Dosage impact of submerged plants extracts on Microcystis aeruginosa growth: From hormesis to inhibition.

Allelopathy has been demonstrated to be an environmentally friendly way to control harmful algal blooms. Allelochemicals of submerged plants have attracted extensive research due to their bioavailability. The dose-response of submerged plant extracts on algae growth is worth further study to improve the efficiency of bioremediation. In this study, the ultrasonic-enzymatic assistance method was utilized to extract allelochemicals from Ceratophyllum, Myriophyllum spicatum, and Vallisneria. The effects of low-dosage and high-dosage extracts on the growth of Microcystis aeruginosa were compared based on cell biomass and morphology, photosynthetic parameters, reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) levels. The results showed that the three submerged plant extracts exhibited hormetic effects at low dosages and inhibitory effects at high dosages on algal growth. Within 48 h of cultivation, the enzymatic activities of Microcystis aeruginosa fluctuated, suggesting that the extracts of the three submerged plants induced different oxidative reactions. After 120 h of cultivation with high-dosage extracts, the physiological and biochemical reactions of Microcystis aeruginosa significantly decreased, indicating the effectiveness of the allelopathy of Ceratophyllum, Myriophyllum spicatum, and Vallisneria extracts in controlling algal blooms. The phenomenon of hormesis and inhibition effect confirmed a significant dose-response relationship between the allelochemicals of submerged plant extracts and Microcystis aeruginosa, which could be attributed to the composition and content of allelochemicals. These findings highlight the importance of the relative concentration of the biological algaecide and will benefit other researchers in determining the safe dosage of plant allelochemicals when used in water.

Methyl salicylate improves the effectiveness of the odor-baited trap tree approach for adult plum curculio, Conotrachelus nenuphar (Coleoptera: Curculionidae), monitoring and attract-and-kill.

In commercial apple orchards, the odor-baited trap tree approach involving the synergistic lure composed of benzaldehyde (BEN) and the PC aggregation pheromone grandisoic acid (GA) serves as an effective monitoring tool as well as an attract-and-kill strategy for plum curculio (PC), Conotrachelus nenuphar Herbst. (Coleoptera: Curculionidae), management. However, the relatively high cost of the lure and the degradation of commercial BEN lures by UV light and heat discourage its adoption by growers. Over a 3-yr period, we compared the attractiveness of methyl salicylate (MeSA), either alone or in combination with GA, to plum curculio (PC) with that of the standard combination of BEN + GA. Our main goal was to identify a potential replacement for BEN. Treatment performance was quantified using 2 approaches: (i) unbaited black pyramid traps (2020, 2021) to capture PC adults and (ii) PC oviposition injury (2021, 2022) on apple fruitlets of trap trees and of neighboring trees to assess potential spillover effects. Traps baited with MeSA captured significantly more PCs than unbaited traps. Trap trees baited with a single MeSA lure and 1 GA dispenser attracted a similar number of PCs as trap trees baited with the standard lure composed of 4 BEN lures and 1 GA dispenser based on PC injury. Trap trees baited with MeSA + GA received significantly more PC fruit injury than neighboring trees suggesting no or limited spill-over effects. Our collective findings suggest that MeSA is a replacement for BEN thereby cutting costs of lures by ca. 50% while maintaining trap tree effectiveness.

Tea green leafhopper-induced synomone attracts the egg parasitoids, mymarids to suppress the leafhopper.

BACKGROUND: The tea green leafhopper, Empoasca flavescens is the most important pest of tea plants in China. Mymarid attractants based on herbivore-induced plant volatiles (HIPVs) from leafhopper feeding and oviposition-induced plant volatiles (OIPVs) were formulated and tested as a novel pest control agent against the leafhopper in tea plantations. RESULTS: Results showed that two mymarid species, Stethynium empoascae and Schizophragma parvula, had a reducing effect on leafhopper populations. The HIPVs and OIPVs were identified and bioassayed to screen the key synomones showing strong attraction to the mymarids. They were formulated into different blends, of which Field Attractant 1, comprising linalool, methyl salicylate, (E)-2-hexenal, perillen and α-farnesene at ratio of 1:2:3:58:146 (20 mg/lure), showed the strongest attraction to the mymarids. In field trials with the attractant, the average parasitism rate (60.46 ± 23.71%) of tea leafhoppers by the two mymarids in the attractant-baited area was significantly higher than that (42.85 ± 19.24%) in the CK area. Also, the average leafhopper density (46 ± 30 per 80 tea shoots) in the attractant-baited area was significantly lower than that (110 ± 70 per 80 tea shoots) in the CK area. CONCLUSION: This study showed that a synthetic blend of key volatiles from HIPVs and OIPVs at an optimal ratio can be formulated into an attractant with the potential to attract and retain wild mymarid populations to suppress leafhopper populations in infested tea plantations, so as to reduce or avoid the spraying of insecticides. © 2023 Society of Chemical Industry.

