Compostos orgânicos voláteis de folhas de feijão-de-porco (Canavalia ensiformis (L.) DC) e seu potencial uso no manejo ecológico de pragas

Volatile compounds and extrafloral nectar are common defenses of wild plants; however, in crops they bear an as-yet underused potential for biological control of pests and diseases. Odor emission and nectar secretion are multigene traits in wild plants, and thus form difficult targets for breeding. Furthermore, domestication has changed the capacity of crops to express these traits. We propose that breeding crops for an enhanced capacity for tritrophic interactions and volatile-mediated direct resistance to herbivores and pathogens can contribute to environmentally-friendly and sustainable agriculture. Natural plant volatiles with antifungal or repellent properties can serve as direct resistance agents. In addition, volatiles mediating tritrophic interactions can be combined with nectar-based food rewards for carnivores to boost indirect plant defense.

Western flower thrips (WFTs) are significant pests affecting various crops globally. Developing sustainable strategies for managing WFTs is essential for improving thrips management. Ethological control methods, particularly those employing volatile organic compounds (VOCs) emitted by plants to influence insect behavior, have emerged as a promising avenue for pest management. Natural hosts such as Alstroemeria provide an intriguing yet underexplored opportunity for developing attractants tailored to WFT management. This study examined the behavioral preferences of WFTs towards flowers of four commercial Alstroemeria cultivars, focusing on variations in VOC profiles. Using headspace solid-phase microextraction (HS-SPME), VOCs were captured in vivo from cultivars with contrasting levels of WFT infestation. Gas chromatography coupled with mass spectrometry (GC-MS) was employed to analyze the VOCs, with linear retention indices aiding compound identification. An untargeted volatile profiling-based comparative analysis revealed key VOCs that differed among cultivars, shedding light on their potential correlation with WFT behavior. Behavioral assays identified three specific VOCs-butyl butyrate, 1-methylnaphthalene, and citronellyl acetate-as influential in attracting WFTs. Attraction responses were concentration-dependent, with two tested concentrations eliciting significant behavioral effects. These findings highlight the potential of these active VOCs as components of novel attractants for WFT management. The results direct future research and the development of tools to integrate ethological strategies into sustainable pest management practices for crops.

Most crop pests find a suitable host through chemical cues released from plants, but little is known about the odorscape encountered by host-seeking gravid females under natural, outdoor conditions. In this field study, the volatile organic compound (VOC) composition of maize (Zea mays, L.), a host for the European corn borer (ECB) (Ostrinia nubilalis Hub.) was characterized during the oviposition flight and compared with a forest odorscape. VOCs from maize fields and the forest atmosphere were collected by solid phase microextraction and characterized by gas chromatography-mass spectrometry. The electroantennographic (EAG) response of female ECB antennae to candidate VOCs was tested. Analyses revealed clear differences between the maize field and the forest odorscapes, mainly composed of ubiquitous VOCs but in specific ratios. The maize field odorscape is more complex than the forest odorscape for maize found 18 VOCs but only eight in the forest. Both biotopes shared seven VOCs—green leaf volatiles (GLV), monoterpenes (MT) and homoterpenes. In addition, we found in the forest a distinctive sesquiterpene (SQT) identified as isoledene. The highest EAG responses were elicited by two GLVs and a MT shared by the two biotopes. SQT elicited weak EAG responses, except β-farnesene, only found in the maize field odorscape. Our results suggest that the two biotopes produce specific chemical signatures that insects may use as host cues. To the best of our knowledge this paper is the first report on the maize odorscapes under field conditions. The putative role of the VOCs in host plant detection and selection is discussed.

Soil bacterial diffusible and volatile organic compounds inhibit Phytophthora capsici and promote plant growth.

The emission of inducible volatile organic compounds (VOCs), i.e., inducible terpenes, and green leaf volatiles (GLVs), is a common response of plants to herbivore attack. These VOCs are involved in the orientation of natural enemies, i.e., predators and parasitoids, toward their herbivore prey or hosts (indirect defense of plants). Terpenes and some GLVs are readily oxidized by ozone (O(3)), an important oxidant of the low atmosphere and predicted to increase as a result of anthropogenic activity. It has been recently reported that O(3) degradation of terpenes and GLVs does not affect signaling in two selected tritrophic systems. Natural enemies may have learned to use oxidation products that are more stable in nature to locate their prey. To understand the role of these compounds on the tritrophic system Brassica oleracea-Plutella xylostella-Cotesia plutellae, we assessed the preference of wasps to different combinations of cabbage VOCs (intact vs. herbivore-induced and herbivore-induced vs. herbivore-induced VOCs) in the presence or absence of O(3). We found that C. plutellae preferred P. xylostella-damaged plants at 0 and 120 nl l(-1) O(3) to intact plants at 0 nl l(-1) O(3). However, wasps preferred P. xylostella-damaged plants at 0 nl l(-1) to P. xylostella-damaged plants at 120 nl l(-1) O(3). The results suggest that compounds other than terpenes and GLVs are crucial for the orientation of the wasps, but terpenes and GLVs contribute to the behaviorally active VOC blend of herbivore-damaged cabbages by increasing their attraction to them. The products resulting from oxidation of terpenes and GLVs do not seem to play a role in the host location process as speculated previously.

