Methyl Jasmonate Application Induces Increased Densities of Glandular Trichomes on Tomato, <Emphasis Type="Italic">Lycopersicon esculentum</Emphasis>

This study was designed to address whether applications of methyl jasmonate (MJ) or Benzothiadiazole (BTH) to cultivated tomato, Lycopersicon esculentum, induced elevated densities of defense-related glandular trichomes on new leaves. Four-leaf tomato plants were sprayed with MJ, BTH, or control solutions, and the density of type VI glandular trichomes on new leaves was subsequently determined at 3, 7, 14, 21, and 28 d. At 7, 14, and 21 d, the density of type VI glandular trichomes on new leaves was significantly higher on MJ-treated plants than on BTH- or control-treated plants. At 7 and 14 d after treatment, the mean density of glandular trichomes on new leaves of MJ-treated plants was ninefold higher than on leaves of control-treated plants. We observed entrapment of immature western flower thrips in trichomes on MJ-treated plants at higher rates than on BTH or control plants. Studies to evaluate potential trade-offs between reductions in pest populations by increased trichome density and possible negative impacts of trichome induction on biological control agents are needed.     

Sexual Isolation and Cuticular Hydrocarbon Differences between <Emphasis Type="Italic">Drosophila santomea</Emphasis> and <Emphasis Type="Italic">Drosophila yakuba</Emphasis>

Drosophila santomea and Drosophila yakuba are two sister species inhabiting Saõ Tomé island. Previous studies showed that both species display strong reproductive isolation, although they can produce a few viable hybrids. Our study tried to understand the mechanism of this ethological isolation between two allopatric strains. A strong sexual isolation was confirmed, with a marked asymmetry. Comparisons of latency times to either courtship or copulation suggest that males do not discriminate females, whereas D. yakuba females, but not D. santomea females, accept their homospecifics more quickly. Cuticular hydrocarbon compositions of both species and sexes were also established with gas chromatography (GC) and GC/mass spectrometry analysis. All have (Z)-7-tricosene as their major compound. There are several quantitative differences between species for few minor compounds. The largest difference concerns n-heneicosane, which is more abundant in D. santomea than in D. yakuba flies (up to seven times more between males). A similar quantitative difference was also found in a pair of sympatric strains. Furthermore, D. yakuba males artificially perfumed with n-heneicosane were discriminated negatively by D. yakuba females, suggesting a role for this compound in the sexual isolation between these two species.     

Relationship Between the Endophyte <Emphasis Type="Italic">Embellisia</Emphasis> spp. and the Toxic Alkaloid Swainsonine in Major Locoweed Species (<Emphasis Type="Italic">Astragalus</Emphasis> and <Emphasis Type="Italic">Oxytropis)</Emphasis>

Locoweeds (Astragalus and Oxytropis spp. that contain the toxic alkaloid swainsonine) cause widespread poisoning of livestock on western rangelands. There are 354 species of Astragalus and 22 species of Oxytropis in the US and Canada. Recently, a fungal endophyte, Embellisia spp., was isolated from Astragalus and Oxytropis spp. and shown to produce swainsonine. We conducted a survey of the major locoweeds from areas where locoweed poisoning has occurred to verify the presence of the endophyte and to relate endophyte infection with swainsonine concentrations. Species found to contain the fungal endophyte and produce substantial amounts of swainsonine were A. wootoni, A. pubentissimus, A. mollissimus, A. lentiginosus, and O. sericea. Astragalus species generally had higher concentrations of swainsonine than Oxytropis. Swainsonine was not detected in A. alpinus, A. cibarius, A. coltonii, A. filipes, or O. campestris. The endophyte could not be cultured from A. mollissimus var. thompsonii or A. amphioxys, but was detected by polymerase chain reaction, and only 30% of these samples contained trace levels of swainsonine. Further research is necessary to determine if the endophyte is able to colonize these and other species of Astragalus and Oxytropis and determine environmental influences on its growth and synthesis of swainsonine.     

