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1.
Plant Physiol Biochem ; 147: 322-335, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31911359

RESUMO

It is well known that parasitic weeds such as Orobanche (broomrape) significantly decrease crop growth and yield. Although hormonal priming is a well-known inducer of plant resistance against broomrapes (Orobanche spp.), the metabolic events associated with such resistance are poorly understood. Therefore, the current work was undertaken to elucidate the role of SA in inducing tomato resistance against Orobanche, considering its impact on carbon and nitrogen metabolism of the host. Total carbon and nitrogen and levels of carbon (sugars, organic acids and fatty acids) and nitrogen (amino acids and polyamines)-containing metabolites as well as the activities of some key enzymes involved in their metabolic pathways were evaluated. Broomrape infection significantly disrupted C/N ratio in the host roots. On contrary, SA treatment markedly induced accumulation of sugars, organic acids, fatty acids, amino acids as well as polyamines in healthy plants. Under broomrape challenge, SA mitigated the infection-induced growth inhibition by improving the level of nitrogen-containing osmoprotectants (proline, arginine and some polyamines). However, a decrease was observed in some C and N assimilates which are well known to be potentially transferred to the parasite, such as sucrose, asparagine, alanine, serine and glutamate. Interestingly, SA treatment induced the catapolism of polyamines and fatty acids in the host root. Accordingly, our study suggests that SA-induced resistance against broomrape relies on the rational utilization of C and N assimilates in a manner that disturbs the sink strength of the parasite and/or activates the defense pool of the host.


Assuntos
Carbono , Resistência à Doença , Lycopersicon esculentum , Nitrogênio , Orobanche , Ácido Salicílico , Carbono/metabolismo , Resistência à Doença/efeitos dos fármacos , Lycopersicon esculentum/efeitos dos fármacos , Lycopersicon esculentum/parasitologia , Nitrogênio/metabolismo , Orobanche/fisiologia , Ácido Salicílico/farmacologia
2.
PLoS One ; 15(1): e0227556, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31929586

RESUMO

Oxathiapiprolin is a fungicide effective against downy mildews of cucumber (Pseudoperonospora cubensis) and basil (Peronospora belbahrii) and late blight of tomato (Phytophthora infestans). To avoid fungicide resistance, it is recommended to apply oxathiapiprolin as a mixture with a partner fungicide that have a different mode of action. Here it is shown that a single application of oxathiapiprolin, benthiavalicarb, or their mixture (3+7, w/w) to the root of nursery plants grown in multi-cell trays provided prolonged systemic protection against late blight and downy mildews in growth chambers and in field tests. Soil application of 1mg active ingredient per plant provided durable protection of up to four weeks in tomato against late blight, cucumber against downy mildew and basil against downy mildew. Not only did the mixture of oxathiapiprolin and benthiavalicarb provide excellent systemic control of these diseases but also mutual protection against resistance towards both oxathiapiprolin and benthiavalicarb.


Assuntos
Carbamatos/farmacologia , Fungicidas Industriais/farmacologia , Hidrocarbonetos Fluorados/farmacologia , Peronospora/efeitos dos fármacos , Doenças das Plantas/prevenção & controle , Pirazóis/farmacologia , Cucumis sativus/efeitos dos fármacos , Cucumis sativus/crescimento & desenvolvimento , Cucumis sativus/parasitologia , Lycopersicon esculentum/efeitos dos fármacos , Lycopersicon esculentum/crescimento & desenvolvimento , Lycopersicon esculentum/parasitologia , Peronospora/patogenicidade , Doenças das Plantas/parasitologia , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/parasitologia
3.
J Agric Food Chem ; 68(2): 523-529, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31908169

RESUMO

The present work sought to contribute to the development of new nematicides. Benzaldehydes were initially converted to nitrile oxides that underwent 1,3-dipolar cycloaddition reactions with methyl acrylate to generate 4,5-dihydroisoxazoles. In in vitro tests, methyl 3-phenyl-4,5-dihydroisoxazole-5-carboxylate (1) and methyl 3-(4-chlorophenyl)-4,5-dihydroisoxazole-5-carboxylate (4) increased the mortality of Meloidogyne exigua and Meloidogyne incognita second-stage juveniles (J2). Compounds 1 and 4 presented necessary concentrations of 398 and 501 µg mL-1, respectively, to kill 50% of M. incognita J2 (LC50 values), while the value for carbofuran (positive control) was 168 µg mL-1. In in vivo tests, compounds 1 and 4 reduced the number of M. incognita galls in tomato roots by 70 and 40%, respectively, and the number of eggs by 89 and 44%. Using an in silico approach, we showed that compounds 1 and 4 were toxic to the nematodes by binding to the allosteric binding sites of the agonist-binding domains of the nematode nicotinic acetylcholine receptors. These results opened up possibilities for further investigations aimed at developing novel commercial nematicides.