Application of UPLC-Orbitrap-HRMS targeted metabolomics in screening of allelochemicals and model plants of ginseng.

Continuous cropping of ginseng leads to serious declines in yield and quality because of self-toxicity of allelochemicals and other factors in soil. However, because of the long growth cycle and low survival rate of ginseng, rapid screening of autotoxic activity is difficult. Therefore, it is important to analyze the allelochemicals and identify a model plant with autotoxic responses similar to those of ginseng. In this study, UPLC-Orbitrap-HRMS targeted metabolomics and verification of autotoxic activity were used to analyze a problem soil from continuously cropped ginseng. Allelochemical markers were screened by OPLS-DA. Seeds and seedlings of maize, Chinese cabbage, cucumber, green beans, wheat, sunflower, and oats were selected to identify potential model plants. Model plants with autotoxic responses similar to those of ginseng were evaluated by comparing morphological, physiological, and biochemical characteristics. The n-butanol extract of the continuously cropped problem soil had the most significant autotoxic activity. Twenty-three ginsenosides and the contributions to autotoxic effects were screened and evaluated. Of potential model plants, seeds and seedlings of cucumber showed similar growth inhibition to that of ginseng under the action of allelochemicals. Thus, metabolomics can be used to screen allelochemicals in soil and predict the autotoxic effects, and the cucumber plant model can be used to rapidly screen allelopathic activity of ginseng. The study will provide reference for methodology in allelopathy research on ginseng.

Effects of Different Drying Methods on the Quality of Bletilla striata Scented Tea.

Flower tea is widely loved as a drink, especially for the beautiful and rich flowers of the orchid family, and the drying method for different flowers is also unique. GC-MS is widely used to study volatile substances to determine the quality of flower teas. The findings show that the freeze-drying method can retain the original aroma and flavor of Bletilla striata has the highest sensory evaluation score, with the key flavor substances ethyl caproate and N-heptanal containing 1.14% and 6.28%, respectively, and their ROAV values reaching 54.46 and 100.00. Additionally, the freeze-drying method can well retain flavonoids, polysaccharides, and phenolic components, while providing better antioxidant and antibacterial properties. The stove-drying method would make Bletilla striata slightly burnt and less flavorful and efficacious than freeze-drying; the air-drying method is difficult to retain the special odor and fragrance of Bletilla striata flowers and has the lowest sensory evaluation score, with the presence of volatile components with irritating and unpleasant odors such as pyrazine and 2-pentylfuran, while not showing better efficacy. In addition, steam fixation would destroy the morphology and flavor of Bletilla striata, lose polysaccharide and phenolic components, and reduce the efficacy of Bletilla striata scented tea, but could retain the flavonoid components well. In summary, direct freeze-drying without steam fixation is the best process for drying Bletilla striata scented tea, stove-drying without steam fixation is more economical and convenient in actual production and application, steam fixation and air-drying are not suitable as drying processes for Bletilla striata scented tea. This study analyzed the quality of Bletilla striata scented tea under different drying methods, promoted the further processing of Bletilla striata scented tea, and provided a reference for the comprehensive utilization of Bletilla striata scented tea.

Metabolomic Responses of Lettuce (Lactuca sativa) to Allelopathic Benzoquinones from Iris sanguinea Seeds.