Attraction of the Parasitoid <Emphasis Type="Italic">Anagrus nilaparvatae</Emphasis> to Rice Volatiles Induced by the Rice Brown Planthopper <Emphasis Type="Italic">Nilaparvata lugens</Emphasis>

Anagrus nilaparvatae, an egg parasitoid of the rice brown planthopper Nilaparvata lugens, was attracted to volatiles released from N. lugens-infested plants, whereas there was no attraction to volatiles from undamaged plants, artificially damaged plants, or volatiles from N. lugens nymphs, female adults, eggs, honeydew, and exuvia. There was no difference in attractiveness between plants infested by N. lugens nymphs or those infested by gravid females. Attraction was correlated with time after infestation and host density; attraction was only evident between 6 and 24 hr after infestation by 10 adult females per plant, but not before or after. Similarly, after 24 hr of infestation, wasps were attracted to plants with 10 to 20 female planthoppers, but not to plants with lower or higher numbers of female planthoppers. The attractive time periods and densities may be correlated with the survival chances of the wasps' offspring, which do not survive if the plants die before the wasps emerge. Wasps were also attracted to undamaged mature leaves of a rice plant when one of the other mature leaves had been infested by 10 N. lugens for 1 d, implying that the volatile cues involved in host location by the parasitoid are systemically released. Collection and analyses of volatiles revealed that 1 d of N. lugens infestation did not result in the emission of new compounds or an increase in the total amount of volatiles, but rather the proportions among the compounds in the blend were altered. The total amounts and proportions of the chemicals were also affected by infestation duration. These changes in volatile profiles might provide the wasps with specific information on host habitat quality and thus could explain the observed behavioral responses of the parasitoid.     

Laboratory Evaluation of <Emphasis Type="Italic">Artemisia annua</Emphasis> L. Extract and Artemisinin Activity against <Emphasis Type="Italic">Epilachna paenulata</Emphasis> and <Emphasis Type="Italic">Spodoptera eridania</Emphasis>

Ethanolic extract of aerial parts of Artemisia annua L. and artemisinin were evaluated as anti-insect products. In a feeding deterrence assay on Epilachna paenulata Germ (Coleoptera: Coccinellidae) larvae, complete feeding rejection was observed at an extract concentration of 1.5 mg/cm² on pumpkin leaf tissue. The same concentration produced a feeding inhibition of 87% in Spodoptera eridania (Cramer) (Lepidoptera: Noctuidae). In a no-choice assay, both species ate less and gained less weight when fed on leaves treated with the extract. Complete mortality in E. paenulata and 50% mortality in S. eridania were observed with extract at 1.5 mg/cm². Artemisinin exhibited a moderate antifeedant effect on E. paenulata and S. eridania at 0.03–0.375 mg/cm². However, a strong effect on survival and body weight was observed when E. paenulata larvae were forced to feed on leaves treated at 0.03 and 0.075 mg/cm². Artemisia annua ethanolic extract of aerial parts at 1.5 mg/cm² showed no phytotoxic effect on pumpkin seedlings.     

<Emphasis Type="Italic">Santalum </Emphasis><Emphasis Type="Italic">insulare</Emphasis> Acetylenic Fatty Acid Seed Oils: Comparison within the <Emphasis Type="Italic">Santalum</Emphasis> Genus

The sandalwood kernels of Santalum insulare (Santalaceae) collected in French Polynesia give seed oils containing significant amounts of ximenynic acid, E-11-octadecen-9-oic acid (64–86%). Fatty acid (FA) identifications were performed by gas chromatography/mass spectrometry (GC/MS) of FA methyl esters. Among the other main eight identified fatty acids, oleic acid was found at a 7–28% level. The content in stearolic acid, octadec-9-ynoic acid, was low (0.7–3.0%). An inverse relationship was demonstrated between ximenynic acid and oleic acid using 20 seed oils. Results obtained have been compared to other previously published data on species belonging to the Santalum genus, using multivariate statistical analysis. The relative FA S. insulare composition, rich in ximenynic acid is in the same order of those given for S. album or S. obtusifolium. The other compared species (S. acuminatum, S. lanceolatum, S. spicatum and S. murrayanum) are richer in oleic acid (40–59%) with some little differences in linolenic content.     