Assuntos
Antinematódeos/toxicidade , Isoxazóis/toxicidade , Doenças das Plantas/parasitologia , Tylenchoidea/efeitos dos fármacos , Animais , Antinematódeos/química , Simulação por Computador , Proteínas de Helminto/química , Proteínas de Helminto/metabolismo , Isoxazóis/química , Lycopersicon esculentum/parasitologia , Raízes de Plantas/parasitologia , Receptores Nicotínicos/química , Receptores Nicotínicos/metabolismo , Tylenchoidea/crescimento & desenvolvimento , Tylenchoidea/metabolismo
4.
Molecules ; 25(1)2019 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-31861560

RESUMO

Apocarotenoids, such as ß-cyclocitral, α-ionone, ß-ionone, and loliolide, are derived from carotenes via chemical or enzymatic processes. Recent studies revealed that ß-cyclocitral and loliolide play an important role in various aspects of plant physiology, such as stress responses, plant growth, and herbivore resistance. However, information on the physiological role of α-ionone is limited. We herein investigated the effects of α-ionone on plant protection against herbivore attacks. The pretreatment of whole tomato (Solanum lycopersicum) plants with α-ionone vapor decreased the survival rate of western flower thrips (Frankliniella occidentalis) without exhibiting insecticidal activity. Exogenous α-ionone enhanced the expression of defense-related genes, such as basic ß-1,3-glucanase and basic chitinase genes, in tomato leaves, but not that of jasmonic acid (JA)- or loliolide-responsive genes. The pretreatment with α-ionone markedly decreased egg deposition by western flower thrips in the JA-insensitive Arabidopsis (Arabidopsis thaliana) mutant coi1-1. We also found that common cutworm (Spodoptera litura) larvae fed on α-ionone-treated tomato plants exhibited a reduction in weight. These results suggest that α-ionone induces plant resistance to western flower thrips through a different mode of action from that of JA and loliolide.


Assuntos
Resistência à Doença , Lycopersicon esculentum/efeitos dos fármacos , Norisoprenoides/farmacologia , Tisanópteros/efeitos dos fármacos , Animais , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Arabidopsis/parasitologia , Ciclopentanos/metabolismo , Feminino , Flores/efeitos dos fármacos , Flores/parasitologia , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Lycopersicon esculentum/genética , Lycopersicon esculentum/parasitologia , Oxilipinas/metabolismo , Doenças das Plantas/genética , Doenças das Plantas/parasitologia , Doenças das Plantas/prevenção & controle , Proteínas de Plantas/genética
5.
J Chem Ecol ; 45(11-12): 972-981, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31713110

RESUMO

Microplitis croceipes is a solitary parasitoid that specializes on noctuid larvae of Helicoverpa zea and Heliothis virescens. Both the parasitoid and its hosts are naturally distributed across a large part of North America. When parasitoids deposit their eggs into hosts, venom and polydnaviruses (PDVs) are also injected into the caterpillars, which can suppress host immune responses, thus allowing parasitoid larvae to develop. In addition, PDVs can regulate host oral cues, such as glucose oxidase (GOX). The purpose of this study was to determine if parasitized caterpillars differentially induce plant defenses compared to non-parasitized caterpillars using two different caterpillar host/plant systems. Heliothis virescens caterpillars parasitized by M. croceipes had significantly lower salivary GOX activity than non-parasitized caterpillars, resulting in lower levels of tomato defense responses, which benefited parasitoid performance by increasing the growth rate of parasitized caterpillars. In tobacco plants, parasitized Helicoverpa zea caterpillars had lower GOX activity but induced higher plant defense responses. The higher tobacco defense responses negatively affected parasitoid performance by reducing the growth rate of parasitized caterpillars, causing longer developmental periods, and reduced cocoon mass and survival of parasitoids. These studies demonstrate a species-specific effect in different plant-insect systems. Based on these results, plant perception of insect herbivores can be affected by parasitoids and lead to positive or negative consequences to higher trophic levels depending upon the particular host-plant system.


Assuntos
Lycopersicon esculentum/parasitologia , Mariposas/fisiologia , Tabaco/parasitologia , Vespas/fisiologia , Animais , Feminino , Glucose Desidrogenase/metabolismo , Glucose Oxidase/metabolismo , Interações Hospedeiro-Parasita , Larva/metabolismo , Lycopersicon esculentum/metabolismo , Oviposição/fisiologia , Parasitos , Doenças das Plantas/parasitologia , Extratos Vegetais/química , Extratos Vegetais/metabolismo , Folhas de Planta/química , Folhas de Planta/metabolismo , Especificidade da Espécie , Tabaco/metabolismo
6.
Plant Dis ; 103(11): 2764-2770, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31490090