Behavioural responses of Sitophilus granarius (L.) and Rhyzopertha dominica (F.) to odours of old and modern wheat genotypes

The effect of warming and enhanced ultraviolet radiation on gender-specific emissions of volatile organic compounds from European aspen

Semivolatile organic compounds (SVOCs) in surface microlayer (SML) and subsurface water (SSW) from Dianshan Lake were studied to investigate their occurrence, distributions, as well as enrichment and potential sources. A sample was concentrated by solid-phase micro-extraction (SPME). Identification and quantification were carried out by gas chromatography coupled to mass spectrometry (GC-MS). Total SVOCs concentrations ranged from 25.93 to 47.49μg/L in SSW and 38.19 to 77.23μg/L in SML. The phthalic acid esters (PAE) concentrations in both SSW and SML are the highest of the total SVOC. The enrichment factors (EFs) of total SVOCs ranged from 0.80 to 2.98, while the highest EF was found in benzyl phthalate and dibutyl phthalate, compounds of PAEs (4.06). The EFs values calculated in this study were consistent with the EFs reported for other water ecosystems. Compared with other place, the EF of PAHs were in the normal level (0.88-2.37). The results of correlation analysis, principal component analysis (PCA) suggested that at least three sources, i.e., agricultural residual pesticides, industrial sewage and miscellaneous sources, were responsible for the presence of SVOCs in Dianshan Lake examined, accounting for 94.16% of the total variance in the dataset. Environmental risk assessment revealed that a majority of SVOCs posed relatively low risks (the values of risk quotient were less than 0.1), while naphthalene, acenaphthene, 2,4-dinitrotoluene, and dibutyl phthalat exhibited moderate risks (values of risk quotient were more than 0.1 but less than 1fore) to aquatic organisms.

When attacked by herbivores, plants release volatile organic compounds (VOCs) that attract natural enemies of the herbivores and function as indirect defenses. Whether or not neighboring plants 'eavesdrop' on these VOCs remains controversial because most studies use unrealistic experimental conditions and VOC exposures. In order to manipulate exposures of wild-type (WT) Nicotiana attenuata'receiver' plants, we elicited transformed 'emitter' plants, whose production of herbivore-induced C6 green leaf volatiles (GLVs) or terpenoid volatiles was genetically silenced, and placed them up-wind of WT 'receiver' plants in open-flow experimental chambers. We compared the transcriptional and secondary metabolite defense responses of WT receiver plants exposed to VOCs from these transgenic emitter plants with those of plants exposed to VOCs from WT emitter plants. No differences in the constitutive accumulation of defense metabolites and the signal molecule jasmonic acid (JA) were found. Additional elicitation of receiver plants revealed that exposure to WT, GLV-deficient and terpenoid-deficient volatile blends did not prime induced defenses, JA accumulation, or the expression of lipoxygenase 3 (NaLOX3), a gene involved in JA biosynthesis. However, exposure to wound- and herbivore-induced VOCs significantly altered the transcriptional patterns in receiver plants. We identified GLV-dependent genes by complementing the GLV-deficient volatile blend with a mixture of synthetic GLVs. Blends deficient in GLVs or cis-alpha-bergamotene regulated numerous genes in receiver plants that did not respond to the complete VOC blends of WT emitters, indicating a suppressive effect of GLVs and terpenoids. Whether these transcriptional responses translate into changes in plant fitness in nature remains to be determined.

