The most prominent component of chemical ecology has to do with the effects of plant chemicals on the behavior and development of phytophagous insects. This chapter examines the volatile compounds given off by one group of plants, the genus Ipomoea, and their influence on the behavior of one insect, the sweetpotato weevil, Cylas formicarius. Sweet potato is an important staple crop in much of the world, while water spinach is cultivated as a vegetable in some areas. The best known member of the genus, C. formicarius, feeds and reproduces on a variety of Ipomoea species worldwide and is the most important pest of cultivated sweet potato. There are considerable morphological differences between the sexes of C. formicarius in their putative olfactory apparati which may correlate with host finding behavior. The range of host plants acceptable to C. formicarius has yet to be established, but present indications are that the weevil is restricted predominately to the family Convolvulaceae.

Green leaf surface chemistry of tobaccos resistant to the tobacco budworm, Heliothis virescens (Fabricius), was. quite diverse in this study. The major cuticular components determined included diterpenes (duvanes and labdanea). fatty alcohols (docos8Dol), sucrose esters, and aliphatic hydrocarbons. The most resistant tobaccos had very low or high duvane levels. Low budworm populations were related to tobaccos with low levels of a and B duystrienediols (4.8,13-duvatriene-l,3-diols) and a and B duystriene-ols (4,8,13-duvBtriene-l­ ols). An increase in either of these to normal levels increased larval numbers. Larval mortality more closely paralleled high duva1lienediol and sucrose ester levele. Plant resistance associated with larval nonpreference for 8 food source appeared most evident in tobaccos with low leaf surface chemistry pronIes. The importance of labdanes (cis·abienol and a lS·0H abienol) was questionable, and no relationship was apparent between the hydrocarbons and resistance. Also, one tobacco with low docos8Dol and high sucrose ester levels was resistant to budwonn larval damage.

Cylas formicarius (F.) shows a strong overall sexual monomorophism, with external differences noted in only three organs: (a) relative size of the hind wings; (b) form of the antennal club and numbers of its different types of sensillum; and (c) size of the compound eyes and their individual facets. We relate these to known or predicted behavioural differences. Eye dimorphism is used to test a theoretical rule on the relationship between differences in overall eye size and in the size of individual ommatidia. Some sexually monomorphic features are briefly discussed, including two types of putatively sensory hairs not found on the antennae.

Epicuticular waxes were analyzed to explain the visible differences in the waxy bloom of conditioned broccoli ( Brassica oleracea L. Group Italica `Green Duke') transplants. Seedlings (22 days old) were subjected to brushing (40 cycles per minute, 1 minute twice daily), wind (7 m·s -1 for 5 minutes twice daily), or moisture-stress conditioning (MSC; visible wilt for 2 to 4 hours daily) for 16 (1987) or 21 (1988) days during transplant production in the greenhouse. The epicuticular waxes of the uppermost fully expanded leaves were removed by dipping detached leaves into methylene chloride. The extract was derivatized with trimethylsilyl reagents and subjected to capillary gas chromatography. The primary epicuticular wax components were the nonpolar C 29 compounds nonacosane, nonacosan-15-ol, and nonacosan-15-one, which were identified by mass spectrometry. In a Summer 1987 experiment, cuticle samples taken over time of treatment indicated acclimation to the conditioning treatments relative to untreated plants. After 9 days of treatment, the amount of total epicuticular waxes present on the leaves was reduced 38%, 31%, or 11% by wind, brushing, or MSC, respectively. However, after 15 days of treatment, the amount of cuticle present was reduced 15% by brushing but only 6% by wind and was 17% greater in MSC-treated plants. Two weeks after transplanting to the field there were no differences in the amount or composition of the epicuticular waxes. In Fall 1988, all treatments reduced plant growth, but only MSC tended to increase the amount of C 29 epicuticular components during greenhouse production. Differences in the amounts of epicuticular waxes were no longer significant after 8 days in the field.

