Feeding of Spodoptera eridania (Lepidoptera: Noctuidae) on soybean genotypes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Novo registro de Trichospilus diatraeae Cherian & Margabandhu, 1942 (Hymenoptera: Eulophidae), como parasitóide de Spodoptera cosmioides Walker, 1858 (Lepidoptera: Noctuidae) no Brasil

Spodoptera cosmioides (Lepidoptera: Noctuidae)é uma espécie polífaga e alimenta-se de grande número de plantas cultivadas e espontâneas. No Brasil, as culturas do abacaxi, algodoeiro, arroz, berinjela, cebola, eucalipto, pimentão e tomateiro, entre outras hortaliças, são consideradas hospedeiras da praga. Entretanto, apesar da ampla gama de hospedeiros, sua ocorrência como praga é relatada relacionada a desequilíbrios provocados pelo uso excessivo de inseticidas de amplo espectro, o que vem causando a resistência da praga a inseticidas. Devido a essa complexidade, métodos alternativos de controle têm sido propostos, por exemplo, o controle biológico através da utilização de parasitóides. Trichospilus diatraeae (Hymenptera: Eulophidae) é um parasitóide gregário pupal preferencialmente de espécies da ordem Lepidoptera. Este é o primeiro relato de T. diatraeae parasitando pupas de S. cosmioides, parasitóide que oferece novas perspectivas para os programas de controle biológico.

Tipos e graus de resistência de genótipos de soja a Spodoptera eridania (Cramer, 1782) (Lepidoptera: Noctuidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Aspectos biológicos de Spodoptera cosmioides Walker, 1858 (Lepidoptera: Noctuidae) nas cultivares de algodoeiro DeltaOPAL e NuOPAL (Bollgard I)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comprehensive Analysis of Gene Expression Profiles of the Beet Armyworm Spodoptera exigua Larvae Challenged with Bacillus thuringiensis Vip3Aa Toxin

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Antibiosis in Soybean Genotypes and the Resistance Levels to Spodoptera eridania (Cramer) (Lepidoptera: Noctuidae)

The southern armyworm (SAW) Spodoptera eridania (Cramer) is one of the most common armyworm species defoliating soybeans. Preliminary screening trials have indicated that some soybean genotypes exhibit resistance to SAW. Therefore, in this study, we evaluated the development of SAW larvae fed on ten soybean genotypes in order to identify genotypes with antibiosis-type resistance. Neonate SAW larvae were daily fed with young leaves collected from plants at the vegetative growth stages V4-V5. Larval development and survival were recorded. Genotypes PI 227687 and PI 227682 delayed larval, pupal, and larva-adult development and yielded larvae with the lowest weight and survival and pupae with the lowest weight. Genotypes IAC 100 and DM 339 also negatively affected larval and pupal development and larval survival but at a lower level. Based on our results, the soybean lines PI 227687 and PI 227682 could be used as sources of genes for soybean breeding programs aiming to develop high yield, SAW-resistant cultivars. Moreover, further trials must be carried out under field conditions to validate if the commercial cultivars IAC 100 and DM 339, which expressed moderate levels of antibiosis-type resistance in the laboratory, are effective in suppressing SAW larvae populations.

Determinação dos tipos de resistência de genótipos de soja ao ataque de Spodoptera cosmioides (Walker, 1858) (Lepdoptera: Noctuidae)

The aim of this work was to evaluate the types of resistance of soybean genotypes to the attack of Spodoptera cosmioides (Walker, 1858), under laboratory conditions. Plants of the soybean genotypes, IAC 100, Dowling, PI 227687, PI 274454, BR 16, IGRA RA 626 RR, PI 227682, BRSGO 8360, IGRA RA 516 RR e P 98Y11 RR, were cultivated in vases and placed in a greenhouse in order to have their leaves used afterwards in free-choice and no-choice no-preference for feeding tests and evaluation of the biological parameters of S. cosmioides fed on the genotypes. For free-choice no preference for feeding test, 10 leaf discs were prepared and placed in Petri dishes equidistantly among themselves, and then two recently-hatched caterpillar per genotype were release in the center of the plate. The same test was performed for third instar larvae, so that one caterpillar per genotype was used. In non-choice test, only one genotype was used in each Petri dish, where two recently-hatched or one third instar caterpillars were released, respectively. For both tests, the attractiveness was assessed at 1, 3, 5, 10, 15, 30, 60, 120, 360, 720 and 1440 minutes after the release of the insects. In addition, the leaf area consumed was evaluated. Randomized blocks design and completely randomized design were used for free-choice and non-choice tests, respectively, with 10 replications. In biology test, recently-hatched larvae were transferred to Petri dishes with leaves of the genotypes, evaluating the period of larvae, pupae and overall (larvae + pupae), viability of larvae, pupae and overall, weight of 12 days-old larvae and 24 hours-old pupae and longevity of the adults. Completely randomized design was used for this test, with 30 replications. Genotypes IGRA RA 516 RR and IGRA RA 626 RR were the least and the most consumed by recently-hatched larvae of S. cosmioides, respectively, in non-choice non-preference for feeding test. Genotypes PI 274454 and PI 227687 were...

