Comparison of anacardic acid biosynthetic capability between insect-resistant and-susceptible geraniums

The garden geranium (Pelargonium xhortorum) has been shown to secrete anacardic acids in the form of a viscous sticky exudate from tall glandular trichomes, and this exudate provides a sticky trap defense against small pest species. The anacardic acids from genetically related pest-resistant and -susceptible plants have been characterized, and resistance has been shown to depend upon the presence of5 unsaturated anacardic acids. In this study, the biosynthesis of these anacardic acids was comparatively investigated by incubating [¹⁴C]methyl palmìtate, margarate, stearate, oleate and linoleate on floral buds of resistant and susceptible plants. In addition, the incorporation of [¹⁴C]valine, -isoleucine, and -leucine into anacardic acids was also studied. Nineteen anacardic acids were quantitated utilizing an improved HPLC technique. Fatty acids and, to a much lesser extent, amino acids were incorporated into anacardic acids. There are at least two pathways of biosynthesis operating: direct elongation, and -oxidation with reincorporation of the [¹⁴C]acetate, the latter being more prevalent in the resistant plant. The amino acids were processed into branched chain anacardic acids, isoleucine being the precursor of the anteiso compounds, and valine the iso branched ones. The major difference between resistant and susceptible plants was the ability of resistant plants, but not the susceptible plants, to synthesize5 unsaturated anacardic acids. Both types of plants were capable of directly incorporating¹⁴C-labeled fatty acid methy esters into anacardic acids regardless of the plant's normal anacardic acid composition, thus bypassing the plant's tightly controlled regulation of the chemical structures of anacardic acids. No evidence was found for5 desaturation of saturated anacardic acids. A revised biosynthesis scheme is presented.     

Geranium defensive agents. IV. Chemical and morphological bases of resistance

Insect-resistant and -susceptible geranium plants (Pelargonium xhortorum) were chemically and morphologically compared to assess the relative importance of resistance components. Glandular and nonglandular trichome density and quantification of trichome exudate (anacardic acids) from inbred resistant and susceptible lines were determined. Three different extraction procedures were employed to quantify the anacardic acids: (1) capillary solvent extract, (2) leaf wipe, and (3) whole leaf extract. The results support the conclusion that tall glandular trichomes and the exudate they produce are the most important factors in small pest resistance in the geranium. In addition, it was shown that tall glandular trichome densities are less and the ability of the plant to express the anacardic acids as exudate on the trichome head exterior is lacking in the susceptible lines analyzed, even though all lines possessed the capability to synthesize the anacardic acids. A plant line of intermediate resistance character was shown to possess high densities of tall glandular trichomes but resembled susceptible plants in lacking the ability to express the anacardic acids as an exudate in appreciable quantities.     

Bioactivity of Lipophilic Metabolites from Glandular Trichomes of Medicago sativa Against the Potato Leafhopper

Medicago sativa cv. G98A is highly resistant to the potato leafhopper, Empoascafabae. Glandular trichome extracts from G98A were fractionated using flash chromatography and tested for settling deterrency against the potato leafhopper. A fraction of intermediate polarity exhibited strong, dose-dependent deterrency when applied to the surface of an artificial diet sachet. Deterrency was not detected, however, when the fraction was applied to the internal surface of the sachet membrane (i.e., when contact was limited to only the leafhoppers' stylets). Major components of the highly deterrent fraction, determined by gas chromatography-mass spectrometry, were a homologous series of fatty acid amides C(n)H(2n+1)NO (n = 19-23) and trace components were 12:0, 13:0, 14:0, 15:0, 16:0, 17:0, 18:0, and possibly 18:1 free fatty acids. Deterrency declined slightly, but was still strong, after fatty acids were removed from crude extracts. When the crude extracts were separated further, a fraction containing only the fatty acid amides was also deterrent. Activity increased when this fraction was supplemented with authentic (C12:0 through C18:0, and C18:1) free fatty acids. However, the authentic free fatty acids were not deterrent when tested without the lipophilic amides. Fatty acid amides and free fatty acids in trichomes of M. sativa G98A may synergize and together function in deterring settling by the potato leafhopper.     