Spectrum of Cyanide Toxicity and Allocation in <Emphasis Type="Italic">Heliconius erato</Emphasis> and <Emphasis Type="Italic">Passiflora</Emphasis> Host Plants

The larvae of three races of Heliconius erato were fed various species of Passiflora containing varying levels of cyanoglucosides. The mortality rate of larvae and pupae rose when larvae were fed species of Passiflora capable of releasing larger quantities of cyanide. When larvae were fed species of Passiflora with these properties, the resulting adult butterflies also released higher levels of cyanide. This may serve as a defense mechanism. The compounds responsible for the release of cyanide were not evenly distributed throughout the adult butterfly’s body. The thorax contained the highest concentration of cyanogenic substances, followed by the head, wings, and abdomen. The younger tissues of Passiflora plants had higher levels of cyanide-releasing compounds than stems and mature leaves. Cyanogenic glycoside distribution within the plants is consistent with optimal allocation theory. The levels of cyanide-releasing substances in plants varied depending on the season.     

Plant Growth Inhibition By <Emphasis Type="Italic">Cis</Emphasis>-Cinnamoyl Glucosides and <Emphasis Type="Italic">Cis</Emphasis>-Cinnamic Acid

Spiraea thunbergii Sieb. contains 1-O-cis-cinnamoyl--_d-glucopyranose (CG) and 6-O-(4-hydroxy-2-methylene-butyroyl)-1-O-cis-cinnamoyl--_d-glucopyranose (BCG) as major plant growth inhibiting constituents. In the present study, we determined the inhibitory activity of CG and BCG on root elongation of germinated seedlings of lettuce (Lactuca sativa), pigweed (Amaranthus retroflexus), red clover (Trifolium pratense), timothy (Phleum pratense), and bok choy (Brassica rapa var chinensis) in comparison with that of two well-known growth inhibitors, 2,4-dichlorophenoxyacetic acid (2,4-D) and (+)-2-cis-4-trans-abscisic acid (cis-ABA), as well as two related chemicals of CG and BCG, cis-cinnamic acid (cis-CA) and trans-cinnamic acid (trans-CA). The EC₅₀ values for CG and BCG on lettuce were roughly one-half to one-quarter of the value for cis-ABA. cis-Cinnamic acid, which is a component of CG and BCG, possessed almost the same inhibitory activity of CG and BCG, suggesting that the essential chemical structure responsible for the inhibitory activity of CG and BCG is cis-CA. The cis-stereochemistry of the methylene moiety is apparently needed for high inhibitory activity, as trans-CA had an EC₅₀ value roughly 100 times that of CG, BCG, and cis-CA. Growth inhibition by CG, BCG, and cis-CA was influenced by the nature of the soil in the growing medium: alluvial soil preserved the bioactivity, whereas volcanic ash and calcareous soils inhibited bioactivity. These findings indicate a potential role of cis-CA and its glucosides as allelochemicals for use as plant growth regulators in agricultural fields.     

Effects of Root Isoquinoline Alkaloids from <Emphasis Type="Italic">Hydrastis canadensis</Emphasis> on <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> Isolated from <Emphasis Type="Italic">Hydrastis</Emphasis> Root Tissue

Goldenseal (Hydrastis canadensis L.) is a popular medicinal plant distributed widely in North America. The rhizome, rootlets, and root hairs produce medicinally active alkaloids. Berberine, one of the Hydrastis alkaloids, has shown antifungal activity. The influence of a combination of the major Hydrastis alkaloids on the plant rhizosphere fungal ecology has not been investigated. A bioassay was developed to study the effect of goldenseal isoquinoline alkaloids on three Fusarium isolates, including the two species isolated from Hydrastis rhizosphere. The findings suggest that the Hydrastis root extract influences macroconidia germination, but that only the combined alkaloids—berberine, canadine, and hydrastine—appear to synergistically stimulate production of the mycotoxin zearalenone in the Fusarium oxysporum isolate. The Hydrastis root rhizosphere effect provided a selective advantage to the Fusarium isolates closely associated with the root tissue in comparison with the Fusarium isolate that had never been exposed to Hydrastis.     

