Maternal Exposure to Ozone Modulates the Endophyte-Conferred Resistance to Aphids in Lolium multiflorum Plants.

Plants are challenged by biotic and abiotic stress factors and the incidence of one can increase or decrease resistance to another. These relations can also occur transgenerationally. For instance, progeny plants whose mothers experienced herbivory can be more resistant to herbivores. Certain fungal endophytes that are vertically transmitted endow plants with alkaloids and resistance to herbivores. However, endophyte-symbiotic plants exposed to the oxidative agent ozone became susceptible to aphids. Here, we explored whether this effect persists transgenerationally. We exposed Lolium multiflorum plants with and without fungal endophyte Epichloë occultans to ozone (120 or 0 ppb), and then, challenged the progeny with aphids (Rhopalosiphum padi). The endophyte was the main factor determining the resistance to aphids, but its importance diminished in plants with ozone history. This negative ozone effect on the endophyte-mediated resistance was apparent on aphid individual weights. Phenolic compounds in seeds were increased by the symbiosis and diminished by the ozone. The endophyte effect on phenolics vanished in progeny plants while the negative ozone effect persisted. Independently of ozone, the symbiosis increased the plant biomass (≈24%). Although ozone can diminish the importance of endophyte symbiosis for plant resistance to herbivores, it would be compensated by host growth stimulation.

Identification of Insect-Deterrent Metabolites from Acremonium masseei strain CICY026, a Saprophytic Fungus from a Sinkhole in Yucatán.

Micromycetes from unexplored sources represent an opportunity to discover novel natural products to control insect pests. With this aim, a strain of Acremonium masseei CICY026 isolated from a tropical sinkhole was identified, cultured on fermented rice, and its ethyl acetate extract (EAE) was evaluated against three serious phytophagous insects (Bemisia tabaci, Myzus persicae, and Rhopalosiphum padi). DNA from A. masseei CICY026 was used to confirm its identity. EAE caused settling inhibition (SI) of M. persicae and R. padi (67.5% and 75.3%, respectively). Bioassay-guided fractionation of the active EAE led to the isolation of a novel metabolite, named hexahydroacremonintriol (1), and of acremonin A glucoside (2). The structures of 1 and 2 were determined using IR, one- and two-dimensional NMR, HRMS, and confirmed by theoretical data. The aphid M. persicae was noticeably sensitive to 1 and 2 (SI: 55.6% and 67.2%, respectively), whereas R. padi was only slightly affected by 1 (SI: 59%). This new knowledge about mycobiota from these special sinkhole ecosystems will inform the development of new biorational pesticides.

Entomofauna associated with Avena sativa in southern Mato Grosso do Sul, Brazil / Entomofauna associada à cultura da aveia branca no sul do Mato Grosso do Sul, Brasil

This study was aimed at examining the composition of insects and fluctuations in their populations in Avena sativa in southern Mato Grosso do Sul. The study was carried out at the experimental farm of the Federal University of Grande Dourados (FAECA) in Dourados, Mato Grosso do Sul, in 2014 and 2015, in an area of three hectares divided into 80 plots of 169 m2 each. The assessments were carried out weekly by sampling the area within a 0.25-m2 metal frame, totaling ten evaluations. Within the frame, ten plants were examined for aphids and all plants were inspected for other insects. Based on the faunistic analysis (abundance, constancy, frequency, and dominance), eight species were observed during the two years of study. The most frequent, abundant, dominant, and recurring species were Rhopalosiphum padi, Spodoptera frugiperda and dipterans of the family Syrphidae (hoverfly). The population of R. padi increased until approximately the 40th day after emergence (DAE), when the highest abundance of hoverflies was also observed. After that, the population of R. padi decreased. The aphid R. padi was the main insect observed in A. sativa during the two years of study but were naturally controlled by hoverflies; therefore, chemical intervention was not needed.(AU)

O objetivo deste trabalho foi analisar a composição faunística de insetos e sua flutuação populacional em Avena sativa na região sul do Mato Grosso do Sul. O experimento foi conduzido na Fazenda Experimental da Universidade Federal de Grande Dourados (FAECA), em Dourados, Mato Grosso do Sul, em uma área de três hectares divididos em 80 lotes de 169 m2 cada, nos anos de 2014 e 2015. As avaliações foram realizadas semanalmente por amostragem da área em uma estrutura metálica de 0,25 m2, perfazendo um total de dez avaliações. Dentro da estrutura, dez plantas foram examinadas para pulgões e todas as plantas foram inspecionadas quanto a outros insetos. Baseado na análise faunística (abundância, constância, frequência e dominância), oito espécies foram observadas durante os dois anos de estudo. As espécies mais frequentes, abundantes, dominantes e constantes foram Rhopalosiphum padi, Spodoptera frugiperda e dípteros da família Syrphidae. A população de R. padi aumentou até aproximadamente o 40° dia após a emergência (DAE), momento esse em que também houve a maior presença de sirfídeos. A partir deste ponto, ocorreu a diminuição na população de R. padi. O pulgão R. padi foi o principal inseto observado em A. sativa durante os dois anos de estudo, mas paralelamente houve um bom controle natural por sirfídeos, sendo dispensável, portanto, a necessidade de intervenções químicas.(AU)

