Effect of neem extract on the cotton aphid

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The mitochondrial genome of the Russian wheat aphid Diuraphis noxia : large repetitive sequences between trnE and trnF in aphids

To characterize aphid mitochondrial genome (mitogenome) features, we sequenced the complete mitogenome of the Russian wheat aphid, Diuraphis noxia. The 15,784-bp mitogenome with a high A + T content (84.76%) and strong C skew (− 0.26) was arranged in the same gene order as that of the ancestral insect. Unlike typical insect mitogenomes, D. noxia possessed a large tandem repeat region (644 bp) located between trnE and trnF. Sequencing partial mitogenome of the cotton aphid (Aphis gossypii) further confirmed the presence of the large repeat region in aphids, but with different repeat length and copy number. Another motif (58 bp) tandemly repeated 2.3 times in the control region of D. noxia. All repeat units in D. noxia could be folded into stem-loop secondary structures, which could further promote an increase in copy numbers. Characterization of the D. noxia mitogenome revealed distinct mitogenome architectures, thus advancing our understanding of insect mitogenomic diversities and evolution.

Identification of a new Polerovirus (family Luteoviridae) associated with cotton bunchy top disease in Australia

Cotton bunchy top (CBT) disease has caused significant yield losses in Australia and is now managed by control of its vector, the cotton aphid (Aphis gossypii). Its mode of transmission and similarities in symptoms to cotton Blue Disease suggested it may also be caused by a luteovirus or related virus. Degenerate primers to conserved regions of the genomes of the family Luteoviridae were used to amplify viral cDNAs from CBT-affected cotton leaf tissue that were not present in healthy plants. Partial genome sequence of a new virus (Cotton bunchy top virus, CBTV) was obtained spanning part of the RNA-dependent-RNA-polymerase (RdRP), all of the coat protein and part of the aphid-transmission protein. CBTV sequences could be detected in viruliferous aphids able to transmit CBT, but not aphids from non-symptomatic plants, indicating that it is associated with the disease and may be the causal agent. All CBTV open-reading frames had their closest similarity to viruses of the genus Polerovirus. The partial RdRP had 90 % amino acid identity to the RdRP of Cotton leafroll dwarf virus (CLRDV) that causes cotton blue disease, while other parts of the genome were more similar to other poleroviruses. The sequence similarity and genome organization of CBTV suggest that it should be considered a new member of the genus Polerovirus. This partial genome sequence of CBTV opens up the possibility for developing diagnostic tests for detection of the virus in cotton plants, aphids and weeds as well as alternative strategies for engineering CBT resistance in cotton plants through biotechnology. © 2012 Australasian Plant Pathology Society Inc.

Biological aspects of Aphis gossypii Glöver, 1877 (Hemiptera: Aphididae) on colored lint cotton cultivars

This paper outlines the results of a study into the biological aspects of Aphis gossypii Glöver on colored cotton cultivars through the construction of life tables. In addition, we evaluate the influence of density of gossypol glands and trichomes of leaves on the biology of the aphid. Tests were conducted in a climate chamber at 25 ± 2°C, with relative humidity (RH) at 70 ± 10%, and a photophase of 12 hours, using the cultivars BRS Rubi, BRS Safira, and BRS Verde. Newly hatched nymphs were individually isolated in petri dishes containing leaf discs of cotton cultivars on a layer of water-agar (1%) of approximately 5 mm thick. An evaluation of the trichomes and gossypol gland densities of the cotton leaf plants was performed under a stereomicroscope, delimited to an area of 1 cm², and a count and identification of those on the surface was made. The feed substrates that were evaluated influenced the nymphal stage of A. gossypii. BRS Verde provided the shortest duration and BRS Safira was the longest during this phase. The cultivar BRS Verde, with the lowest density of trichomes, provided a large number of nymphs and led to a higher net reproductive rate (R0). Given these results, conclusions can be drawn that the colored cotton cultivars influence the duration of nymphal and adult stages of A. gossypii. The cultivar with a high density of trichomes on leaves (BRS Safira) adversely affects the fertility parameters of A. gossypii.