RESUMO

Fusarium wilt (Fusarium oxysporum f. sp. lycopersici), root-knot nematodes (Meloidogyne spp.), and purple nutsedge (Cyperus rotundus L.) are among the most damaging soilborne pests for tomato (Lycopersicon esculentum Mill.) production in the southeastern United States. Allyl isothiocyanate (allyl ITC) was evaluated as a potential fumigant alternative for control of soilborne pathogens, nematodes, and weeds. Shank- or drip-injected allyl ITC at rates ranging from 221 to 367 kg ha-1 exhibited excellent performance, reducing the recovery of total F. oxysporum from treated soils. Shank- or drip-injected allyl ITC at 367 kg ha-1 provided equivalent control of C. rotundus compared with 1,3-dichloropropene + chloropicrin and metam potassium, respectively. Totally impermeable film (TIF) did not further reduce the recovery of F. oxysporum and various nematodes from soil treated with allyl ITC compared with virtually impermeable film (VIF). However, TIF mulch significantly improved C. rotundus control versus shank- or drip-injected allyl ITC treatments under VIF mulch. Overall, allyl ITC is an effective methyl bromide alternative against F. oxysporum, C. rotundus, and plant-parasitic nematodes Criconemella spp. and Hoplolaimus spp. in plasticulture tomato production.


Assuntos
Agricultura , Lycopersicon esculentum , Controle de Pragas , Agricultura/métodos , Animais , Cyperus/efeitos dos fármacos , Fusarium/efeitos dos fármacos , Isotiocianatos/farmacologia , Lycopersicon esculentum/microbiologia , Lycopersicon esculentum/parasitologia , Controle de Pragas/métodos , Solo/parasitologia , Microbiologia do Solo , Sudeste dos Estados Unidos , Tylenchoidea/efeitos dos fármacos
7.
Sensors (Basel) ; 19(16)2019 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-31395823

RESUMO

An electronic nose (E-nose) system equipped with a sensitive sensor array was developed for fast diagnosis of aphid infestation on greenhouse tomato plants at early stages. Volatile organic compounds (VOCs) emitted by tomato plants with and without aphid attacks were detected using both the developed E-nose system and gas chromatography mass spectrometry (GC-MS), respectively. Sensor performance, with fast sensor responses and high sensitivity, were observed using the E-nose system. A principle component analysis (PCA) indicated accurate diagnosis of aphid-stressed plants compared to healthy ones, with the first two PCs accounting for 86.7% of the classification. The changes in VOCs profiles of the healthy and infested tomato plants were quantitatively determined by GC-MS. Results indicated that a group of new VOCs biomarkers (linalool, carveol, and nonane (2,2,4,4,6,8,8-heptamethyl-)) played a role in providing information on the infestation on the tomato plants. More importantly, the variation in the concentration of sesquiterpene VOCs (e.g., caryophyllene) and new terpene alcohol compounds was closely associated with the sensor responses during E-nose testing, which verified the reliability and accuracy of the developed E-nose system. Tomato plants growing in spring had similar VOCs profiles as those of winter plants, except several terpenes released from spring plants that had a slightly higher intensity.


Assuntos
Afídeos/fisiologia , Cromatografia Gasosa-Espectrometria de Massas/métodos , Lycopersicon esculentum/parasitologia , Compostos Orgânicos Voláteis/análise , Animais , Biomarcadores/análise , Nariz Eletrônico , Cromatografia Gasosa-Espectrometria de Massas/instrumentação , Lycopersicon esculentum/química , Lycopersicon esculentum/metabolismo , Doenças das Plantas/parasitologia , Folhas de Planta/química , Folhas de Planta/metabolismo , Folhas de Planta/parasitologia , Análise de Componente Principal
8.
Phytochem Anal ; 30(5): 556-563, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31286582

RESUMO

INTRODUCTION: Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most devastating and harmful pests of tomato (Solanum lycopersicum) crops causing up to 80-100% yield losses. A large arsenal of plant metabolites is induced by the leafminer feeding including defence compounds that could differ among varieties. OBJECTIVE: To compare the metabolomic changes of different genotypes of tomato (tolerant "T", susceptible "S" and "F1" hybrid obtained between T and S) after exposition to T. absoluta. METHODOLOGY: Nuclear magnetic resonance (NMR) spectroscopy followed by multivariate data analysis were performed to analyse the metabolic profiles of control and infested samples on three different tomato genotypes. RESULTS: Signals related to GABA (γ-aminobutyric acid) were relatively much higher in all infested samples compared to the non-infested plants used as control. Infested T genotype samples were the most abundant in organic acids, including fatty acids and acyl sugars, chlorogenic acid, neo-chlorogenic acid and feruloyl quinic acid, indicating a clear link between the exposure to leafminer. Results also showed an increase of trigonelline in all tomato varieties after exposition to T. absoluta. CONCLUSION: Metabolomics approach based on NMR spectroscopy followed by multivariate data analysis allowed for a detailed metabolite profile of plant defences, providing fundamental information for breeding programmes in plant crops.


