Advances in Chemical Ecology

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Applied Sciences applsci	2.7	4.5	2011	16.9 Days	CHF 2400
Biomolecules biomolecules	5.5	8.3	2011	16.9 Days	CHF 2700
Insects insects	3.0	4.2	2010	17 Days	CHF 2600
Molecules molecules	4.6	6.7	1996	14.6 Days	CHF 2700
Plants plants	4.5	5.4	2012	15.3 Days	CHF 2700

17 pages, 3604 KiB

Open AccessArticle

Characterization of CrufCSP1 and Its Potential Involvement in Host Location by Cotesia ruficrus (Hymenoptera: Braconidae), an Indigenous Parasitoid of Spodoptera frugiperda (Lepidoptera: Noctuidae) in China

by Kai-Ru Han, Wen-Wen Wang, Wen-Qin Yang, Xian Li, Tong-Xian Liu and Shi-Ze Zhang

Insects 2023, 14(12), 920; https://doi.org/10.3390/insects14120920 - 01 Dec 2023

Viewed by 1104

Abstract

Chemosensory proteins (CSPs) are a class of soluble proteins that facilitate the recognition of chemical signals in insects. While CSP genes have been identified in many insect species, studies investigating their function remain limited. Cotesia ruficrus (Hymenoptera: Braconidae) holds promise as an indigenous [...] Read more.

Chemosensory proteins (CSPs) are a class of soluble proteins that facilitate the recognition of chemical signals in insects. While CSP genes have been identified in many insect species, studies investigating their function remain limited. Cotesia ruficrus (Hymenoptera: Braconidae) holds promise as an indigenous biological control agent for managing the invasive pest Spodoptera frugiperda (Lepidoptera: Noctuidae) in China. This study aimed to shed light on the gene expression, ligand binding, and molecular docking of CrufCSP1 in C. ruficrus. A RT-qPCR analysis revealed that the expression of CrufCSP1 was higher in the wings, with male adults exhibiting significantly higher relative expression levels than other developmental stages. A fluorescence competitive binding analysis further demonstrated that CrufCSP1 has a high binding ability with several host-related volatiles, with trans-2-hexenal, octanal, and benzaldehyde showing the strongest affinity to CrufCSP1. A molecular docking analysis indicated that specific amino acid residues (Phe24, Asp25, Thr53, and Lys81) of CrufCSP1 can bind to these specific ligands. Together, these findings suggest that CrufCSP1 may play a crucial role in the process of C. ruficrus locating hosts. This knowledge can contribute to the development of more efficient and eco-friendly strategies for protecting crops and managing pests. Full article

(This article belongs to the Topic Advances in Chemical Ecology)

► Show Figures

Figure 1

27 pages, 2635 KiB

Open AccessReview

Deciphering Plant-Insect-Microorganism Signals for Sustainable Crop Production

by Gareth Thomas, Quint Rusman, William R. Morrison III, Diego M. Magalhães, Jordan A. Dowell, Esther Ngumbi, Jonathan Osei-Owusu, Jessica Kansman, Alexander Gaffke, Kamala Jayanthi Pagadala Damodaram, Seong Jong Kim and Nurhayat Tabanca

Biomolecules 2023, 13(6), 997; https://doi.org/10.3390/biom13060997 - 15 Jun 2023

Cited by 1 | Viewed by 5222

Abstract

Agricultural crop productivity relies on the application of chemical pesticides to reduce pest and pathogen damage. However, chemical pesticides also pose a range of ecological, environmental and economic penalties. This includes the development of pesticide resistance by insect pests and pathogens, rendering pesticides [...] Read more.

Agricultural crop productivity relies on the application of chemical pesticides to reduce pest and pathogen damage. However, chemical pesticides also pose a range of ecological, environmental and economic penalties. This includes the development of pesticide resistance by insect pests and pathogens, rendering pesticides less effective. Alternative sustainable crop protection tools should therefore be considered. Semiochemicals are signalling molecules produced by organisms, including plants, microbes, and animals, which cause behavioural or developmental changes in receiving organisms. Manipulating semiochemicals could provide a more sustainable approach to the management of insect pests and pathogens across crops. Here, we review the role of semiochemicals in the interaction between plants, insects and microbes, including examples of how they have been applied to agricultural systems. We highlight future research priorities to be considered for semiochemicals to be credible alternatives to the application of chemical pesticides. Full article

