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1.
Int J Mol Sci ; 22(19)2021 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-34638623

RESUMO

How herbivorous insects adapt to host plants is a key question in ecological and evolutionary biology. The fall armyworm, (FAW) Spodoptera frugiperda (J.E. Smith), although polyphagous and a major pest on various crops, has been reported to have a rice and corn (maize) feeding strain in its native range in the Americas. The species is highly invasive and has recently established in China. We compared behavioral changes in larvae and adults of a corn population (Corn) when selected on rice (Rice) and the molecular basis of these adaptational changes in midgut and antennae based on a comparative transcriptome analysis. Larvae of S. frugiperda reared on rice plants continuously for 20 generations exhibited strong feeding preference for with higher larval performance and pupal weight on rice than on maize plants. Similarly, females from the rice selected population laid significantly more eggs on rice as compared to females from maize population. The most highly expressed DEGs were shown in the midgut of Rice vs. Corn. A total of 6430 DEGs were identified between the populations mostly in genes related to digestion and detoxification. These results suggest that potential adaptations for feeding on rice crops, may contribute to the current rapid spread of fall armyworm on rice crops in China and potentially elsewhere. Consistently, highly expressed DEGs were also shown in antennae; a total of 5125 differentially expressed genes (DEGs) s were identified related to the expansions of major chemosensory genes family in Rice compared to the Corn feeding population. These results not only provide valuable insight into the molecular mechanisms in host plants adaptation of S. frugiperda but may provide new gene targets for the management of this pest.


Assuntos
Spodoptera/genética , Spodoptera/fisiologia , Adaptação Fisiológica/genética , Animais , China , Produtos Agrícolas/parasitologia , Fenômenos Fisiológicos do Sistema Digestório , Comportamento Alimentar/fisiologia , Feminino , Ontologia Genética , Genes de Insetos , Herbivoria/genética , Herbivoria/fisiologia , Adaptação ao Hospedeiro/genética , Adaptação ao Hospedeiro/fisiologia , Especificidade de Hospedeiro/genética , Especificidade de Hospedeiro/fisiologia , Interações Hospedeiro-Parasita/genética , Interações Hospedeiro-Parasita/fisiologia , Larva/fisiologia , Masculino , Oryza/parasitologia , Oviposição/fisiologia , Spodoptera/patogenicidade , Transcriptoma , Zea mays/parasitologia
2.
PLoS One ; 16(10): e0258235, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34679089

RESUMO

Carnivorous plants feed on animal prey, mainly insects, to get additional nutrients. This carnivorous syndrome is widely investigated and reported. In contrast, reports on herbivores feeding on carnivorous plants and related defenses of the plants under attack are rare. Here, we studied the interaction of a pitcher plant, Nepenthes x ventrata, with a generalist lepidopteran herbivore, Spodoptera littoralis, using a combination of LC/MS-based chemical analytics, choice and feeding assays. Chemical defenses in N. x ventrata leaves were analyzed upon S. littoralis feeding. A naphthoquinone, plumbagin, was identified in Nepenthes defense against herbivores and as the compound mainly responsible for the finding that S. littoralis larvae gained almost no weight when feeding on Nepenthes leaves. Plumbagin is constitutively present but further 3-fold increased upon long-term (> 1 day) feeding. Moreover, in parallel de novo induced trypsin protease inhibitor (TI) activity was identified. In contrast to TI activity, enhanced plumbagin levels were not phytohormone inducible, not even by defense-related jasmonates although upon herbivory their level increased more than 50-fold in the case of the bioactive jasmonic acid-isoleucine. We conclude that Nepenthes is efficiently protected against insect herbivores by naphthoquinones acting as phytoanticipins, which is supported by additional inducible defenses. The regulation of these defenses remains to be investigated.


Assuntos
Planta Carnívora/fisiologia , Herbivoria/fisiologia , Naftoquinonas/farmacologia , Compostos Fitoquímicos/farmacologia , Sarraceniaceae/fisiologia , Ácido Abscísico/farmacologia , Animais , Planta Carnívora/efeitos dos fármacos , Ciclopentanos/farmacologia , Dieta , Herbivoria/efeitos dos fármacos , Larva/efeitos dos fármacos , Larva/crescimento & desenvolvimento , Oxilipinas/farmacologia , Reguladores de Crescimento de Plantas/análise , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/fisiologia , Inibidores de Proteases/farmacologia , Ácido Salicílico/farmacologia , Sarraceniaceae/efeitos dos fármacos , Spodoptera/efeitos dos fármacos , Spodoptera/fisiologia
3.
J Insect Sci ; 21(5)2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34581410