(7<Emphasis Type="Italic">Z</Emphasis>,9<Emphasis Type="Italic">E</Emphasis>)-2-Methyl-7,9-Octadecadiene: A Sex Pheromone Component of <Emphasis Type="Italic">Lymantria Bantaizana</Emphasis>

Our objective was to identify the sex pheromone of Lymantria bantaizana (Lepidoptera: Lymantriidae) whose larvae feed exclusively on walnut, Juglans spp., in China, and Japan. Coupled gas chromatographic–electroantennographic detection (GC-EAD) analyses of pheromone gland extracts revealed a single EAD-active component. Retention index calculations of this compound on four GC columns suggested that it was a methyl-branched octadecadiene with conjugated double bonds. In GC-EAD analyses of 2-methyloctadecenes, (Z)-2-methyl-7-octadecene and (E)-2-methyl-7-octadecene elicited the strongest antennal responses, suggesting that the double bond positions were at C7 and C9. In comparative GC-EAD analyses of pheromone gland extract and stereoselectively synthesized isomers (E,E; E,Z; Z,E; Z,Z) of 2-methyl-7,9-octadecadiene, the (E,Z)- and (Z,E)-isomer had retention times identical to that of the candidate pheromone, but only the latter isomer elicited strong EAD activity. Results of field experiments in Japan substantiated that (7Z,9E)-2-methyl-7,9-octadecadiene is the L. bantaizana sex pheromone, a compound previously unknown in the Lepidoptera. Detection surveys in North America for exotic Eurasian forest defoliators could include traps baited with the L. bantaizana pheromone.     

Effect of Volatile Constituents from <Emphasis Type="Italic">Securidaca</Emphasis><Emphasis Type="Italic">Longepedunculata</Emphasis> on Insect pests Of Stored Grain

Securidaca longepedunculata Fers (Polygalaceae) is commonly used as a traditional medicine in many parts of Africa as well as against a number of invertebrate pests, including insects infesting stored grain. The present study showed that S. longepedunculata root powder, its methanol extract, and the main volatile component, methyl salicylate, exhibit repellent and toxic properties to Sitophilus zeamais adults. Adult S. zeamais that were given a choice between untreated maize and maize treated with root powder, extract, or synthetic methyl salicylate in a four-way choice olfactometer significantly preferred the control maize. Methyl salicylate vapor also had a dose-dependant fumigant effect against S. zeamais, Rhyzopertha dominica, and Prostephanus truncates, with a LD₁₀₀ achieved with a 60 l dose in a 1-l container against all three insect species after 24 hr of exposure. Probit analyses estimated LD₅₀ values between 34 and 36 l (95% CI) for all insect species. Furthermore, prolonged exposure for 6 days showed that lower amounts (30 l) of methyl salicylate vapor were able to induce 100% adult mortality of the three insect species. The implications are discussed in the context of improving stored product pest control by small-scale subsistence farmers in Africa.     

Phytotoxic and Antifungal Compounds from Two <Emphasis Type="Italic">Apiaceae</Emphasis> Species, <Emphasis Type="Italic">Lomatium californicum</Emphasis> and <Emphasis Type="Italic">Ligusticum hultenii</Emphasis>, Rich Sources of Z-ligustilide and Apiol,Respectively

The seeds of two Apiaceae species, Ligusticum hultenii and Lomatium californicum, were investigated. Preliminary bioassays indicated that methylene chloride extracts of seeds of both species contained selective phytotoxic activity against monocots and antifungal activity against Colletotrichum fragariae. Active constituents were isolated by bioassay-guided fractionation, and the structures were elucidated by NMR and GC-MS as apiol and Z-ligustilide, isolated from L. hultenii and L. californicum, respectively. Apiol and Z-ligustilide had I₅₀ values of about 80 and 600 μM, respectively, for inhibition of the growth of Lemna paucicostata. The methylene chloride (CH₂Cl₂) extracts of the seeds and the isolated and purified compounds were tested against the 2-methylisoborneol-producing cyanobacterium (blue-green alga) Oscillatoria perornata, and the green alga Selenastrum capricornutum. The CH₂Cl₂ extracts of both Apiaceae species and apiol were weakly toxic to both species of phytoplankton, while Z-ligustilide was toxic to both with a lowest complete inhibitory concentration (LCIC) of 53 μM. Seeds of L. californicum and L. hultenii were found to be rich sources of Z-ligustilide (97 mg/g of dry seed) and apiol (40 mg/g of dry seed), respectively.     

