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15 pages, 571 KiB

Open AccessArticle

First Report on the Synergistic Interaction between Essential Oils against the Pinewood Nematode Bursaphelenchus xylophilus

by Jorge M. S. Faria, Tomás Cavaco, Diogo Gonçalves, Pedro Barbosa, Dora Martins Teixeira, Cristina Moiteiro and Maria L. Inácio

Plants 2023, 12(13), 2438; https://doi.org/10.3390/plants12132438 - 25 Jun 2023

Cited by 5 | Viewed by 1786

Abstract

Control of the pinewood nematode (PWN), the causal agent of pine wilt disease, can be achieved through the trunk injection of nematicides; however, many pesticides have been linked to environmental and human health concerns. Essential oils (EOs) are suitable alternatives due to their [...] Read more.

Control of the pinewood nematode (PWN), the causal agent of pine wilt disease, can be achieved through the trunk injection of nematicides; however, many pesticides have been linked to environmental and human health concerns. Essential oils (EOs) are suitable alternatives due to their biodegradability and low toxicity to mammals. These complex mixtures of plant volatiles often display multiple biological activities and synergistic interactions between their compounds. The present work profiled the toxicity of eight EOs against the PWN in comparison to their 1:1 mixtures, to screen for successful synergistic interactions. Additionally, the main compounds of the most synergistic mixtures were characterized for their predicted environmental fate and toxicity to mammals in comparison to emamectin benzoate, a commercial nematicide used against PWN. The mixtures of Cymbopogon citratus with Mentha piperita and of Foeniculum vulgare with Satureja montana EOs showed the highest activities, with half-maximal effective concentrations (EC₅₀) of 0.09 and 0.05 µL/mL, respectively. For these, complete PWN mortality was reached after only ca. 15 min or 2 h of direct contact, respectively. Their major compounds had a higher predicted affinity to air and water environmental compartments and are reported to have very low toxicity to mammals, with low acute oral and dermal toxicities. In comparison, emamectin benzoate showed lower nematicidal activity, a higher affinity to the soil and sediments environmental compartments and higher reported oral and dermal toxicity to mammals. Overall, uncovering synergistic activities in combinations of EOs from plants of different families may prove to be a source of biopesticides with optimized toxicity against PWNs. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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12 pages, 1657 KiB

Open AccessArticle

Nematicidal Potential of Thymol against Meloidogyne javanica (Treub) Chitwood

by Eleni Nasiou and Ioannis O. Giannakou

Plants 2023, 12(9), 1851; https://doi.org/10.3390/plants12091851 - 30 Apr 2023

Cited by 4 | Viewed by 1669

Abstract

Root-knot nematodes (RKN; Meloidogyne spp.) are obligatory endoparasites with worldwide distribution which cause severe damage to agricultural crops. The present study aimed to define the nematicidal activity of thymol on different life stages of the root-knot nematode Meloidogyne javanica (Treub) Chitwood, at concentrations [...] Read more.

Root-knot nematodes (RKN; Meloidogyne spp.) are obligatory endoparasites with worldwide distribution which cause severe damage to agricultural crops. The present study aimed to define the nematicidal activity of thymol on different life stages of the root-knot nematode Meloidogyne javanica (Treub) Chitwood, at concentrations of 37.5–1000 μL/L. This study is the first to report the effect of thymol on egg differentiation and also its vapor and sublethal concentration activities. A mortality of greater than 90% of M. javanica second-stage juveniles (J2s) occurred after 96 h of exposure at a concentration of 500 μL/L. At this concentration, thymol inhibited 59.7% of nematode hatching. In addition, the use of thymol at sublethal concentrations reduced the number of females per gram in tomato roots in a pot test, as well as inhibiting egg differentiation. On the contrary, no nematostatic effects were observed in paralysis bioassays. The results presented here indicate that the use of thymol may show its potential as a source of a new sustainable nematicidal product. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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14 pages, 3387 KiB

Open AccessArticle

Silene uniflora Extracts for Strawberry Postharvest Protection

by Laura Buzón-Durán, Eva Sánchez-Hernández, Pablo Martín-Ramos, Luis Manuel Navas-Gracia, Mari Cruz García-González, Rui Oliveira and Jesús Martín-Gil

Plants 2023, 12(9), 1846; https://doi.org/10.3390/plants12091846 - 29 Apr 2023

Cited by 3 | Viewed by 1908

Abstract

Halophytes are gaining considerable attention due to their applications in saline agriculture, phytoremediation, medicine, and secondary metabolite production. This study investigated the bioactive components present in Silene uniflora (sea campion) hydromethanolic extract, and their antimicrobial activity was evaluated both in vitro and ex [...] Read more.

Halophytes are gaining considerable attention due to their applications in saline agriculture, phytoremediation, medicine, and secondary metabolite production. This study investigated the bioactive components present in Silene uniflora (sea campion) hydromethanolic extract, and their antimicrobial activity was evaluated both in vitro and ex situ against two strawberry phytopathogens, namely Botrytis cinerea (grey mold) and Colletotrichum nymphaeae (anthracnose fruit rot). The main identified phytochemicals were mome inositol, saturated fatty acid esters, and cyclotetracosane. In vitro tests demonstrated complete inhibition of the growth of B. cinerea and C. nymphaeae at extract concentrations of 1000 and 1500 μg·mL⁻¹, respectively, with an activity comparable to that of fosetyl-Al and substantially higher than that of azoxystrobin. This activity was improved upon conjugation with chitosan oligomers (COS), yielding inhibition values of 750 and 1000 μg·mL⁻¹. The COS-S. uniflora conjugate complexes were then tested as protective treatments for postharvest storage of strawberry fruit, resulting in high protection against artificially inoculated B. cinerea and C. nymphaeae at doses of 3750 and 5000 μg·mL⁻¹, respectively. The reported results open the door to the valorization of this halophyte as a source of biorationals for strawberry protection. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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17 pages, 12172 KiB

Open AccessArticle

Effects of Flavonoids and Phenols from Moringa oleifera Leaf Extracts on Biofilm Processes in Xanthomonas campestris pv. campestris

by Riccardo Fontana, Anna Caproni, Mariaconcetta Sicurella, Stefano Manfredini, Anna Baldisserotto and Peggy Marconi

Plants 2023, 12(7), 1508; https://doi.org/10.3390/plants12071508 - 30 Mar 2023

Cited by 7 | Viewed by 2066

Abstract

Xanthomonas campestris pv. campestris is the causal agent of black rot in crucifers, a plant disease with significant economic impact. Xanthomonadaceae is a large family of Gram-negative bacteria that cause symptoms by blocking water flow in plants by invading the xylem. To accomplish [...] Read more.