Effects of cotton cultivars differing in gossypol content on the quality of Aphis gossypii as prey for two species of Coccinellidae

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Behavior of Orius insidiosus preying on Aphis gossypii reared on transgenic and conventional cotton varieties

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Biologia de aphis gossypii em plantas infectadas pelo vírus do mosaico das nervuras do algodoeiro

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeito de cultivares de algodoeiro sobre a biologia e capacidade predatória de Orius Insidiosus (say, 1832) (hemiptera: anthocoridae) predando Aphis Gossypii Glover, 1877 (Hemiptera: Aphididae)

The objective of this research was to determine the survival, reproduction and predaceous capacity of Orius insidiosus on cotton aphid Aphis gossypii. Cotton plants of Antares, CNPA7H and Acala 90 cultivars (respectively, without tricome, medium tricome density and high tricome density) were individualized and infested with 15 third/fourth instar nymphs of A. gossypii, and then first-instar nymphs of O. insidiosus were released on the plants. The evaluations were made daily, quantifying survival and nymphal development; the number of cotton aphids A. gossypii per day and total; the number of eggs and the population of the predator (number of insects by female); and the conversion efficiency of A. gossypii predaceous. The nymphal development did not differ according to the cotton cultivars. The Antares cultivar favored a higher daily predation rate for the 1st, 2nd and 4th instars and adults of O. insidiosus. The number of eggs and nymphs was smaller when O. insidiosus females were confined on the Acala 90 cultivar. According to the predation rate of O. insidiosus, the efficiency of alimentary conversion was determined for the Antares, CNPA7H and Acala 90 cultivars, being respectively, 4.28, 3.00 and 2.75 cotton aphid predation for each egg of the predator.

Efeitos de fungicidas sobre os aspectos biológicos de Aphis gossypii Glover, 1877 (Hemiptera: Aphididae) em plantas de pepino

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise de sobrevivência aplicada ao desenvolvimento do pulgão Aphis gossypii Glover, 1877 (Hemiptera: Aphididae) em plantas de pepino (Cucumis sativus L.) contaminadas com fungicidas

It was aimed to evaluate the influence of fungicides utilized in cucumber on the development of the aphid Aphis gossypii Glover under greenhouse conditions. The experimental design was completely randomized with four treatments and 45 replicates, being each plot consisting of a first instar nymph coming from an apterous female in early reproductive period. The fungicides utilized and their respective dosages at g i.a.L(-1) were 800 PM sulphur (1.6), 800 PM mancozeb (1.6) and 840 PM copper oxichloride (1.5). The control was made up of water only. The products did not influence the median time of life in each instar and the nymphal stage, being respectively 1 and 4 days. Copper oxychloride and mancozeb increased the median time of life in days and the total life cycle of the adult stage of this species.

Aspectos biológicos de Aphis gossypii Glover, 1877 (Hemiptera: Aphididae) em três cultivares de algodoeiro e em três espécies de plantas daninhas

Este trabalho teve como objetivo estudar os aspectos biológicos de A. gossypii em três cultivares de algodoeiro e em três espécies de plantas daninhas. O experimento foi conduzido no Laboratório de Controle Biológico, sob condições controladas de temperatura (25 ± 1ºC), umidade relativa do ar (70 ± 10%) e fotofase (12 horas). Foram utilizados seis tratamentos, correspondendo às cultivares de algodoeiro CNPA ITA 90, Coodetec 402 e Deltaopal e espécies de plantas daninhas: guanxuma (Sida santaremnensis), malva-preta (Sidastrum micranthum) e trapoeraba (Commelina benghalensis). As unidades experimentais (25 repetições) consistiram de placas de Petri contendo ágar-água a 1% solidificado. Nestas placas, os ofídeos foram mantidos individualmente sobre discos foliares (3cm de diâmetro) de seus respectivos tratamentos. Os menores valores, em dias, para a fase ninfal foram obtidos em CNPA ITA 90 (4,39 ± 0,74), Deltaopal (4,45 ± 0,75), Coodetec 402 (4,47 ± 0,75) e trapoeraba (4,75 ± 0,80). O período reprodutivo e a longevidade dos adultos variaram de 8,21 ± 0,85 a 15,52 ± 0,93 e 11,09 ± 0,97 a 24,33 ± 1,59 dias, respectivamente, sobre guanxuma e Deltaopal. As cultivares de algodoeiro são mais favoráveis a A. gossypii que as plantas daninhas e na ausência de plantas de algodoeiro, as plantas daninhas guanxuma, trapoeraba e malva-preta são hospedeiros potenciais para manutenção da população de A. gossypii.

