Species-Specific Induction of Plant Volatiles by Two Aphid Species in Apple: Real Time Measurement of Plant Emission and Attraction of Lacewings in the Wind Tunnel

Upon damage by herbivores, plants release herbivory-induced plant volatiles (HIPVs). To find their prey, the pest’s natural enemies need to be fine-tuned to the composition of these volatiles. Whereas standard methods can be used in the identification and quantitation of HIPVs, more recently introduced techniques such as PTR-ToF–MS provide temporal patterns of the volatile release and detect additional compounds. In this study, we compared the volatile profile of apple trees infested with two aphid species, the green apple aphid Aphis pomi, and the rosy apple aphid Dysaphis plantaginea, by CLSA-GC–MS complemented by PTR-ToF–MS. Compounds commonly released in conjunction with both species include nonanal, decanal, methyl salicylate, geranyl acetone, (Z)-3-hexenyl acetate, (Z)-3-hexenyl butanoate, (Z)-3-hexenyl 2-methyl-butanoate, (E)-β-caryophyllene, β-bourbonene and (Z)-3-hexenyl benzoate. In addition, benzaldehyde and (E)-β-farnesene were exclusively associated with A. pomi, whereas linalool, (E)-4,8-dimethyl-1,3,7-nonatriene were exclusively associated with D. plantaginea. PTR-ToF–MS additionally detected acetic acid (AA) and 2-phenylethanol (PET) in the blends of both trees attacked by aphid species. In the wind tunnel, the aphid predator, Chrysoperla carnea (Stephens), responded strongly to a blend of AA and PET, much stronger than to AA or PET alone. The addition of common and species-specific HIPVs did not increase the response to the binary blend of AA and PET. In our setup, two host-associated volatiles AA + PET appeared sufficient in the attraction of C. carnea. Our results also show the importance of combining complementary methods to decipher the odor profile associated with plants under pest attack and identify behaviourally active components for predators.

Progress Toward an Attract-and-Kill Device for Asian Citrus Psyllid (Hemiptera: Liviidae) Using Volatile Signatures of Citrus Infected With Huanglongbing as the Attractant

Asian citrus psyllid, Diaphorina citri (Kuwayama), preferentially orient toward citrus hosts infected with the phytopathogenic bacterium, Candidatus liberibacter asiaticus (CLas) the agent of citrus greening (Huanglongbing, HLB), compared to uninfected counterparts. We investigated whether this preference for the odors of infected plants could be useful for the development of an attract-and-kill (AK) device for D. citri. Twenty-nine blends of volatile organic compounds derived from the odor of citrus infected with CLas were tested in laboratory olfactometer tests, and two blends were also assessed under field conditions. A seven component blend of tricosane: geranial: methyl salicylate: geranyl acetone: linalool: phenylacetaldehyde: (E)-β-ocimene in a 0.40: 0.06: 0.08: 0.29: 0.08: 0.06: 0.03 ratio released from a proprietary slow-release matrix attracted twice more D. citri to yellow sticky traps compared with blank control traps. The attractive blend was subsequently co-formulated with spinosad insecticide into a slow-release matrix to create a prototype AK formulation against D. citri. This formulation effectively reduced the population density of D. citri up to 84% as measured with tap counts when deployed at a density of eight 2.5 g dollops per tree as compared with untreated controls in small plot field trials conducted in citrus orchards. Psyllid populations were not statistically affected at a deployment rate of four dollops per tree. Our results indicate that an AK formulation incorporating spinosad and a volatile blend signature of citrus greening into a slow-release matrix may be useful to suppress D. citri populations.

Induced volatiles in the interaction between soybean (Glycine max) and the Mexican soybean weevil (Rhyssomatus nigerrimus)

The present study analyzed the volatile compounds emitted by Glycine max (cv. FT-Cristalina-RCH) soybean plants: healthy plants and plants damaged mechanically or by the Mexican soybean weevil Rhyssomatus nigerrimus. The SPME method was used to compare the volatile profile of soybean plants in four different conditions. The volatile profile of G. max plants infested by R. nigerrimus was qualitatively and quantitatively different from that of healthy and mechanically damaged plants. Emission of 59 compounds was detected in the four treatments. Of these compounds, 19 were identified by comparison of the Kovats index, mass spectrum and retention times with those of synthetic standards. An increase in concentration of the volatiles (Z)-3-hexenyl acetate and the compound 1-octen-3-ol was observed when the soybean plants were mechanically damaged. The compounds mostly produced by the soybean plant during infestation by male and female R. nigerrimus were 1-octen-3-ol, 6-methyl-5-hepten-2-one, (E)-β-ocimene, salicylaldehyde, unknown 10, linalool, methyl salicylate, (Z)-8-dodecenyl acetate (ester 5), ketone 2 and geranyl acetone. Behavioral effects of the identified compounds during the insect-plant interaction and their conspecifics are discussed.