Metodologias de pesquisa e avaliação da resistência de genótipos de amendoim a Spodoptera albula (walker, 1857) (Lepidoptera: Noctuidae)

Pós-graduação em Agronomia (Entomologia Agrícola) - FCAV

Mortalidade e efeitos subletais de Bacillus thuringiensis Berliner em Spodoptera albula (Walker, 1857)

Pós-graduação em Agronomia (Entomologia Agrícola) - FCAV

Determinação dos tipos de resistência a Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) em genótipos de soja

The aim of this work was to evaluate the resistance types in soybean genotypes to Spodoptera cosmioides (Walker) in laboratory. Soybean genotypes assessed were as follows: 'IAC 100'(resistance standard), 'BR16'(susceptible standard), 'Dowling', PI 227687, PI 274454, 'IGRA RA 626 RR', PI 227682, 'BRSGO 8360', 'IGRA RA 516 RR'and 'P 98Y11 RR'. Free-choice and no-choice feeding non-preference tests were done using two newly-hatched larvae per genotype or one third-instar larva per genotype in both tests. Larvae attractiveness was evaluated in different times, and at the end of the experiments the leaf area consumed was quantified. In the antibiosis test, newly-hatched larvae were individualized into Petri dishes, where leaflets of the genotypes were offered over the larval stage, and the following biological parameters were assessed: period and viability of larvae, pupae and overall (larvae + pupae), weight of larvae and pupae, sex ratio and adults longevity. Overall, in the feeding preference tests, significant differences were not found in leaf consumption among the genotypes. In the antibiosis assay, genotypes PI 227687, PI 227682 and 'IAC 100'caused 100% larval mortality and the lowest weight of larvae, ranging between 37.65 and 85.56 mg. All soybean genotypes evaluated do not exhibit feeding non-preference type resistance to S. cosmioides, and PI 227687, PI 227682 and 'IAC 100'highlighted for possessing antibiosis.

Biology and reproductive capacity of Spodoptera eridania (Cramer) (Lepidoptera, Noctuidae) in different soybean cultivars

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A synthetic cryIC gene, encoding a Bacillus thuringiensis δ-endotoxin, confers Spodoptera resistance in alfalfa and tobacco

Spodoptera species, representing widespread polyphagous insect pests, are resistant to Bacillus thuringiensis δ-endotoxins used thus far as insecticides in transgenic plants. Here we describe the chemical synthesis of a cryIC gene by a novel template directed ligation–PCR method. This simple and economical method to construct large synthetic genes can be used when routine resynthesis of genes is required. Chemically phosphorylated adjacent oligonucleotides of the gene to be synthesized are assembled and ligated on a single-stranded, partially homologous template derived from a wild-type gene (cryIC in our case) by a thermostable Pfu DNA ligase using repeated cycles of melting, annealing, and ligation. The resulting synthetic DNA strands are selectively amplified by PCR with short specific flanking primers that are complementary only to the new synthetic DNA. Optimized expression of the synthetic cryIC gene in alfalfa and tobacco results in the production of 0.01–0.2% of total soluble proteins as CryIC toxin and provides protection against the Egyptian cotton leafworm (Spodoptera littoralis) and the beet armyworm (Spodoptera exigua). To facilitate selection and breeding of Spodoptera-resistant plants, the cryIC gene was linked to a pat gene, conferring resistance to the herbicide BASTA.

Opposite Effects on Spodoptera littoralis Larvae of High Expression Level of a Trypsin Proteinase Inhibitor in Transgenic Plants1

This work illustrates potential adverse effects linked with the expression of proteinase inhibitor (PI) in plants used as a strategy to enhance pest resistance. Tobacco (Nicotiana tabacum L. cv Xanthi) and Arabidopsis [Heynh.] ecotype Wassilewskija) transgenic plants expressing the mustard trypsin PI 2 (MTI-2) at different levels were obtained. First-instar larvae of the Egyptian cotton worm (Spodoptera littoralis Boisd.) were fed on detached leaves of these plants. The high level of MTI-2 expression in leaves had deleterious effects on larvae, causing mortality and decreasing mean larval weight, and was correlated with a decrease in the leaf surface eaten. However, larvae fed leaves from plants expressing MTI-2 at the low expression level did not show increased mortality, but a net gain in weight and a faster development compared with control larvae. The low MTI-2 expression level also resulted in increased leaf damage. These observations are correlated with the differential expression of digestive proteinases in the larval gut; overexpression of existing proteinases on low-MTI-2-expression level plants and induction of new proteinases on high-MTI-2-expression level plants. These results emphasize the critical need for the development of a PI-based defense strategy for plants obtaining the appropriate PI-expression level relative to the pest's sensitivity threshold to that PI.