(This article belongs to the Topic Advances in Chemical Ecology)

► Show Figures

Figure 1

17 pages, 2634 KiB

Open AccessArticle

Investigating Photo-Degradation as a Potential Pheromone Production Pathway in Spotted Lanternfly, Lycorma delicatula

by Hajar Faal, Isaiah J. Canlas, Allard Cossé, Tappey H. Jones, Daniel Carrillo and Miriam F. Cooperband

Insects 2023, 14(6), 551; https://doi.org/10.3390/insects14060551 - 13 Jun 2023

Cited by 2 | Viewed by 1268

Abstract

Since its discovery in North America in 2014, the spotted lanternfly (SLF), Lycorma delicatula, has become an economic, ecological, and nuisance pest there. Developing early detection and monitoring tools is critical to their mitigation and control. Previous research found evidence that SLF [...] Read more.

Since its discovery in North America in 2014, the spotted lanternfly (SLF), Lycorma delicatula, has become an economic, ecological, and nuisance pest there. Developing early detection and monitoring tools is critical to their mitigation and control. Previous research found evidence that SLF may use pheromones to help locate each other for aggregation or mating. Pheromone production necessitates specific conditions by the insects, and these must be investigated and described. A chemical process called photo-degradation has been described as a final step in the production of pheromones in several diurnal insect species, in which cuticular hydrocarbons were broken down by sunlight into volatile pheromone components. In this study, photo-degradation was investigated as a possible pheromone production pathway for SLF. Extracts from SLF mixed-sex third and fourth nymphs and male or female adults were either exposed to simulated sunlight to produce a photo-degradative reaction (photo-degraded), or not exposed to light (crude), while volatiles were collected. Behavioral bioassays tested for attraction to volatiles from photo-degraded and crude samples and their residues. In third instars, only the volatile samples from photo-degraded mixed-sex extracts were attractive. Fourth instar males were attracted to both crude and photo-degraded residues, and volatiles of photo-degraded mixed-sex extracts. Fourth instar females were attracted to volatiles of crude and photo-degraded mixed-sex extracts, but not to residues. In adults, only males were attracted to body volatiles from crude and photo-degraded extracts of either sex. Examination of all volatile samples using gas chromatography coupled with mass spectrometry (GC-MS) revealed that most of the identified compounds in photo-degraded extracts were also present in crude extracts. However, the abundance of these compounds in photo-degraded samples were 10 to 250 times more than their abundance in the crude counterparts. Results from behavioral bioassays indicate that photo-degradation probably does not generate a long-range pheromone, but it may be involved in the production of a short-range sex-recognition pheromone in SLF. This study provides additional evidence of pheromonal activity in SLF. Full article

(This article belongs to the Topic Advances in Chemical Ecology)

► Show Figures

Figure 1

26 pages, 2719 KiB

Open AccessArticle

Volatile Characterization of Lychee Plant Tissues (Litchi chinensis) and the Effect of Key Compounds on the Behavior of the Lychee Erinose Mite (Aceria litchii)

by Livia M. S. Ataide, Nurhayat Tabanca, Maria A. Canon, Elena Q. Schnell, Teresa I. Narvaez, Kevin R. Cloonan, Paul E. Kendra, Daniel Carrillo and Alexandra M. Revynthi

Biomolecules 2023, 13(6), 933; https://doi.org/10.3390/biom13060933 - 02 Jun 2023

Cited by 2 | Viewed by 1641

Abstract

Herbivore-Induced Plant Volatiles (HIPVs) are volatile signals emitted by plants to deter herbivores and attract their natural enemies. To date, it is unknown how lychee plants, Litchi chinensis, respond to the induction of leaf galls (erinea) caused by the lychee erinose mite (LEM), [...] Read more.