RESUMO

RNAi is an effective tool for gene function analysis and a promising strategy to provide environmentally friendly control approaches for pathogens and pests. Recent studies support the utility of bacterium-mediated RNAi as a cost-effective method for gene function study and a suitable externally applied delivery mechanism for pest control. Here, we developed a bacterium-mediated RNAi system in Spodoptera frugiperda based on four target genes, specifically, Chitinase (Sf-CHI), Chitin synthase B (Sf-CHSB), Sugar transporter SWEET1 (Sf-ST), and Hemolin (Sf-HEM). RNAi conducted by feeding larvae with bacteria expressing dsRNAs of target genes or injecting pupae and adults with bacterially synthesized dsRNA induced silencing of target genes and resulted in significant negative effects on growth and survival of S. frugiperda. However, RNAi efficiency and effects were variable among different target genes and dsRNA delivery methods. Injection of pupae with dsCHI and dsCHSB induced a significant increase in wing malformation in adults, suggesting that precise regulation of chitin digestion and synthesis is crucial during wing formation. Injection of female moths with dsHEM resulted in lower mating, fecundity, and egg hatching, signifying a critical role of Sf-HEM in the process of egg production and/or embryo development. Our collective results demonstrate that bacterium-mediated RNAi presents an alternative technique for gene function study in S. frugiperda and a potentially effective strategy for control of this pest, and that Sf-CHI, Sf-CHSB, Sf-ST, and Sf-HEM encoding genes can be potent targets.


Assuntos
Interferência de RNA , RNA de Cadeia Dupla/farmacologia , Spodoptera , Animais , Bactérias/genética , Quitinases/efeitos dos fármacos , Quitinases/genética , Fertilidade/efeitos dos fármacos , Genes de Insetos/efeitos dos fármacos , Imunoglobulinas/efeitos dos fármacos , Imunoglobulinas/genética , Proteínas de Insetos/efeitos dos fármacos , Proteínas de Insetos/genética , Larva/efeitos dos fármacos , Larva/genética , Larva/fisiologia , Controle Biológico de Vetores , Pupa/efeitos dos fármacos , Pupa/genética , Pupa/fisiologia , Reprodução/efeitos dos fármacos , Spodoptera/efeitos dos fármacos , Spodoptera/genética , Spodoptera/fisiologia
4.
J Chem Ecol ; 47(8-9): 799-809, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34347233

RESUMO

Fall armyworm (Spodoptera frugiperda) is a major global pest of many crops, including maize (Zea mays). This insect is known to use host plant-derived volatile organic compounds to locate suitable hosts during both its adult and larval stages, yet the function of individual compounds remains mostly enigmatic. In this study, we use a combination of volatile profiling, electrophysiological assays, pair-wise choice behavioral assays, and chemical supplementation treatments to identify and assess specific compounds from maize that influence S. frugiperda host location. Our findings reveal that methyl salicylate and (E)-alpha-bergamotene are oviposition attractants for adult moths but do not impact larval behavior. While geranyl acetate can act as an oviposition attractant or repellent depending on the host volatile context and (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) is an oviposition deterrent. These compounds can also be attractive to the larvae when applied to specific maize inbreds. These data show that S. frugiperda uses different plant volatile cues for host location in its adult and larval stage and that the background volatile context that specific volatiles are perceived in, alters their impact as behavioral cues.


Assuntos
Herbivoria/efeitos dos fármacos , Oviposição/efeitos dos fármacos , Spodoptera/fisiologia , Compostos Orgânicos Voláteis/farmacologia , Zea mays/química , Animais , Compostos Bicíclicos com Pontes/isolamento & purificação , Compostos Bicíclicos com Pontes/farmacologia , Cromatografia Gasosa-Espectrometria de Massas , Larva/fisiologia , Folhas de Planta/química , Folhas de Planta/metabolismo , Análise de Componente Principal , Salicilatos/isolamento & purificação , Salicilatos/farmacologia , Spodoptera/crescimento & desenvolvimento , Terpenos/isolamento & purificação , Terpenos/farmacologia , Compostos Orgânicos Voláteis/química , Zea mays/metabolismo
5.
Sci Rep ; 11(1): 15885, 2021 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-34354173

RESUMO

Given the new spread and potential damage of the fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) in Asia, it has become imperative to understand the development biology of this invasive species on selected vegetable crops in newer geographical regions. In this study, we investigated the ovipositional preference of FAW females on different host plants, under choice- and non-choice tests. In addition, using the age-stage, two-sex life table theory, we assessed the performance of immature FAW individuals fed and reared on selected vegetable crops to get information related to development time, survival, reproduction and longevity. Fall armyworm females had an oviposition preference on maize compared to other vegetable crops, including cabbage and soybean, and reluctance for tomato, which was confirmed during the choice and non-choice tests. In contrast to the oviposition preference, our results also suggest that despite low preference for cabbage, soybean, and tomato, these crops seemed to provide a high benefit for an appropriate offspring performance, exceeding in some cases the benefits from a maize-based diet. Information from this study was discussed in terms of FAW ecology and how female's decision affects their reproductive fitness, and the survival and performance of its offspring.