Surface Composition of Myrmecophilic Plants: Cuticular Wax and Glandular Trichomes on Leaves of <Emphasis Type="Italic">Macaranga tanarius</Emphasis>

Primary plant surfaces, covered with cuticles consisting of cutin and waxes, are important substrates for interaction with insects. The composition of leaf surfaces of the myrmecophilic plant Macaranga tanarius was studied. The prenylated flavanone nymphaeol-C was identified in surface extracts and was localized exclusively in glandular trichomes on the abaxial leaf side. The epidermal pavement cells surrounding these trichomes were covered with a smooth film of epicuticular wax from which few small wax crystals protruded. The epicuticular wax amounted to approximately 8 μg cm⁻², corresponding to 85% of the wax load on the adaxial as well as the abaxial leaf sides. The epicuticular wax mixtures from both leaf surfaces contained more than 70% primary alcohols, 14% fatty acids, 2% aldehydes, and traces of alkyl acetates, with chain lengths ranging from C₂₀ to C₃₈. In contrast, the intracuticular wax layer was largely dominated by triterpenoid alcohols α-amyrin, β-amyrin, and lupeol. Consequently, these characteristic compounds are not available for direct contact with insects on the plant surface.     

Determination of Oil Content and Fatty Acid Composition of Sesame Mutants Suited for Intensive Management Conditions

Sesame mutants with closed capsules, determinate growth habit and wilt resistance, have been proposed to be suitable for intensive management conditions facilitating mechanized harvesting. The objective of our experiment was to determine the oil content and fatty acid composition of these mutants before they are placed on the market. Oil content and fatty acids were studied in 19 mutants, 6 breeding lines and 4 control source genotypes. The oil contents of the seeds ranged from 46.4 to 62.7%. The mutants had generally a lower oil content than the control genotypes except the wilting tolerant group. For unsaturated fatty acids, oleic acid was higher in the mutants and breeding lines while linoleic acid was lower in the seed oil. However, no mutants or breeding lines were found with radically different composition or with any undesirable lipid component. The closed capsule and determinate growth habit mutants need to be improved for oil content while their fatty acid composition is fine.     

Synergistic interaction between potato glycoalkaloidsα-solanine andα-chaconine in relation to destabilization of cell membranes: Ecological implications

In studies of the lysis of rabbit erythrocytes, red beet cells, andPenicillium notatum protoplasts by the potato glycoalkaloids -solanine and -chaconine, the latter was consistently the more membrane-disruptive compound and erythrocytes the more susceptible cell type. A 11 mixture of solanine and chaconine produced pronounced synergistic effects in all three test systems. In beet cells, such effects were apparent from an early stage of treatment and persisted over a period of several hours. With erythrocytes and fungal protoplasts, the synergism was maximal with mixtures containing approximately 70% chaconine, whereas with beet cells it peaked at approximately 40% chaconine. Synergistic interactions between solanine and chaconine also occurred with regard to cholesterol binding in vitro, with a maximum response corresponding to the 50% mixture. The implications of these findings for the nature and efficacy of chemical defense systems in plants are discussed.     

Influence of source,rate, and method of applicating controlled release fertilizer on nutrient release and growth of ‘Savannah’ holly

An experiment was conducted to determine the effect of rate of fertilizer application and method of application on the rate of nutrient release and growth of Savannah holly (Ilex ×attenuata Ashe) using three controlled release fertilizers. The controlled release fertilizers used were Osmocote 17N—3P—9.9K, Sierrablen 17N—3P—8.3K, and High-N 24N—1.7P—5.8K, all 12 to 14 month formulations. The three fertilizers had different release rates as determined by leachate nitrate—N and electrical conductivity (EC) measurements. Topdressing of fertilizer had the greatest release rate at seven days after treatment compared to fertilizer incorporation which had the lowest EC readings at 120 days after treatment. Fertilizer source had no effect on the shoot growth of Savannah holly. Growth index and shoot dry weight of Savannah holly increased linearly as N rate increased from 0.9 to 2.1 kg N m^–3. A significant linear relationship (R² = 0.97, Nitrate—N = 409 (EC)) between nitrate—N and EC indicates that nitrate—N concentration can be estimated from EC readings when the pour-through method is used with multicoated controlled release fertilizers. The controlled release fertilizers used in this study provided adequate nutrient release rates for up to four months under outdoor nursery conditions during the months of June through October.     

Effect of the naturally occurring salt ‘Kanwa’ as a fertilizer on the productivity ofStylosanthes in the subhumid zone of Nigeria

Soil nutrient deficiencies pose a serious limitation to higher crop and forage yields in the Nigerian subhumid zone. Some of the deficiencies may be alleviated by using as a fertilizer a salt mined locally called Kanwa which is traditionally used as a cattle lick. Yields ofStylosanthes hamata cv Verano andS. guianensis cv Cook seed and dry matter increased with Kanwa application at different locations. The effect of Kanwa was enhanced when phosphorus was adequately supplied. Improvements to soil physical properties were proportional to the yield of the legume. The implications of good quality fodder and improved soil conditions in Agro-pastoral Systems in the Nigerian SHZ are discussed.     