Entomofauna associated with Avena sativa in southern Mato Grosso do Sul, Brazil / Entomofauna associada à cultura da aveia branca no sul do Mato Grosso do Sul, Brasil

This study was aimed at examining the composition of insects and fluctuations in their populations in Avena sativa in southern Mato Grosso do Sul. The study was carried out at the experimental farm of the Federal University of Grande Dourados (FAECA) in Dourados, Mato Grosso do Sul, in 2014 and 2015, in an area of three hectares divided into 80 plots of 169 m2 each. The assessments were carried out weekly by sampling the area within a 0.25-m2 metal frame, totaling ten evaluations. Within the frame, ten plants were examined for aphids and all plants were inspected for other insects. Based on the faunistic analysis (abundance, constancy, frequency, and dominance), eight species were observed during the two years of study. The most frequent, abundant, dominant, and recurring species were Rhopalosiphum padi, Spodoptera frugiperda and dipterans of the family Syrphidae (hoverfly). The population of R. padi increased until approximately the 40th day after emergence (DAE), when the highest abundance of hoverflies was also observed. After that, the population of R. padi decreased. The aphid R. padi was the main insect observed in A. sativa during the two years of study but were naturally controlled by hoverflies; therefore, chemical intervention was not needed.(AU)

O objetivo deste trabalho foi analisar a composição faunística de insetos e sua flutuação populacional em Avena sativa na região sul do Mato Grosso do Sul. O experimento foi conduzido na Fazenda Experimental da Universidade Federal de Grande Dourados (FAECA), em Dourados, Mato Grosso do Sul, em uma área de três hectares divididos em 80 lotes de 169 m2 cada, nos anos de 2014 e 2015. As avaliações foram realizadas semanalmente por amostragem da área em uma estrutura metálica de 0,25 m2, perfazendo um total de dez avaliações. Dentro da estrutura, dez plantas foram examinadas para pulgões e todas as plantas foram inspecionadas quanto a outros insetos. Baseado na análise faunística (abundância, constância, frequência e dominância), oito espécies foram observadas durante os dois anos de estudo. As espécies mais frequentes, abundantes, dominantes e constantes foram Rhopalosiphum padi, Spodoptera frugiperda e dípteros da família Syrphidae. A população de R. padi aumentou até aproximadamente o 40° dia após a emergência (DAE), momento esse em que também houve a maior presença de sirfídeos. A partir deste ponto, ocorreu a diminuição na população de R. padi. O pulgão R. padi foi o principal inseto observado em A. sativa durante os dois anos de estudo, mas paralelamente houve um bom controle natural por sirfídeos, sendo dispensável, portanto, a necessidade de intervenções químicas.(AU)

Low bacterial community diversity in two introduced aphid pests revealed with 16S rRNA amplicon sequencing.

Bacterial endosymbionts that produce important phenotypic effects on their hosts are common among plant sap-sucking insects. Aphids have become a model system of insect-symbiont interactions. However, endosymbiont research has focused on a few aphid species, making it necessary to make greater efforts to other aphid species through different regions, in order to have a better understanding of the role of endosymbionts in aphids as a group. Aphid endosymbionts have frequently been studied by PCR-based techniques, using species-specific primers, nevertheless this approach may omit other non-target bacteria cohabiting a particular host species. Advances in high-throughput sequencing technologies are complementing our knowledge of microbial communities by allowing us the study of whole microbiome of different organisms. We used a 16S rRNA amplicon sequencing approach to study the microbiome of aphids in order to describe the bacterial community diversity in introduced populations of the cereal aphids, Sitobion avenae and Rhopalosiphum padi in Chile (South America). An absence of secondary endosymbionts and two common secondary endosymbionts of aphids were found in the aphids R. padi and S. avenae, respectively. Of those endosymbionts, Regiella insecticola was the dominant secondary endosymbiont among the aphid samples. In addition, the presence of a previously unidentified bacterial species closely related to a phytopathogenic Pseudomonad species was detected. We discuss these results in relation to the bacterial endosymbiont diversity found in other regions of the native and introduced range of S. avenae and R. padi. A similar endosymbiont diversity has been reported for both aphid species in their native range. However, variation in the secondary endosymbiont infection could be observed among the introduced and native populations of the aphid S. avenae, indicating that aphid-endosymbiont associations can vary across the geographic range of an aphid species. In addition, we discuss the potential role of aphids as vectors and/or alternative hosts of phytopathogenic bacteria.