Assuntos
Oviposição/fisiologia , Spodoptera/crescimento & desenvolvimento , Spodoptera/metabolismo , Animais , Produtos Agrícolas , Larva/crescimento & desenvolvimento , Reprodução/fisiologia , Estações do Ano , Spodoptera/fisiologia , Taiwan , Verduras , Zea mays
6.
Sci Rep ; 11(1): 14484, 2021 07 14.
Artigo em Inglês | MEDLINE | ID: mdl-34262071

RESUMO

The agricultural use of silica (SiO2) nanoparticles (NPs) has the potential to control insect pests while the safety and tritrophic effects on plants and beneficial natural enemies remains unknown. Here, we evaluate the effects of silica NPs on insect pests with different feeding niches, natural enemies, and a plant. Silica NPs were applied at different concentrations (75-425 mg/L) on field-cultivated faba bean and soybean for two growing seasons. The faba bean pests, the cowpea aphid Aphis craccivora and the American serpentine leafminer Liriomyza trifolii, and the soybean pest, the cotton leafworm Spodoptera littoralis, were monitored along with their associated predators. Additional laboratory experiments were performed to test the effects of silica NPs on the growth of faba bean seedlings and to determine whether the rove beetle Paederus fuscipes is attracted to cotton leafworm-infested soybean treated with silica NPs. In the field experiments, silica NPs reduced the populations of all three insect pests and their associated predators, including rove beetles, as the concentration of silica NPs increased. In soybean fields, however, the total number of predators initially increased after applying the lowest concentration. An olfactometer-based choice test found that rove beetles were more likely to move towards an herbivore-infested plant treated with silica NPs than to a water-treated control, suggesting that silica NPs enhance the attraction of natural enemies via herbivore-induced plant volatiles. In the laboratory, while silica NPs inhibited the development of faba bean roots at 400 mg/L, they did not affect germination percentage, germination time, shoot length, or vigor index compared to the control.


Assuntos
Insetos/efeitos dos fármacos , Insetos/fisiologia , Inseticidas/farmacologia , Nanopartículas , Animais , Afídeos/efeitos dos fármacos , Afídeos/fisiologia , Besouros/efeitos dos fármacos , Besouros/fisiologia , Relação Dose-Resposta a Droga , Egito , Germinação/efeitos dos fármacos , Inseticidas/química , Nanopartículas/química , Densidade Demográfica , Comportamento Predatório/efeitos dos fármacos , Dióxido de Silício , Soja , Spodoptera/efeitos dos fármacos , Spodoptera/fisiologia , Vicia faba/efeitos dos fármacos , Vicia faba/crescimento & desenvolvimento
7.
PLoS One ; 16(7): e0254328, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34252127

RESUMO

Fall armyworm (FAW; Spodoptera frugiperda), an exotic moth which recently invaded Africa, is a highly destructive pest of cereals especially maize a highly valued staple crop in Nigeria. The use of natural enemies such as predators or parasitoids for FAW control is more economically viable and environmentally safer than currently recommended synthetic insecticides. Natural enemies to combat the pest have not yet been reported in Nigeria. An exploration for the pests' natural enemies was undertaken by collecting FAW eggs and larvae from maize fields. These were reared in the laboratory for emergence, identification and efficacy as natural enemies. This yielded Euplectrus laphygmae (Hymenoptera: Eulophidae); Telenomus remus (Hymenoptera: Platygastridae) and Trombidium sp. (Acari.: Trombidiidae). Cotesia or Apanteles spp. were inferred to occur since Stictopisthus sp. (Hym.: Ichneumonidae), a secondary parasitoid, that attacks cocoons of Microgasterinae (e.g. Cotesia, Apanteles etc.) also emerged. Species of yet-to-be identified predators were also observed in various niches of maize plants. A positive relationship was found between FAW instar and the number of E. laphygmae eggs/instar ranging, on average, from 1.5 on second instar to 5.5 on fourth instars hosts. Parasitism rate of T. remus on FAW eggs was 100%. Parasitic mite infestation resulted in increasing paleness, reduced feeding, growth and movement as well as death of FAW 1st instars. Thus, the occurrence of FAW natural enemies in Nigeria calls for advocacy campaign to incorporate their use into integrated pest management strategies that attract and allow natural enemies to thrive for FAW management.