Identification and preparation of antiinsectan dienols fromDipterocarpus kerrii tree resins

Originally isolated fromDipterocarpus kerrii, the two previously uncharacterized sesquiterpenes,1 and20, were synthesized from α-gurjunene. A novel process involvingm-chloroperoxybenzoic acid oxidation ofα-gurjunene produced20 in one step. Spectroscopic studies determined that the diene moiety in20 is nonconjugated and also found the C-4 tertiary alcohol center to have theα-configuration, while the other stereocenters have configurations matching the corresponding centers inα-gurjunene. Bioassays with termites demonstrated that20 was more toxic than1, resulting in a 50% mortality in seven days when offered toNeotermes ?dalbergiae on filter papers. The chemicals appear to result from biotransformation ofα-gurjunene. In view of its similarity to the known sesquiterpeneγ-gurjunene, we suggest that20 be referred to asγ-gurjunenol.     

Antitermitic and Antifungal Activities of Essential Oil of Calocedrus formosana Leaf and Its Composition

Calocedrus formosana Florin (Cupressaceae) is an endemic tree species in Taiwan; its timber is recognized for natural decay resistance. To examine the antitermitic and antifungal activities of leaf essential oil and its main constituents, C. formosana leaves were extracted and the essential oils analyzed by GC-MS. Bioactivity tests against the termite Coptotermes formosanus demonstrate that the LC50 value of leaf essential oil is 27.6 mg/g. Furthermore, exposure to T-muurolol caused 100% mortality at a dosage of 5 mg/g after 14 d. Leaf oil constituents displayed activity against four fungi, Lenzites betulina, Pycnoporus coccineus, Trametes versicolor, and Laetiporus sulphureus. Two compounds, alpha-cadinol and T-muurolol, exhibited the strongest antifungal activity. The LC50 values of alpha-cadinol against L. sulphureus, L. betulina, and T. versicolor are 9.9, 28.6, and 30.4 microg/ml, respectively.     

Investigation of sex pheromone components of female asian corn borer,Ostrinia furnacalis (Hübner) (Lepidoptera: Pyralidae) in Taiwan

(E)-12-Tetradecenyl acetate (E12–14OAc), (Z)-12-tetradecenyl acetate (Z12–143nOAc), and tetradecanyl acetate (14OAc) were extracted and identified as major chemical components from female tips of the Asian corn borer,Ostrinia furnacalis (Hübner) (Lepidoptera: Pyralidae) in Taiwan, with a combined wash ratio of 483715 and an individual female ratio of 453916. The average amount ofE12-,Z12–14OAc and 14OAc in each female gland was 6.6±4.6, 5.8±3.5, and 2.4±1.7 ng/female, respectively. The mixture of these three synthetic chemicals not only gave strong activities in male antennae but also could catch significantly more males than virgin females in field-trapping tests. The field test also showed no significant difference in trapping ability among the three-component Taiwan formulations, the two-component Taiwan formulation (Z12–14OAc andZ1214OAc, 5347), and the Japan formulation (Z12–14 OAc andE 12–14OAc, 3:2).     

Synergistic Effect of Ethanol to α-Pinene in Primary Attraction of the Larger Pine Shoot Beetle, Tomicus piniperda

-Pinene and ethanol were released in the approximate proportions 1:0.1, 1:0.9 and 1:9 (at 21°C). Ethanol, released in the range of 3–279 mg/day, generally synergized the attraction of T. piniperda to -pinene (30 mg/day at 21°C), although attraction to the mixtures varied within and between years. The low release rate of ethanol together with -pinene attracted a significantly higher number of beetles than -pinene alone in 1995, April of 1996, and in 1997. Lures with the medium release rate of ethanol were the most attractive only in March of 1996. The high dose of ethanol significantly synergized attraction to -pinene in 1995 and 1997. The variable attraction of T. pinipeda to ethanol and -pinene at various release rates and proportions may be due to the temperature dependent nature of beetle antennal sensitivity. At ambient temperatures of 10–13°C. T. piniperda was most attracted to the lures with -pinene and high release rates of ethanol, at 14–17°C it was most attracted to those with medium release rates of ethanol, and at 18°C and higher it was most attraacted to those with low release rates of ethanol.     