Changes in the concentration of individual sugars in sweetpotato storage roots with cooking and their relationship to the formation of volatile compounds were studied. During cooking maltose concentration increased from 0.03% fwt at 25.C to a maximum of 4.33% at WC. Microwave pretreatment (2-4 minutes) resulted in a significant decrease in amounts of maltose and volatiles formed. At 80°C, approximately 80% of maltose synthesis was inhibited when pretreated with microwaves. Adding maltose into microwave pretreated samples and then cooking in a convection oven restored most of the volatile profile with the exception of phenylacetaldehyde. Upon heating (200°C), sweetpotato root material that was insoluble in both methanol and methylene chloride produced similar volatile profiles to those from sweetpotatoes baked conventionally. Volatiles derived via thermal degradation of the non-polar methylenc chloride fraction and the polar methanol fraction did not display chromatographic profiles similar to those from conventionally baked sweetpotatoes. Initial reactions in the formation of critical volatiles appear to occur in the methanol and methylene chloride insoluble components. Maltol (3-hydroxy-2-methyl-4-pyrone) was found to be one of the critical components making up the characteristic aroma of baked sweetpotatoes. It was concluded that maltose represents a primary precursor for many of the volatile compounds emanating from baked `Jewel' sweetpotatoes and the formation of these volatiles appears to involve both enzymatic and thermal reactions.

(1993). Antibiotic Activities of Sugar Esters Isolated from Selected Nicotiana Species. Bioscience, Biotechnology, and Biochemistry: Vol. 57, No. 8, pp. 1355-1356.

The effect of plant to plant variation and root size, weight, and location on storage root surface terpene chemistry of Centennial sweetpotato was investigated under field conditions. In plants grown in pots, the magnitude of the variation in concentration of boehmerol and boehmeryl acetate between plants in different pots, plants within pots, roots from a single plant, and location on individual roots was evaluated. Significant differences in boehmerol or boehmeryl acetate due to storage root location order along the axis of the underground stem were found for some individual plants, but the trend was not consistent among plants. A similar response was found for the distance down the underground stem at which the storage root was attached. Differences in surface chemistry between roots from a single plant appeared to be controlled by factors other than location along the main axis. Storage root length to diameter ratio accounted for 42% of the variation in boehmerol. The inverse of root density and its squared value combined accounted for 36% of the variation in boehmeryl acetate. These relationships were found among roots growing within a 5-m-diameter area of field, but were not present when the roots were from different sites. In pot experiments the greatest variance was due to pots; the within root variation was the smallest. Results of this study suggest that when selecting against boehmerol or boehmeryl acetate, more than one root per plant should be used to compensate for within plant variation, while one measurement per root was adequate.

Plant surface chemistry is known to have a pronounced effect on the behavior of many agriculturally important insects. We assessed the qualitative and quantitative effects of N and K nutrition on storage root surface chemistry of three sweetpotato [Ipomoea batatas (L.) Lam.) cultivars: two displaying moderate resistance (Jewel and Regal), and one susceptible (Centennial) to the sweetpotato weevil, Cylas formcarius (Summers). One field and one pot experiments were conducted.. Boehmerol and boehmeryl acetate identified by GC-MS were found on the surface of Centennial but not Jewel or Regal Toots. Another compound, previously identified as ''peak 4'', was found on Regal with a retention time very close to that of boehmeryl acetate. In the field, boehmerol increased quadratically with increases in K rate (0, 112, or 224 kg K/ha); the same was true for boehmeryl acetate, but at 112 kg N/ha only. ''Peak 4'' increased linearly (pot experiment) or quadratically (field experiment) with increases in the K rate, while N did not have a significant effect. Nutrition was found to affect storage root surface chemistry and may be a significant factor modulating differences in weevil susceptibility over location and time. The effect may in part explain inconsistencies in published estimates of field resistance to the weevil, Nitrogen and K nutrition should be taken into account when selecting progeny for boehmeryl acetate content in a breeding program.