Xanthomonas campestris pv. campestris is the causal agent of black rot in crucifers, a plant disease with significant economic impact. Xanthomonadaceae is a large family of Gram-negative bacteria that cause symptoms by blocking water flow in plants by invading the xylem. To accomplish this, the main mechanism the bacteria use to adapt to environmental changes and colonize tissues is biofilm formation. In recent years, growing interest in natural antimicrobial compounds has led to the study of different phytocomplexes derived from plants. In this work, Moringa oleifera was selected, as its leaves are rich in phenols, essential oils, and vitamins that exert antibacterial activity. X. campestris pv. campestris biofilm, one of its major virulence factors, was studied. Biofilm formation and removal were analyzed on abiotic and biotic surfaces with and without M. oleifera leaf extracts. The data from the analysis show that Moringa oleifera leaf extracts and single phenols were able to inhibit biofilm growth on abiotic surfaces, but the activity of the whole phytocomplex was significantly higher compared to that of individual phenols. The effect of Moringa oleifera extracts on cabbage leaves in vivo was also found to be very important, as scanning electron microscopy showed that treatment with the extracts led to clear unblocking of the xylem, implying many advantages for use in black rot control. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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16 pages, 1164 KiB

Open AccessArticle

In Vivo Antiphytoviral and Aphid Repellency Activity of Essential Oils and Hydrosols from Mentha suaveolens and Foeniculum vulgare to Control Zucchini Yellow Mosaic Virus and Its Vector Aphis gossypii

by Anna Taglienti, Livia Donati, Immacolata Dragone, Luca Ferretti, Andrea Gentili, Fabrizio Araniti, Filippo Sapienza, Roberta Astolfi, Simona Fiorentino, Valerio Vecchiarelli, Claudia Papalini, Rino Ragno and Sabrina Bertin

Plants 2023, 12(5), 1078; https://doi.org/10.3390/plants12051078 - 28 Feb 2023

Cited by 7 | Viewed by 2279

Abstract

In recent years, natural compounds have gained attention in many fields due to their wide-range biological activity. In particular, essential oils and their associated hydrosols are being screened to control plant pests, exerting antiviral, antimycotic and antiparasitic actions. They are more quickly and [...] Read more.

In recent years, natural compounds have gained attention in many fields due to their wide-range biological activity. In particular, essential oils and their associated hydrosols are being screened to control plant pests, exerting antiviral, antimycotic and antiparasitic actions. They are more quickly and cheaply produced and are generally considered safer for the environment and non-target organisms than conventional pesticides. In this study, we report the evaluation of the biological activity of two essential oils and their corresponding hydrosols obtained from Mentha suaveolens and Foeniculum vulgare in the control of zucchini yellow mosaic virus and its vector, Aphis gossypii, in Cucurbita pepo plants. The control of the virus was ascertained with treatments applied either concurrently with or after virus infection; choice tests were performed to verify repellency activity against the aphid vector. The results indicated that treatments could decrease virus titer as measured using real-time RT-PCR, while the experiments on the vector showed that the compounds effectively repelled aphids. The extracts were also chemically characterized using gas chromatography–mass spectrometry. Mentha suaveolens and Foeniculum vulgare hydrosol extracts mainly comprised fenchone and decanenitrile, respectively, while essential oils analysis returned a more complex composition, as expected. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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15 pages, 5505 KiB

Open AccessArticle

The Dual Benefit of Plant Essential Oils against Tuta absoluta

by Saoussen Ben Abdallah, Chaymaa Riahi, Sandra Vacas, Vicente Navarro-Llopis, Alberto Urbaneja and Meritxell Pérez-Hedo

Plants 2023, 12(5), 985; https://doi.org/10.3390/plants12050985 - 21 Feb 2023

Cited by 8 | Viewed by 2814

Abstract

Plant essential oils (PEOs) are being studied as a potential alternative to synthetic pesticides in agriculture. PEOs have the potential to control pests both directly, by being toxic or repellent to pests, and indirectly, by activating plant’s defense mechanisms. In this study, the [...] Read more.

Plant essential oils (PEOs) are being studied as a potential alternative to synthetic pesticides in agriculture. PEOs have the potential to control pests both directly, by being toxic or repellent to pests, and indirectly, by activating plant’s defense mechanisms. In this study, the effectiveness of five PEOs (Achillea millefolium, Allium sativum, Rosmarinus officinallis, Tagetes minuta, and Thymus zygis) on controlling Tuta absoluta and their impact on the predator Nesidiocoris tenuis was examined. The study revelead that PEOs from A. millefolium and A. sativum-sprayed plants significantly reduced the number of T. absoluta-infested leaflets and did not affect the establishment and reproduction of N. tenuis. Additionally, the spraying of A. millefolium and A. sativum increased the expression of defense genes in the plants, triggering the release of herbivory-induced plant volatiles (HIPVs), such as C6 green leaf volatiles, monoterpenes, and aldehydes, which can be messengers in tritrophic interactions. The results suggest that PEOs from A. millefolium and A. sativum can provide a dual benefit for controlling arthropod pests, as they can directly exhibit toxicity against these pests while also activating plant defense mechanisms. Overall, this study provides new insights into using PEOs as a sustainable solution for controlling pests and diseases in agriculture, by reducing synthetic pesticides and promoting the use of natural predators. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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19 pages, 1704 KiB

Open AccessArticle

Metabolomic Profiling, Antibacterial, and Molluscicidal Properties of the Medicinal Plants Calotropis procera and Atriplex halimus: In Silico Molecular Docking Study

by Mostafa Y. Morad, Heba El-Sayed, Manal F. El-Khadragy, Asmaa Abdelsalam, Eman Zakaria Ahmed and Amina M. Ibrahim

Plants 2023, 12(3), 477; https://doi.org/10.3390/plants12030477 - 19 Jan 2023

Cited by 16 | Viewed by 2841

Abstract

The potential of plant-based natural compounds in the creation of new molluscicidal and antimicrobial medications has gained attention in recent years. The current study compared the metabolic profiles, antibacterial, and molluscicidal properties of the medicinal plants Calotropis procera (C. procera) and [...] Read more.

The potential of plant-based natural compounds in the creation of new molluscicidal and antimicrobial medications has gained attention in recent years. The current study compared the metabolic profiles, antibacterial, and molluscicidal properties of the medicinal plants Calotropis procera (C. procera) and Atriplex halimus (A. halimus). In both plants, 118 metabolites were identified using gas chromatography-mass spectrometry. Palmitic acid, stigmasterol, and campesterol were the most prevalent constituents. C. procera extract showed stronger antibacterial activity than A. halimus against Escherichia coli and Proteus mirabilis. Both extracts exhibited molluscicidal activity against Biomphalaria alexandrina, with LC₅₀ values of C. procera (135 mg/L) and A. halimus (223.8 mg/L). Survival rates of snails exposed to sub-lethal concentrations (LC₂₅) of C. procera and A. halimus extracts were 5% and 20%, respectively. The hatchability of snail eggs exposed to both extracts has been dramatically reduced. Both extracts significantly decreased the levels of alkaline phosphatase, acid phosphatase, total protein, and albumin in snails, as well as causing DNA damage and resulting in numerous hermaphrodite and digestive gland damages and distortions. Molecular docking showed palmitic acid binding with acid, alkaline, and alanine aminotransferases in treated digestive gland snails. In conclusion, C. procera and A. halimus have antibacterial and molluscicidal properties. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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17 pages, 7142 KiB

Open AccessArticle

Research Trends, Biases, and Gaps in Phytochemicals as Insecticides: Literature Survey and Meta-Analysis

by Lara J. Collares, Leonardo M. Turchen and Raul Narciso C. Guedes

Plants 2023, 12(2), 318; https://doi.org/10.3390/plants12020318 - 10 Jan 2023

Cited by 10 | Viewed by 3329

Abstract

A 76-year literature survey and meta-analyses were carried out to recognize the trends, biases, and knowledge gaps of studies focusing on major groups of compounds of botanical origin, or phytochemicals, as insecticides. The survey found that the main phytochemicals prospected as insecticides belong [...] Read more.