Características biológicas de Orius insidiosus alimentado com Aphis gossypii em algodão transgênico e convencional

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Aspectos biológicos e tabela de vida de fertilidade de Aphis gossypii Glover (Hemiptera: Aphididae) em cultivares de algodoeiro DeltaOPAL e NuOPAL

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efecto de la infección por virus persistentes y no persistentes sobre el comportamiento alimenticio, la preferencia, tasa de aterrizaje y asentamiento y la eficacia biológica de Aphis gossypii Glover

En el complejo de plagas que atacan a los principales cultivos hortícolas protegidos, destacan principalmente los Hemípteros, y dentro de estos los pulgones, dada su importancia como vectores de virus que provocan considerables daños y pérdidas económicas. Debido a que la dispersión de la mayoría de los virus de plantas puede ser eficaz con densidades bajas de vectores y su control es muy complicado al no existir métodos curativos para su control, es necesario generar nuevos conocimientos sobre las interacciones virus-vector con el fin de desarrollar nuevas y eficaces estrategias de control. Por ello, el objetivo general de esta Tesis ha sido conocer el efecto de la infección viral (directo-mediado por la presencia del virus en el vector- e indirecto-mediado por las alteraciones físico-químicas que se originan en la planta como consecuencia de la infección viral-) sobre el comportamiento y eficacia biológica del vector Aphis gossypii Glover y sus posibles repercusiones en la epidemiología de virosis de transmisión no persistente (Cucumber mosaic virus, CMV, Cucumovirus) y persistente (Cucurbit aphid-borne yellows virus, CABYV, Polerovirus). El primer objetivo de esta Tesis Doctoral, se centró en el estudio del efecto indirecto del virus de transmisión no persistente CMV sobre el comportamiento alimenticio y la preferencia del pulgón A. gossypii en el cultivo de pepino. Los ensayos de despegue y aterrizaje mostraron que los pulgones que fueron liberados en las plantas de pepino infectadas con CMV tuvieron una mayor propensión en migrar hacia las plantas no infectadas (60, 120 y 180 minutos después de la liberación) que aquellos que fueron sometidos al tratamiento contrario (planta no infectada hacia planta infectada con CMV). El estudio de preferencia y asentamiento mostró que el vector A. gossypii prefiere asentarse en plantas infectadas con CMV en una etapa temprana de evaluación (30 minutos después de la liberación). Sin embargo, este comportamiento se revirtió en una etapa posterior (4 y 48 horas después de la liberación), donde los pulgones se asentaron más en las plantas no infectadas. A través de la técnica de Gráficos de Penetración Eléctrica (EPG) se observó un efecto indirecto del virus CMV, revelado por un cambio brusco en el comportamiento de prueba del pulgón a lo largo del tiempo, cuando éstos fueron expuestos a las plantas infectadas con CMV. Los primeros 15 minutos de registro EPG mostraron que los pulgones hicieron un número mayor de punciones intracelulares (potencial drops - pds) y pruebas en las plantas infectadas con CMV que en las plantas no infectadas. Por otra parte, la duración de la primera prueba fue más corta y la duración total de las pds por insecto fue mucho más larga en las plantas infectadas con CMV. Se observaron diferencias significativas en el tiempo transcurrido desde el final de la última pd hasta el final de la prueba, siendo ese tiempo más corto para los pulgones que estaban alimentándose en plantas infectadas con CMV. En la segunda hora de registro los pulgones rechazaron las plantas infectadas con CMV como fuente de alimento, permaneciendo menos tiempo en las fases de prueba en floema (fase de salivación – E1 y fase de ingestión del floema – E2). El comportamiento alimenticio observado sobre las plantas infectadas con CMV favorece la adquisición y posterior transmisión de los virus de transmisión no persistente, los cuales son adquiridos e inoculados durante la realización de pruebas intracelulares en las primeras pruebas de corta duración. En el segundo objetivo de la Tesis se evaluó el efecto directo e indirecto del virus de transmisión persistente CABYV en el comportamiento alimenticio y preferencia del pulgón A. gossypii en cultivo de pepino, especie susceptible al virus, y algodón, especie inmune al virus. No se observó un efecto directo del virus relevante en el comportamiento alimenticio del vector, ya que los resultados obtenidos a nivel floemático en plantas de pepino no se observaron en plantas de algodón, inmune al virus CABYV. Esto sugiere que los resultados obtenidos en pepino, pueden deberse a un “posible efecto indirecto” originado por la infección de las plantas susceptibles