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The entomopathogenic bacterium Bacillus thuringiensis (Bt) has been studied widely and intensively in terms of isolation and transmission, characterization, mode of action, improved formulations, and compatibility with natural enemies and Bt crops. This knowledge has resulted in the availability of extremely competitive biopesticides, with remarkable selectivity and specificity, on the market. The biopesticide Dipel is available on the worldwide pesticide market since the 1970s and recently had an outstanding performance against the noctuids Helicoverpa armigera and Chrysodeixis includens in Brazilian pest outbreaks. This chapter describes the scientific background that made Bt become the most important microbial control agent in the integration of agricultural pest management with low environmental constrains, with higher efficacy than chemical pesticides.

The efficiency of isolates from entomopathogenic fungus Beauveria bassiana, Lecanicillium muscarium and Metarhizium rileyi in the control of eggs and third-instar nymphs of whitefly, Bemisia tabaci biotype B, was evaluated by pathogenicity and virulence tests, under laboratory conditions. For the pathogenicity tests, five leaflets of bean (Phaseolus vulgaris) plants containing 20 nymphs or 20 eggs of B. tabaci biotype B were used. The leaflets were immersed in suspension containing a concentration of 108 conidia/ml of each fungus isolate. Nymph mortality and egg viability were evaluated after seven days. The isolates that caused nymph mortality and egg viability above 80% were submitted to virulence tests, in order to estimate the lethal concentration (LC50) of each isolate. All isolates were pathogenic to eggs and third-instar nymphs of B. tabaci Biotype B. JAB07 of B. bassiana and LCMAP3790 of L. muscarium isolates presented the best results, with nymphs mortality of 96.68 ± 2.25% and 97.74 ± 1.56%, respectively. Additionally, JAB07 was the most virulent isolate, both for eggs and third-instar nymphs, with LC50 estimated of 0.012 and 0.006 × 103 conidia/ml, respectively. We suggest, future field trials are required in order to analyze the real efficiency of this isolate in the control of eggs and nymphs of B. tabaci biotype B in field conditions.

Made available in DSpace on 2021-06-25T11:10:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-04 Helicoverpa armigera is a major insect pest of several crops worldwide. This insect is susceptible to some Bacillus thuringiensis (Bt) Cry insecticidal proteins expressed in transgenic crops or used in biopesticides. Previously, we identified H. armigera prohibitin (HaPHB) as a Cry1Ac-binding protein. Here, we further analyzed the potential role of PHB as a Cry toxin receptor in comparison to cadherin (CAD), well recognized as a Cry1Ac receptor. HaPHB-2 midgut protein and HaCAD toxin-binding region (TBR) fragment from H. armigera were expressed in Escherichia coli cells, and binding assays with different Cry1 toxins were performed. We demonstrated that Cry1Ab, Cry1Ac, and Cry1Fa toxins bound to HaPHB-2 in a manner similar to that seen with HaCAD-TBR. Different Cry1Ab mutant toxins located in domain II (Cry1AbF371A and Cry1AbG439D) or domain III (Cry1AbL511A and Cry1AbN514A), which were previously characterized and found to be affected in receptor binding, were analyzed regarding their binding interaction with HaPHB-2 and toxicity against H. armigera One β-16 mutant (Cry1AbN514A) showed increased binding to HaPHB-2 that correlated with 6-fold-higher toxicity against H. armigera, whereas the other β-16 mutant (Cry1AbL511A) was affected in binding to HaPHB-2 and lost toxicity against H. armigera Our data indicate that β-16 from domain III of Cry1Ab is involved in interactions with HaPHB-2 and in toxicity. This report identifies a region of Cry1Ab involved in binding to HaPHB-2 from a Lepidoptera insect, suggesting that this protein may participate as a novel receptor in the mechanism of action of the Cry1 toxins in H. armigeraIMPORTANCEHelicoverpa armigera is a polyphagous pest that feeds on important crops worldwide. This insect pest is sensitive to different Cry1 toxins from Bacillus thuringiensis In this study, we analyzed the potential role of PHB-2 as a Cry1 toxin receptor in comparison to CAD. We show that different Cry1 toxins bound to HaPHB-2 and HaCAD-TBR similarly and identify β-16 from domain III of Cry1Ab as a binding region involved in the interaction with HaPHB-2 and in toxicity. This report characterized HaPHB-Cry1 binding interaction, providing novel insights into potential target sites for improving Cry1 toxicity against H. armigera. Department of Agricultural Production Sciences School of Agricultural and Veterinarian Sciences São Paulo State University (Unesp) Department of Molecular Microbiology Instituto de Biotecnología Universidad Nacional Autónoma de Mexico State Key Laboratory for Biology of Plant Diseases and Insect Pests Institute of Plant Protection Chinese Academy of Agricultural Sciences Department of Applied Biology to Farming School of Agricultural and Veterinarian Sciences São Paulo State University (Unesp) Department of Agricultural Production Sciences School of Agricultural and Veterinarian Sciences São Paulo State University (Unesp) Department of Applied Biology to Farming School of Agricultural and Veterinarian Sciences São Paulo State University (Unesp)