Herbivore-Induced Plant Volatiles (HIPVs) are volatile signals emitted by plants to deter herbivores and attract their natural enemies. To date, it is unknown how lychee plants, Litchi chinensis, respond to the induction of leaf galls (erinea) caused by the lychee erinose mite (LEM), Aceria litchii. Aiming to reveal the role of HIPVs in this plant-mite interaction, we investigated changes in the volatile profile of lychee plants infested by LEM and their role on LEM preferences. The volatile profile of uninfested (flower buds, fruit, leaves and new leaf shoots) and infested plant tissue were characterized under different levels of LEM infestation. Volatiles were collected using head-space-solid phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS) analyses. Fifty-eight volatiles, including terpenoids, alcohols, aldehydes, alkanes, esters, and ketones classes were identified. Using dual-choice bioassays, we investigated the preference of LEM to uninfested plant tissues and to the six most abundant plant volatiles identified. Uninfested new leaf shoots were the most attractive plant tissues to LEM and LEM attraction or repellence to volatiles were mostly influenced by compound concentration. We discuss possible applications of our findings in agricultural settings. Full article

(This article belongs to the Topic Advances in Chemical Ecology)

► Show Figures

Figure 1

17 pages, 2638 KiB

Open AccessArticle

Piperitone (p-Menth-1-En-3-One): A New Repellent for Tea Shot Hole Borer (Coleoptera: Curculionidae) in Florida Avocado Groves

by Paul E. Kendra, Wayne S. Montgomery, Nurhayat Tabanca, Elena Q. Schnell, Aimé Vázquez, Octavio Menocal, Daniel Carrillo and Kevin R. Cloonan

Biomolecules 2023, 13(4), 656; https://doi.org/10.3390/biom13040656 - 06 Apr 2023

Cited by 1 | Viewed by 2005

Abstract

The tea shot hole borer, Euwallacea perbrevis, has been recently established in Florida, USA, where it vectors fungal pathogens that cause Fusarium dieback in avocado. Pest monitoring uses a two-component lure containing quercivorol and α-copaene. Incorporation of a repellent into IPM programs [...] Read more.

The tea shot hole borer, Euwallacea perbrevis, has been recently established in Florida, USA, where it vectors fungal pathogens that cause Fusarium dieback in avocado. Pest monitoring uses a two-component lure containing quercivorol and α-copaene. Incorporation of a repellent into IPM programs may reduce the incidence of dieback in avocado groves, particularly if combined with lures in a push–pull system. This study evaluated piperitone and α-farnesene as potential repellents for E. perbrevis, comparing their efficacy to that of verbenone. Replicate 12-week field tests were conducted in commercial avocado groves. Each test compared beetle captures in traps baited with two-component lures versus captures in traps containing lures plus repellent. To complement field trials, Super-Q collections followed by GC analyses were performed to quantify emissions from repellent dispensers field-aged for 12 weeks. Electroantennography (EAG) was also used to measure beetle olfactory response to each repellent. Results indicated that α-farnesene was ineffective; however, piperitone and verbenone were comparable in repellency, achieving 50–70% reduction in captures, with longevity of 10–12 weeks. EAG responses to piperitone and verbenone were equivalent, and significantly greater than response to α-farnesene. Since piperitone is less expensive than verbenone, this study identifies a potential new E. perbrevis repellent. Full article

(This article belongs to the Topic Advances in Chemical Ecology)

► Show Figures

Figure 1

17 pages, 851 KiB

Open AccessReview

A Review of the Host Plant Location and Recognition Mechanisms of Asian Longhorn Beetle

by Fei Lyu, Xiaoxia Hai and Zhigang Wang

Insects 2023, 14(3), 292; https://doi.org/10.3390/insects14030292 - 17 Mar 2023

Cited by 2 | Viewed by 1924

Abstract

The Asian longhorn beetle (ALB), Anoplophora glabripennis Motschulsky, is a polyphagous xylophage with dozens of reported host tree species. However, the mechanisms by which individuals locate and recognize host plants are still unknown. We summarize the current knowledge of the host plant list, [...] Read more.