Roquefortine/Oxaline Biosynthesis Pathway Metabolites in <Emphasis Type="Italic">Penicillium</Emphasis> ser. <Emphasis Type="Italic">Corymbifera</Emphasis>: <Emphasis Type="Italic">In Planta</Emphasis> Production and Implications for Competitive Fitness

Three strains of each of the seven taxa comprising the Penicillium series Corymbifera were surveyed by direct injection mass spectrometry (MS) and liquid chromatography–MS for the production of terrestric acid and roquefortine/oxaline biosynthesis pathway metabolites when cultured upon macerated tissue agars prepared from Allium cepa, Zingiber officinale, and Tulipa gesneriana, and on the defined medium Czapek yeast autolysate agar (CYA). A novel solid-phase extraction methodology was applied for the rapid purification of roquefortine metabolites from a complex matrix. Penicillium hordei and P. venetum produced roquefortine D and C, whereas P. hirsutum produced roquefortine D and C and glandicolines A and B. P. albocoremium, P. allii, and P. radicicola carried the pathway through to meleagrin, producing roquefortine D and C, glandicolines A and B, and meleagrin. P. tulipae produced all previously mentioned metabolites yet carried the pathway through to an end product recognized as epi-neoxaline, prompting the proposal of a roquefortine/epi-neoxaline biogenesis pathway. Terrestric acid production was stimulated by all Corymbifera strains on plant-derived media compared to CYA controls. In planta, production of terrestric acid, roquefortine C, glandicolines A and B, meleagrin, epi-neoxaline, and several other species-related secondary metabolites were confirmed from A. cepa bulbs infected with Corymbifera strains. The deposition of roquefortine/oxaline pathway metabolites as an extracellular nitrogen reserve for uptake and metabolism into growing mycelia and the synergistic role of terrestric acid and other Corymbifera secondary metabolites in enhancing the competitive fitness of Corymbifera species in planta are proposed.     

Role of (3<Emphasis Type="Italic">Z</Emphasis>,6<Emphasis Type="Italic">Z</Emphasis>,8<Emphasis Type="Italic">E</Emphasis>)-Dodecatrien-1-ol in Trail Following,Feeding, and Mating Behavior of <Emphasis Type="Italic">Reticulitermes hesperus</Emphasis>

Trail pheromones mediate communication among western subterranean termites, Reticulitermes hesperus Banks. Repetitive passages of ≥28 termites were required to establish a pheromone trail and trails needed to be reinforced because they lasted <48 hr. The minimal threshold concentration for inducing responses from termite workers and secondary reproductives was between 0.01 and 0.1 fg/cm of (3Z,6Z,8E)-dodecatrien-1-ol (henceforth, dodecatrienol). Workers showed optimal trail-following behavior to dodecatrienol at a concentration of 10 fg/cm. Trails with concentrations >10 pg/cm were repellent to workers. Workers did not detect pheromone gradients, responding equally to increasing or decreasing gradients of dodecatrienol, and termite workers were not able to differentiate between different concentrations of dodecatrienol. Termites preferred dodecatrienol trails to 2-phenoxyethanol trails. Antennae played a key role in trail pheromone perception. Dodecatrienol acted as an arrestant for worker termites (10 fg/cm²) and male alates (5 ng/cm²), whereas sternal gland extracts from females attracted male alates. Workers and alates, upon contact with filter paper disks treated with higher doses (10 fg/cm² and 5 ng/cm², respectively) of dodecatrienol, were highly excited (increased antennation and palpation) and repeatedly returned to the treated disks. Dodecatrienol did not act as a phagostimulant when offered on a paper towel disk. Reticulitermes hesperus is highly responsive to dodecatrienol, and it may play an important role in orientation of workers and alates.     