Assuntos
Lepidópteros/fisiologia , Lycopersicon esculentum/parasitologia , Espectroscopia de Ressonância Magnética/métodos , Metabolômica , Animais , Comportamento Alimentar , Genes de Plantas , Lycopersicon esculentum/genética , Análise Multivariada
9.
PLoS Pathog ; 15(6): e1007897, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31206553

RESUMO

Pandemics of vector-borne human and plant diseases often depend on the behaviors of their arthropod vectors. Arboviruses, including many bunyaviruses, manipulate vector behavior to accelerate their own transmission to vertebrates, birds, insects, and plants. However, the molecular mechanism underlying this manipulation remains elusive. Here, we report that the non-structural protein NSs of Tomato spotted wilt orthotospovirus, a prototype of the Tospoviridae family and the Orthotospovirus genus, is a key viral factor that indirectly modifies vector preference and increases vector performance. NSs suppresses the biosynthesis of plant volatile monoterpenes, which serve as repellents of the vector western flower thrips (WFT, Frankliniella occidentalis). NSs directly interacts with MYC2, the jasmonate (JA) signaling master regulator and its two close homologs MYC3 and MYC4, to disable JA-mediated activation of terpene synthase genes. The dysfunction of the MYCs subsequently attenuates host defenses, increases the attraction of thrips, and improves thrips fitness. Moreover, MYC2 associated with NSs of Tomato zonate spot orthotospovirus, another Euro/Asian-type orthotospovirus, suggesting that MYC2 is an evolutionarily conserved target of Orthotospovirus species for suppression of terpene-based resistance to promote vector performance. These findings elucidate the molecular mechanism through which an orthotospovirus indirectly manipulates vector behaviors and therefore facilitates pathogen transmission. Our results provide insights into the molecular mechanisms by which Orthotospovirus NSs counteracts plant immunity for pathogen transmission.


Assuntos
Bunyaviridae/metabolismo , Ciclopentanos/metabolismo , Lycopersicon esculentum , Oxilipinas/metabolismo , Proteínas de Plantas/metabolismo , Vírus de Plantas/metabolismo , Transdução de Sinais , Tisanópteros/fisiologia , Fatores de Transcrição/metabolismo , Proteínas não Estruturais Virais/metabolismo , Animais , Lycopersicon esculentum/metabolismo , Lycopersicon esculentum/parasitologia , Lycopersicon esculentum/virologia , Terpenos/metabolismo
10.
J Chem Ecol ; 45(7): 598-609, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31218595

RESUMO

Insect herbivory induces plant defense responses that are often modulated by components in insect saliva, oral secretions or regurgitant, frass, or oviposition fluids. These secretions contain proteins and small molecules that act as elicitors or effectors of plant defenses. Several non-protein elicitors have been identified from insect oral secretions, whereas studies of insect saliva have focused mainly on protein identification. Yet, insect saliva may also contain non-protein molecules that could activate defense responses in plants. The goal of this study was to identify non-protein plant defense elicitors present in insect saliva. We used the fall armyworm (FAW), Spodoptera frugiperda and its host plants tomato, maize, and rice as a model system. We tested the effect of protein-digested saliva or non-protein components on herbivore-induced defense responses in maize, rice and tomato. We identified phytohormones in FAW saliva using high performance liquid chromatography coupled with mass spectrometry. The results of this study show that non-protein components in FAW saliva modulated defense responses in different plant species. The saliva of this insect contains benzoic acid, and the phytohormones jasmonic acid, salicylic acid, and abscisic acid at concentrations of <5 ng per µl of saliva. Plant treatment with similar phytohormone quantities detected in FAW saliva upregulated the expression of a maize proteinase inhibitor gene in maize, and down-regulated late herbivore-induced defenses in tomato plants. We conclude that FAW saliva is a complex fluid that, in addition to known enzymatic plant defense elicitors, contains phytohormones and other small molecules.