The Asian longhorn beetle (ALB), Anoplophora glabripennis Motschulsky, is a polyphagous xylophage with dozens of reported host tree species. However, the mechanisms by which individuals locate and recognize host plants are still unknown. We summarize the current knowledge of the host plant list, host kairomones, odorant-binding proteins (OBPs) and microbial symbionts of this beetle and their practical applications, and finally discuss the host localization and recognition mechanisms. A total of 209 species (or cultivars) were reported as ALB host plants, including 101 species of higher sensitivity; host kairomones were preferentially bound to ALB recombinant OBPs, including cis-3-hexen-1-ol, δ-3-carene, nonanal, linalool, and β-caryophyllene. In addition, microbial symbionts may help ALB degrade their host. Complementarity of tree species with different levels of resistance may reduce damage, but trapping effectiveness for adults was limited using a combination of host kairomones and sex pheromones in the field. Therefore, we discuss host location behavior from a new perspective and show that multiple cues are used by ALB to locate and recognize host plants. Further research into host resistance mechanisms and visual signal recognition, and the interaction of sex pheromone synthesis, symbiont microbiota, and host plants may help reveal the host recognition mechanisms of ALBs. Full article

(This article belongs to the Topic Advances in Chemical Ecology)

► Show Figures

Figure 1

12 pages, 1187 KiB

Open AccessArticle

Synthesis of Phthalimide Derivatives and Their Insecticidal Activity against Caribbean Fruit Fly, Anastrepha suspensa (Loew)

by Fatih Tok, Xiangbing Yang, Nurhayat Tabanca and Bedia Koçyiğit-Kaymakçıoğlu

Biomolecules 2023, 13(2), 361; https://doi.org/10.3390/biom13020361 - 14 Feb 2023

Cited by 1 | Viewed by 1988

Abstract

In this study, thirteen phthalimide derivatives were designed and synthesized. All synthesized compounds were evaluated to determine their potential for inhibitory activities against females of the Caribbean fruit fly, Anastrepha suspensa (Loew) (Diptera: Tephritidae). These efforts led to the discovery of three compounds [...] Read more.

In this study, thirteen phthalimide derivatives were designed and synthesized. All synthesized compounds were evaluated to determine their potential for inhibitory activities against females of the Caribbean fruit fly, Anastrepha suspensa (Loew) (Diptera: Tephritidae). These efforts led to the discovery of three compounds 4a, 4c, and 4d with potent insecticidal activity (LD₅₀ range from 0.70 to 1.91 μg/fly). Among these compounds, 4a exhibited the highest inhibitory potency with 0.70 μg/fly. In addition, in silico models indicated that compound 4a is less toxic than phthalimide and other precursors. Therefore, our results suggest that 4a has strong potential as a candidate component for developing a novel environmentally friendly insecticide for control of pest fruit flies. Full article

(This article belongs to the Topic Advances in Chemical Ecology)

► Show Figures

Figure 1

17 pages, 1543 KiB

Open AccessArticle

Comparative Analysis of Epicuticular Lipids in Locusta migratoria and Calliptamus italicus: A Possible Role in Susceptibility to Entomopathogenic Fungi

by Mariya D. Ganina, Maksim V. Tyurin, Ulzhalgas T. Zhumatayeva, Georgy R. Lednev, Sergey V. Morozov and Vadim Yu. Kryukov

Insects 2022, 13(8), 736; https://doi.org/10.3390/insects13080736 - 16 Aug 2022

Cited by 1 | Viewed by 1551

Abstract

Cuticular lipids protect insects from desiccation and may determine resistance to fungal pathogens. Nonetheless, the trade-off between these lipid functions is still poorly understood. The migratory locust Locusta migratoria and the Italian locust Calliptamus italicus have dissimilar hygrothermal preferences: L. migratoria inhabits areas [...] Read more.

Cuticular lipids protect insects from desiccation and may determine resistance to fungal pathogens. Nonetheless, the trade-off between these lipid functions is still poorly understood. The migratory locust Locusta migratoria and the Italian locust Calliptamus italicus have dissimilar hygrothermal preferences: L. migratoria inhabits areas near water bodies with a reed bed, and C. italicus exploits a wide range of habitats and prefers steppes and semideserts with the predominance of sagebrushes. This paper presents significant differences between these species’ nymphs in epicuticular lipid composition (according to gas chromatography with mass spectrometry) and in susceptibility to Metarhizium robertsii and Beauveria bassiana. The main differences in lipid composition are shifts to longer chain and branched hydrocarbons (di- and trimethylalkanes) in C. italicus compared to L. migratoria. C. italicus also has a slightly higher n-alkane content. Fatty acids showed low concentrations in the extracts, and L. migratoria has a wider range of fatty acids than C. italicus does. Susceptibility to M. robertsii and the number of conidia adhering to the cuticle proved to be significantly higher in C. italicus, although conidia germination percentages on epicuticular extracts did not differ between the species. We propose that the hydrocarbon composition of C. italicus may be an adaptation to a wide range of habitats including arid ones but may make the C. italicus cuticle more hospitable for fungi. Full article