Assuntos
Spodoptera/fisiologia , Animais , Fazendas , Larva/fisiologia , Funções Verossimilhança , Nigéria , Óvulo/fisiologia , Parasitos/fisiologia , Filogenia , Comportamento Predatório/fisiologia , Zea mays/parasitologia
8.
J Chem Ecol ; 47(8-9): 768-776, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34185213

RESUMO

In natural and agricultural ecosystems, plants are often simultaneously or sequentially exposed to combinations of stressors. Here we tested whether limited water availability (LWA) affects plant response to insect herbivory using two populations of Eruca sativa from desert and Mediterranean habitats that differ in their induced defenses. Considering that such differences evolved as responses to biotic and possibly abiotic stress factors, the two populations offered an opportunity to study ecological aspects in plant response to combined stresses. Analysis of chemical defense mechanisms showed that LWA significantly induced total glucosinolate concentrations in the Mediterranean plants, but their concentrations were reduced in the desert plants. However, LWA, with and without subsequent jasmonate elicitation, significantly induced the expression of proteinase inhibitor in the desert plants. Results of a no-choice feeding experiment showed that LWA significantly increased desert plant resistance to Spodoptera littoralis larvae, whereas it did not affect the relatively strong basal resistance of the Mediterranean plants. LWA and subsequent jasmonate elicitation increased resistance against the generalist insect in Mediterranean plants, possibly due to both increased proteinase inhibitor expression and glucosinolate accumulation. The effect of LWA on the expression of genes involved in phytohormone signaling, abscisic acid (ABA-1) and jasmonic acid (AOC1), and the jasmonate responsive PDF1.2, suggested the involvement of abscisic acid in the regulation of defense mechanisms in the two populations. Our results indicate that specific genotypic responses should be considered when estimating general patterns in plant response to herbivory under water deficiency conditions.


Assuntos
Brassicaceae/metabolismo , Ecossistema , Spodoptera/fisiologia , Água/química , Ácido Abscísico/metabolismo , Animais , Brassicaceae/química , Ciclopentanos/metabolismo , Defensinas/genética , Defensinas/metabolismo , Clima Desértico , Inibidores Enzimáticos/metabolismo , Expressão Gênica/efeitos dos fármacos , Glucosinolatos/análise , Glucosinolatos/metabolismo , Glucosinolatos/farmacologia , Herbivoria/efeitos dos fármacos , Larva/crescimento & desenvolvimento , Larva/fisiologia , Região do Mediterrâneo , Oxilipinas/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Spodoptera/crescimento & desenvolvimento , Estresse Fisiológico , Água/metabolismo
9.
PLoS One ; 16(6): e0249042, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34115755

RESUMO

Fall armyworm, Spodoptera frugiperda (J. E. Smith) has rapidly spread in sub-Saharan Africa (SSA) and has emerged as a major pest of maize and sorghum in the continent. For effective monitoring and a better understanding of the bioecology and management of this pest, a Community-based Fall Armyworm Monitoring, Forecasting, Early Warning and Management (CBFAMFEW) initiative was implemented in six eastern African countries (Ethiopia, Kenya, Tanzania, Uganda, Rwanda and Burundi). Over 650 Community Focal Persons (CFPs) who received training through the project were involved in data collection on adult moths, crop phenology, cropping systems, FAW management practices and other variables. Data collection was performed using Fall Armyworm Monitoring and Early Warning System (FAMEWS), a mobile application developed by the Food and Agricultural Organization (FAO) of the United Nations. Data collected from the CBFAMFEW initiative in East Africa and other FAW monitoring efforts in Africa were merged and analysed to determine the factors that are related to FAW population dynamics. We used the negative binomial models to test for effect of main crops type, cropping systems and crop phenology on abundance of FAW. We also analysed the effect of rainfall and the spatial and temporal distribution of FAW populations. The study showed variability across the region in terms of the proportion of main crops, cropping systems, diversity of crops used in rotation, and control methods that impact on trap and larval counts. Intercropping and crop rotation had incident rate 2-times and 3-times higher relative to seasonal cropping, respectively. The abundance of FAW adult and larval infestation significantly varied with crop phenology, with infestation being high at the vegetative and reproductive stages of the crop, and low at maturity stage. This study provides an understanding on FAW bioecology, which could be vital in guiding the deployment of FAW-IPM tools in specific locations and at a specific crop developmental stage. The outcomes demonstrate the relevance of community-based crop pest monitoring for awareness creation among smallholder farmers in SSA.