Volatile organic compounds (VOCs) emitted by plants consist of a broad range of gasses which serve purposes such as protecting against herbivores, communicating with insects and neighboring plants, or increasing the tolerance to environmental stresses. Evidence is accumulating that the composition of VOC blends plays an important role in fulfilling these purposes. Constitutional emissions give insight into species-specific stress tolerance potentials and are an important first step in linking metabolism and function of co-occurring VOCs. Here, we investigate the blend composition and interrelations among co-emitted VOCs in unstressed seedlings of four broad-leaved tree species, Quercus robur, Fagus sylvatica, Betula pendula, and Carpinus betulus. VOCs of Q. robur and F. sylvatica mainly emitted isoprene and monoterpenes, respectively. B. pendula had relatively high sesquiterpene emission; however, it made up only 1.7% of its total emissions while the VOC spectrum was dominated by methanol (∼72%). C. betulus was emitting methanol and monoterpenes in similar amounts compared to other species, casting doubt on its frequent classification as a close-to-zero VOC emitter. Beside these major VOCs, a total of 22 VOCs could be identified, with emission rates and blend compositions varying drastically between species. A principal component analysis among species revealed co-release of multiple compounds. In particular, new links between pathways and catabolites were indicated, e.g., correlated emission rates of methanol, sesquiterpenes (mevalonate pathway), and green leaf volatiles (hexanal, hexenyl acetate, and hexenal; lipoxygenase pathway). Furthermore, acetone emissions correlated with eugenol from the Shikimate pathway, a relationship that has not been described before. Our results thus indicate that certain VOC emissions are highly interrelated, pointing toward the importance to improve our understanding of VOC blends rather than targeting dominant VOCs only.

Plants respond to attacks by herbivorous insects by releasing specific blends of volatile organic compounds (VOCs). These herbivore-induced VOCs are known to play a major role in the interaction between plants and insects and may directly protect the plant by being toxic or deterrent, but may also benefit the plant indirectly by attracting natural enemies of the herbivores. The chemical composition of herbivore-induced VOC blends is known for many plant–herbivore systems. Some VOCs are taxon-specific, whereas other VOCs appear to be common to many different plant families. These common compounds mainly include ‘green leaf volatiles’ (C6 aldehydes, alcohols and derivatives), cyclic and acyclic terpenes, phenolic compounds and nitrogenous compounds. Our model plant is maize, which shows a rapid reaction to an attack by caterpillars and root feeding beetle larvae. Belowground, maize roots respond within hours to feeding of larvae by releasing the sesquiterpene (E)-beta-caryophyllene. The emission of this compound results in increased recruitment of entomopathogenic nematodes (tiny worms that parasitize and kill insect larvae). Similarly, after being attacked by caterpillars aboveground, maize leaves emit a complex blend of volatiles that is attractive to parasitic wasps, which use the volatiles to find and kill the caterpillars. It remains largely unclear which VOCs within the blend are the key compounds mediating this parasitoid attraction. To study the importance of individual volatiles we combine different methods to generate and modify herbivore-induced VOC blends by manipulating the plant genotype, the plant phenotype and the headspace of volatiles produced by the plant. We focus on ‘subtractive’ approaches used to obtain blends differing in only few known VOCs and ‘additive’ approaches to generate blends of known composition. All blends are analyzed with gas chromatography/mass spectrometry and tested for attraction to the wasps in olfactometer studies. By combining the above approaches, we aim to provide new insights into the relevance of individual VOCs involved in indirect defenses, which might help to develop ecologically sound methods to control pest insects.

Plants have evolved diverse secondary metabolites to counteract biotic stress. Volatile organic compounds (VOCs) are released upon herbivore attack or pathogen infection. Recent studies suggest that VOCs can act as signalling molecules in plant defence and induce resistance in distant organs and neighbouring plants. However, knowledge is lacking on the function of VOCs in biotrophic fungal infection on cereal plants. We analysed VOCs emitted by 13 ± 1-day-old barley plants (Hordeum vulgare L.) after mechanical wounding using passive absorbers and TD-GC/MS. We investigated the effect of pure VOC and complex VOC mixtures released from wounded plants on the barley-powdery mildew interaction by pre-exposure in a dynamic headspace connected to a powdery mildew susceptibility assay. Untargeted metabolomics and lipidomics were applied to investigate metabolic changes in sender and receiver barley plants. Green leaf volatiles (GLVs) dominated the volatile profile of wounded barley plants, with (Z)-3-hexenyl acetate (Z3HAC) as the most abundant compound. Barley volatiles emitted after mechanical wounding enhanced resistance in receiver plants towards fungal infection. We found volatile-mediated modifications of the plant-pathogen interaction in a concentration-dependent manner. Pre-exposure with physiologically relevant concentrations of Z3HAC resulted in induced resistance, suggesting that this GLV is a key player in barley anti-pathogen defence. The complex VOC mixture released from wounded barley and Z3HAC induced e.g. accumulation of chlorophyll, linolenic acid and linolenate-conjugated lipids, as well as defence-related secondary metabolites, such as hordatines in receiving plants. Barley VOCs hence induce a complex physiological response and disease resistance in receiver plants.

