Defensive Role of Tomato Polyphenol Oxidases against Cotton Bollworm (<Emphasis Type="Italic">Helicoverpa armigera</Emphasis>) and Beet Armyworm (<Emphasis Type="Italic">Spodoptera exigua</Emphasis>)

Tomato (Solanum lycopersicum) polyphenol oxidases (PPOs), enzymes that oxidize phenolics to quinones, have been implicated in plant resistance to insects. The role of PPO in resistance to cotton bollworm [Helicoverpa armigera (Hübner)] and beet armyworm [Spodoptera exigua (Hübner)] (Lepidoptera: Noctuidae) was evaluated. Consumption, weight gains, and mortality of larvae feeding on foliage of transgenic tomato lines overexpressing PPO (OP lines) and of larvae feeding on foliage of transgenic tomato lines with suppressed PPO (SP lines) were compared with consumption, weight gains, and mortality of larvae feeding on non-transformed (NT) plants. Increases in foliage consumption and weight gains were observed for cotton bollworms feeding on leaves of SP plants compared to NT and OP plants. PPO activity was negatively correlated with both weight gains and foliar consumption of cotton bollworm, substantiating the defensive role of PPO against this insect. Similarly, beet armyworm consumed less foliage (both young and old leaves) from OP plants than SP plants. Larvae feeding on OP leaves generally exhibited lower weight gains than those feeding on SP leaves. These results indicate that tomato PPO plays a role in resistance to both cotton bollworm and beet armyworm.     

Detoxification of Gramine by the Cereal Aphid <Emphasis Type="Italic">Sitobion avenae</Emphasis>

Secondary metabolites play an important role in host plant resistance to insects, and insects, in turn, may develop mechanisms to counter plant resistance mechanisms. In this study, we investigated the toxicity of gramine to the cereal aphid Sitobion avenae and some enzymatic responses of S. avenae to this alkaloid. When S. avenae fed on an artificial diet containing gramine, mortality occurred in a dose-dependent manner. The LC₅₀ of gramine was determined to be 1.248 mM. In response to gramine, S. avenae developed increased activities of carboxylesterase and glutathione S-transferase, two important detoxification enzymes. The activities of both enzymes were positively correlated with the concentration of dietary gramine. In addition, the activities of peroxidase and polypheolic oxidase, two important oxidoreductase enzymes in S. avenae, increased in response to gramine; however, catalase activity decreased when insects were exposed to higher levels of dietary gramine. The potential role of gramine in host plant resistance and S. avenae counter-resistance is discussed.     

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.     

Combined Effect of Intercropping and Turnip Root Fly (<Emphasis Type="Italic">Delia floralis</Emphasis>) Larval Feeding on the Glucosinolate Concentrations in Cabbage Roots and Foliage

The effects of plant competition and herbivory on glucosinolate concentrations in cabbage root and foliage were investigated in a cabbage-red clover intercropping system. Cabbage plants were grown under different competitive pressures and with varying degrees of attack by root-feeding Delia floralis larvae. Glucosinolate concentrations in cabbage were affected both by intercropping and by D. floralis density. Glucosinolate concentrations in foliage generally decreased as a response to intercropping, while the responses to insect root damage of individual glucosinolates were weaker. Root glucosinolates responded more strongly to both intercropping and egg density. Total root glucosinolate concentration decreased with clover density, but only at high egg densities. Increased egg density led to opposite reactions by the indole and aliphatic glucosinolates in roots. The responses of individual root glucosinolates to competition and root damage were complex and, on occasion, nonlinear. Reduced concentrations of several glucosinolates and the tendency towards a decrease in total concentration in cabbage foliage caused by intercropping and larval damage suggest that competing plants or plants with root herbivory do not allocate the same resources as unchallenged plants towards sustaining levels of leaf defensive compounds. This could also be true for root glucosinolate concentrations at high egg densities. In addition, the results suggest that changes occurring within a structural group of glucosinolates may be influenced by changes in a single compound, e.g., glucobrassicin (indol-3-ylmethyl) in foliage or sinigrin (2-propenyl) in roots.     

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.     

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.     

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.     

Electrosynthesis of nitroso compounds from (<Emphasis Type="Italic">1</Emphasis><Emphasis Type="Bold">S</Emphasis>, <Emphasis Type="Italic">2</Emphasis><Emphasis Type="Bold">S</Emphasis>)-2-amino-l-(4-nitrophenyl)-propane-1,3-diol derivatives

Nitroso compounds were electrogenerated from (1S, 2S)-2-amino-1-(4-nitrophenyl)-propane-1,3-diol derivatives (derivatives of p-nitrophenylserinol) in a “redox” flow cell equipped with two consecutive porous electrodes of opposite polarities. In spite. of the relative instability in methanol-acetate buffer of the hydroxylamine intermediates produced at the first porous electrode (cathode), the nitroso derivatives were prepared in good yields at the second one (anode). A coupling reaction between some nitroso derivatives and p-toluenesulphinic acid led to N-sulphonylphenylhydroxylamines.     