al virus durante la realización del ensayo, lo que indirectamente puede modificar el comportamiento del pulgón durante la fase de evaluación. Sin embargo, el virus CABYV modificó indirectamente el comportamiento alimenticio de su vector a través de cambios en la planta infectada. Los pulgones tardaron menos tiempo en llegar al floema, realizaron un mayor número de pruebas floemáticas y permanecieron durante más tiempo en actividades floemáticas en plantas infectadas con CABYV. El comportamiento observado sobre las plantas infectadas con CABYV favorece la adquisición de virus persistentes, los cuales son adquiridos durante la alimentación sostenida en floema. El estudio de preferencia y asentamiento de A. gossypii mostró que los pulgones virulíferos prefieren asentarse en plantas no infectadas a corto y largo plazo de evaluación (2, 4 y 48 horas después de la liberación). Los ensayos de despegue y aterrizaje mostraron que los pulgones virulíferos que fueron liberados en las plantas de pepino infectadas con CABYV tuvieron una mayor propensión en migrar hacia las plantas no infectadas (3, 6, 24 y 48 horas después de la liberación) que aquellos que fueron sometidos al tratamiento contrario (planta no infectada hacia planta infectada con CABYV). Sin embargo, los pulgones no virulíferos no mostraron preferencia por plantas de pepino no infectadas o infectadas con CABYV en ninguno de los ensayos (preferencia o despegue) o periodos evaluados (corto y largo plazo). Los resultados indican que el virus CABYV es capaz de modificar indirectamente el comportamiento alimenticio de su vector a través de cambios en la planta infectada, favoreciendo su adquisición por su principal vector, A. gossypii. Una vez que los pulgones tienen capacidad de transmitir el virus (virulíferos) se produce un cambio en su comportamiento prefiriendo asentarse sobre plantas no infectadas optimizándose así la dispersión viral. El tercer objetivo de la Tesis, fue evaluar los efectos directos e indirectos del virus CABYV así como los efectos indirectos del virus CMV en la eficacia biológica del vector A. gossypii. Los resultados obtenidos en los ensayos realizados con el virus persistente CABYV indican que el virus parece no modificar directamente ni indirectamente la eficacia biológica del vector en plantas de pepino o algodón, no observándose diferencias estadísticas en ninguno de los parámetros poblacionales evaluados (tiempo de desarrollo, tasa intrínseca de crecimiento, tiempo generacional medio, tasa media de crecimiento relativo y ninfas totales). En cuanto a los ensayos realizados con el virus no persistente, CMV, los resultados muestran un efecto indirecto del virus sobre la biología del vector. Así resultó que tanto la tasa intrínseca de crecimiento natural (rm) como la tasa media de crecimiento relativo (RGR) fueron más altas para pulgones crecidos sobre plantas infectadas con CMV que sobre plantas no infectadas, favoreciendo la reproducción y crecimiento poblacional del vector sobre plantas infectadas con CMV. Los resultados obtenidos en la presente Tesis, ofrecen un ejemplo de como los virus de plantas pueden manipular directa e indirectamente a su vector, maximizando así su dispersión entre las plantas. Esos nuevos conocimientos generados tienen implicaciones importantes en la transmisión, dispersión y en la epidemiología de los virus y deben ser considerados para diseñar o ajustar los modelos de simulación existentes y patrones de dispersión que describen las epidemias de estos virus. ABSTRACT The main objective of this Thesis has been to understand the effect of the viral infection (direct-mediated by the presence of the virus in the vector and indirect mediated by the chemical and physical changes originated in the plant as a consequence of the viral infection) on the behaviour and biological efficacy of the vector Aphis gossypii Glover and its consequences in the epidemiology of two viral diseases, one with non-persistent transmission (Cucumber mosaic virus, CMV, Cucumovirus) and another with persistent transmission (Cucurbit aphid-borne yellows virus, CABYV, Polerovirus). The first objective of this Thesis was the study of the indirect effect of the nonpersistent virus CMV on the feeding behaviour and preference of the aphid A. gossypii in cucumber plants. The results of the alighting and settling behaviour studies showed that aphids exhibited no preference to migrate from CMV-infected to mock-inoculated plants at short time intervals (1, 10 and 30 min after release), but showed a clear shift in preference to migrate from CMV-infected to mock-inoculated plants 60 min after release. Our free-choice preference assays showed that A. gossypii alates preferred CMV-infected over mockinoculated plants at an early