Assuntos
Estações do Ano , Spodoptera/fisiologia , África , Animais , Larva , Zea mays
10.
J Chem Ecol ; 47(7): 707-718, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34125370

RESUMO

Flooding is a major plant abiotic stress factor that is frequently experienced by plants simultaneously with other biotic stresses, including herbivory. How plant volatile emissions, which mediate interactions with a wide range of organisms, are influenced by flooding and by multiple co-occurring stress factors remains largely unexplored. Using Spodoptera frugiperda (Lepidoptera: Noctuidae) (fall armyworm) as the insect pest and two maize (Zea mays, L. Poaceae) hybrids differentially marketed for conventional and organic production, we assessed the effects of flooding, herbivory, and both stress factors on the composition of blends of emitted volatiles. Headspace volatiles were collected from all treatment combinations seven days after flooding. We documented metrics indicative of biomass allocation to determine the effects of individual and combined stressors on plant growth. We also evaluated relationships between volatile emissions and indicators of soil chemical characteristics as influenced by treatment factors. Flooding and herbivory induced the emission of volatile organic compounds (VOCs) in similar ways on both maize hybrids, but the interaction of both stress factors produced significantly larger quantities of emitted volatiles. Thirty-eight volatile compounds were identified, including green leaf volatiles, monoterpenes, an aldehyde, a benzoate ester, sesquiterpenes, a diterpene alcohol, and alkane hydrocarbons. The hybrid marketed for organic production was a stronger VOC emitter. As expected, plant biomass was detrimentally affected by flooding. Soil chemical properties were less responsive to the treatment factors. Taken together, the results suggest that flooding stress and the interactions of flooding and insect attack can shape the emission of plant volatiles and further influence insect-plant interactions.


Assuntos
Inundações , Spodoptera/fisiologia , Compostos Orgânicos Voláteis/química , Zea mays/química , Animais , Quimera , Cromatografia Gasosa-Espectrometria de Massas , Herbivoria , Larva/fisiologia , Folhas de Planta/química , Folhas de Planta/metabolismo , Solo/química , Spodoptera/crescimento & desenvolvimento , Compostos Orgânicos Voláteis/análise , Zea mays/metabolismo
11.
J Insect Physiol ; 132: 104248, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33945808

RESUMO

Since 2016, the fall armyworm (FAW, Spodoptera frugiperda) has invaded large parts of Africa and Asia, impacting millions of hectares of maize crops and thereby posing a major threat to food security. The rapid geographic spread and outbreak dynamics of S. frugiperda are tied to its unique dispersal ability and long-distance migration capability. Yet, up till present, limited research has been conducted on the physiological determinants of S. frugiperda flight and migration. In this study, we used laboratory experiments to assess whether mating and oviposition affect S. frugiperda flight ability and wingbeat frequency. During 2019-2020, migratory FAW females were trapped in Yunnan (China) and dissected to assess ovarian development. Tethered flight assays showed that gravid S. frugiperda females exhibited strong flight ability at 1-3 days following the onset of oviposition. Flight distance and duration negatively correlated with the number of deposited eggs. Ovarian dissections further showed that over 50% of migrant females were mated and 46-54% had initiated oviposition. Our study shows the complex, yet nuanced effects of reproductive status on flight capacity, with possibly a facultative trade-off between flight and reproduction. These novel insights into S. frugiperda physiology and migration behavior can guide future monitoring and integrated pest management (IPM) programs against this newly-invasive pest in China and abroad.


Assuntos
Voo Animal/fisiologia , Reprodução/fisiologia , Spodoptera/fisiologia , Distribuição Animal/fisiologia , Animais , Feminino , Oviposição , Controle de Pragas
13.
J Chem Ecol ; 47(7): 689-706, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34056671

RESUMO

A large percentage of crop loss is due to insect damage, especially caterpillar damage. Plant chitinases are considered excellent candidates to combat these insects since they can degrade chitin in peritrophic matrix (PM), an important protective structure in caterpillar midgut. Compared to chemical insecticides, chitinases could improve host plant resistance and be both economically and environmentally advantageous. The focus of this research was to find chitinase candidates that could improve plant resistance by effectively limiting caterpillar damage. Five classes of endochitinase (I-V) genes were characterized in the maize genome, and we isolated and cloned four chitinase genes (chitinase A, chitinase B, chitinase I, and PRm3) present in two maize (Zea mays L.) inbred lines Mp708 and Tx601, with different levels of resistance to caterpillar pests. We also investigated the expression of these maize chitinases in response to fall armyworm (Spodoptera frugiperda, FAW) attack. The results indicated that both chitinase transcript abundance and enzymatic activity increased in response to FAW feeding and mechanical wounding. Furthermore, chitinases retained activity inside the caterpillar midgut and enzymatic activity was detected in the food bolus and frass. When examined under scanning electron microscopy, PMs from Tx601-fed caterpillars showed structural damage when compared to diet controls. Analysis of chitinase transcript abundance after caterpillar feeding and proteomic analysis of maize leaf trichomes in the two inbreds implicated chitinase PRm3 found in Tx601 as a potential insecticidal protein.