Weed management is important in modern crop protection. Chemical weed control using synthetic herbicides, however, suffers from resistance and ecotoxicity. Metabolomic investigation of allelopathy (or allelochemicals) may provide novel alternatives to synthetic herbicides. This study aimed to investigate the detailed metabolomic responses of plants to allelochemicals in Iris seed extracts. The seed extracts of Iris sanguinea showed the strongest growth inhibitory activity against alfalfa, barnyard grass, lettuce, and mustard. 3-Hydroxyirisquinone (3-[10(Z)-heptadecenyl]-2-hydroxy-5-methoxy-1,4-benzoquinone) was isolated as a major allelochemical from I. sanguinea seeds through bioassay-guided fractionation. The compound inhibited the growth of shoots and roots by browning root tips. Discriminant analysis identified 33 differentially regulated lettuce metabolites after treatment with 3-hydroxyirisquinone (3HIQ). Metabolic pathway analysis revealed that several metabolic pathways, including aromatic amino acid biosynthesis and respiratory pathways, were affected by the compounds. Differential responses of membrane lipids (accumulation of unsaturated fatty acids) and extensive formation of reactive oxygen species were observed in root tissues following treatment with 3HIQ. Overall, alkylbenzoquinone from I. sanguinea induced extensive metabolic modulation, oxidative stress, and growth inhibition. The metabolomic responses to allelochemicals may provide fundamental information for the development of allelochemical-based herbicides.

The monodominance of Acuri in Pantanal formations: allelochemical effects of its leaves and the presence of Acurizais.

The presence of monodominant vegetative formations almost exclusively composed of Acuri palm trees (Attalea phalerata) stands out in some regions of the Pantanal Sul-Mato-Grossense. These formations are generally associated with anthropic, edaphic and/or hydrological factors. However, little is known about the effect of allelopathy on the formation and maintenance of these areas. Herein, we investigated the chemical composition of A. phalerata aqueous leaf extract and the potential allelopathic effects on germination and growth of target L. sativa, L. esculentum and S. obtusifolia species. Thus, extracts at concentrations of 0, 2.5, 5, 10, 15, and 20% were used for germination and growth bioassays with a completely randomised design in a germination chamber and greenhouse. The results showed that the A. phalerata extracts negatively affected the germination speed index and mean germination time of the target species and positively affected seedling length under controlled conditions and were also stimulated in the greenhouse. Thus, the formation of Acurizals can be related to the presence of secondary metabolites in the leaves, in addition to other environmental factors.

An innovative strategy to control Microcystis growth using tea polyphenols sustained-release particles: preparation, characterization, and inhibition mechanism.

Allelochemicals have been shown to inhibit cyanobacterial blooms for several years. In view of the disadvantages of "direct-added" mode, natural and pollution-free tea polyphenolic allelochemicals with good inhibitory effect on cyanobacteria were selected to prepare sustained-release particles by microcapsule technology. Results showed that the encapsulation efficiency of tea polyphenols sustained-release particles (TPSPs) was 50.6% and the particle size ranged from 700 to 970 nm, which reached the nanoscale under optimum preparation condition. Physical and chemical properties of TPSPs were characterized to prove that tea polyphenols were well encapsulated and the particles had good thermal stability. The optimal dosage of TPSPs was determined to be 0.3 g/L, at which the inhibition rate on Microcystis aeruginosa in logarithmic growth period could be maintained above 95%. Simultaneous decrease in algal density and chlorophyll-a content indicated that the photosynthesis of algal cells was affected leading to cell death. Significant changes of antioxidant enzyme activities suggested that Microcystis aeruginosa's antioxidant systems had been disrupted. Furthermore, TPSPs increased the concentration of O2- which led to lipid peroxidation of cell membrane and a subsequent increase in malondialdehyde (MDA) content. Meanwhile, the protein content, nucleic acid content, and electrical conductivity in culture medium rose significantly indicating the cell membrane was irreversibly damaged. This work can provide a basis for the utilization of environmentally friendly algal suppressants.

Phytotoxic activity of Ulex europaeus, an invasive plant on Chilean ecosystems: separation and identification of potential allelochemicals.