A 76-year literature survey and meta-analyses were carried out to recognize the trends, biases, and knowledge gaps of studies focusing on major groups of compounds of botanical origin, or phytochemicals, as insecticides. The survey found that the main phytochemicals prospected as insecticides belong to the following major chemical groups: terpenoids, terpenes, and carbonyl, all of which were tested, mainly against beetles (Coleoptera), caterpillars (i.e., larvae of Lepidoptera), and mosquitoes and other flies (i.e., Diptera). These studies are burgeoning at an exponential rate, with an evident focus on mortality endpoint estimates, but they are also neglecting sublethal assessments. China and India in Asia, as well as Brazil in the Americas, were responsible for most studies. The majority of the papers used stored grain insects as experimental models, which limits the applicability and representativeness of the findings. As a result, the main modes of exposure tested were fumigation and contact, which leads to the prevalence of estimates of lethal concentration in these studies. Therefore, a broader range of insect species deserves testing, with suitable modes of exposure identifying and characterizing the main molecules responsible for the insecticidal activity, which is seldom performed. Attention to these needs will circumvent current biases and allow the recognition of the main patterns of association between the origin and structure of phytochemicals and their insecticidal effects. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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18 pages, 2065 KiB

Open AccessEditor’s ChoiceArticle

Valorization of Quercus suber L. Bark as a Source of Phytochemicals with Antimicrobial Activity against Apple Tree Diseases

by Eva Sánchez-Hernández, Vicente González-García, José Casanova-Gascón, Juan J. Barriuso-Vargas, Joaquín Balduque-Gil, Belén Lorenzo-Vidal, Jesús Martín-Gil and Pablo Martín-Ramos

Plants 2022, 11(24), 3415; https://doi.org/10.3390/plants11243415 - 7 Dec 2022

Cited by 9 | Viewed by 2614

Abstract

Cork, an anatomic adaptation of the bark of Quercus suber L. through its suberization process, finds its main application in the production of bottle stoppers. Its processing results in a large waste stream of cork fragments, granulates, and dust, which may be susceptible [...] Read more.

Cork, an anatomic adaptation of the bark of Quercus suber L. through its suberization process, finds its main application in the production of bottle stoppers. Its processing results in a large waste stream of cork fragments, granulates, and dust, which may be susceptible to valorization. The work presented here explored the use of its extracts to inhibit the growth of phytopathogenic microorganisms associated with apple tree diseases. The in vitro antimicrobial activity of cork aqueous ammonia extract was assayed against four fungi, viz. Monilinia fructigena and M. laxa (brown rot), Neofussicoccum parvum (dieback), and Phytophthora cactorum (collar and root rot), and two bacteria, viz. Erwinia amylovora and Pseudomonas syringae pv. syringae, either alone or in combination with chitosan oligomers (COS). Effective concentration values of EC₉₀ in the 675–3450 μg·mL⁻¹ range, depending on the fungal pathogen, were obtained in growth inhibition tests, which were substantially improved for the conjugate complexes (340–801 μg·mL⁻¹) as a result of strong synergism with COS. Similar enhanced behavior was also observed in antibacterial activity assays, with MIC values of 375 and 750 μg·mL⁻¹ for the conjugate complexes against P. syringae pv. syringae and E. amylovora, respectively. This in vitro inhibitory activity was substantially higher than those exhibited by azoxystrobin and fosetyl-Al, which were tested for comparison purposes, and stood out among those reported for other natural compounds in the literature. The observed antimicrobial activity may be mainly attributed to the presence of glycerin and vanillic acid, identified by gas chromatography–mass spectroscopy. In the first step towards in-field application, the COS–Q. suber bark extract conjugate complex was further tested ex situ against P. cactorum on artificially inoculated excised stems of the ‘Garnem’ almond rootstock, achieving high protection at a dose of 3750 μg·mL⁻¹. These results suggest that cork industrial leftovers may, thus, be a promising source of bioactive compounds for integrated pest management. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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24 pages, 1672 KiB

Open AccessArticle

Using of Essential Oils and Plant Extracts against Pseudomonas savastanoi pv. glycinea and Curtobacterium flaccumfaciens pv. flaccumfaciens on Soybean

by Rashit I. Tarakanov and Fevzi S.-U. Dzhalilov

Plants 2022, 11(21), 2989; https://doi.org/10.3390/plants11212989 - 5 Nov 2022

Cited by 7 | Viewed by 3031

Abstract

The bacteria Pseudomonas savastanoi pv. glycinea (Coerper, 1919; Gardan et al., 1992) (Psg) and Curtobacterium flaccumfaciens pv. flaccumfaciens (Hedges 1922) (Cff) are harmful pathogens of soybean (Glycine max). Presently, there are several strategies to control these bacteria, and the usage of [...] Read more.

The bacteria Pseudomonas savastanoi pv. glycinea (Coerper, 1919; Gardan et al., 1992) (Psg) and Curtobacterium flaccumfaciens pv. flaccumfaciens (Hedges 1922) (Cff) are harmful pathogens of soybean (Glycine max). Presently, there are several strategies to control these bacteria, and the usage of environmentally friendly approaches is encouraged. In this work, purified essential oils (EOs) from 19 plant species and total aqueous and ethanolic plant extracts (PEs) from 19 plant species were tested in vitro to observe their antimicrobial activity against Psg and Cff (by agar diffusion and broth microdilution method). Tested EOs and PEs produced significant bacterial growth inhibition with technologically acceptable MIC and MBC values. Non-phytotoxic concentrations for Chinese cinnamon and Oregano essential oils and leather bergenia ethanolic extract, which previously showed the lowest MBC values, were determined. Testing of these substances with artificial infection of soybean plants has shown that the essential oils of Chinese cinnamon and oregano have the maximum efficiency against Psg and Cff. Treatment of leaves and seeds previously infected with phytopathogens with these essential oils showed that the biological effectiveness of leaf treatments was 80.6–77.5% and 86.9–54.6%, respectively, for Psg and Cff. GC-MS and GC-FID analyzes showed that the major compounds were 5-Methyl-3-methylenedihydro-2(3H)-furanone (20.32%) in leather bergenia ethanolic extract, cinnamaldehyde (84.25%) in Chinese cinnamon essential oil and carvacrol (62.32%) in oregano essential oil. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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14 pages, 2077 KiB