While crop and grassland usage continues to increase, the full diversity of plant-specific volatile organic compounds (VOCs) emitted from these ecosystems, including their implications for atmospheric chemistry and carbon cycling, remains poorly understood. It is particularly important to investigate VOCs in the context of potential biofuels: aside from the implications of large-scale land use, harvest may shift both the flux and speciation of emitted VOCs. To this point, we evaluate the diversity of VOCs emitted both pre and postharvest from "Alkar" tall wheatgrass (Thinopyrum ponticum), a candidate biofuel that exhibits greater tolerance to frost and saline land compared to other grass varieties. Mature plants grown under field conditions (n = 6) were sampled for VOCs both pre- and postharvest (October 2022). Via hierarchical clustering of emitted VOCs from each plant, we observe distinct "volatilomes" (diversity of VOCs) specific to the pre- and postharvest conditions despite plant-to-plant variability. In total, 50 VOCs were found to be unique to the postharvest tall wheatgrass volatilome, and these unique VOCs constituted a significant portion (26%) of total postharvest signal. While green leaf volatiles (GLVs) dominate the speciation of postharvest emissions (e.g., 54% of unique postharvest VOC signal was due to 1-penten-3-ol), we demonstrate novel postharvest VOCs from tall wheatgrass that are under characterized in the context of carbon cycling and atmospheric chemistry (e.g., 3-octanone). Continuing evaluations will quantitatively investigate tall wheatgrass VOC fluxes, better informing the feasibility and environmental impact of tall wheatgrass as a biofuel.

Quantification and transformation of organic compounds are pivotal in understanding atmospheric processes, because such compounds contribute to the oxidative capacity of the atmosphere and drive climate change. It has recently been recognized that chemical reactions in snow play a role in the production or destruction of photolabile volatile organic compounds (VOC). We present an environmentally friendly method for determination of VOC and semi-VOC in snow collected at three sites-remote, urban, and (sub-)arctic. A solid-phase micro-extraction (SPME) procedure was developed and (semi-)VOC were identified by gas chromatography with mass spectrometric detection (GC-MS). A broad spectrum of (semi-)VOC was found in snow samples, including aldehydes, and aromatic and halogenated compounds. Quantification was performed for 12 aromatic and/or oxygenated compounds frequently observed in snow by use of neat standard solutions. The concentrations detected were between 0.12 (styrene and ethylbenzene) and 316 microg L(-1) (toluene) and limits of detection varied between 0.11 (styrene) and 1.93 microg L(-1) (benzaldehyde). These results indicate that the SPME technique presented is a broad but selective, versatile, solvent-free, ecological, economical, and facile method of analysis for (semi-)VOC in natural snow samples.

The application aspects of chemicals which attract the forest cockchafer, Melolontha hippocastani F., were investigated in field and laboratory experiments. Previous studies have shown that males of M. hippocastani are attracted by a synthetic mixture of green leaf volatiles (GLV) and the sex pheromone 1,4‐benzoquinone (BQ), that synergistically enhances the male response to GLV. In the present study, we demonstrated that BQ also synergised the male response to one single component of the GLV mixture, the leaf alcohol (Z)‐3‐hexen‐1‐ol (Z‐3‐ol). BQ enhanced the attractiveness of Z‐3‐ol at doses between 0.05 and 5 mg per trap, reaching a maximum at 5 × 10−1 mg day−1. The addition of an insecticide (cyhalothrin) to traps baited with BQ and Z‐3‐ol did not affect the lures’ attractiveness. However, when a conidiospore formulation of the entomopathogenic fungus Beauveria brongniartii (Saccardo) Petch was added, the attractiveness of baited traps was significantly reduced.Furthermore, two types of dispensers baited with a solution of BQ in Z‐3‐ol at 20 mg ml−1 were tested over the entire 4‐week flight season. Both a membrane dispenser and a dispenser based on a porous polyethylene (PPE) absorbent disk attracted more males than controls over the entire 4 weeks. The membrane dispenser attracted as many males each week as a reference formulation that was renewed daily. Furthermore, the membrane dispenser attracted more males than the PPE dispenser in weeks 2–4, although laboratory experiments showed that the latter released even higher or at least equal amounts of the joined lure over the entire 4 weeks. However, estimation of the BQ/Z‐3‐ol ratios of the released material by solid phase microextraction (SPME) and coupled gas chromatography–mass spectrometry (GC‐MS) revealed that the membrane dispenser released a higher proportion of BQ than the PPE dispenser in weeks 2–4. Therefore, a higher BQ/Z‐3‐ol ratio might be responsible for the advantage of the membrane dispenser in the field.