Despite its worldwide relevance as an invasive plant, there are few studies on Ulex europaeus (gorse) and its allelopathic activity is almost unexplored. The allelochemical profile of gorse was analysed through methanolic extract of pods and roots, and its phytotoxic effects on Lactuca sativa germination. The methanolic extract of pods had no effect in germination, while extract of roots resulted in a U-shaped dose-response curve: reducing the germination at concentration 0.5 mg mL-1. GC-MS analysis detected compounds with proven antimicrobial and antioxidant activities in the pods and cytotoxic compounds in the roots, which could explain the bioassay results. The quinolizidine alkaloids (QAs) composition was evaluated to predict possible biological functions. It showed the presence of QAs in gorse that are absent in their native range, indicating broad defense strategies against bacteria, fungi, plants, and insects in the Chilean ecosystem. This could explain the superiority of gorse in the invaded areas.

Functional disparity of four pheromone-binding proteins from the plum fruit moth Grapholita funebrana Treitscheke in detection of sex pheromone components.

Grapholita funebrana, also known as the plum fruit moth, is an oligophagous pest species that causes enormous economic losses of the fruits of Rosaceae. An eco-friendly method for the control of G. funebrana besides chemical control has not yet been developed. The sex pheromone communication system plays an important role in moth courtship and mating, in which pheromone-binding proteins (PBPs) are critical. In this research, we identified four PBPs, namely, GfunPBP1.1, GfunPBP1.2, GfunPBP2, and GfunPBP3, from the antennae of G. funebrana. The results of real-time quantitative PCR (RT-qPCR) showed that all four GfunPBPs were overwhelmingly expressed in the antennae and that GfunPBP1.2 and GfunPBP2 showed male-biased expression patterns, whereas GfunPBP1.1 and GfunPBP3 were equally expressed between sexes. The results of ligand-binding assays illustrated that although all four recombinant GfunPBPs (rGfunPBPs) had binding activity with the tested sex pheromone compounds, their preferred ligands were significantly different. rGfunPBP2 had the strongest binding affinity to Z8-12:Ac and Z8-12:OH; rGfunPBP1.1 preferred to bind Z8-14:Ac, Z10-14:Ac, and 12:OH more than to the other three GfunPBPs; and rGfunPBP1.2 exhibited stronger binding affinity to E8-12:Ac than to the other rGfunPBPs. Molecular docking results demonstrated that hydrophobic forces, especially van der Waals forces and hydrogen bonds, were the most important forces that maintained GfunPBP-pheromone ligand complexes. This study will improve our understanding of the sex pheromone recognition mechanisms of G. funebrana and promote the development of novel strategies for controlling G. funebrana.

Field Confirmation of (Z)-9-Heptacosene and (3Z,6Z,9Z)-Tricosatriene as Key Sex Pheromone Components of Korean Conogethes punctiferalis Guenée (Lepidoptera: Crambidae).

Recently, insufficient attractiveness of Conogethes punctiferalis Guenée adult males to sex pheromone, -(E)-10-hexadecenal and (Z)-10-hexadecenal, has been reported. To identify the other essential components of sex pheromone, male and female body extracts were analyzed. Two hydrocarbon components, (Z)-9-heptacosene (Z9-27:HC) and (3Z,6Z,9Z)-tricosatriene (Z3,Z6,Z9-23:HC), were identified from only female body extract. There was a significant difference in the electroantennogram (EAG) response of male antennae to Z3,Z6,Z9-23:HC and Z9-27:HC at all test concentrations compared to the response to the hexane control. In field attraction testing, the addition of Z9-27:HC and Z3,Z6,Z9-23:HC to binary aldehyde pheromones significantly increased trap catches of C. punctiferalis male adults. Based on the female and male body extract analysis and field attraction test, Z9-27:HC and Z3,Z6,Z9-23:HC were determined to be other essential sex pheromone components of the Korean C. punctiferalis population. No significant difference was observed in the number of male captures between the bucket trap and delta trap. Pheromone traps with a color close to yellow shade attracted more male adults than traps with a color close to blue shade.

Diet and pheromones interact to shape honey bee (Apis mellifera) worker physiology.