Open AccessEditor’s ChoiceArticle

Antifungal Potential of Canarian Plant Extracts against High-Risk Phytopathogens

by Carolina P. Reyes, Samuel Rodríguez Sabina, Rocío López-Cabeza, Cristina G. Montelongo, Cristina Giménez, Ignacio A. Jiménez, Raimundo Cabrera and Isabel L. Bazzochi

Plants 2022, 11(21), 2988; https://doi.org/10.3390/plants11212988 - 5 Nov 2022

Cited by 4 | Viewed by 2289

Abstract

Phytopathogens are responsible for great losses in agriculture. In particular, Fusarium, Alternaria and Botrytis are fungal diseases that affect crops worldwide. In the search for eco-friendly solutions to pest control, plants and their chemo-biodiversity are promising sources of biopesticides for integrated pest [...] Read more.

Phytopathogens are responsible for great losses in agriculture. In particular, Fusarium, Alternaria and Botrytis are fungal diseases that affect crops worldwide. In the search for eco-friendly solutions to pest control, plants and their chemo-biodiversity are promising sources of biopesticides for integrated pest management. The aim of the present study is to report the evaluation of sixteen plant species from the Canary Islands Archipelago against the phytopathogenic fungi Botrytis cinerea, Fusarium oxysporum, and Alternaria alternata. The plants were selected on the basis of their traditional uses in medicine and/or pest control, as well as on scientific studies reporting their uses in crop protection. Their growth inhibition (% I), in an in vitro test-assay on mycelium, was used to identify six ethanolic plant extracts displaying activity (% I > 30% at 1 mg/mL) against at least one of the assayed fungi. The most effective plant extracts were further fractionated by liquid–liquid partition, using solvents of increasing polarity. This procedure led to an improvement of the bioactivity against the phytopathogens, even affecting the hexane fraction from S. canariensis and achieving an 83.93% of growth inhibition at 0.5 mg/mL on B. cinerea. These findings identified five plant-derived extracts as potential candidates for the future development of new biofungicides, which could be applied in integrated pest management. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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12 pages, 2209 KiB

Open AccessArticle

Anthracnose Disease Control and Postharvest Quality of Hass Avocado Stored in Biobased PLA/PBAT/Pine Essential Oil/Chitosan Active Packaging Nets

by Zormy N. Correa-Pacheco, Rosa I. Ventura-Aguilar, Leonor Zavaleta-Avejar, Laura L. Barrera-Necha, Mónica Hernández-López and Silvia Bautista-Baños

Plants 2022, 11(17), 2278; https://doi.org/10.3390/plants11172278 - 31 Aug 2022

Cited by 5 | Viewed by 2400

Abstract

For sale in the domestic market, Hass avocados are kept in non-biodegradable plastic nets and stored at an ambient temperature. The fungus Colletotrichum gloeosporioides can cause important losses at this stage. Consequently, formulations based on polylactic acid (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) 60/40 biodegradable [...] Read more.

For sale in the domestic market, Hass avocados are kept in non-biodegradable plastic nets and stored at an ambient temperature. The fungus Colletotrichum gloeosporioides can cause important losses at this stage. Consequently, formulations based on polylactic acid (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) 60/40 biodegradable blends added with pine essential oil (PEO) at 10, 12, 14, and 20% and coated with 1% chitosan (CH) were used for the elaboration of nets, which were evaluated on C. gloeosporioides and Rhizopus stolonifer on nutrient media and fruit and on the ripening behavior of Hass avocados at ambient temperature. The spore germination stage of C. gloeosporioides was the most extensively damaged (78% inhibition). The incidence of anthracnose was notably reduced by almost 80% in the avocados stored in the 60/40 PLA/PBAT nets coated with 1% CH. The overall values regarding weight loss, °Brix, and dry matter were c.a. 23.5%, 7.5, and 24.5%, respectively. The changes in firmness, color, and CO₂ production were particularly associated with the initial harvest index and storage temperature rather than with the nets. In future research, essays on nets should include evaluations at the commercial levels. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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14 pages, 3332 KiB

Open AccessArticle

Nematicidal Screening of Aqueous Extracts from Plants of the Yucatan Peninsula and Ecotoxicity

by Jesús Aviles-Gomez, Jairo Cristóbal-Alejo, María Fé Andrés, Azucena González-Coloma, Germán Carnevali, Daisy Pérez-Brito, Felicia Amalia Moo-Koh and Marcela Gamboa-Angulo

Plants 2022, 11(16), 2138; https://doi.org/10.3390/plants11162138 - 17 Aug 2022

Cited by 5 | Viewed by 2287

Abstract

Active metabolites from plants are considered safer than synthetic chemicals for the control of plant-parasitic nematodes of the genus Meloidogyne. In the present work, 75 aqueous extracts (AEs) from different vegetative parts of 34 native plant species of the Yucatan Peninsula were [...] Read more.

Active metabolites from plants are considered safer than synthetic chemicals for the control of plant-parasitic nematodes of the genus Meloidogyne. In the present work, 75 aqueous extracts (AEs) from different vegetative parts of 34 native plant species of the Yucatan Peninsula were evaluated against second-stage juveniles (J2s) of Meloidogyne incognita and M. javanica in microdilution assays. The highest mortality (M) against both Meloidogyne species was produced by the foliar AE from Alseis yucatanensis (M ≥ 94%) and Helicteres baruensis (M ≥ 77%) at 3% w/v after 72 h. Other active AEs at 3% were from the leaves of Croton itzaeus and stems of H. baruensis (M: 87–90%) on M. javanica and the stems of Annona primigenia and the leaves of Morella cerifera on M. incognita (M: 92–97%). The AEs from A. yucatanensis had the lowest LD₅₀ against M. incognita (0.36% w/v), and against M. javanica (3.80% w/v). In an acute ecotoxicity assay of the most promising AEs using non-target earthworms (Eisenia fetida), the AE of A. yucatanensis had slight acute toxicity (LD₅₀: 2.80% w/v), and the rest of the most active AEs were not ecotoxic. These tropical plants are potential candidates for further studies as biorational agents for controlling Meloidogyne species. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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11 pages, 1277 KiB

Open AccessArticle

Evaluation of Ethanolic Powdered Extract of Magnolia tamaulipana Vazquez against Oligonychus punicae Hirst (Trombidiformes: Tetranychidae)

by Francisco Reyes-Zepeda, Rapucel Tonantzin Quetzalli Heinz-Castro, Fabian Eliseo Olazaran-Santibañez, Salvador Ordaz-Silva, José Guadalupe Pedro-Méndez and Julio César Chacón-Hernández

Plants 2022, 11(13), 1711; https://doi.org/10.3390/plants11131711 - 28 Jun 2022

Cited by 3 | Viewed by 1859

Abstract

Avocado bronze mite (ABM), Oligonychus punicae Hirst (Trombidiformes: Tetranychidae) has potential for development in several plant species of agricultural importance. ABM is one of the most economically important pests in avocado cultivars, causing major damage to fruit and defoliation. At present, the control [...] Read more.