Assuntos
Reguladores de Crescimento de Planta/análise , Saliva/química , Zea mays/metabolismo , Animais , Cromatografia Líquida de Alta Pressão , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Herbivoria , Larva/metabolismo , Lycopersicon esculentum/metabolismo , Lycopersicon esculentum/parasitologia , Espectrometria de Massas , Reguladores de Crescimento de Planta/farmacologia , Folhas de Planta/metabolismo , Folhas de Planta/parasitologia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Saliva/metabolismo , Spodoptera/crescimento & desenvolvimento , Zea mays/parasitologia
11.
BMC Infect Dis ; 19(1): 410, 2019 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-31088390

RESUMO

BACKGROUND: Consumption of unwashed, raw or unhygienically prepared fruits and vegetables act as potential source for the spread of various parasitic diseases. Moreover, the level of contamination and species of contaminant parasites vary from place to place because of variations in environmental and human factors. Therefore local determination of the level of contamination and associated factors is important for efficient intervention of infections acquired via those food items. METHODS: A Cross-sectional study was conducted among purchased vegetables in selected markets of Arba Minch town from January to March, 2018. A structured questionnaire was used to capture data about factors associated with parasitic contamination of vegetables in the marketing phase. Selected vegetables were purchased and processed for examination of parasitic contamination using direct wet mount, iodine wet mount and modified zeihl Neelson staining following standard protocols. All data were analyzed using SPSS version 20.0. RESULTS: Among 347 vegetable samples examined, 87(25.1%) were contaminated with at least one parasite species. Tomato (35.0%) was the most commonly contaminated vegetable while green pepper (10.6%) was the least contaminated one. Entameoba histolytica/dispar (29, 8.4%) was the commonest parasitic contaminant detected followed by Giardia lamblia (24, 6.9%) and oocyst of Cryptosporidium species (5.8%). Vegetable type (X2 = 13.5; p = 0.009) and source of vegetables (X2 = 24.1; p < 0.001) were significantly associated with parasitic contamination of vegetables. CONCLUSION: Parasitic contamination rate among marketed vegetables in the present study is significantly considerable. Entameoba histolytica /dispar was the most frequently detected parasite. We recommend to the local public health sector to establish a system for continuous monitoring of contamination of vegetables sold at local markets.


Assuntos
Entamoeba/isolamento & purificação , Verduras/parasitologia , Animais , Estudos Transversais , Cryptosporidium/crescimento & desenvolvimento , Cryptosporidium/isolamento & purificação , Etiópia , Frutas/parasitologia , Giardia lamblia/isolamento & purificação , Humanos , Lycopersicon esculentum/parasitologia , Oocistos/isolamento & purificação
12.
Pest Manag Sci ; 75(12): 3363-3370, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31074102

RESUMO

BACKGROUND: Two field experiments were conducted to determine the efficacy and field performance of three new non-fumigant chemical nematicides (fluensulfone, fluopyram, and fluazaindolizine) and two biological nematicides (Burkholderia rinojensis strain A396 and Purpureocillium lilacinus strain 251) for management of root-knot nematodes (Meloidogyne javanica) on tomato and associated double-crops in Florida. RESULTS: In experiment 1, soil fumigation with metam potassium increased plant growth and reduced root galling on tomato by 77% relative to that of the untreated soil. All non-fumigant chemical nematicides reduced root galling on tomato (47-85% reduction); however, only fluensulfone showed a trend towards yield enhancement. In experiment 2, soil fumigation with chloropicrin increased plant growth and reduced root galling on tomato by 35% relative to that of the untreated soil; however, end-of-season populations of M. javanica in soil were larger than that of the non-fumigated soil. Fluensulfone showed a trend towards reduced root galling and enhanced fruit yield, whereas other non-fumigant nematicides did not. Double-cropped cucumber was 69% more galled when planted into soil previously fumigated with chloropicrin relative to that of untreated soil, and also showed reduced plant vigor and fruit yield. CONCLUSION: Fluensulfone shows significant potential to be a component of an integrated pest management strategy for tomato in Florida. © 2019 Society of Chemical Industry.


Assuntos
Antinematódeos/administração & dosagem , Ascomicetos/fisiologia , Burkholderia/fisiologia , Lycopersicon esculentum/crescimento & desenvolvimento , Controle Biológico de Vetores/métodos , Doenças das Plantas/prevenção & controle , Tylenchoidea , Animais , Benzamidas/administração & dosagem , Produção Agrícola/métodos , Proteção de Cultivos/métodos , Cucumis sativus/crescimento & desenvolvimento , Florida , Compostos Heterocíclicos com 2 Anéis/administração & dosagem , Lycopersicon esculentum/parasitologia , Doenças das Plantas/parasitologia , Piridinas/administração & dosagem , Sulfonamidas/administração & dosagem , Sulfonas/administração & dosagem , Tiazóis/administração & dosagem
13.
J Chem Ecol ; 45(5-6): 515-524, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31127421