Response of the Aphid Parasitoid <Emphasis Type="Italic">Aphidius funebris</Emphasis> to Volatiles from Undamaged and Aphid-infested <Emphasis Type="Italic">Centaurea nigra</Emphasis>

Two issues have hindered the understanding of the ecology and evolution of volatile-mediated tritrophic interactions: few studies have addressed noncrop systems; and few statistical techniques have been applied that are suitable for the analysis of complex volatile blends. In this paper, we addressed both of these issues by studying the noncrop system involving the plant Centaurea nigra, the specialist aphid Uroleucon jaceae, and the parasitoid Aphidius funebris. In a Y-tube olfactometer, A. funebris was attracted to the odor from undamaged C. nigra, but preferred the plant–host complex (PHC) after 3 d of feeding by 200 U. jaceae over the undamaged plant, but not after three or 5 d of feeding by 50 U. jaceae. When aphids were removed, the initial preference for the damaged plant remained, but the final preference was not greater than for the undamaged plant. No qualitative differences were detected between the headspaces of C. nigra and the C. nigra–U. jaceae PHC. For quantitative analysis, we used a compositional approach, which treats each compound produced as part of a blend, and not as a compound released in isolation, thus allowing analysis of the relative contribution of each compound to the blend as a whole. With this approach, subtle increases and decreases of some green leaf volatiles and monoterpenoids on the third day of aphid infestation were detected. Mechanically damaged C. nigra had a volatile profile that differed from undamaged C. nigra and the PHC. One and 10 ng of (Z)-3-hexenyl acetate, and 10 or 100 ng of 6-methyl-5-hepten-2-one were attractive to the parasitoid when placed in solution on filter paper. A. funebris appears to be using a combination of chemical cues to locate host-infested plants.     

CHARACTERIZATION OF A SALIVARY LYSOZYME IN LARVAL <Emphasis Type="Italic">Helicoverpa zea</Emphasis>

The cDNA sequence of a salivary lysozyme in Helicoverpa zea (Lepidoptera: Noctuidae) was determined. The full-length cDNA is 1,032 bp, and it encodes a protein of 142 amino acids. This lysozyme has 90% identity with Heliothis virescens lysozyme and 76% identity with Manduca sexta lysozyme. There is a signal peptide of 20 amino acids at the N-terminus. The mature protein is about 14.4 kDa without the signal peptide. The pI value is greater than 9.5 as determined by isoelectric focusing. From genomic DNA, two introns and three exons were within the open reading frame (ORF). Southern blot analysis indicated that it is a single-copy gene. A time-course study revealed that the H. zea lysozyme gene was differentially expressed in the labial glands during the development of fifth-instar larvae, with the peak level of lysozyme mRNA being detected on day 1. Dot blot analysis showed different levels of H. zea lysozyme expression when the caterpillars fed on different plants. Further, the H. zea lysozyme could be detected with antibodies raised against the M. sexta lysozyme, and it was one of the most abundant secreted proteins in saliva collected directly from the caterpillars spinneret. The potential role of the lysozyme on host plants in mediating susceptibility to bacterial disease is discussed in the context of tritrophic interactions.     

Fractionation and characterization of proteins from <Emphasis Type="Italic">Gevuina avellana</Emphasis> and <Emphasis Type="Italic">Rosa rubiginosa</Emphasis> seeds

Gevuina avellana and Rosa rubiginosa proteins were evaluated for their potential food use. The proteins were sequentially separated into five fractions according to their solubilities in deionized water, 0.5 M NaCl, 70% (vol/vol) isopropyl alcohol, 50% (vol/vol) glacial acetic acid, and 0.1 M NaOH. The five fractionated protein groups were then characterized by SDS-PAGE and gel filtration chromatography to determine their M.W. profiles. Ninety-six percent of G. avellana total protein was solubilized in three extraction stages, and 88% of R. rubiginosa total protein was solubilized in one extraction stage. Albumins were the major protein fraction in G. avellana and glutelins-1 the most abundant in R. rubiginosa. The protein solubility profile determined over the pH range 1–12 showed minimal solubilities at pH 3–5 and pH 3–7 for G. avellana and R. rubiginosa, respectively. Electrophoretic studies revealed the existence of proteins composed of two major kinds of polypeptides linked together via disulfide bonds and with molecular masses ranging from 13 to 119 kDa. Gel filtration chromatography profiles of globulins and albumins were studied for both seeds. Isoelectric focusing showed an isoelectric point in the ranges of 4.5–6 and 3–6.5 for G. avellana and R. rubiginosa proteins, respectively.     