Avocado bronze mite (ABM), Oligonychus punicae Hirst (Trombidiformes: Tetranychidae) has potential for development in several plant species of agricultural importance. ABM is one of the most economically important pests in avocado cultivars, causing major damage to fruit and defoliation. At present, the control of ABM depends mainly on agrochemicals. Therefore, it is necessary to find alternatives to agrochemicals that can help minimize environmental impact and health risks for humans and mammals. The aim of this research was to assess the effect of different concentrations (5, 10, 50, 100, 250, 500, 1000 µg/mL) of ethanolic powdered extract of M. tamaulipana leaves against adult ABM females. The different concentrations of M. tamaulipana extract did not cause mortality of O. punicae. Females treated with 5 and 1000 µg/mL of the extract showed a decrease in the number of eggs laid per female at 24 (5.17 and 1.27), 48 (5.07 and 1.17), and 72 h (4.97 and 0.80), compared to the control treatment (5.20, 6.60 and 6.87), respectively, which led to a reduction in the growth rate. Percentage of feeding damage decreased with the increasing concentration of the extract. The ethanolic powdered extract of M. tamaulipana leaf has potential to control O. punicae. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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19 pages, 2045 KiB

Open AccessArticle

Biopesticide Activity of Guayule Resin

by Guayente Latorre, María Mercedes García-Martínez, María Martín-Bejerano, Luis F. Julio, Amaya Zalacain, María Engracia Carrión and Manuel Carmona

Plants 2022, 11(9), 1169; https://doi.org/10.3390/plants11091169 - 26 Apr 2022

Cited by 5 | Viewed by 2383

Abstract

The extensive use of synthetic pesticides has created considerable concern for both human health and the environment, which has prompted the search for safer alternatives, such as the resin of guayule (Parthenium argentatum). Thus, in the present study, we aimed to [...] Read more.

The extensive use of synthetic pesticides has created considerable concern for both human health and the environment, which has prompted the search for safer alternatives, such as the resin of guayule (Parthenium argentatum). Thus, in the present study, we aimed to test the biopesticide activity of crude guayule resin and three derived fractions and compare them to reference products that act against four of the most economically significant plant pests: Tetranychus urticae, Bemisia tabaci, Myzus persicae and Frankliniella occidentalis. None of the guayule products caused plant damage. The crude guayule resin and the hexane and ethyl acetate fractions displayed moderate to high contact mortality against T. urticae and B. tabaci, as well as moderate to high antifeedant activity against T. urticae, B. tabaci and M. persicae. No significant activity was observed against F. occidentalis. A correlation analysis of the activity and fraction composition revealed that guayulins C and D, isoargentatins A and B, argentatins A, B and D and an unknown compound C6 were likely responsible for the contact mortality. By contrast, the antifeedant activity appeared to be caused by guayulins A and B against T. urticae and B. tabaci and by guayulins C and D and argentatin B against M. persicae. The feeding reduction in F. occidentalis was associated with an unknown compound C2 and argentatin C. Therefore, guayule appears to be a promising novel biopesticide. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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14 pages, 1190 KiB

Open AccessEditor’s ChoiceArticle

Complex Synergistic Interactions among Volatile and Phenolic Compounds Underlie the Effectiveness of Allelopathic Residues Added to the Soil for Weed Control

by María Pardo-Muras, Carolina G. Puig and Nuria Pedrol

Plants 2022, 11(9), 1114; https://doi.org/10.3390/plants11091114 - 20 Apr 2022

Cited by 18 | Viewed by 2346

Abstract

The introduction of allelopathic cover crops for green manuring or mulching is a regular practice in Integrated Weed Management. In this context, the alternative use of the abundant phytotoxic residues of allelopathic plants from the agroecosystem, e.g., the foliage of Eucalyptus, Acacia [...] Read more.

The introduction of allelopathic cover crops for green manuring or mulching is a regular practice in Integrated Weed Management. In this context, the alternative use of the abundant phytotoxic residues of allelopathic plants from the agroecosystem, e.g., the foliage of Eucalyptus, Acacia, or Cytisus species, is promising. Previous studies identified the phytotoxic compounds potentially involved in the effectiveness of some plant residues when added to the soil for weed control. The low quantities of allelochemicals present in the tissues and the weak phytotoxicity of each of them in their natural concentrations did not explain the significant levels of weed control observed at field scale. Here, to study hypothetical synergistic interactions among the volatile (VOCs) and water-soluble compounds released to the soil matrix, complex mixtures of VOCs, phenolics, or both, mimicking the chemical profiles of Cytisus scoparius were prepared and then tested in vitro on the germination and early growth of two weeds. The effects were calibrated against the VOCs naturally emitted by the fresh plant material and aqueous extract, acting together or not, and with or without soil. The presence of the aqueous extract significantly increased the phytotoxicity of VOCs on Amaranthus retroflexus root growth compared to the volatiles emitted alone. In addition, the soil factor enhanced synergistic interactions among VOCs and water-soluble compounds, resulting in a 54% decrease in total germination and an 80% inhibition of root and shoot growth. Multi-level synergistic chemical interactions should explain the bioherbicidal effectiveness of allelopathic residues applied as a soil amendment. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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19 pages, 5551 KiB

Open AccessArticle

Control of Erwinia amylovora Growth by Moringa oleifera Leaf Extracts: In Vitro and in Planta Effects

by Riccardo Fontana, Giovanna Macchi, Anna Caproni, Mariaconcetta Sicurella, Mattia Buratto, Francesca Salvatori, Mariangela Pappadà, Stefano Manfredini, Anna Baldisserotto and Peggy Marconi

Plants 2022, 11(7), 957; https://doi.org/10.3390/plants11070957 - 31 Mar 2022

Cited by 18 | Viewed by 3954

Abstract

Erwinia amylovora (EA) is a phytopathogenic bacterium, the causative agent of bacterial fire blight, a disease that affects Rosaceaes. In order to replace antibiotics and copper, the antimicrobial activity of three extracts of Moringa oleifera Lam., methanolic (MeOH-MOE), hydroalcoholic (HA-MOE) and hydroalcoholic with [...] Read more.