Honey bee colony health is a function of the individuals, their interactions, and the environment. A major goal of honey bee research is to understand how colonies respond to stress. Individual-level studies of the bee stress response are tractable, but their results do not always translate to the colony level. Nutritional stress is an important factor in colony declines. Nutrition studies are typically conducted on individual nurse workers (nurses), who are primarily responsible for converting pollen into brood. Nurse physiology is sensitive to both pollen and pheromones, which communicate signals among colony members. Here, we asked whether pheromones influence nurse nutrient pathways involved in brood care, and whether diet influences colony communication. We exposed caged, nurse-aged workers to different combinations of pheromones and pollen, and measured traits related to brood care. We found that pheromones enhanced pollen-dependent processes such as hypopharyngeal gland growth and mrjp1 expression, and buffered the negative effects of starvation. Pollen also enhanced how nurse phenotypes respond to pheromones. Therefore, diet and pheromones interact to influence nurse nutritional physiology and aspects of brood care. These findings have implications for studying colony function and health in an increasingly stressful climate.

Selected Aspects of Invasive Solidago canadensis with an Emphasis on Its Allelopathic Abilities: A Review.

Solidago canadensis L., native to North America, is now an invasive plant worldwide. Its abundant seeds, rapid vegetative reproduction ability, and allelopathy to other plants are the main reasons for its successful invasion. It has negative impacts on the ecological environment of the invaded area and causes a reduction in local biodiversity and economic losses of agriculture and stock farming. Each part of the plant contains a variety of allelochemicals (terpenoids, phenolics, and flavonoids), including a large number of essential oil components. These allelochemicals can be released in various ways to inhibit the growth of adjacent plants and promote their invasion; they can also affect soil properties and soil microorganisms. This article summarizes the allelopathic effects of S. canadensis on other plant species and the interaction mechanism between it and the ecosystem.

1-Octanol emitted by Oecophylla smaragdina weaver ants repels and deters oviposition in Queensland fruit fly.

Humans have used weaver ants, Oecophylla smaragdina, as biological control agents to control insect pests in orchards for many centuries. Over recent decades, the effectiveness of weaver ants as biological control agents has been attributed in part to deterrent and oviposition inhibiting effects of kairomones produced by the ants, but the chemical identity of these kairomones has remained unknown. We have identified the kairomone responsible for deterrence and oviposition inhibition by O. smaragdina, providing a significant advance in understanding the chemical basis of their predator/prey interactions. Olfactometer assays with extracts from weaver ants demonstrated headspace volatiles to be highly repellent to Queensland fruit fly, Bactrocera tryoni. Using electrophysiology and bioassays, we demonstrate that this repellence is induced by a single compound, 1-octanol. Of 16 compounds identified in O. smaragdina headspace, only 1-octanol evoked an electrophysiological response from B. tryoni antennae. Flies had greatly reduced oviposition and spent significantly less time in an olfactometer arm in the presence of 1-octanol or a synthetic blend of headspace volatiles containing 1-octanol than in the presence of a synthetic blend of headspace volatiles without 1-octanol, or clean air. Taken together, our results demonstrate that 1-octanol is the functional kairomone component of O. smaragdina headspace that explains repellence and oviposition deterrence, and is hence an important contributor to the effectiveness of these ants as biological control agents.

Biochar increases Panax notoginseng's survival under continuous cropping by improving soil properties and microbial diversity.

Replant problem is widespread in agricultural production and causes serious economic losses, which has limited sustainable cultivation of Panax notoginseng (PN), a well-known medicinal plant in Asia. Here we conducted a field experiment to investigate the effectiveness and possible mechanisms of biochar to improve its survival under continuous cropping. Biochar from tobacco stems was applied at 4 rates of 9.0, 12, 15, and 18 t/ha to a soil where PN has been continuously cultivated for 10 years. After 18 months, soil properties, 5 allelochemicals, including p-hydroxybenzoic acid, vanillic acid, syringic acid, p-coumaric acid, and ferulic acid, key pathogen Fusarium oxysporum, microbial community, and PN survival rate were investigated. Our results show that 10 years' continuous PN cropping led to soil acidification, accumulation of NH4+-N and F. oxysporum, and low PN survival rate. However, biochar increased its survival rate from 6.0% in the control to 69.5% under 15 t/ha treatment. Moreover, soil pH, available P and K, organic matter content, and microbial diversity were increased while NH4+-N and allelochemicals vanillic acid and syringic acid contents were decreased under biochar treatment (P<0.05). Soil available K increased from 177 to 283 mg·kg-1 while NH4+-N decreased from 6.73 to 4.79 mg·kg-1 under 15 t/ha treatment. Further, soil pH, available P and K, and microbial diversity (bacteria and fungi) were positively correlated with PN survival rate, however, NH4+-N content was negatively correlated (P<0.05). Our study indicates that biochar effectively increased the survival rate of Panax notoginseng under continuous cropping by improving soil properties and microbial diversity.