Assuntos
Quitinases/farmacologia , Proteínas de Plantas/farmacologia , Spodoptera/efeitos dos fármacos , Zea mays/metabolismo , Sequência de Aminoácidos , Animais , Quitinases/classificação , Quitinases/genética , Quitinases/metabolismo , Clonagem Molecular , DNA de Plantas/química , DNA de Plantas/genética , DNA de Plantas/metabolismo , Regulação da Expressão Gênica de Plantas , Herbivoria/efeitos dos fármacos , Larva/efeitos dos fármacos , Larva/fisiologia , Filogenia , Folhas de Planta/metabolismo , Proteínas de Plantas/classificação , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Análise de Sequência de DNA , Spodoptera/crescimento & desenvolvimento , Spodoptera/fisiologia
14.
Appl Environ Microbiol ; 87(13): e0283120, 2021 06 11.
Artigo em Inglês | MEDLINE | ID: mdl-33893115

RESUMO

Rhizobacteria in the genus Pseudomonas can enhance plant resistance to a range of pathogens and herbivores. However, resistance to these different classes of plant antagonists is mediated by different molecular mechanisms, and the extent to which induced systemic resistance by Pseudomonas can simultaneously protect plants against both pathogens and herbivores remains unclear. We screened 12 root-colonizing Pseudomonas strains to assess their ability to induce resistance in Arabidopsis thaliana against a foliar pathogen (Pseudomonas syringae DC3000) and a chewing herbivore (Spodoptera littoralis). None of our 12 strains increased plant resistance against herbivory; however, four strains enhanced pathogen resistance, and one of these (Pseudomonas strain P97-38) also made plants more susceptible to herbivory. Phytohormone analyses revealed stronger salicylic acid induction in plants colonized by P97-38 (versus controls) following subsequent pathogen infection but weaker induction of jasmonic acid (JA)-mediated defenses following herbivory. We found no effects of P97-38 inoculation on herbivore-relevant nutrients such as sugars and protein, suggesting that the observed enhancement of susceptibility to S. littoralis is due to effects on plant defense chemistry rather than nutrition. These findings suggest that Pseudomonas strains that enhance plant resistance to pathogens may have neutral or negative effects on resistance to herbivores and provide insight into potential mechanisms associated with effects on different classes of plant antagonists. Improved understanding of these effects has potentially important implications for the use of rhizobacteria inoculation in agriculture. IMPORTANCE Plant-associated microbes have significant potential to enhance agricultural production, for example, by enhancing plant resistance to pathogens and pests. Efforts to identify beneficial microbial strains typically focus on a narrow range of desirable plant traits; however, microbial symbionts can have complex effects on plant phenotypes, including susceptibility and resistance to different classes of plant antagonists. We examined the effects of 12 strains of Pseudomonas rhizobacteria on plant (Arabidopsis) resistance to a lepidopteran herbivore and a foliar pathogen. None of our strains increased plant resistance against herbivory; however, four strains enhanced pathogen resistance, and one of these made plants more susceptible to herbivory (likely via effects on plant defense chemistry). These findings indicate that microbial strains that enhance plant resistance to pathogens can have neutral or negative effects on resistance to herbivores, highlighting potential pitfalls in the application of beneficial rhizobacteria as biocontrol agents.


Assuntos
Arabidopsis/microbiologia , Resistência à Doença , Interações Hospedeiro-Patógeno , Defesa das Plantas contra Herbivoria , Raízes de Plantas/microbiologia , Pseudomonas/fisiologia , Spodoptera/fisiologia , Animais , Fluorescência , Doenças das Plantas/microbiologia
15.
Neotrop Entomol ; 50(2): 208-217, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33656657

RESUMO

The development, survival, and reproduction of ectothermic organisms such as insects are strongly influenced by temperature. Because insects respond to temperature by accelerating or reducing their development rate, population growth is directly associated with temperature variations. Here, daily minimum and maximum temperatures and degree-day model approaches were used to estimate the number generation per year (voltinism) of Mythimna sequax Franclemont, Neoleucinodes elegantalis (Guenée), Spodoptera cosmioides (Walker), and Spodoptera eridania (Cramer) over a 34-year period in southern Brazil. Additionally, we assessed the effects of El Niño Southern Oscillation (ENSO) events on voltinism. While an increased number of generations were estimated in warmer regions, comprising mainly northwestern Paraná, fewer generations were estimated in the colder regions of Santa Catarina and Rio Grande do Sul. For all species, the location was the factor that explained most of the variation observed in voltinism (average of 76.9%). Inter-annual changes in voltinism also varied depending on location, and differences of up to five generations among years were obtained in colder regions. On the other hand, ENSO events had a minor influence on the species voltinism. Our findings provide an important contribution to the understanding of spatio-temporal variations in voltinism of insects, and how temperature changes may increase their population growth.