Erwinia amylovora (EA) is a phytopathogenic bacterium, the causative agent of bacterial fire blight, a disease that affects Rosaceaes. In order to replace antibiotics and copper, the antimicrobial activity of three extracts of Moringa oleifera Lam., methanolic (MeOH-MOE), hydroalcoholic (HA-MOE) and hydroalcoholic with maltodextrins (HAMD-MOE), was tested on eleven strains of EA isolated from apple trees by the Emilia-Romagna Phytosanitary Department. MIC and MBC have been evaluated; biofilm formation, swarming motility and amylovoran production were performed with the crystalviolet, soft-agar assay and the amylovoran method. All extracts demonstrated bacteriostatic activity at a concentration of 1 mg/mL, resulting in a 80% reduction in biofilm formation. HAMD-MOE, MeOH-MOE and HA-MOE caused an inhibition of motility of 60%, 65% and 30% after 6 days and a decrease in amylovoran synthesis of 84%, 63% and 93%, respectively. In planta results showed how the compounds were able to inhibit EA virulence on apple trees, mainly if they were applied as a preventive treatment, although the treatment showed a significant reduction in fire blight symptoms progression. The antibacterial activity of the extracts is mainly due to the high concentration of polyphenolic compounds detected in the extracts that was able to alter the permeability of bacterial membrane, resulting in slowing the synthesis of ATP and consequently of all ATP-dependent functions, such as motility and less selectivity towards harmful compounds, which can, thus, enter the cytoplasm and inhibit enzymes involved in replication and quorum sensing. The efficacy, eco-compatibility and low cost make such extracts a potential tool for the control of bacterial fire blight. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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16 pages, 350 KiB

Open AccessArticle

Pistacia Root and Leaf Extracts as Potential Bioherbicides

by Marta I. Saludes-Zanfaño, Ana M. Vivar-Quintana and María Remedios Morales-Corts

Plants 2022, 11(7), 916; https://doi.org/10.3390/plants11070916 - 29 Mar 2022

Cited by 8 | Viewed by 3017

Abstract

The allelopathic effect of pistachios was analyzed by field and laboratory tests. The parameters analyzed in the field trials were the biomass, weed density, weed diversity, and specific richness of the weed community. The studies were carried out in the area under the [...] Read more.

The allelopathic effect of pistachios was analyzed by field and laboratory tests. The parameters analyzed in the field trials were the biomass, weed density, weed diversity, and specific richness of the weed community. The studies were carried out in the area under the canopy and in the area beyond the influence of the pistachio tree, and the results obtained were compared. In the laboratory, germination bioassays were carried out on seeds of 11 weed species in root water extract, rhizosphere soil, and leaf water extract. The germination percentage, radicle elongation, epicotyl elongation, and germination index were determined. The results obtained show that significantly less biomass was present in the area under the influence of the trees, and fewer different weed species were detected in that area. In addition, germination bioassays showed that the aqueous leaf extract was a potent inhibitor of germination. The total content of flavonoids and phenols according to the organs (roots or leaves) was also studied. Extracts obtained from leaves showed higher concentrations of total phenols and also of flavones and flavanols than roots. Gallic acid, catechin, myricetin, and quercetin were identified in extracts obtained from both leaves and roots, while naringenin and rutin were identified only in the leaf extract. The presence of phenolic compounds in which allelopathic activity has been previously described and the results obtained in the trials seem to indicate that there is an allelopathic effect of the leaf extract, which could be used for weed control, thus facilitating ecological and/or sustainable management. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

14 pages, 728 KiB

Open AccessEditor’s ChoiceArticle

Dwarf Pomegranate (Punica granatum L. var. nana): Source of 5-HMF and Bioactive Compounds with Applications in the Protection of Woody Crops

by Eva Sánchez-Hernández, Laura Buzón-Durán, José A. Cuchí-Oterino, Jesús Martín-Gil, Belén Lorenzo-Vidal and Pablo Martín-Ramos

Plants 2022, 11(4), 550; https://doi.org/10.3390/plants11040550 - 18 Feb 2022

Cited by 10 | Viewed by 2937

Abstract

While the properties of edible pomegranate varieties have been widely explored, there is little information on ornamental types. In this study, possible alternatives for the valorization of dwarf pomegranate fruits have been explored. The characterization of their hydromethanolic extract by gas chromatography−mass spectrometry [...] Read more.

While the properties of edible pomegranate varieties have been widely explored, there is little information on ornamental types. In this study, possible alternatives for the valorization of dwarf pomegranate fruits have been explored. The characterization of their hydromethanolic extract by gas chromatography−mass spectrometry evidenced the presence of high contents of 5-hydroxymethylfurfural (a carbon-neutral feedstock for the production of fuels and other chemicals) and β- and γ-sitosterol stereoisomers. The microbicidal activity of the crude extract, both alone and in a conjugate complex with chitosan oligomers (COS), was investigated against three plant pathogenic microorganisms that cause significant losses in woody crops: Erwinia amylovora, E. vitivora, and Diplodia seriata. In in vitro assays, a strong synergistic behavior was found after conjugation of the bioactive constituents of the fruit extract with COS, resulting in minimum inhibitory concentration (MIC) values of 750 and 375 μg·mL⁻¹ against E. amylovora and E. vitivora, respectively, and an EC₉₀ value of 993 μg·mL⁻¹ against D. seriata. Hence, extracts from the non-edible fruits of this Punicaceae may hold promise as a source of high value-added phytochemicals or as environmentally friendly agrochemicals. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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13 pages, 1039 KiB

Open AccessArticle

Toxicity, Deterrent and Repellent Activities of Four Essential Oils on Aphis punicae (Hemiptera: Aphididae)

by Samy Sayed, Mohamed Mohamed Soliman, Saad Al-Otaibi, Mohamed M. Hassan, Sayed-Ashraf Elarrnaouty, Samia M. Abozeid and Ahmed M. El-Shehawi

Plants 2022, 11(3), 463; https://doi.org/10.3390/plants11030463 - 8 Feb 2022

Cited by 23 | Viewed by 3627

Abstract

Chemical insecticides have many harmful effects, including as foodborne residues and environmental contaminants, as well as side effects on natural enemies and serious risks for human health. The use of plant-derived essential oils (EOs) as effective bio-agents has become an essential component of [...] Read more.

Chemical insecticides have many harmful effects, including as foodborne residues and environmental contaminants, as well as side effects on natural enemies and serious risks for human health. The use of plant-derived essential oils (EOs) as effective bio-agents has become an essential component of integrated pest management. In this study, the contact toxicity, deterrent, and repellent activities were evaluated for essential oils obtained from Mentha piperita, Mentha longifolia, Salvia officinalis, and Salvia rosmarinus, grown at high altitudes in the Taif region, KSA, on Aphis punicae. Furthermore, the toxicity of these EOs against the predator Coccinella undecimpunctata was estimated. A total of 17, 14, 16, and 26 compounds were identified in the EOs of M. piperita, M. longifolia, S. officinalis, and S. rosmarinus, respectively. They showed a variation in the major compounds: M. piperita (Carvone, 61.16%), M. longifolia (Pulegone, 48.6%), S. officinalis (Eucalyptol, 33.52%), and S. rosmarinus (α-pinene, 36.65%). A contact toxicity test on A. punicae imago and C. undecimpunctata larvae showed that LC₅₀ were approximately four-fold greater for all tested EOs towards aphids compared to towards the predator, while the two species of Salvia sp. were more effective than the other two species of Mentha sp. The LC₅₀ values on A. punicae ranged from 1.57 to 2.97 µg/mL, while on C. undecimpunctata larvae, they ranged from 5.96 to 10.33 µg/mL. Furthermore, the EOs of two species of Salvia sp. showed excellent repellence and deterrence against A. punicae. In conclusion, the tested EOs, especially those from Salvia sp., have been shown to be promising natural aphicides, repellent, and deterrent against A. punicae, and they are safe for important insect predators. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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15 pages, 2021 KiB