RESUMO

Although the tritrophic interactions of plants, insect herbivores and their natural enemies have been intensely studied for several decades, the roles of entomopathogens in their indirect modulation of plant-insect relationships is still unclear. Here, we employed a sublethal dose of a baculovirus with a relatively broad host range (AcMNPV) to explore if feeding by baculovirus-challenged Helicoverpa zea caterpillars induces direct defenses in the tomato plant. We examined induction of plant defenses following feeding by H. zea, including tomato plants fed on by healthy caterpillars, AcMNPV-challenged caterpillars, or undamaged controls, and subsequently compared the transcript levels of defense related proteins (i.e., trypsin proteinase inhibitors, peroxidase and polyphenol oxidase) and other defense genes (i.e., proteinase inhibitor II and cysteine proteinase inhibitor) from these plants, in addition to comparing caterpillar relative growth rates. As a result, AcMNPV-challenged caterpillars induced the highest plant anti-herbivore defenses. We examined several elicitors and effectors in the secretions of these caterpillars (i.e., glucose oxidase, phospholipase C, and ATPase hydrolysis), which surprisingly did not differ between treatments. Hence, we suggest that the greater induction of plant defenses by the virus-challenged caterpillars may be due to differences in the amount of these secretions deposited during feeding or to some other unknown factor(s).


Assuntos
Baculoviridae/patogenicidade , Lycopersicon esculentum/metabolismo , Mariposas/fisiologia , Animais , Catecol Oxidase/genética , Catecol Oxidase/metabolismo , Comportamento Alimentar , Regulação da Expressão Gênica de Plantas , Herbivoria , Interações Hospedeiro-Parasita , Larva/efeitos dos fármacos , Larva/fisiologia , Larva/virologia , Lycopersicon esculentum/parasitologia , Mariposas/crescimento & desenvolvimento , Mariposas/virologia , Peroxidase/genética , Peroxidase/metabolismo , Folhas de Planta/metabolismo , Folhas de Planta/parasitologia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , RNA de Plantas/isolamento & purificação , RNA de Plantas/metabolismo , Glândulas Salivares/metabolismo
14.
Plant Dis ; 103(7): 1551-1558, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31059388

RESUMO

Root-knot nematodes (Meloidogyne spp.) cause serious crop losses worldwide. The colonization of tomato roots by endophytic bacteria Bacillus cereus BCM2 can greatly reduce Meloidogyne incognita damage, and tomato roots carrying BCM2 were repellent to M. incognita second-stage juveniles (J2). Here, the effects of BCM2 colonization on the composition of tomato root exudates was evaluated and potential mechanisms for BCM2-mediated M. incognita control explored using a linked twin-pot assay and GC-MS. On water agar plates, J2 preferentially avoided filter paper treated with tomato root exudates (organic phase only) from plants inoculated with BCM2, visiting these 67.1% less than controls. In a linked twin-pot assay, BCM2 treatment resulted in a 42.0% reduction in the number of nematodes in the soil, a 43.3% reduction in the number of galls and a 47.7% decrease in the density of M. incognita in root tissues. Analysis of root exudate composition revealed that BCM2 inoculation increased the number of components in exudates. Among these, 2,4-di-tert-butylphenol, 3,3-dimethyloctane, and n-tridecane secretions markedly increased. In repellency trials on water agar plates, J2 avoided 2,4-di-tert-butylphenol, n-tridecane, and 3,3-dimethyloctane at concentrations of 4 mmol/liter. In a linked twin-pot assay, inoculation with 2,4-di-tert-butylphenol or 3,3-dimethyloctane reduced the number of nematodes in the soil (by 54.9 and 70.6%, respectively), the number of galls (by 53.7 and 52.4%), and the number of M. incognita in root tissues (by 67.5 and 36.3%). BCM2 colonization in tomato roots affected the composition of root exudates, increasing the secretion of substances that appear to be repellent, thus decreasing M. incognita J2 infection of roots.


Assuntos
Bacillus cereus , Lycopersicon esculentum , Tylenchoidea , Animais , Bacillus cereus/fisiologia , Cromatografia Gasosa-Espectrometria de Massas , Lycopersicon esculentum/microbiologia , Lycopersicon esculentum/parasitologia , Raízes de Plantas/microbiologia , Raízes de Plantas/parasitologia , Tylenchoidea/microbiologia
15.
Bull Entomol Res ; 109(6): 812-820, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30968782

RESUMO

Tuta absoluta (Meyrick), a key pest of tomato, is quickly spreading over the world and biological control is considered as one of the control options. Worldwide more than 160 species of natural enemies are associated with this pest, and an important challenge is to quickly find an effective biocontrol agent from this pool of candidate species. Evaluation criteria for control agents are presented, with the advantages they offer for separating potentially useful natural enemies from less promising ones. Next, an aggregate parameter for ranking agents is proposed: the pest kill rate km. We explain why the predator's intrinsic rate of increase cannot be used for comparing the control potential of predators or parasitoids, while km can be used to compare both types of natural enemies. As an example, kill rates for males, females and both sexes combined of three Neotropical mirid species (Campyloneuropsis infumatus (Carvalho), Engytatus varians (Distant) and Macrolophus basicornis (Stål)) were determined, taking all life-history data (developmental times, survival rates, total nymphal and adult predation, sex ratios and adult lifespan) into account. Based on the value for the intrinsic rate of increase (rm) for T. absoluta and for the kill rate km of the predators, we predict that all three predators are potentially able to control the pest, because their km values are all higher than the rm of the pest. Using only km values, we conclude that E. varians is the best candidate for control of T. absoluta on tomato, with C. infumatus ranking second and M. basicornis last.