Laminar and turbulent mass transfer simulations in a parallel plate reactor

Laminar and turbulent mass transfer in a parallel plate reactor at high Schmidt number obtained from numerical simulation is compared with literature data. In a first step, the fluid flow is determined numerically in the reactor by solving the Navier–Stokes equations. For turbulent flow, a low Reynolds number k— model is used to calculate the turbulent viscosity. Using the obtained flow field and turbulent viscosity, the current density distribution is calculated for different flow velocities by solving the equations describing the transport of multiple ions due to diffusion, convection and migration. For the laminar case, a very good agreement with literature data is obtained. For turbulent flow, different numerical models for turbulent mass transfer are proposed in the literature. A detailed study of the behaviour close to the wall of these different turbulence models is presented, together with a comparison of the calculated results with literature correlations. This allows identification of the benefits and disadvantages of each of the turbulence models for the numerical calculation of mass transfer at high Schmidt numbers in a parallel plate reactor.     

Isothiocyanates as alleopathic compounds fromRorippa indica Hiern. (Cruciferae) roots

The ethyl acetate extracts ofRorippa indica Hiern. contained hirsutin, arabin, camelinin, and three novel -methylsulfonylalkyl isothiocyanates (n=8, 9, and 10). These compounds severely inhibited lettuce (Lactucasaliva) hypocotyl and root growth at 0.1 mM or above. The precursor glucosinolates of hirsutin, arabin, and camelinin were isolated. Presence of the three -methylsulfonylalkylglucosinolates, along with other glucosinolates in the roots were verified by the isolation and identification of their desulfoderivatives. Using the continuous root exudate trapping apparatus and GC-MS, hirsutin and the three-methlylsulfonylalkyl isothiocyanates were detected in the root exudates ofR. indica, suggesting that these isothiocyanates are the primary candidate of allelopathic compounds contributing to the aggressiveness of this cruciferous weed.     

Inhibition of Fungal Spore Germination by Nasutitermes: Evidence for a Possible Antiseptic Role of Soldier Defensive Secretions

The antifungal property of two of the principal components of the terpenoid frontal gland secretions of nasute termite soldiers was studied by incubating spore suspensions of the fungus Metarhizium anisopliae with -pinene and limonene singly or in combination at different concentrations. In vitro assays showed that these substances reduced spore germination through direct and indirect (vapor) contact. To determine if the frontal gland secretions protected termites from fungal infection in vivo, the effect of M. anisopliae on the time course of survival of Nasutitermes costalis and N. nigriceps was studied by exposing termites to either a 4.3 × 10⁷ spores/ml or a control sporeless suspension. The caste composition of experimental groups was manipulated to create mixed-caste subcolonies and monocaste groups. Relative to Coptotermes formosanus, a species that relies on the mechanical defenses of soldiers, N. costalis and N. nigriceps were less susceptible to fungal infection. Spore-exposed N. costalis and N. nigriceps termites had 1.2 times the hazard ratio of death of controls, while the hazard ratio of death of spore-exposed C. formosanus was 11.4 times that of controls. Although the lower susceptibility to infection in Nasutitermes may be explained in part by the antifungal properties of -pinene and limonene, group composition also played a major role in the survival of spore-exposed termites. Mixed-caste and soldier monocaste groups had 3.4 and 4.7 times the hazard ratio of death, respectively, relative to the worker monocaste treatment. These results suggest that although Nasutitermes terpenoid secretions may have antifungal properties, the caste composition of groups and the social interactions of termites also play a role in determining susceptibility to fungal infection.     

An equilibrium and stability study of Δ1-pyrroline

Several properties of the compound 3,4-dihydro-2H-pyrrole(A1-pyrroline), which has been reported as a component of the male-produced Mediterranean fruit fly pheromone, have been determined by [¹H]- and [¹³C]nuclear magnetic resonance spectroscopy. The stability of ¹-pyrroline in several solvents and at moderately elevated temperatures has been investigated, and it has been established that it exists as both a monomer and trimer in solution. Although equilibrium studies indicate that the trimer is thermodynamically more stable than the monomer in solution, only the monomer was found in the vapor phase based on infrared analysis.This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or recommendation for its use by USDA.     