Assuntos
Mariposas , Temperatura , Animais , Brasil , Fertilidade , Mariposas/fisiologia , Reprodução , Análise Espaço-Temporal , Spodoptera/fisiologia
16.
Fungal Genet Biol ; 150: 103508, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33675988

RESUMO

The pathogenicity of Metarhizium rileyi is a multi-faceted process that depends on many factors. This study attempts to decipher those factors of M. rileyi by investigating its pathogenicity against Spodoptera litura (Lepidoptera: Noctuidae) larvae. Through morphogenesis analysis, we for the first time demonstrated the infection structure, appressorium, of M. rileyi that can generate a more than 4 MPa turgor pressure. The Mrpmk1 gene was found to be essential for appressorium differentiation and mycelium reemerging, ΔMrpmk1 mutant exhibited no pathogenicity towards S. litura by natural infection process. Delayed appressorium formation time, decreased appressorium formation rate and turgor pressure of ΔMrpbs2 mutant manifested itself in postponed death time and lower mortality against S. litura. Following invasion into the larval hemocoel, M. rileyi cells transformed into blastospores, which may be conducive to dispersal and propagation, moreover, the blastospore form M. rileyi may subverted phagocytic defenses. Then M. rileyi cells morphed into extended hyphal body to cope with elongated hemocytes that participated in encapsulation. In the end, M. rileyi mycelia reemerged from the larval cadaver evenly to form muscardine cadaver. Eventually, conidia were produced to complete the infection cycle. During the infection, M. rileyi triggered both cellular and humoral immunity of S. litura. Besides morphological changes, stage-specifically produced oxalic acid and F-actin arrangement may play roles in nutrient acquisition and mycelium reemerging, respectively.


Assuntos
Proliferação de Células , Hemolinfa/microbiologia , Larva/imunologia , Larva/fisiologia , Metarhizium/patogenicidade , Micélio/crescimento & desenvolvimento , Spodoptera/fisiologia , Animais , Imunidade Celular , Imunidade Humoral , Metarhizium/genética , Metarhizium/crescimento & desenvolvimento , Spodoptera/imunologia , Virulência
17.
Ecotoxicol Environ Saf ; 213: 112076, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33639562

RESUMO

We executed a pot experiment to examine the differences of absorption, chemical forms, subcellular distribution, and toxicity of Cd between two cultivars of Chinese flowering cabbage Brassica campestris [Lvbao701 (low-Cd cultivar) and Chicaixin No.4 (high-Cd cultivar)]. Compared to Chicaixin No.4, the presence of Lvbao701 enhanced the proportion of insoluble Cd forms in soil, Lvbao701 roots and leaves had higher proportion of Cd converted into insoluble phosphate precipitates and pectate-or protein-bound forms and lower proportion of inorganic Cd, which result in low accumulation and toxicity of Cd to Lvbao701 and cutworm Spodoptera litura fed on Lvbao701 leaves. Instead of total Cd, Cd transfer and toxicity in B. campestris-S. litura system depend on chemical Cd forms in soil and cabbages and subcellular Cd distributions in cabbages and insects, and the proportions of them were not the highest among all chemical forms and subcellular distributions of Cd. Although exchangeable Cd was major Cd chemical form in cabbage planted soil, Cd bound to iron and manganese oxides and to organic matter were significantly correlated with growth indices and photosynthesis parameters of cabbages. Despite major part of Cd was precipitated in cell wall of roots, Cd in organelle fraction was closely associated with the fitness of cabbages. Metal-rich granules, not cytosolic fraction (the major subcellular Cd distribution), affected the food utilization of S. litura. Therefore, cabbage cultivars significantly affected Cd transfer and toxicity in B. campestris-S. litura system, and the use of Lvbao701 in Cd polluted soil could reduce potential risks for Cd entering food chains.


Assuntos
Brassica/fisiologia , Cádmio/toxicidade , Poluentes do Solo/toxicidade , Animais , Brassica/metabolismo , Cádmio/metabolismo , China , Cadeia Alimentar , Larva/metabolismo , Raízes de Plantas/metabolismo , Reprodução , Solo , Poluentes do Solo/análise , Poluentes do Solo/metabolismo , Spodoptera/crescimento & desenvolvimento , Spodoptera/fisiologia
18.
Sci Rep ; 11(1): 1268, 2021 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-33446737