(This article belongs to the Topic Advances in Chemical Ecology)

► Show Figures

Figure 1

16 pages, 1109 KiB

Open AccessArticle

Electroantennographic Responses of Wild and Laboratory-Reared Females of Xyleborus affinis Eichhoff and Xyleborus ferrugineus (Fabricius) (Coleoptera: Curculionidae: Scolytinae) to Ethanol and Bark Volatiles of Three Host-Plant Species

by Patricia Romero, Luis A. Ibarra-Juárez, Daniel Carrillo, José A. Guerrero-Analco, Paul E. Kendra, Ana L. Kiel-Martínez and Larissa Guillén

Insects 2022, 13(7), 655; https://doi.org/10.3390/insects13070655 - 21 Jul 2022

Cited by 3 | Viewed by 2258

Abstract

Chemical ecology studies on ambrosia beetles are typically conducted with either wild or laboratory-reared specimens. Unlike laboratory-reared insects, important aspects that potentially influence behavioral responses, such as age, physiological state, and prior experience are unknown in wild specimens. In this study, we compared [...] Read more.

Chemical ecology studies on ambrosia beetles are typically conducted with either wild or laboratory-reared specimens. Unlike laboratory-reared insects, important aspects that potentially influence behavioral responses, such as age, physiological state, and prior experience are unknown in wild specimens. In this study, we compared the electroantennographic (EAG) responses of laboratory-reared and wild X. affinis and X. ferrugineus to 70% ethanol and bark odors (host kairomones) of Bursera simaruba, Mangifera indica, and Persea schiedeana aged for 2, 24, and 48 h. Chemical analyses of each odor treatment (bark species x length of aging) were performed to determine their volatilome composition. EAG responses were different between laboratory-reared and wild X. ferrugineus when exposed to ethanol, whereas wild X. affinis exhibited similar EAG responses to the laboratory-reared insects. Ethanol elicited the strongest olfactory responses in both species. Among the bark-odors, the highest responses were triggered by B. simaruba at 48 h in X. affinis, and P. schiedeana at 24 and 48 h in X. ferrugineus. Volatile profiles varied among aged bark samples; 3-carene and limonene were predominant in B. simaruba, whereas α-copaene and α-cubebene were abundant in P. schiedeana. Further studies are needed to determine the biological function of B. simaruba and P. schiedeana terpenes on X. affinis and X. ferrugineus, and their potential application for the development of effective lures. Full article

(This article belongs to the Topic Advances in Chemical Ecology)

► Show Figures

Figure 1

16 pages, 2555 KiB

Open AccessArticle

Comparison of Extraction Techniques for the Determination of Volatile Organic Compounds in Liverwort Samples

by Małgorzata Guzowska, Wiesław Wasiak and Rafał Wawrzyniak

Molecules 2022, 27(9), 2911; https://doi.org/10.3390/molecules27092911 - 03 May 2022

Cited by 6 | Viewed by 2266

Abstract

This article focuses on the comparison of four popular techniques for the extraction of volatile organic compounds (VOCs) from liverworts of the Calypogeia azurea species. Since extraction is the most important step in the sample analysis of ingredients present in botanical preparations, their [...] Read more.

This article focuses on the comparison of four popular techniques for the extraction of volatile organic compounds (VOCs) from liverworts of the Calypogeia azurea species. Since extraction is the most important step in the sample analysis of ingredients present in botanical preparations, their strengths, and weaknesses are discussed. In order to determine the VOCs present in plants, selecting the appropriate one is a key step of the extraction technique. Extraction should ensure the isolation of all components present in the oily bodies of Calypogeia azurea without the formation of any artifacts during treatment. The best extraction method should yield the determined compounds in detectable amounts. Hydrodistillation (HD), applying Deryng apparatus and solid-liquid extraction (SLE), microwave-assisted extraction (MAE), and headspace solid-phase microextraction (HS-SPME) were used for volatile extraction. The extracts obtained were analysed by gas chromatography coupled to mass spectrometry (GC-MS) to determine the compounds. Full article