Leaf discs from pecan, Carya illinoensis (Wangenh.) K. Koch, pea, Pisum sativum L., peach, Prunus persica (L.) Batsch, and fig, Fiscus benjamina L. were presented to nymph and adult blackmargined aphids, Monellia caryella (Fitch) in no-choice and choice bioassays. Nymph longevity and developmental rates, and adult longevity and reproductive rates were significantly greater when aphids were placed on pecan than on pea, peach or fig. In no-choice bioassays, both nymph and adult aphids preferred to settle-on pecan, while they preferred to wander- or settle-off of pea, peach and fig. In choice bioassays, both nymph and adult aphids preferred to settle-on pecan than to settle-on pea, peach and fig. Analysis of pecan, pea, peach and fig leaf cuticular chemistry showed that n-alkane distribution patterns and the major cuticular components, specifically triterpenes and their oxidation products, differed among the four plant species. This study provides the first evidence within the pecan/aphid interactive system which suggests that the distinct foliar cuticular chemistry of pecan may have an influence on the host recognition behavior of M. caryella.

Pecan, Carya illinoensis (Wang.) K. Koch, harbors a complex of three foliar-feeding aphid species, with Monellia caryella (Fitch) considered to be the most economically important among the three species.

Levels of major root surface components for two sweetpotato [Ipomoea batatas (L.) Lam.] cultivars that differ in susceptibility to the sweetpotato weevil [Cylas formicarius elegantulus (Summers)] were determined. Analyses were made 30 days before harvest, at harvest, after curing, and after 2 months of storage during two seasons. Significant variation in the amounts of individual components, especially boehmeryl acetate, which is known to be an ovipositional stimulant for the weevil, was found before and after harvest, with season, and between cultivars. These results suggest that variation in field susceptibility of cultivars displaying moderate levels of resistance may be due in part to seasonal variation in the level of ovipositional stimulants.

A major diversion of carbon from branched-chain amino acid biosynthesis/catabolism to form acyl moieties of sucrose esters (6-O-acetyl-2,3,4-tri-O-acyl-alpha-D-glucopyranosyl-beta-D- fructofuranosides) was observed to be associated with specialized trichome head cells which secrete large amounts of sucrose esters. Surface chemistry and acetyl and acyl substituent groups of tobacco (T.I. 1068) sucrose esters were identified and quantified by gas chromatography/mass spectrometry. Sucrose esters were prominent surface constituents and 3-methylvaleric acid, 2- and 3-methylbutyric acid, and methylpropionic acid accounted for 60%, 25% and 9%, respectively, of total C3--C7 acyl substituents. Radiolabeled Thr, Ile, Val, Leu, pyruvate and Asp, metabolites of branched-chain amino acid pathways, were compared with radioactively labeled acetate and sucrose as donors of carbon to sucrose, acetyl and acyl components of sucrose esters using epidermal peels with undisturbed trichomes. Preparations of biosynthetically competent trichome heads (site of sucrose ester formation) were also examined. Results indicate that 3-methylvaleryl and 2-methylbutyryl groups are derived from the Thr pathway of branched-chain amino acid metabolism, 3-methylbutyryl and methylpropionyl groups are formed via the pyruvate pathway, and that acetyl groups are principally formed directly via acetyl-CoA. Arguments are presented which rule out participation of fatty acid synthase in the formation of prominent acyl acids. Results suggest that the shunting of carbon away from the biosynthesis of Val, Leu and Ile may be due to a low level of amino acid utilization in protein synthesis in specialized glandular head cells of trichomes. This would result in the availability of corresponding oxo acids for CoA activation and esterification to form sucrose esters. Preliminary evidence was found for the involvement of cycling reactions in oxo-acid-chain lengthening and for utilization of pyruvate-derived 2-oxobutyrate to form straight-chain acyl substituents.

Colonies of Reticulitermes flavipes and R. 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 of R. santonensis in Europe and R. 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 of R. 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 in R. flavipes and one in R. 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 in R. 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 that R. santonensis was introduced into Europe in the last century from one R. flavipes colony. (2) Chemical variability characterizes the sibling species that can be grouped into the same subspecies R. flavipes. Unknown mechanisms of reproductive isolation separate them.

Colonies of and 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 of in Europe and 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 of 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 in and one in 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 in 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 that was introduced into Europe in the last century from one colony. (2) Chemical variability characterizes the sibling species that can be grouped into the same subspecies. Unknown mechanisms of reproductive isolation separate them.