Antioxidants in grasshoppers: higher levels defend the midgut tissues of a polyphagous species than a graminivorous species

Polyphagous grasshoppers consume plants that contain markedly greater amounts of potentially prooxidant allelochemicals than the grasses eaten by graminivorous grasshoppers. Therefore, levels of antioxidant defenses maintained by these herbivores might be expected to differ in accordance with host plant ranges. Antioxidant levels were compared in midgut tissues and gut fluids of a polyphagous grasshopper, Melanoplus sanguinipes, and a graminivorous grasshopper, Aulocara ellioti. Glutathione concentrations in midgut tissues of M. sanguinipes (10.6 mM) are among the highest measured in animal tissues and are twice as high as those in A. ellioti. -Tocopherol levels are 126% higher in midgut tissues of M. sanguinipes than in those of A. ellioti, and remain at high levels when M. sanguinipes is reared on plants containing a wide range of -tocopherol concentrations. Ascorbate levels in M. sanguinipes midgut tissues are 27% higher than in those of A. ellioti, but vary depending on the host plant on which they are reared. Midgut fluids of both species contain elevated levels of glutathione, as well as large (millimolar) amounts of undetermined antioxidants that are produced in the insects. The consumption of tannic acid decreases ascorbate concentrations in midgut tisssues and gut fluids of A. ellioti but has no effect on ascorbate levels in M. sanguinipes. The results of this study provide the first measurements of antioxidants in grasshoppers and suggest that the maintenance of high levels of antioxidants in the midgut tissues of polyphagous grasshoppers might effectively protect them from oxidative stress.     

Lipase-Catalyzed Synthesis of d-Psicose Fatty Acid Diesters and their Emulsification Activities

The diesterification of d-psicose (the C-3 epimer of d-fructose) with fatty acid vinyl esters of selected acyl chain lengths (C₈, C₁₀, and C₁₂) was successfully carried out using Candida antarctica lipase (Novozym 435) at 45 °C for 24 h to give the 1,6-diacyl-d-psicofuranoses with a high regioselectivity in good yields (83–90%). These diesters of d-psicose have hydrophilic-lipophilic balance (HLB) values (6.5–8.2) similar to HLB values of monoglyceride compounds which constitute the largest single type of emulsifiers employed by the food industry. Ability of the d-psicose diesters to stabilize oil-in-water emulsions and the weight-averaged oil-droplet diameter in the emulsions was evaluated in this study. Emulsion stability of oil droplets stabilized by d-psicose dicaprylate (0.3%, w/v in oil phase) was comparable to d-fructose dicaprylate (0.2%, w/v). It was further confirmed that the d-psicose diesters exhibited an emulsification activity depending on the chain length of fatty acid; d-psicose dicaprate showed better emulsion stability than the other diesters.     

Vulgarone B,the antifungal constituent in the steam-distilled fraction of Artemisia douglasiana

Antifungal activity of the steam distilled essential oil fraction of Artemisia douglasiana was detected by bioautography on silica gel TLC plates against three Colletotrichum spp. The active principle was isolated by bioassay-directed fractionation using column chromatography followed by crystallization and was characterized as vulgarone B by ¹H and ¹³C NMR and GC-MS. Antifungal activity of vulgarone B was further evaluated using 96-well microtiter assay against Colletotrichum acutatum, C. fragariae, C. gloeosporioides, and Botrytis cinerea. In addition, the antifungal activity of vulgarone B and verbenone, and their corresponding alcohols was tested by bioautography and microtiter assay. Structure–activity studies revealed that the , -unsaturated carbonyl functionality is a prerequisite for the antifungal activity of these mono and sesquiterpene ketones. This is the first report of antifungal activity of vulgarone B. The yield of essential oil from A. douglasiana is about 0.6–0.8% by weight of the dry material, including plant stems.     

Isolation of the diterpenoids, ent-kauran-16alpha-ol and ent-atisan-16alpha-ol, from sunflowers, as oviposition stimulants for the banded sunflower moth, Cochylis hospes

Two diterpenoid alcohols, ent-kauran-16-ol (1) and ent-atisan-16-ol (2), were isolated from pre bloom (R3-R4 stage) sunflower heads as oviposition stimulants for the banded sunflower moth, Cochylis hospes. Fractionation of a sunflower head extract, by normal-phase flash column chromatography, resulted in an early eluting fraction exhibiting significant activity in an egg-laying bioassay. Compounds 1 and 2, along with ent-trachyloban- 19-oic acid (3) and ent-kaur-16-en-19-oic acid (4), were isolated as the major components of this fraction and identified by their NMR and mass spectra. The purified compounds were individually tested for ovipositional activity in dose-response bioassays. In these bioassays, compounds 1 and 2 gave linear dose responses, with increasing numbers of eggs laid as the dosage of either increased. Compounds 3 and 4 failed to stimulate significant egg-laying at any of the dosages tested. A factorial design bioassay, using compounds 1 and 2, showed that 1 was relatively more stimulatory than 2, and that there was no synergistic effect on oviposition when the two compounds were combined.