stage (30 min), but this behaviour was reverted at a later stage and aphids preferred to settle and reproduce on mock-inoculated plants. The electrical penetration graph (EPG) technique revealed a sharp change in aphid probing behaviour over time when exposed to CMV-infected plants. At the beginning (first 15 min) aphid vectors dramatically increased the number of short superficial probes and intracellular punctures when exposed to CMV-infected plants. At a later stage (second hour of recording) aphids diminished their feeding on CMV-infected plants as indicated by much less time spent in phloem salivation and ingestion (E1 and E2). This particular probing behaviour including an early increase in the number of short superficial probes and intracellular punctures followed by a phloem feeding deterrence is known to enhance the transmission efficiency of viruses transmitted in a NP manner. We conclude that CMV induces specific changes in a plant host that modify the alighting, settling and probing behaviour of its main vector A. gossypii, leading to optimum transmission and spread of the virus. The second objective of this work was to evaluate the effects that the persistently aphid transmitted Cucurbit aphid-borne yellows virus (CABYV) can induce directly and indirectly on the alighting, settling and probing behaviour activities of the cotton aphid A. gossypii. Only minor direct changes on aphid feeding behaviour was observed due to CABYV when viruliferous aphids fed on mock-inoculated plants. However, the feeding behaviour of non-viruliferous aphids was very different on CABYV-infected than on mockinoculated plants. Non-viruliferous aphids spent longer time feeding from the phloem when plants were infected by CABYV than on mock-inoculated plants, suggesting that CABYV indirectly manipulates aphid feeding behaviour through its shared host plant in order to favour viral acquisition. The vector alighting and settling preference was compared between nonviruliferous and viruliferous aphids. Viruliferous aphids showed a clear preference for mockinoculated over CABYV-infected plants at short and long time, while such behaviour was not observed for non-viruliferous aphids. Overall, our results indicate that CABYV induces changes in its host plant that modifies aphid feeding behaviour in a way that virus acquisition from infected plants is enhanced. Once the aphids become viruliferous they prefer to settle on healthy plants, leading to optimize the transmission and spread of the virus. The third objective was to evaluate the direct and indirect effects of CABYV and indirect effects of the CMV on the A. gossypii fitness. Obtained results for the persistent virus CABYV showed that the virus did not modify the vector fitness in cucumber or cotton plants. None of the evaluated variables was statistically significant (development time (d), intrinsic growth rate (rm), mean relative growth rate (RGR) and total number of nymphs). On the other hand, data obtained for the non-persistent virus (CMV) showed an indirect effect of the virus on the vector fitness. Thus, the rm and RGR were higher for aphids grown on CMV-infected plants compared to aphids grown on mock-inoculated plants. Overall, the obtained results are clear examples of how plant viruses could manipulate directly and indirectly vector behaviour to optimize its own dispersion. These results are important for a better understanding of transmission, dispersion and epidemiology of plant viruses transmitted by vectors. This information could be also considered to design or adjust simulation models and dispersion patterns that describe plant virus epidemics.

Identification of mutations conferring insecticide-insensitive AChE in the cotton-melon aphid, Aphis gossypii Glover

We have identified two mutations in the ace1 gene of Aphis gossypii that are associated with insensitivity of acetylcholinesterase (AChE) to carbamate and organophosphate insecticides. The first of these, S431F (equivalent to F331 in Torpedo californica), is associated with insensitivity to the carbamate insecticide pirimicarb in a range of A. gossypii clones. The S431F mutation is also found in the peach-potato aphid, Myzus persicae (Sulzer), and a rapid RFLP diagnostic allows the identification of individuals of both aphid species with a resistant genotype. This diagnostic further revealed the presence of S431 in several other pirimicarb-susceptible aphid species. The serine at this position in the wild-type enzyme has only been reported for aphids and provides a molecular explanation of why pirimicarb has a specific aphicidal action. A less specific insensitivity to a wide range of carbamates and organophosphates is associated with a second mutation, A302S (A201 in T. californica).