Biosurfactant production by <Emphasis Type="Italic">Bacillus coagulans</Emphasis>

A new biosurfactant producer, Bacillus coagulans, was isolated from soil. Its 24-h-old culture broth had a low surface tension (27–29 mN/m). Optimization of cell growth of this bacterium led to maximal biosurfactant production with glucose or starch as the organic carbon source, a pH in the range 4.0–7.5, and incubation temperatures from 20 to 45°C. The crude biosurfactants obtained after neutralization and lyophilization of the acid precipitate yielded a minimal aqueous solution surface tension value of 29 mN/m and an interfacial tension value of 4.5 mN/m against hexadecane. The critical micelle concentration of the crude biosurfactants was 17 mg/L. Addition of NaCl to the aqueous solution of the crude product caused lowering of surface tension at both the aqueous solution-air and aqueous solution-n-hexadecane interfaces. These results indicate that the biosurfactants obtained have potential environmental and industrial applications and may have uses in microbially enhanced oil recovery.     

Volatile Allelochemicals in the <Emphasis Type="Italic">Ageratum conyzoides</Emphasis> Intercropped Citrus Orchard and their Effects on Mites <Emphasis Type="Italic">Amblyseius newsami</Emphasis> and <Emphasis Type="Italic">Panonychus citri</Emphasis>

Ageratum conyzoides L. weed often invades cultivated fields and reduces crop productivity in Southeast Asia and South China. However, intercropping this weed in citrus orchards may increase the population of predatory mite Amblyseius newsami, an effective natural enemy of citrus red mite Panonychus citri, and keep the population of P. citri at low and noninjurious levels. This study showed that A. conyzoides produced and released volatile allelochemicals into the air in the intercropped citrus orchard, and these volatiles influenced the olfactory responses of A. newsami and P. citri. At test temperature (25°C), A. conyzoides fresh leaves, its essential oil, and major constituents, demethoxy-ageratochromene, β-caryophyllene, α-bisabolene, and E-β-farnesene, attracted A. newsami and slightly repelled P. citri. Field experiments demonstrated that spraying A. conyzoides essential oil emulsion in an A. conyzoides nonintercropped citrus orchard increased the population density of A. newsami from below 0.1 to over 0.3 individuals per leaf, reaching the same level as in an A. conyzoides intercropped citrus orchard. However, this effect could not be maintained beyond 48 hr because of the volatility of the essential oil. In contrast, in the A. conyzoides intercropped citrus orchard, A. conyzoides plants continuously produced and released volatile allelochemicals and maintained the A. newsami population for a long time. The results suggest that intercropping of A. conyzoides not only made the citrus orchard ecosystem more favorable for the predatory mite A. newsami, but also that the volatile allelochemicals released from A. conyzoides regulated the population of A. newsami and P. citri.     

Fatty Acid Composition of Turkish <Emphasis Type="Italic">Rhododendron</Emphasis> Species

This study describes work aimed at the rapid evaluation of the fatty acid (FA) composition of Turkish Rhododendron species, particularly the leaves and the flowers of the toxic plants, R. ponticum and R. luteum. The FA profiles of the available parts of three other nonpoisonous Rhododendron species were also investigated. Subtotal extracts obtained (using n-hexane, chloroform and methanol) from total chloroform:methanol (1:1) extracts were analyzed and compared to each other. Palmitic acid was found to be the most abundant FA in almost all Rhododendron extracts, and the majority of leaf and flower extracts contained significant portions of C18 unsaturated FAs (18:1n-9, 18:2n-6, 18:3n-3). The n-hexane extracts of R. ponticum leaves and R. luteum flowers were unique, as they contained an unusual series of even-chain iso FAs (C16–C24). Especially the n-hexane extracts were found to comprise uncommon FAs with odd-numbered carbons (C13–C29). Overall, n-hexane proved to be the best solvent by representing the richest FA profile, whereas chloroform or methanol appeared less suitable for FA analyses. Appreciable intra-species variations in FA compositions among the leaves as well as other anatomical parts examined were observed. This study highlights the chemotaxonomical importance of the FAs for the genus Rhododendron.