Adults of a generalist herbivore, the lubber grasshopper,Romalea guttata, can be converted to functional specialists by feeding them exclusively on catnip,Nepeta cataria. No obvious adverse effects on adult development resulted from this enforced monophagy. Notwithstanding the fact thatR. guttata has had no coevolutionary relationship with this Eurasian mint, it readily sequesters compounds that are identical to or derived from the terpenoid lactones that are characteristic ofN. cataria. R. guttata appears to both biomagnify minor allelochemicals and to sequester metabolites of theNepeta terpenes in its paired defensive glands. The levels of autogenously produced phenolics are not affected by feeding onN. cataria and the defensive secretions of catnip-fed grasshoppers are more repellent to ants than those of wild-fed acridids. Metabolites of theN. cataria monoterpenes are sequestered in the defensive glands when catnip is added to the natural diet ofR. guttata. The ability of a generalist,R. guttata, to facilely bioaccumulate a potpourri of foreign allelochemicals when feeding in a specialist mode is analyzed in terms of its biochemical, physiological, and functional significance. Sequestration is examined as a response to the enteric effronteries represented by the phytochemicals that can be characteristic of the "overload" in a monophagous diet.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCharacterization of the sucrose ester fraction from Nicotiana glutinosaRichard F. Arrendale, Ray F. Severson, Verne A. Sisson, Catherine E. Costello, Julie A. Leary, David S. Himmelsbach, and Herman Van HalbeekCite this: J. Agric. Food Chem. 1990, 38, 1, 75–85Publication Date (Print):January 1, 1990Publication History Published online1 May 2002Published inissue 1 January 1990https://pubs.acs.org/doi/10.1021/jf00091a015https://doi.org/10.1021/jf00091a015research-articleACS PublicationsRequest reuse permissionsArticle Views296Altmetric-Citations37LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

Cores from sweet potato [Ipomoea batatas (L.) Lam.] storage roots (Centennial, Jewel, Resisto, and Regal cultivars) were presented to sweet potato weevils [Cylas formicarius elegantulus (Summers) (Coleoptera; Curculionidae)] in multiple-choice, limited-choice, and no-choice bioassays. Centennial, a susceptible cultivar in field-plot experiments, was preferred for feeding and oviposition by female weevils in choice bioassays, and for ovi-position in no-choice bioassays, compared to three other cultivars. Analysis of root surface chemistry showed a tentatively identified triterpenol acetate in Centennial, which was not found in the more resistant cultivars; another root surface component was found in higher concentrations in the more resistant cultivars.

A model system involving severalNicotiana species containing novel nicotine alkaloids was used to study heritability and expression of alkaloid production in leaf trichomes. The three species that comprise the section Repandae (N. repanda, N. stocktonii, andN. nesophila) were hybridized with eitherN. tabacum orN. sylvestris (neither of which producesN-acylnornicotine). The progeny of the hybrid with sylvestris produced theN-acylnornicotines at a level found in the Repandae parent.Nicotiana repanda was crossed toN. tabacum, and the F2 progeny produced the alkaloid at the same level as the original Repandae parent. Inheritance of the ability to acylate nornicotine in Repandae species is inherited in hybrids in a dominant manner These and other data obtained suggest that theN-acyltransferase that acylates nornicotine in Repandae species inherited in hybrids is in a dominant manner and that the regulatory sequence(s) for the gene is expressed in leaf trichomes when the gene is in a foreignNicotiana background.

A dual-choice olfactometer was developed to study the responses of sweet potato weevils,Cylas formicarius elegantulus (Summers), to volatiles from the sweet potato,Ipomoea batatas (L.) Lam. Both males and females were attracted by volatiles from sweet potato leaves and a methylene chloride leaf extract. Females, but not males, responded to volatiles from storage roots and a methylene chloride root extract. Leaves and storage roots from four sweet potato cultivars (Centennial, Jewel, Resisto, and Regal) were attractive to female weevils; however, the attractant response varied with cultivar. GC profiles from leaf and root extracts, and GC-MS analysis of leaf extract, for Jewel cultivar enabled the volatile peaks to be identified as sesquiterpenes.