Open AccessArticle

Warburgia ugandensis Leaf and Bark Extracts: An Alternative to Copper as Fungicide against Downy Mildew in Organic Viticulture?

by Christian Kraus, Rada Abou-Ammar, Andreas Schubert and Michael Fischer

Plants 2021, 10(12), 2765; https://doi.org/10.3390/plants10122765 - 14 Dec 2021

Cited by 3 | Viewed by 3364

Abstract

In organic viticulture, copper-based fungicides are commonly used to suppress Downy Mildew infection, caused by the oomycete Plasmopara viticola. However, the frequent and intensive use of such fungicides leads to accumulation of the heavy metal in soil and nearby waters with adverse [...] Read more.

In organic viticulture, copper-based fungicides are commonly used to suppress Downy Mildew infection, caused by the oomycete Plasmopara viticola. However, the frequent and intensive use of such fungicides leads to accumulation of the heavy metal in soil and nearby waters with adverse effects on the ecosystem. Therefore, alternative, organic fungicides against Downy Mildew are urgently needed to reduce the copper load in vineyards. In this study, the use of Warburgia ugandensis Sprague (Family Canellacea) leaf and bark extracts as potential fungicides against Downy Mildew were evaluated. In vitro (microtiter) and in vivo (leaf discs, seedlings) tests were conducted, as well as field trials to determine the efficacy of the extracts against Downy Mildew. The results revealed an MIC₁₀₀ of 500 µg/mL for the leaf extract and 5 µg/mL for the bark extract. Furthermore, experiments with leaf discs and seedlings demonstrated a strong protective effect of the extracts for up to 48 h under (semi-) controlled conditions. However, in field trials the efficacy of the extracts distinctly declined, regardless of the extracts’ origin and concentration. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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14 pages, 1353 KiB

Open AccessArticle

Antifungal Activity against Fusarium oxysporum of Botanical End-Products: An Integration of Chemical Composition and Antifungal Activity Datasets to Identify Antifungal Bioactives

by Diego Cárdenas-Laverde, Ricardo Barbosa-Cornelio and Ericsson Coy-Barrera

Plants 2021, 10(12), 2563; https://doi.org/10.3390/plants10122563 - 24 Nov 2021

Cited by 15 | Viewed by 3055

Abstract

Plants produce various compounds as defensive barriers to naturally control fungal diseases. Among them, vascular wilt caused by Fusarium oxysporum is one of the most destructive diseases in crops, causing relevant economic losses. The application of synthetic fungicides is the most used management [...] Read more.

Plants produce various compounds as defensive barriers to naturally control fungal diseases. Among them, vascular wilt caused by Fusarium oxysporum is one of the most destructive diseases in crops, causing relevant economic losses. The application of synthetic fungicides is the most used management for this disease. However, this kind of method also involves adverse environmental impacts. Therefore, alternative methods are continuously being developed as a strategy to be involved in integrated pest management programs. Thus, as part of our research on antifungals of plant origin, a group of botanical extracts was assessed for the respective inhibitory effect on mycelium and conidia of F. oxysporum. Mycelial growth inhibition was measured in 12-well plates containing amended semi-solid medium, whereas conidial susceptibility was determined through microdilution. The identification of the bioactive compounds among test extracts was performed using an indirect approach, consisting of the integration of chemical composition and antifungal activity datasets through single-Y orthogonal partial least squares (OPLS) regression. Results showed that Piper aduncum extract was the most potent mycelial growth inhibitor whereas P. elongatum exhibited the best effect on conidia susceptibility. The active compounds identified through statistical integration and subsequent isolation were piperaduncin C, asebogenin and (−)-methyllinderatin. These findings indicated that the integrative, indirect approach is useful for the identification of bioactive metabolites from botanical extracts to be further used as biological protective agents against this phytopathogen. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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9 pages, 522 KiB

Open AccessArticle

Use of Natural Products on the Control of Aspergillus flavus and Production of Aflatoxins In Vitro and on Tomato Fruit

by Mario Alberto Segura-Palacios, Zormy Nacary Correa-Pacheco, Maria Luisa Corona-Rangel, Ollin Celeste Martinez-Ramirez, Dolores Azucena Salazar-Piña, Margarita de Lorena Ramos-García and Silvia Bautista-Baños

Plants 2021, 10(12), 2553; https://doi.org/10.3390/plants10122553 - 23 Nov 2021

Cited by 14 | Viewed by 2853

Abstract

Aspergillus flavus affects fresh and dry fruit and vegetable products, and its toxic metabolites, namely aflatoxins, cause serious damage in humans. The objective of this research study was to evaluate the effect of commercial natural products as well as edible and nanostructured chitosan [...] Read more.

Aspergillus flavus affects fresh and dry fruit and vegetable products, and its toxic metabolites, namely aflatoxins, cause serious damage in humans. The objective of this research study was to evaluate the effect of commercial natural products as well as edible and nanostructured chitosan coatings on the development of A. flavus and on the production of aflatoxins in vitro and in tomato. Treatments were as follows: chitosan 1%, chitosan coating, chitosan nanostructured coating, Citrocover 1% (citrus seed extract), Resinadher 0.5% (pine resin extract), mancozeb 2%, and water. The variables were as follows: halo inhibition, spore production, and aflatoxins content. In fruit, the following were evaluated: disease incidence, mycelial growth, and aflatoxin production. An ANOVA (Tukey: p < 0.05) was used. In vitro results showed that Citrocover and Resinadher reduced sporulation (0.2 and 0.9 × 10⁵ spores mL⁻¹, respectively), while chitosan inhibited the production of aflatoxins. With Resinadher and Citrocover, tomato fruit had the lowest incidence, mycelial growth, and aflatoxin production with corresponding values of 0%, 0.0 cm², and 0.95 ppb, respectively, and 7%, 0.2 cm², and 1.77 ppb, respectively. The use of Citrocover and Resinadher could be a viable alternative to decrease the development of A. flavus in tomato fruit. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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17 pages, 1457 KiB

Open AccessArticle

First Report of Protective Activity of Paronychia argentea Extract against Tobacco Mosaic Virus Infection

by Ahmed Abdelkhalek, Abdulaziz A. Al-Askar, Maha M. Alsubaie and Said I. Behiry

Plants 2021, 10(11), 2435; https://doi.org/10.3390/plants10112435 - 11 Nov 2021

Cited by 32 | Viewed by 3553

Abstract

The widespread use of chemical control agents and pesticides for plant-pathogen control has caused many human health and environmental issues. Plant extracts and biocontrol agents have robust antimicrobial activity against different plant pathogens. However, their antiviral activities are still being investigated. In the [...] Read more.