Insect deterrent and nematicidal screening of microfungi from Mexico and anti-aphid compounds from Gliomastix masseei.

Fungal metabolites are promising alternatives for the development of biorational pesticides. In this sense, microfungi from tropical regions are valuable sources of natural compounds for pest management. With the aim of broadening the search for new eco-friendly products to manage plant pests, this study was carried out to evaluate the biological activity of 23 tropical fungal extracts on three species of phytophagous insects and a plant parasitic nematode. In addition, the active principles of the most effective extract were identified. The insect deterrent activity of fungal extracts was evaluated on the settling of aphids Myzus persicae and Rhopalosiphum padi, and on the feeding of lepidoptera larva Spodoptera littoralis; the nematostatic activity was evaluated on the mobility of Meloidogyne javanica. Active metabolites from Gliomastix masseei were identified by GC-MS techniques and by comparison with commercial standards. Results showed seven extracts with strong effect on the settling of M. persicae and R. padi (settling inhibition >80%). The calculated median of effective concentration (EC50) values ranged from 8 to 38µg/cm2 for the extracts of Clonostachys rosea and G. masseei, respectively. Bioassay-guided separation of the ethyl acetate extract of G. masseei revealed the presence of fatty acids and their derivatives, where methyl 9-octadecenoate was the most active compound with EC50 values of 16µg and 35µg/cm2 for M. persicae and R. padi, respectively. Extracts of C. rosea and G. masseei could be a promising option in the control of pest aphids in agriculture.

Insect deterrent and nematicidal screening of microfungi from Mexico and anti-aphid compounds from Gliomastix masseei / Evaluación de la actividad disuasiva de insectos y nematotóxica de microhongos de México y compuestos anti-áfidos de Gliomastix masseei

Fungal metabolites are promising alternatives for the development of biorational pesticides. In this sense, microfungi from tropical regions are valuable sources of natural compounds for pest management. With the aim of broadening the search for new eco-friendly products to manage plant pests, this study was carried out to evaluate the biological activity of 23 tropical fungal extracts on three species of phytophagous insects and a plant parasitic nematode. In addition, the active principles of the most effective extract were identified. The insect deterrent activity of fungal extracts was evaluated on the settling of aphids Myzus persicae and Rhopalosiphum padi, and on the feeding of lepidoptera larva Spodoptera littoralis; the nematostatic activity was evaluated on the mobility of Meloidogyne javanica. Active metabolites from Gliomastix masseei were identified by GC-MS techniques and by comparison with commercial standards. Results showed seven extracts with strong effect on the settling of M. persicae and R. padi (settling inhibition >80%). The calculated median of effective concentration (EC50) values ranged from 8 to 38 µg/cm² for the extracts of Clonostachys rosea and G. masseei, respectively. Bioassay-guided separation of the ethyl acetate extract of G. masseei revealed the presence of fatty acids and their derivatives, where methyl 9-octadecenoate was the most active compound with EC50 values of 16 µg and 35 µg/cm² for M. persicae and R. padi, respectively. Extracts of C. rosea and G. masseei could be a promising option in the control of pest aphids in agriculture.

Los metabolitos fúngicos son agentes prometedores para el desarrollo de plaguicidas biorracionales. En este sentido, los hongos microscópicos de zonas tropicales representan una valiosa fuente de compuestos naturales para el manejo de plagas. Con la finalidad de ampliar la investigación en productos amigables con el medio ambiente, en este estudio se evaluó la actividad biológica de 23 extractos de hongos sobre 3 especies de insectos fitófagos y un nematodo fitoparásito; además se identificaron los componentes del extracto más activo. El efecto disuasivo de los extractos fúngicos se evaluó en el asentamiento de Myzus persicae y Rhopalosiphum padi, así como en la alimentación de Spodoptera littoralis; la actividad nematostática se evaluó sobre la movilidad de Meloidogyne javanica. Los metabolitos activos de Gliomastix masseei se identificaron por cromatografía de gases-espectrometría de masas y por comparación con muestras comerciales. Los resultados mostraron 7 extractos con fuerte efecto en la inhibición del asentamiento (> 80%) de M. persicae y R. padi. Los valores de la concentración efectiva media (CE50) estuvieron en el rango de 8 a 38 µg/cm² para los extractos de Clonostachys rosea y G. masseei, respectivamente. El extracto de acetato de etilo de G. masseei se fraccionó por un proceso biodirigido y reveló la presencia de ácidos grasos y sus derivados, donde el 9-octadecenoato de metilo fue el más activo, con una CE50 de 16 µg/cm² para M. persicae y 35 µg/cm² para R. padi. Los extractos fúngicos de C. rosea y G. masseei pueden ser una alternativa promisoria en el control de áfidos que son plaga en la agricultura.