RESUMO

Higher volumes of conventional and novel chemical insecticides are applied by farmers to control resistant strains of armyworm (Spodoperta litura) in Pakistan without knowing their risks to the environment and to public health. Ten reduced-risk insecticides were tested for their compatibility with two entomopathogenic nematodes (EPNs); Heterorhabditis indica and Steinernema carpocapsae against S. litura. The insecticide emamectin benzoate was highly toxic (LC50 = 2.97 mg/l) against 3rd instar S. litura larvae when applied alone whereas, novaluron and methoxyfenozide were the least toxic (LC50 = 29.56 mg/l and 21.06 mg/l), respectively. All the insecticides proved harmless against the two EPNs even 96 h after treatment. Indoxacarb, flubendiamide and spinetoram produced the greatest mortalities (72-76%) of S. litura larvae after 72 h when applied in mixtures with H. indica. Lowest mortalities (44.00 ± 3.74% and 48.00 ± 2.89) were observed for mixtures of H. indica with methoxyfenozide and chlorfenapyr, respectively. The positive control treatments with both EPNs (S. carpocapsae and H. indica) produced > 50% mortality 96 h after treatment. For insecticide mixtures with S. carpocapsae, only indoxacarb produced 90% mortality of larvae, whereas, indoxacarb, flubendiamide, emamectin benzoate, and spinetoram produced 90-92% mortality of larvae when applied in mixtures with H. indica. Additive interactions (Chi-square < 3.84) of EPN mixtures with reduced volumes of reduced-risk insecticides suggest opportunities to develop more environmentally favorable pest management programs for S. litura.


Assuntos
Inseticidas/toxicidade , Nematoides/efeitos dos fármacos , Spodoptera/efeitos dos fármacos , Animais , Desinfetantes/toxicidade , Nematoides/fisiologia , Controle de Pragas , Spodoptera/fisiologia , Testes de Toxicidade
19.
Sci Rep ; 11(1): 1401, 2021 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-33446680

RESUMO

Stemborers (Busseola fusca, Sesamia calamistis and Chilo partellus), the fall armyworm (Spodoptera frugiperda) and associated parasitoids constitute an interacting system in maize fields in Kenya. This work aims at developing and evaluating models that represent the evolution of those interactions by applying system thinking and system dynamics approaches with its archetypes [causal loop diagram (CLD), reinforcing (R) and balancing (B)] to analyse the population of these multi-species systems. The software Vensim PLE 8.0.9 was used to implement the models and carry out the simulations of single- and multi-species systems. The results showed that when a single pest species with its associated parasitoids interact with the host plant, the species was able to establish and sustain by cyclical relationship between populations of the pest and the associated parasitoids. However, in multi- pest species systems, dominance of S. frugiperda and C. partellus over B. fusca and S. calamistis was observed, but without extinction. However, there was a likelihood for B. fusca being displaced by C. partellus. Overall, the models predict the co-existence of fall armyworm with stemborer species as an additional pest of maize in Africa that need to be considered henceforth in designing IPM strategies in maize.


Assuntos
Produtos Agrícolas/parasitologia , Interações Hospedeiro-Parasita/fisiologia , Modelos Biológicos , Controle Biológico de Vetores , Spodoptera/fisiologia , Vespas/fisiologia , Animais
20.
Ecotoxicol Environ Saf ; 208: 111581, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33396104

RESUMO

Lead (Pb) stress affects hormone-mediated responses (e.g., reproduction) in insects. In this study, the effects of Pb stress (12.5-50 mg Pb/kg in larval artificial diets) on the reproduction of the common cutworm Spodoptera litura (Lepidoptera: Noctuidae) were investigated after 7 generations. The results showed that Pb stress did not reduce the longevity of adult females, but 50 mg Pb/kg significantly reduced the longevity of adult males, regardless of the generation. After 50 mg Pb/kg stress for one or 7 generations, the peak time of egg-laying was delayed, and egg production and hatchability were decreased significantly. The vitellin content in eggs was significantly inhibited by Pb stress. The S. litura vitellogenin (Vg) gene promoter was cloned and analyzed. Multiple putative transcription factors were predicted for the 2321 bp Vg promoter region, including the TATA box, GATA, basic helix-loop-helix (bHLH) transcription factor, Broad-Complex (BR-C) binding sites, etc. The fragment from -2222 to -211 bp of the Vg promoter was the activation domain for Vg, whereas the region from -211 to -55 bp repressed the activity of the Vg promoter. The construct promoter (-782/+76) in Trichoplusia ni (Hi5) cells significantly improved Vg expression, which was not affected by Pb stress (1 or 10 mg/ml). Therefore, Pb stress significantly inhibited the reproduction of S. litura but not by regulating the Vg promoter.


Assuntos
Poluentes Ambientais/toxicidade , Chumbo/toxicidade , Spodoptera/fisiologia , Vitelogeninas/genética , Animais , Dieta , Poluentes Ambientais/metabolismo , Feminino , Larva/efeitos dos fármacos , Chumbo/metabolismo , Longevidade , Masculino , Mariposas , Oviposição/efeitos dos fármacos , Reprodução/efeitos dos fármacos , Spodoptera/efeitos dos fármacos , Vitelogeninas/metabolismo
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