Differences in olfactory sensitivity and odor detection correlate with foraging task specialization in honeybees Apis mellifera.

Division of labor is central to the ecological success of social insects. Among honeybees foragers, specialization for collecting nectar or pollen correlates with their sensitivity to gustatory stimuli (e.g. sugars). We hypothesize that pollen and nectar foragers also differ in their sensitivity to odors, and therefore in their likelihood to show odor-mediated responses. To assess foragers sensitivity to natural odors, we quantified the conditioning of the proboscis extension reflex (PER) to increasing concentrations (0.001; 0.01; 0.1; 1 M) of linalool or nonanal. Furthermore, we compared electroantennogram (EAG) recordings to correlate bees' conditioned responses with the electrophysiological responses of their antennae. To further explore differences of the antennal response of foragers in relation to task-related odors, we registered EAG signals for two behaviorally ''meaningful'' odors that mediate pollen collection: fresh pollen odors and the brood pheromone (E)-ß-ocimene. Pollen foragers performed better than nectar foragers in PER conditioning trials when linalool and nonanal were presented at low concentrations (0.001, 0.01 M). Consistently, their antennae showed stronger EAG signals (higher amplitudes) to these odors, suggesting that differences in sensitivity can be explained at the periphery of the olfactory system. Pollen and nectar foragers detect pollen odors differently, but not (E)-ß-ocimene. Pollen volatiles evoked EAG signals with hyper and depolarization components. In pollen foragers, the contribution of the hyperpolarization component was higher than in nectar foragers. We discuss our findings in terms of adaptive advantages to learn subtle olfactory cues that influence the ability to better identify/discriminate food sources.

A single vomeronasal receptor promotes intermale aggression through dedicated hypothalamic neurons.

The pheromonal information received by the vomeronasal system plays a crucial role in regulating social behaviors such as aggression in mice. Despite accumulating knowledge of the brain regions involved in aggression, the specific vomeronasal receptors and the exact neural circuits responsible for pheromone-mediated aggression remain unknown. Here, we identified one murine vomeronasal receptor, Vmn2r53, that is activated by urine from males of various strains and is responsible for evoking intermale aggression. We prepared a purified pheromonal fraction and Vmn2r53 knockout mice and applied genetic tools for neuronal activity recording, manipulation, and circuit tracing to decipher the neural mechanisms underlying Vmn2r53-mediated aggression. We found that Vmn2r53-mediated aggression is regulated by specific neuronal populations in the ventral premammillary nucleus and the ventromedial hypothalamic nucleus. Together, our results shed light on the hypothalamic regulation of male aggression mediated by a single vomeronasal receptor.

Synthesis of an organic-inorganic composite from calcium carbonate and Kraft lignin and its use as carrier material for controlled release of semiochemical agents.

The control of pests in agricultural systems is currently based on the widespread use of pesticides that efficiently control pests but have negative effects on the environment and humans. Thus, several studies have been conducted to develop alternative sustainable ways to control pests in agriculture. The use of semiochemicals presents a good alternative to develop a sustainable tool monitoring and control insect pests in crops areas. The dispensing carriers of semiochemicals are typically made of non-degradable material, often petroleum derivatives such as butyl rubber, that become polluting waste after application. To develop a biodegradable and low-cost dispenser for semiochemicals, particles of CaCO3 and a CaCO3/Kraft lignin composite were synthesized using CO2 bubbling, characterized and evaluated for 30 days as a dispenser of the limonene molecule, which is a common semiochemical in plants and also pheromone component is some insect species, such as the lesser mealworm Alphitobius diaperinus. Furthermore, limonene is volatile molecule that is easy to acquire and low-cost, which makes it an ideal semiochemical to evaluate the potential of the CaCO3 particles and CaCO3/Kraft lignin composite as a semiochemical dispenser for use in agriculture. The pure calcium carbonate I, pure calcium carbonate II, and composite I synthesized particles presented a larger specific surface area than the other composites. All the particles evaluated showed a slow limonene release rate between the 5th and 30th days evaluated, indicating the potential of these materials as pheromone dispensers. The composites with higher specific surface area, calcium carbonate II (19.5 m2/g) and composite I (23.1 m2/g), released a higher level of limonene during the 30 days evaluated.