Differential Attractiveness of Potato Tuber Volatiles to <Emphasis Type="Italic">Phthorimaea operculella</Emphasis> (Gelechiidae) and the Predator <Emphasis Type="Italic">Orius insidiosus</Emphasis> (Anthocoridae)

The behavioral responses of the potato tuberworm moth Phthorimaea operculella and the polyphagous predator Orius insidiosus to volatiles emanating from exposed tubers were studied by four-arm olfactometer bioassays. Mated females of P. operculella distinguished volatiles released by intact potato tubers from volatiles damaged mechanically or by conspecific larvae. Volatiles from intact potato tubers were attractive to them. On the other hand, unmated females of P. operculella did not respond to tuber volatiles. Adults of O. insidiosus were attracted to volatiles from tubers damaged by P. operculella larvae, but did not respond to intact or mechanically damaged tubers. Methyl jasmonate (MeJA) was the only compound identified from the headspace of potato tubers (GC-MS of direct headspace sampling). The amount varied with the type of induction, being 0.001 ± 0.0003 ng g⁻¹ in tissues of intact fresh tubers, 0.002 ± 0.0007 ng g⁻¹ in mechanically damaged tubers, and showing a six- to tenfold increase in P. operculella damaged tubers (0.090 ± 0.006 ng g⁻¹). Behavioral bioassays with synthetic MeJA confirmed that the response of the insects is dependent on MeJA concentration. Mated females of P. operculella showed the highest response at 0.001 ng g⁻¹ (concentration released by intact tubers), whereas O. insidiosus showed the highest response, between 0.01 and 0.05 ng g⁻¹, which is close to the concentration released by P. operculella damaged tubers. Based on these results, we postulate that P. operculella and O. insidiosus have adapted their responses to plant volatiles differently, enabling them to locate suitable hosts or prey.     

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.     

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.     

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.     

<Emphasis Type="Italic">Desmoscaris tripsinosa</Emphasis> and <Emphasis Type="Italic">Palaemonetes africanus</Emphasis> Responses to Concentrations of Neatex and Norust CR486 in Sediment

The assessment of water and sediment quality from chemical pollutants in the Nigerian Niger Delta were conducted using bioindicators (Desmoscaris tripsinosa and Palaemonetes africanus). The Organization for Economic Cooperation and Development (OECD) (2004), No.218 direct sediment toxicity assessment was employed. Shrimp were exposed to sediments treated with Neatex (liquid detergent) and Norust CR 486 (corrosion inhibitor) at concentrations of 31.25, 62.5, 125, 250 and 500 mg/kg. Percentage mortality was measured as the ecological endpoint. Mean % mortality and estimated lethal concentration LC50 values varied with species type, concentration and exposure duration. Observed % mean mortality of the test organisms in both chemicals were significantly different from that of the control test suggesting that mortality may be induced by the effect of the chemicals. LC50s were significantly different for both chemicals at p < 0.05, t = 6.06 (fresh water) and p < 0.05, t = 12.34 (brackish). The values from this study are an indication that the chemicals have the potential to cause acute lethal toxicity. It is a prediction of likely adverse effects on shrimp populations in benthic sediment of the Niger Delta ecological zone. Consequently, there is a great need to protect some of the more sensitive invertebrates representing the major proportion of the diet of many other species.

(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.     

Identification of Volatile Compounds Used in Host Location by the Black Bean Aphid, <Emphasis Type="Italic">Aphis fabae</Emphasis>

Behavioral and electrophysiological responses of winged Aphis fabae to volatiles of faba bean, Vicia faba (var. Sutton dwarf), plants were studied and semiochemicals used in host location were identified. In olfactometer bioassays, aphids spent significantly more time in the region of the olfactometer where V. faba volatiles from an intact plant were present than in control regions with clean air. This response also occurred when an air entrainment sample of a V. faba plant was used as the odor source. Coupled gas chromatography-electroantennography revealed the presence of 16 electrophysiologically active compounds in the air entrainment sample. Fifteen of these were identified as (Z)-3-hexen-1-ol, 1-hexanol, (E)-2-hexenal, benzaldehyde, 6-methyl-5-hepten-2-one, octanal, (Z)-3-hexen-1-yl acetate, (R)-(-)-linalool, methyl salicylate, decanal, undecanal, (E)-caryophyllene, (E)-beta-farnesene, (S)-(-)-germacrene D, and (E,E,)-4,8,12-trimethyl-1,3,7,11-tridecatetraene. An olfactometer response was observed to a 15-component synthetic blend that comprised all identified compounds at the same concentration and ratio as in the natural sample, with the aphids spending significantly more time in the treated regions of the olfactometer where volatiles were present than in the control regions. These data are discussed in the context of insect host location and crop protection.     

Synthesis and Properties of 1,1-bis{[3-(<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dimethylamino)propyl]amido}alkane-di-<Emphasis Type="Italic">N</Emphasis>-oxides

A homologous series of new surface-active 1,1-bis{[3-(N,N-dimethylamino)propyl]amido}alkane-di-N-oxides were synthesized in the reaction of an appropriate diethyl 2-alkylmalonate with N,N-dimethylamino-1,3-propanediamine followed by oxidation with aqueous hydrogen peroxide. The adsorption isotherms of their aqueous solutions were measured and evaluated to obtain adsorption parameters: critical micelle concentration (CMC), surface excess concentration (Γ_CMC), equilibrium surface tension at the CMC (γ_CMC), cross-sectional area of the adsorbed surfactant molecule (A _CMC), efficiency of surface adsorption (pC₂₀), standard free energies of adsorption (ΔG°_ads), and micellization (ΔG°_CMC). All investigated di-amidoamines and di-N-oxides were practically non-toxic to selected bacteria and yeasts. These compounds are readily biodegradable in the Closed Bottle Test inoculated with activated sludge. Surface and biological properties showed that this group of N-oxide-type compounds has high surface activity and fulfills requirements for environmental acceptance.

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.     

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.