Adaptation of Spodoptera exigua larvae to plant proteinase inhibitors by induction of gut proteinase activity insensitive to inhibition.

Tobacco plants were transformed with a cDNA clone of chymotrypsin/trypsin-specific potato proteinase inhibitor II (PI2) under the control of a constitutive promoter. Although considerable levels of transgene expression could be demonstrated, the growth of Spodoptera exigua larvae fed with detached leaves of PI2-expressing plants was not affected. Analysis of the composition of tryptic gut activity demonstrated that only 18% of the proteinase activity of insects reared on these transgenic plants was sensitive to inhibition by PI2, whereas 78% was sensitive in insects reared on control plants. Larvae had compensated for this loss of tryptic activity by a 2.5-fold induction of new activity that was insensitive to inhibition by PI2. PI2-insensitive proteolytic activity was also induced in response to endogenous proteinase inhibitors of tobacco; therefore, induction of such proteinase activity may represent the mechanism by which insects that feed on plants overcome plant proteinase inhibitor defense.

Combinación de diferentes estrategias de aplicación de hongos entomopatógenos para el control de Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) y Bemisia tabaci (Gennadius) (Hemiptera:Aleyrodidae)

Los ascomicetos mitospóricos entomopatógenos, que actúan por vía tegumentaria, han sido utilizados para el control microbiano de plagas mediante distintas estrategias que permiten el contacto de sus conidios con los insectos diana. Sin embargo, se conocen nuevos aspectos sobre su función ecológica tales como su capacidad secretora de compuestos con actividad insecticida, así como su sorprendente comportamiento como endófitos, que complementan su empleo clásico y que pueden pantag ermitir el desarrollo de nuevas estrategias de control de plagas. El empleo conjunto de estos hongos y sus extractos para el control de un insecto polífago de importancia mundial Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) es abordado en el capítulo II, donde se pone de manifiesto la existencia de variación intra- e interespecífica en la virulencia y estrategias patogénicas de las cepas de Beauveria bassiana y Metarhizium brunneum evaluadas frente a larvas del noctuido. La aplicación conjunta de cepas con distintas estrategias patogénicas junto con sus extractos a larvas del lepidóptero tuvo efecto aditivo, y alguno antagónico, de lo que depende su empleo conjunto. Los capítulos III y IV revelan la existencia de colonización endofítica transitoria tras la aplicación foliar de suspensiones de conidios de cepas de las especies mencionadas en alfalfa, tomate y melón, así como el impacto de esta colonización sobre dos fitófagos con diferentes hábitos de alimentación, uno masticador S. littoralis y otro picador-suctor Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). El capítulo III muestra la contribución aditiva de la mortalidad causada por la alimentación de larvas de S. littoralis a expensas de material vegetal colonizado endofíticamente por cepas de B. bassiana y M. anisopliae con la debida al tratamiento tópico de las mismas con las suspensiones fúngicas. El origen de la mortalidad iniciada a través de la vía digestiva en larvas de este lepidóptero permanece incierto para las cepas de B. bassiana, pero podría estar asociado a la presencia en la planta de metabolitos fúngicos en las cepas de M. brunneum como denota la presencia de destruxina (dtx) A en el 11,0% de los cadáveres. El capítulo IV revela que cepas de ambas especies fúngicas pueden iniciar ciclos de infección en insectos picadores-suctores cuando se alimentan a expensas de sustrato vegetal colonizado endofíticamente, si bien, ambas especies presentan estrategias diferentes. Así, B. bassiana muestra una gran capacidad para colonizar el melón, incluso con efecto traslaminar, que causa la infección de ninfas de B. tabaci por contacto con el tegumento. Sin embargo, la mortalidad de las mismas causada por M. brunneum, de crecimiento mucho más localizado en la hoja, está relacionada una vez mas con la presencia de dtx A en el 43,0% de los cadáveres. Estos resultados deben ser considerados para la evaluación del impacto real de los tratamientos con hongos entomopatógenos, y abren nuevas vías en el control de plagas.