Assuntos
Agentes de Controle Biológico/classificação , Mariposas , Comportamento Predatório , Animais , Feminino , Heterópteros/fisiologia , Estágios do Ciclo de Vida , Lycopersicon esculentum/parasitologia , Masculino , Controle Biológico de Vetores/métodos
16.
Insect Mol Biol ; 28(5): 662-675, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-30834620

RESUMO

The whitefly Bemisia tabaci is a major pest to agriculture. Adults are able to fly for long distances and to colonize staple crops, herbs and ornamentals, and to vector viruses belonging to several important taxonomic groups. During their early development, whiteflies mature from eggs through several nymphal stages (instars I to IV) until adults emerge from pupae. We aim at reducing whitefly populations by inhibiting the emergence of adults from nymphs. Here we targeted dystrophin, a conserved protein essential for the development of the muscle system in humans, other animals and insects. We have exploited the fact that whitefly nymphs developing on tomato leaves feed from the plant phloem via their stylets. Thus, we delivered dystrophin-silencing double-stranded RNA to nymphs developing on leaves of tomato plantlets with their roots bathing in the silencing solution. Downregulation of dystrophin expression occurred mainly in pupae. Dystrophin silencing induced also the downregulation of the dystrophin-associated protein genes actin and tropomyosin, and disrupted F-actin. Most significantly, the treatment inhibited the emergence of adults from pupae, suggesting that targeting dystrophin may help to restrain whitefly populations. This study demonstrates for the first time the important role of dystrophin in the development of a major insect pest to agriculture.


Assuntos
Distrofina/metabolismo , Hemípteros/crescimento & desenvolvimento , Hemípteros/metabolismo , Actinas/genética , Actinas/metabolismo , Animais , Regulação para Baixo , Distrofina/genética , Hemípteros/genética , Lycopersicon esculentum/parasitologia , Metamorfose Biológica , Pupa/crescimento & desenvolvimento , RNA de Cadeia Dupla/genética , Tropomiosina/genética , Tropomiosina/metabolismo
17.
Proc Natl Acad Sci U S A ; 116(15): 7387-7396, 2019 04 09.
Artigo em Inglês | MEDLINE | ID: mdl-30910967

RESUMO

The whitefly Bemisia tabaci is one of the world's most important invasive crop pests, possibly because it manipulates plant defense signaling. Upon infestation by whiteflies, plants mobilize salicylic acid (SA)-dependent defenses, which mainly target pathogens. In contrast, jasmonic acid (JA)-dependent defenses are gradually suppressed in whitefly-infested plants. The down-regulation of JA defenses make plants more susceptible to insects, including whiteflies. Here, we report that this host-plant manipulation extends to neighboring plants via airborne signals. Plants respond to insect attack with the release of a blend of inducible volatiles. Perception of these volatiles by neighboring plants usually primes them to prepare for an imminent attack. Here, however, we show that whitefly-induced tomato plant volatiles prime SA-dependent defenses and suppress JA-dependent defenses, thus rendering neighboring tomato plants more susceptible to whiteflies. Experiments with volatiles from caterpillar-damaged and pathogen-infected plants, as well as with synthetic volatiles, confirm that whiteflies modify the quality of neighboring plants for their offspring via whitefly-inducible plant volatiles.


Assuntos
Hemípteros/fisiologia , Interações Hospedeiro-Parasita/fisiologia , Lycopersicon esculentum , Ácido Salicílico/metabolismo , Compostos Orgânicos Voláteis/metabolismo , Animais , Lycopersicon esculentum/metabolismo , Lycopersicon esculentum/parasitologia
18.
Mol Plant Microbe Interact ; 32(9): 1077-1087, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30908943

RESUMO

Sporangia of the potato late blight agent Phytophthora infestans are often used in studies of pathogen biology and plant responses to infection. Investigations of spore biology can be challenging in oomycetes because their sporangia are physiologically active and change in response to environmental factors and aging. Whether sporangia from artificial media and plant lesions are functionally equivalent has been a topic of debate. To address these issues, we compared the transcriptomes and infection ability of sporangia from rye-sucrose media, potato and tomato leaflets, and potato tubers. Small differences were observed between the mRNA profiles of sporangia from all sources, including variation in genes encoding metabolic enzymes, cell-wall-degrading enzymes, and ABC transporters. Small differences in sporangia age also resulted in variation in the transcriptome. Taking care to use sporangia of similar maturity, we observed that those sourced from media or plant lesions had similar rates of zoospore release and cyst germination. There were also no differences in infection rates or aggressiveness on leaflets, based on single-spore inoculation assays. Such results are discordant with those of a recent publication in this journal. Nevertheless, we conclude that sporangia from plant and media cultures are functionally similar and emphasize the importance of using "best practices" in experiments with sporangia to obtain reliable results.