The widespread use of chemical control agents and pesticides for plant-pathogen control has caused many human health and environmental issues. Plant extracts and biocontrol agents have robust antimicrobial activity against different plant pathogens. However, their antiviral activities are still being investigated. In the present study, the methanol extract of Paronychia argentea was characterized and evaluated for its protective activity against the tobacco mosaic virus (TMV) infection in tomato plants under greenhouse conditions at 21 days post-inoculation. The results showed that the foliar application of P. argentea extract (10 µg/mL) enhanced tomato plant growth, resulting in significant increases in shoot and root parameters and total chlorophyll contents. Moreover, a significant reduction in TMV accumulation level in P. argentea-treated plants of 77.88% compared to non-treated plants was reported. Furthermore, induction of systemic resistance with significant elevation in production of antioxidant enzymes (PPO, CAT, and SOD) and transcriptional levels of the pathogenesis-related proteins (PR-1 and PR-7) and polyphenolic genes (CHS and HQT) were also observed. Out of 16 detected compounds, HPLC analysis revealed that the most abundant polyphenolic compounds found in P. argentea extract were gallic acid (5.36 µg/mL), kaempferol (7.39 µg/mL), quercetin (7.44 µg/mL), ellagic acid (7.89 µg/mL), myricetin (8.36 µg/mL), and ferulic acid (8.69 µg/mL). The findings suggest that the use of P. argentea extract as an effective and safe source for the production of bioactive compounds may offer a solution for a promising approach for the management of plant viral infections. To the best of our knowledge, this is the first report of the protective activity of P. argentea extract against plant viral diseases. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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Review

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29 pages, 2952 KiB

Open AccessReview

Can Essential Oils Be a Natural Alternative for the Control of Spodoptera frugiperda? A Review of Toxicity Methods and Their Modes of Action

by Virginia L. Usseglio, José S. Dambolena and María P. Zunino

Plants 2023, 12(1), 3; https://doi.org/10.3390/plants12010003 - 20 Dec 2022

Cited by 11 | Viewed by 3176

Abstract

Spodoptera frugiperda is a major pest of maize crops. The application of synthetic insecticides and the use of Bt maize varieties are the principal strategies used for its control. However, due to the development of pesticide resistance and the negative impact of insecticides [...] Read more.

Spodoptera frugiperda is a major pest of maize crops. The application of synthetic insecticides and the use of Bt maize varieties are the principal strategies used for its control. However, due to the development of pesticide resistance and the negative impact of insecticides on the environment, natural alternatives are constantly being searched for. Accordingly, the objective of this review was to evaluate the use of essential oils (EOs) as natural alternatives for controlling S. frugiperda. This review article covers the composition of EOs, methods used for the evaluation of EO toxicity, EO effects, and their mode of action. Although the EOs of Ocimum basilicum, Piper marginatum, and Lippia alba are the most frequently used, Ageratum conyzoides, P. septuplinervium. O. gratissimum and Siparuna guianensis were shown to be the most effective. As the principal components of these EOs vary, then their mode of action on the pest could be different. The results of our analysis allowed us to evaluate and compare the potential of certain EOs for the control of this insect. In order to obtain comparable results when evaluating the toxicity of EOs on S. frugiperda, it is important that methodological issues are taken into account. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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18 pages, 1743 KiB

Open AccessEditor’s ChoiceReview

The Role of Biostimulants as Alleviators of Biotic and Abiotic Stresses in Grapevine: A Review

by Eliana Monteiro, Berta Gonçalves, Isabel Cortez and Isaura Castro

Plants 2022, 11(3), 396; https://doi.org/10.3390/plants11030396 - 31 Jan 2022

Cited by 47 | Viewed by 8977

Abstract

The viticulture and wine industry contribute to the economy and reputation of many countries all over the world. With the predicted climate change, a negative impact on grapevine physiology, growth, production, and quality of berries is expected. On the other hand, the impact [...] Read more.

The viticulture and wine industry contribute to the economy and reputation of many countries all over the world. With the predicted climate change, a negative impact on grapevine physiology, growth, production, and quality of berries is expected. On the other hand, the impact of these changes in phytopathogenic fungi development, survival rates, and host susceptibility is unpredictable. Grapevine fungal diseases control has been a great challenge to winegrowers worldwide. The use of chemicals in viticulture is high, which can result in the development of pathogen resistance, increasingly raising concerns regarding residues in wine and effects on human and environmental health. Promoting sustainable patterns of production is one of the overarching objectives and essential requirements for sustainable development. Alternative holistic approaches, such as those making use of biostimulants, are emerging in order to reduce the consequences of biotic and abiotic stresses in the grapevine, namely preventing grape fungal diseases, improving grapevine resistance to water stress, and increasing yield and berry quality. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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Other

Jump to: Research, Review

14 pages, 1618 KiB

Open AccessSystematic Review

Insecticidal Activity of Essential Oils against Mealybug Pests (Hemiptera: Pseudococcidae): A Systematic Review and Meta-Analysis

by Miriam del Valle Avila, Fernanda Achimón, Vanessa Daniela Brito, Ramiro Aguilar, Romina Paola Pizzolitto, María Paula Zunino and María Laura Peschiutta

Plants 2023, 12(1), 109; https://doi.org/10.3390/plants12010109 - 26 Dec 2022

Cited by 6 | Viewed by 3823

Abstract

Most mealybugs of the Pseudococcidae family are important pests of agriculture and ornamental gardens. Our aim was to perform a review and meta-analysis on 14 published scientific articles on the insecticidal activity of essential oils (EOs) against mealybug species of the Pseudococcidae family. [...] Read more.

Most mealybugs of the Pseudococcidae family are important pests of agriculture and ornamental gardens. Our aim was to perform a review and meta-analysis on 14 published scientific articles on the insecticidal activity of essential oils (EOs) against mealybug species of the Pseudococcidae family. Data on (1) species, genus, families, and plant parts from which the EO was extracted; (2) the main compounds of each EO; (3) the highest and lowest concentrations tested; and (4) the application method used for the toxicological studies was collected from each study. The metafor package (R software) was used to perform a three-level random effects meta-analysis. The families Lamiaceae, Rutaceae, Myrtaceae, Zingiberaceae and Euphorbiaceae and the genera Citrus, Cymbopogon, Syzygium, Cinnamomum and Jatropha were the most used among the studies. According to the results from the meta-analyses, 13 out of 24 genera analyzed were effective against mealybugs. All methods were effective, but fumigation and indirect contact were the most frequently used methodologies. The results obtained from the present review and meta-analysis could be used for the potential development of natural biopesticide formulations against mealybugs belonging to the Pseudococcidae family. Full article

(This article belongs to the Special Issue Plant Extracts as Biological Protective Agents)

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