Chemical Composition and Bioactivity of the Essential Oil of Cassia singueana Flowers Growing in Nigeria

Cassia singueana (Delile) Lock from the family Fabaceae is a well-known medicinal plant that grows abundantly in Nigeria and other African countries, and has long been used in the treatment of various ailments including malaria and other infectious diseases. The present study aimed at assessing the composition, and bioactivity of the essential oil of the flowers of C. singueana collected from Nigeria. The essential oil was extracted by hydrodistillation and the chemical composition was analyzed by gas chromatography (GC) coupled with a flame ionization detector (GC-FID) and GC coupled to mass spectrometry (GC–MS). The bioactivity of the oil was determined using the brine shrimp lethality assay, agar diffusion antimicrobial test, the 2, 2-diphenylpicrylhydrazyl, metal chelation, and superoxide anion antioxidant assays. The essential oil yield and the percentage of identified compounds were 1.58% and 97.91%, respectively. More than 20 compounds were identified. The major component was geranyl acetone (36.82%) followed by phytol (18.12%). The essential oil showed lethality against the brine shrimp larvae with an LC50 value of 18.7 µg/ml, and antimicrobial activity with largest inhibition zones of 32-33 mm against Candida albicans, Streptococcus pneumoniae, and Staphylococcus aureus. The oil also exhibited considerable antioxidant activity as evident from its ability to scavenge free-radicals such as DPPH, superoxide anions, and metal-chelation.

The Honey Volatile Code: A Collective Study and Extended Version

Background: The present study comprises the second part of a new theory related to honey authentication based on the implementation of the honey code and the use of chemometrics. Methods: One hundred and fifty-one honey samples of seven different botanical origins (chestnut, citrus, clover, eucalyptus, fir, pine, and thyme) and from five different countries (Egypt, Greece, Morocco, Portugal, and Spain) were subjected to analysis of mass spectrometry (GC-MS) in combination with headspace solid-phase microextraction (HS-SPME). Results: Results showed that 94 volatile compounds were identified and then semi-quantified. The most dominant classes of compounds were acids, alcohols, aldehydes, esters, ethers, phenolic volatiles, terpenoids, norisoprenoids, and hydrocarbons. The application of classification and dimension reduction statistical techniques to semi-quantified data of volatiles showed that honey samples could be distinguished effectively according to both botanical origin and the honey code (p < 0.05), with the use of hexanoic acid ethyl ester, heptanoic acid ethyl ester, octanoic acid ethyl ester, nonanoic acid ethyl ester, decanoic acid ethyl ester, dodecanoic acid ethyl ester, tetradecanoic acid ethyl ester, hexadecanoic acid ethyl ester, octanal, nonanal, decanal, lilac aldehyde C (isomer III), lilac aldehyde D (isomer IV), benzeneacetaldehyde, alpha-isophorone, 4-ketoisophorone, 2-hydroxyisophorone, geranyl acetone, 6-methyl-5-hepten-2-one, 1-(2-furanyl)-ethanone, octanol, decanol, nonanoic acid, pentanoic acid, 5-methyl-2-phenyl-hexenal, benzeneacetonitrile, nonane, and 5-methyl-4-nonene. Conclusions: New amendments in honey authentication and data handling procedures based on hierarchical classification strategies (HCSs) are exhaustively documented in the present study, supporting and flourishing the state of the art.

