similar results have been found for Trichoplusia (cabbage looper) and Drosophilia (fruitfly) species. However, it is likely that the cuticular wax has a more stable composition over the adult life of most insects and is only synthesized at (low) rates sufficient to replace that lost by wear and tear. The site of synthesis has been demonstrated to be in the cuticle in a cockroach species no hydrocarbon synthesis occurred in preparations from fat bodies . 

Most Nicotiana species have multicellular, glanded leaf trichomes which may produce chemical secretions containing diterpenes and/or sugar esters with C2 to C,o acyl moieties. These components affect tobacco aphids, Myzus nicotianae Blackman, in several ways, including influencing the acceptance or rejection of plants for colonization by alate migrant aphids, and the survival and fecundity of alate and apterous aphids. Cuticular diterpenes and sucrose esters were isolated from the cuticular extracts of aphid resistant and susceptible N. tabacum genotypes. These compounds were applied topically to the backs of apterous aphids. 

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