Electroantennogram and machine learning reveal a volatile blend mediating avoidance behavior by Tuta absoluta females to a wild tomato plant.

Tomato cultivation is threatened by the infestation of the nocturnal invasive tomato pinworm, Tuta absoluta. This study was based on field observations that a wild tomato plant, Solanum lycopersicum var. cerasiforme, grown in the Mount Kenya region, Kenya, is less attacked by T. absoluta, unlike the cultivated tomato plants like S. lycopersicum (var. Rambo F1). We hypothesized that the wild tomato plant may be actively avoided by gravid T. absoluta females because of the emission of repellent allelochemical constituents. Therefore, we compared infestation levels by the pest in field monocrops and intercrops of the two tomato genotypes, characterized the headspace volatiles, then determined the compounds detectable by the insect through gas chromatography-linked electroantennography (GC-EAG), and finally performed bioassays using a blend of four EAG-active compounds unique to the wild tomato. We found significant reductions in infestation levels in the monocrop of the wild tomato, and intercrops of wild and cultivated tomato plants compared to the monocrop of the cultivated tomato plant. Quantitative and qualitative differences were noted between volatiles of the wild and cultivated tomato plants, and between day and night volatile collections. The most discriminating compounds between the volatile treatments varied with the variable selection or machine learning methods used. In GC-EAG recordings, 16 compounds including hexanal, (Z)-3-hexenol, α-pinene, ß-myrcene, α-phellandrene, ß-phellandrene, (E)-ß-ocimene, terpinolene, limonene oxide, camphor, citronellal, methyl salicylate, (E)-ß-caryophyllene, and others tentatively identified as 3,7,7-Trimethyl-1,3,5-cycloheptatriene, germacrene D and cis-carvenone oxide were detected by antennae of T. absoluta females. Among these EAG-active compounds, (Z)-3-hexenol, α-pinene, α-phellandrene, limonene oxide, camphor, citronellal, (E)-ß-caryophyllene and ß-phellandrene are in the top 5 discriminating compounds highlighted by the machine learning methods. A blend of (Z)-3-hexenol, camphor, citronellal and limonene oxide detected only in the wild tomato showed dose-dependent repellence to T. absoluta females in wind tunnel. This study provides some groundwork for exploiting the allelochemicals of the wild tomato in the development of novel integrated pest management approaches against T. absoluta.

Head and Tail Oxidized Terpenoid Esters from Androconia of Heliconius erato Butterflies.

Heliconius erato is a neotropical butterfly species that is part of a complex mimicry ring, with colorful wing patterns. For intraspecific communication, males use pheromones that are released from two different scent-emitting structures. Scent glands located near the abdominal claspers of males, containing antiaphrodisiac pheromones, release a highly complex mixture of compounds that is transferred to females during mating, rendering them unattractive to other males. On the other hand, androconia, scent-emitting scale areas on the wings of male butterflies, release a structurally more restricted set of compounds that likely serves an aphrodisiac role. We report here on two structurally related compounds that are the major androconial constituents, produced in high amounts and are not volatile due to their high molecular mass. Their structures were established by extensive analysis of mass, infrared, and NMR spectra, as well as microderivatization reactions of the natural extract. After establishing synthetic access, the compounds were unequivocally identified as two unusual head and tail oxidized terpenoids, (4E,8E,12E)-4,8,12-trimethyl-16-oxoheptadeca-4,8,12-trien-1-yl oleate (1) and stearate (2). Although behavioral assays are necessary to fully comprehend their role in the chemical communication of the species, hypotheses for their use by the butterflies are also discussed.