Distribution of Volatile Compounds in Different Fruit Structures in Four Tomato Cultivars

Distribution of volatile compounds in different fruit structures were analyzed in four tomato cultivars by headspace-solid-phase microextraction (SPME)-gas chromatography-mass spectrometry (GC-MS). A total of 36 volatile compounds were identified in fruit samples, which were primarily aldehydes, hydrocarbons, alcohols, ketones, furans, esters, nitrogen compounds, and sulfur and nitrogen-containing heterocyclic compounds. The volatile compositions in pericarp (PE), septa and columella (SC), locular gel and seeds (LS), and stem end (SE) tissues showed different profiles. The PE tissue showed the highest total volatile concentration due to a high abundance of aldehydes, especially cis-3-hexenal and benzaldehyde. Meanwhile, it showed higher aromatic proportion and herbaceous series intensity than other tissues. Floral and fruity series showed higher intensity in SC and LS tissues. The concentration of alcohols in the LS was higher than that in other tissues in association with the higher abundances of 2-methyl propanol, 3-methyl butanol, and 2-methyl butanol. However, the numbers and concentrations of volatile compounds, especially cis-3-hexenal, benzaldehyde, and geranyl acetone were lower in SE than in the other tissues, indicating less tomato aromas in SE. SE tissues were also lacking in floral and fruity characteristic compounds, such as geranyl acetone, 1-nitro-pentane, and 1-nitro-2-phenylethane. “FL 47” contained more volatile compounds than the other three, and the contents of aldehydes, ketones and oxygen-containing heterocyclic compounds in the “Tygress” fruit were higher than the other cultivars.

Essential Oils of Morus alba and M. nigra Leaves: Effect of Drying on the Chemical Composition

Detailed GC and GC/MS analyses of essential-oil samples obtained by hydrodistillation of Morus alba L. and M. nigra L. leaves (four samples) allowed the identification of 131 constituents representing 95.1 – 96.4% of the total GC peak areas. The most abundant compounds classes were alkanes, diterpenoids, carotenoid-derived compounds and fatty acid-related constituents with trans-phytol (7.9 – 71.2%), ( E,E)-geranyl linalool (0.2 – 8.0%), ( Z)-bovolide (8.1%) and n-chain alkanes (in total, 17.5 – 52.4%) as the major constituents of the analyzed samples. In general, there were only quantitative differences noted between M. nigra essential oils from fresh and dry leaves. The most discernable changes included a variation in the content of the major constituents (e.g. the relative amount of trans-phytol and the total amount of alkanes decreased by 5.8% and ≈ 2%, respectively, while that of ( E,E)-geranyl linalool increased by 7.8%). On the other hand, the composition of M. alba essential oil was much more significantly affected by the drying process. The highest quantitative differences were noted for trans-phytol, geranyl acetone, and all isomers of 4,6,8-megastigmatrien-3-one. Also, a rare plant metabolite, ( Z)-bovolide, characteristic of leaf senescence, was only identified (8.1%) in the essential oil of M. alba dried leaves.

Constituents and Insecticidal Activity of Deinbollia pinnata Essential Oil

The volatile constituents and insecticidal activity of the essential oil obtained by hydrodistillation of pulverized air-dried leaves of Dehinbollia pinnata Schum. & Thonn (Sapindaceae) growing in Nigeria were studied. The constituents of the oil were analyzed by gas chromatography (GC) and gas chromatography coupled with mass spectrometry (GC-MS). The percentage yield of the oil was 0.04% (v/w). Fourteen compounds were characterized, representing 94.0% of the total volatile component of the oil. The major constituents of the oil were hexahydrofarnesyl acetone (37.5%), farnesyl acetone (17.2%) and geranyl acetone (14.6%). The essential oil, at a concentration of 120 mg/mL, displayed 100% mortality against Sitophilus zeamais at 72 h with a LC50 > 40.00 mg/mL air.

11-Hydroxy-2,4-cycloeudesmane from the Leaf Oil of Juglans regia and Evaluation of its Larvicidal Activity

Leaves of Juglans regia L. collected from two different locations [Adana (A) and Ankara (B)] from Turkey were subjected to hydrodistillation in a Clevenger type apparatus to yield the essential oils (EOs). GC/MS and GC-FID analyses revealed that the A EO was rich in thymol (23.1%), while caryophyllene oxide (33.8%) was found as the main constituent of B EO. Both contained β-eudesmol (1.4% - 9.5 %), ( E)-geranyl acetone (3.7% - 5.8%) and the eudesmane type constituent juglaterpene A (3.1% - 11.0%). Using a HP Innowax preparative capillary column connected to a preparative fraction collector, an unknown constituent, juglaterpene A (1, 11-hydroxy-2,4-cycloeudesmane), was isolated in a rapid one-step manner with > 94.0% purity. Structure determination was accomplished from 1D- and 2D-NMR spectroscopic data. Oil B demonstrated significant larvicidal activity against 1st instar Aedes aegypti L.