Made available in DSpace on 2019-10-04T12:33:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-12-06 Direccion General de Asuntos del personal Academico DGAPA Fronteras de la Ciencia Consejo Nacional de Ciencia y Tecnologia CONACyT Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) DGAPA CONACyT Fronteras de la Ciencia Helicoverpa armigera is a polyphagous pest sensitive to Cry1Ac protein from Bacillus thuringiensis (Bt). The susceptibility of the different larval instars of H. armigera to Cry1Ac protoxin showed a significant 45-fold reduction in late instars compared to early instars. A possible hypothesis is that gut surface proteins that bind to Cry1Ac differ in both instars, although higher Cry toxin degradation in late instars could also explain the observed differences in susceptibility. Here we compared the Cry1Ac-binding proteins from second and fifth instars by pull-down assays and liquid chromatography coupled to mass spectrometry analysis (LC-MS/MS). The data show differential protein interaction patterns of Cry1Ac in the two instars analyzed. Alkaline phosphatase, and other membrane proteins, such as prohibitin and an anion selective channel protein were identified only in the second instar, suggesting that these proteins may be involved in the higher toxicity of Cry1Ac in early instars of H. armigera. Eleven Cry1Ac binindg proteins were identified exclusively in late instar larvae, like different proteases such as trypsin-like protease, azurocidin-like proteinase, and carboxypeptidase. Different aminopeptidase N isofroms were identified in both instar larvae. We compared the Cry1Ac protoxin degradation using midgut juice from late and early instars, showing that the midgut juice from late instars is more efficient to degrade Cry1Ac protoxin than that of early instars, suggesting that increased proteolytic activity on the toxin could also explain the low Cry1Ac toxicity in late instars. Univ Estadual Paulista, Fac Ciencias Agr & Vet, Dept Fitossanidade, Jaboticabal, SP, Brazil Univ Nacl Autonoma Mexico, Inst Biotecnol, Cuernavaca, Morelos, Mexico Embrapa Milho & Sorgo, Sete Lagoas, MG, Brazil Univ Estadual Paulista, Fac Ciencias Agr & Vet, Dept Fitossanidade, Jaboticabal, SP, Brazil Direccion General de Asuntos del personal Academico DGAPA: IN201016 Fronteras de la Ciencia: 008 Consejo Nacional de Ciencia y Tecnologia CONACyT: 2015/24330-5 Consejo Nacional de Ciencia y Tecnologia CONACyT: 2016/21464-3 DGAPA: IN201016 CONACyT Fronteras de la Ciencia: 008 FAPESP: 2015/24330-5 FAPESP: 2016/21464-3

This work evaluated the infectivity and production of occlusion bodies (OBs) of the SfMNPV-6NR on fall armyworm (FAW), Spodoptera frugiperda , when fed on different host plants. The experiment was performed in laboratory, in a completely randomized design using two concentrations of SfMNPV-6NR (2×106 and 2×107 OBs/mL) and six different host plants (soybean, corn, cotton, bean, sorghum and millet). The larval mortality, larval weight (LW), pupal weight (PW) of S. frugiperda and the production of OBs by virus were evaluated. S. frugiperda larvae were less susceptible to baculovirus when fed on cotton leaves (38 ± 4.17 and 70 ± 6.44% mortality) in the two concentrations tested (2×106 and 2×107 OBs/mL, respectively). The LW was affected by the virus concentration depending on the plant species consumed and the virus concentrations. The PW was affected by the plant species used to feed larvae. There was no effect of the host plant on the OBs virus production. The results demonstrate adverse effects of the host plant on the infectivity of the SfMNPV-6NR in S. frugiperda , especially a deleterious effect of the cotton plant in the virus infection capacity. Keywords: Fall armyworm, entomopathogenic virus, tritrophic interaction, plant host, cotton. A INFECTIVIDADE DE SfMNPV SOBRE A LAGARTA-DO-CARTUCHO E INFLUENCIADA PELA PLANTA HOSPEDEIRA RESUMO – Este trabalho avaliou a capacidade de infeccao e producao de corpos de oclusao (CO) de SfMNPV- 6NR sobre a lagarta-do-cartucho, Spodoptera frugiperda , quando alimentada em diferentes plantas hospedeiras. O experimento foi realizado em laboratorio, em delineamento inteiramente casualizado, utilizando duas concentracoes de SfMNPV-6NR (2×106 e 2×107 CO/mL) e seis diferentes plantas hospedeiras (soja, milho, algodao, feijao, sorgo e milheto). Foram avaliados a mortalidade larval, o peso de larvas mortas (PL), o peso de pupa (PP) e a producao de CO do virus. As larvas de S. frugiperda foram menos suscetiveis ao baculovirus quando alimentadas com folhas de algodao, apresentando as menores taxas de mortalidade (38 ± 4,17 e 70 ± 6,44%) com as duas concentracoes testadas (2×106 e 2×107 CO/mL, respectivamente). O PL foi afetado pela concentracao de virus, dependendo da especie de planta consumida e concentracao de virus testada. O PP foi afetado pela especie de planta com a qual as larvas foram alimentadas. Nao houve efeito da planta hospedeira na producao de CO do virus. Nossos resultados demonstram um efeito adverso da planta hospedeira sobre a infectividade do virus em S. frugiperda , especialmente um efeito deleterio da planta de algodao na capacidade de infeccao do virus. Palavras-chave: lagarta-do-cartucho-do-milho, virus entomopatogenico, interacao tritrofica, planta hospedeira, algodao.