Exposure to Bacillus thuringiensis (Bt) toxins in low- and moderate-dose transgenic crops may induce sublethal effects and increase the rate of Bt resistance evolution, potentially compromising control efficacy against target pests. We tested this hypothesis using the fall armyworm Spodoptera frugiperda, a major polyphagous lepidopteran pest relatively tolerant to Bt notorious for evolving field-relevant resistance to single-gene Bt maize. Late-instar larvae were collected from Bt Cry1Ab and non-Bt maize fields in five locations in Brazil, and their offspring was compared for survival, development, and population growth in rearing environment without and with Cry1Ab throughout larval development. Larval survival on Cry1Ab maize leaves varied from 20 to 80% among the populations. Larvae reared on Cry1Ab maize had seven-day delay in development time in relation to control larvae, and such delay was shorter in offspring of armyworms from Cry1Ab maize. Population growth rates were 50–70% lower for insects continuously exposed to Cry1Ab maize relative to controls, showing the population-level effect of Cry1Ab, which varied among the populations and prior exposure to Cry1Ab maize in the field. In three out of five populations, armyworms derived from Bt maize reared on Cry1Ab maize showed higher larval weight, faster larval development and better reproductive performance than the armyworms derived from non-Bt maize, and one of these populations showed better performance on both Cry1Ab and control diets, indicating no fitness cost of the resistance trait. Altogether, these results indicate that offspring of armyworms that developed on field-grown, single-gene Bt Cry1Ab maize had reduced performance on Cry1Ab maize foliage in two populations studied, but in other three populations, these offspring had better overall performance on the Bt maize foliage than that of the armyworms from non-Bt maize fields, possibly because of Cry1Ab resistance alleles in these populations. Implications of these findings for resistance management of S. frugiperda in Bt crops are discussed.

IOcorrência do ácaro fitófago Catarhinus tricholaenae Keifer (Acari: Diptilomiopidae) em cultivares de milho Bt RESUMO O objetivo deste trabalho foi avaliar a ocorrência do microácaro-da-face-inferior-das-folhas-de-milho Palavras-chave: plantas geneticamente modificadas,proteínas Cry, Diptilomiopidae. ABSTRACT The objective of this study was to evaluate the occurrence of "microácaro-da-face-inferior-das-folhas-demilho" Catarhinus tricholaenae

Resumo -O objetivo deste trabalho foi avaliar os aspectos biológicos de Helicoverpa zea e Helicoverpa armigera (Lepidoptera: Noctuidae) em híbridos de milho com expressão de diferentes proteínas. Foram avaliadas as proteínas Cry1F, Cry1A(b), Cry1A.105 + Cry2Ab2 e Vip3A e seus respectivos isogênicos convencionais. As larvas foram alimentadas com espiguetas de milho Bt e convencional, trocadas a cada dois dias. Os parâmetros avaliados foram: sobrevivência 48 horas após eclosão, sobrevivência larval, peso de larvas e de pupas, período de desenvolvimento larval e período pré-imaginal. Observou-se efeito significativo da interação entre evento de milho Bt e espécie de Helicoverpa para todas as variáveis biológicas avaliadas. Larvas de H. armigera apresentaram maior sobrevivência 48 horas após eclosão em milho expressando a proteína Cry1F e a Vip3 em relação a H. zea. O período letal foi maior em H. armigera do que em H. zea, mas, em milho com expressão da proteína Cry1A(b), foi quatro vezes menor. Não houve sobrevivente para ambas as espécies de Helicoverpa em nenhum dos híbridos Bt avaliados. Nos isogênicos convencionais, o índice de adaptação de H. armigera foi superior ao de H. zea, o que indica maior facilidade de adaptação ao ambiente dessa espécie.Termos para indexação: biotecnologia, manejo de resistência de insetos, manejo integrado de pragas, Noctuidae, proteínas Bt. Development of Helicoverpa spp. in Bt maize expressing different proteinsAbstract -The objective of this work was to evaluate the biological responses of Helicoverpa zea and Helicoverpa armigera (Lepidoptera: Noctuidae) in maize hybrids expressing different proteins. The Cry1F, Cry1A(b), Cry1A.105 + Cry2Ab2, and Vip3A proteins and their isogenic conventional counterparts were evaluated. Larvae were fed on spikelets of Bt and conventional maize, which were changed every two days. The variables evaluated were: survival 48 hours after hatching, larval survival, larval and pupal weight, larval development period, and pre-imaginal period. There was a significant interaction between Bt maize event and Helicoverpa species for all evaluated biological variables. Helicoverpa armigera larvae showed higher survival 48 hours after hatching on maize expressing the Cry1F and Vip3 proteins when compared to H. zea. Lethal period was greater for H. armigera than for H. zea, but, in maize expressing Cry1A(b) protein, it was four times lower. There were no survivals for both Helicoverpa species in the evaluated Bt hybrids. In isogenic conventional counterparts, the adaptation index of H. armigera was higher than that of H. zea, which indicates greater ease of adaptation to the environment of that species.

This study evaluated the effects of the sugarcane borer Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) on cultivars of sweet and biomass sorghum for the selection of resistant cultivars. The present work consisted of two trials, with natural pest infestation. In the first one, 10 sweet sorghum cultivars were analyzed for the following variables: plant height, number of healthy and damaged internodes, gallery position and size, stem infestation level and soluble solids content (°Brix). In the second trial, it was analyzed 16 genotypes of high biomass sorghum, with the same variables above mentioned, in addition to the lignin, cellulose and hemicellulose contents. Among sweet sorghum genotypes evaluated, the genotype CMSXS647 stood out due to the traits: plant height, infestation level, gallery size and soluble solids content. Among the sorghum genotypes evaluated, CMSXS7030, CMSXS7012 and CMSXS7028 presented ideal characteristics for infestation level, plant height and number of lignocellulosic compounds. Such information, in addition to supporting the bioenergy sorghum breeding program, will assist in integrated pest management for sorghum cultivation.