Assuntos
Regulação da Expressão Gênica , Lycopersicon esculentum , Phytophthora infestans , Solanum tuberosum , Esporângios , Perfilação da Expressão Gênica , Lycopersicon esculentum/parasitologia , Phytophthora infestans/genética , Solanum tuberosum/parasitologia , Esporângios/genética , Transcriptoma
19.
PLoS One ; 14(3): e0213071, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30822326

RESUMO

Horticulturalists and gardeners in temperate regions often claim that planting marigolds next to tomato plants protects the tomatoes from the glasshouse whitefly (Trialeurodes vaporariorum Westwood). If shown to hold true, this technique could be used in larger-scale tomato production, protecting the crop and helping to introduce greater plant diversity into these agro-ecosystems. Here we present two large-scale glasshouse trials corresponding to the two main ways growers are likely to use marigolds to control whiteflies. In the first, marigolds are grown next to tomato throughout the growing period and we quantify whitefly population growth from the seedling stage over a 48 day infestation period. Here we show that association with marigolds significantly slows whitefly population development. Introducing additional whitefly-attractive 'pull' plants around the perimeter of plots has little effect, but reducing the proportion of marigolds and introducing other non-hosts of whiteflies (basil, nasturtium and Chinese cabbage) also reduces whitefly populations on tomato. The second experiment assesses the efficacy of marigolds when used as an 'emergency' measure. Here we allow whitefly populations to build to a high density on unprotected tomatoes then introduce marigolds and assess whitefly population over a further period. Following laboratory work showing limonene to be a major chemical component of French marigolds and a negative behaviour response of whiteflies to this compound, limonene dispensers are added as an additional treatment to this experiment. "Emergency" marigold companion planting yielded minimal reductions in whitefly performance, but the use of limonene dispensers was more effective. Our work indicates that companion planting short vine tomatoes with French marigolds throughout the growing season will slow development of whitefly populations. Introducing marigolds to unprotected tomatoes after significant whitefly build-up will be less effective. The use of limonene dispensers placed near to tomato plants also shows promise. It is argued that this work supports the possibility of the development of a mixture of tomato companion plants that infer 'associational resistance' against many major invertebrate pests of tomato. Such a mixture, if comprising edible or ornamental plants, would be economically viable, would reduce the need for additional chemical and biological control, and, if used outdoors, would generate plant-diverse agro-ecosystems that are better able to harbour invertebrate wildlife.


Assuntos
Asteraceae/metabolismo , Agentes de Controle Biológico/metabolismo , Hemípteros/efeitos dos fármacos , Limoneno/metabolismo , Lycopersicon esculentum/parasitologia , Animais , Asteraceae/crescimento & desenvolvimento , Agentes de Controle Biológico/farmacologia , Produção Agrícola/métodos , Hemípteros/patogenicidade , Limoneno/farmacologia , Lycopersicon esculentum/crescimento & desenvolvimento
20.
Plant Cell Physiol ; 60(5): 1011-1024, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30715458

RESUMO

Western flower thrips (WFT) are a major pest on many crops, including tomato. Thrips cause yield losses, not only through feeding damage, but also by the transmission of viruses of which the Tomato Spotted Wilt Virus is the most important one. In cultivated tomato, genetic diversity is extremely low, and all commercial lines are susceptible to WFT. Several wild relatives are WFT resistant and these resistances are based on glandular trichome-derived traits. Introgression of these traits in cultivated lines did not lead to WFT resistant commercial varieties so far. In this study, we investigated WFT resistance in cultivated tomato using a F2 population derived from a cross between a WFT susceptible and a WFT resistant cultivated tomato line. We discovered that this WFT resistance is independent of glandular trichome density or trichome-derived volatile profiles and is associated with three QTLs on chromosomes 4, 5 and 10. Foliar metabolic profiles of F3 families with low and high WFT feeding damage were clearly different. We identified α-tomatine and a phenolic compound as potential defensive compounds. Their causality and interaction need further investigation. Because this study is based on cultivated tomato lines, our findings can directly be used in nowadays breeding programs.


Assuntos
Flores/metabolismo , Flores/parasitologia , Lycopersicon esculentum/metabolismo , Lycopersicon esculentum/parasitologia , Tisanópteros/patogenicidade , Tricomas/metabolismo , Animais , Flores/genética , Lycopersicon esculentum/genética , Locos de Características Quantitativas/genética , Tricomas/genética
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