(This article belongs to the Topic Advances in Chemical Ecology)

► Show Figures

Figure 1

25 pages, 5407 KiB

Open AccessArticle

Seasonal Variability and Effect of Sample Storage on Volatile Components in Calypogeia azurea

by Małgorzata Guzowska, Rafał Wawrzyniak and Wiesław Wasiak

Molecules 2022, 27(8), 2426; https://doi.org/10.3390/molecules27082426 - 09 Apr 2022

Cited by 2 | Viewed by 1263

Abstract

A change in the composition of specialized metabolites is often observed in stressed plants. Phytochemicals play an important role in adapting plants to the environment, particularly overcoming stress conditions such as temperature, humidity, and light intensity. In this study, seasonal variations in the [...] Read more.

A change in the composition of specialized metabolites is often observed in stressed plants. Phytochemicals play an important role in adapting plants to the environment, particularly overcoming stress conditions such as temperature, humidity, and light intensity. In this study, seasonal variations in the concentrations of volatile organic compounds (VOCs) were analysed in species of Calypogeia azurea. The article presents the effect of sample storage on volatile organic compounds present in Calypogeia liverwort cells and whether the collection habitats of the sample affect the content of phytochemicals. The VOCs of the species within the liverwort Calypogeia azurea were analysed by GC-MS. Compounds were isolated from plant material using the HS-SPME technique. The samples were collected over several years (2019–2021). Of the several dozen samples collected, 79 compounds were isolated, of which 47 were identified. Full article

(This article belongs to the Topic Advances in Chemical Ecology)

► Show Figures

Figure 1

18 pages, 2013 KiB

Open AccessArticle

Patterns of Plumericin Concentration in Leaves of Himatanthus tarapotensis (Apocynaceae) and Its Interactions with Herbivory in the Peruvian Amazon

by Carlos A. Amasifuen Guerra, Kirti Patel, Piero G. Delprete, Andréa P. Spina, Juan Grados, Pedro Vásquez-Ocmín, Alice Gadea, Rosario Rojas, Jesús Guzmán and Michel Sauvain

Plants 2022, 11(8), 1011; https://doi.org/10.3390/plants11081011 - 08 Apr 2022

Cited by 1 | Viewed by 2302

Abstract

We explored the concentration patterns of the bioactive metabolite plumericin produced by Himatanthus tarapotensis (Apocynaceae) under different edaphic conditions and variations in rainfall intensity, as well as its potential role in the chemical defense against insect herbivores. Values of plumericin concentration from leaves [...] Read more.

We explored the concentration patterns of the bioactive metabolite plumericin produced by Himatanthus tarapotensis (Apocynaceae) under different edaphic conditions and variations in rainfall intensity, as well as its potential role in the chemical defense against insect herbivores. Values of plumericin concentration from leaves were obtained by High-Performance Liquid Chromatography, and evaluated as a function of differences in soil types, variation of precipitation, and variation of the abundance of insect herbivores, using first a Repeated Measures Correlation (rmcorr) and then a Generalized Linear Mixed Model (GLMM) analysis. Plumericin concentration is highly variable among plants, but with a significantly higher concentration in plants growing on clay soil compared to that of the white-sand soil habitat (p < 0.001). Plumericin concentration is not affected by precipitation. The caterpillar of Isognathus leachii (Lepidoptera: Sphingidae) is the most conspicuous herbivore of H. tarapotensis, and its presence is continuous but not related to plumericin concentration, probably because of its capacity to elude the chemical defense of this plant. Nevertheless, our multivariate model revealed that plumericin concentration is related to the abundance of Hymenoptera (Formicidae), and this relationship is significantly influenced by the soil parameters of carbon percentage, clay percentage, and phosphorous percentage (p < 0.001). Plumericin is a mediating agent in the interaction between H. tarapotensis and its natural environment. Variation in plumericin concentration would be induced by the abundance of Hymenoptera (Formicidae), probably as a chemical response against these insects, and by differences in soil nutrient availability. Full article

(This article belongs to the Topic Advances in Chemical Ecology)

► Show Figures

Figure 1

Topic Menu

Topic Editors

Advances in Chemical Ecology

Topic Information

Keywords

Participating Journals

Published Papers (12 papers)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI