Abstract Anticarsia gemmatalis Hübner, 1818 (Lepidoptera) is a major pest of soybean in the Brazil. It is known that the reduction of proteolytic activity by the ingestion of protease inhibitors reduces digestion and larval development of the insects. Control via inhibition of the digestive enzymes necessitates deeper knowledge of the enzyme kinetics and the characterization of the inhibition kinetics of these proteases, for better understanding of the active centers and action mechanisms of this enzyme. Trypsin-like proteases found in the gut of Anticarsia gemmatalis were purified in a p-aminobenzamidine agarose column. Kinetic characterization showed KM 0.503 mM for the L-BApNA substrate; Vmax= 46.650 nM s-1; Vmax/[E]= 9.256 nM s-1 mg L-1 and Vmax/[E]/KM= 18.402 nM s-1 mg L-1 mM. The Ki values for the inhibitors benzamidine, berenil, SKTI and SBBI were 11.2 µM, 32.4 µM, 0.25 nM and 1.4 nM, respectively, and all revealed linear competitive inhibition. The SKTI showed the greatest inhibition, which makes it a promising subject for future research to manufacture peptide mimetic inhibitors.

Abstract: Twig girdlers have a short adult life and a long larval stage (up to one year in some species). This fact, together with lack of morphological traits to identify the species from the larval stage, poses obstacles for the taxonomic identification and characterization of the many twig girdlers found in the wild. To solve this matter, Random Amplified Polymorphic DNA (RAPD) molecular markers have been applied to identify some insect species and to determine species boundaries. The aim of this study was to identify three species of Oncideres using the RAPD technique. Adults and larvae of O. saga, O. ocularis and O. ulcerosa were collected in Minas Gerais, Brazil. Two RAPD primers were used (OPA-05 and OPB-13), which produced different electrophoretic profiles that were used to construct a UPGMA phenogram. Three groups identified in the analyses accurately separated the three species, based on individuals in two different stages of development (adults and larvae): I: O. saga, II: O. ulcerosa, and III: O. ocularis. Molecular markers, such as RAPD, are valuable tools that help taxonomists in species identification.

Abstract The response of plants to grazing includes the production of chemical defense compounds such as proteases inhibitors and secondary metabolites as flavonoids, which makes them less palatable to feeding and negatively affecting the physiology of insects. The aim of this study was to evaluate the phytochemical response of soybean cultivars (Glycine max (L.) Merrill) resistant (IAC-17, IAC-24) and susceptible (IAC-P1) to insects after mechanical damage. These cultivars were mechanically injured, and after 24 hours samples of these plants were analyzed by HPLC to identify and quantify flavonoids. The flavonoids daidzein, quercetin, and rutin were quantified, with the highest concentration of daidzin in soybean cultivars after mechanical damage. Rutin was biosynthesized by IAC-24. The cultivars IAC-PL1, IAC-17, and IAC-24 did not show a flavonoid response to mechanical damage. The soybean cultivars are not dependent on mechanical damage to produce flavonoids.

Endogenous mechanisms of plant resistance to herbivorous insects could be adapted to enable the development of alternative strategies for pest control. Activation of the lipoxygenase (LOX) pathway by jasmonic acid, the hormone responsible for activating genes encoding protease inhibitors (PI), is one of the main direct defenses of plants against insects. In this study, soybean cultivars at the V3 stage that were either susceptible or resistant to herbivorous insects were used to investigate changes in the activity of LOX and concentration of PIs in response to 24- or 48-h feeding by fourth and fifth instar Anticarsia gemmatalis (Lepidoptera: Noctuidae) larvae. LOX activity (0.0-0.007 nm s-1/mg) and the PI concentration (60 to 125 mg of trypsin inhibitor / mg of protein and 90 to 120 mg of trypsin inhibitor / mg protein after 24 and 48 h after attack, respectively) both increased in response to damage caused by A. gemmatalis. Proteolytic activity decreased by approximately 50% in cultivars with different degrees of resistance. Raised enzyme profiles in the midgut of A. gemmatalis may be related to tryptic enzymes that increased, compensating for the inhibition of proteases by entomotoxic substances of the soybean cultivars.

Los mecanismos de resistencia endógenos de las plantas contra insectos herbívoros pueden permitir el desarrollo de estrategias alternativas para el control de plagas. La activación de la vía de las lipoxigenasas con la producción de ácido jasmónico, hormona responsable por la activación de los genes inhibidores de proteasa, es una de las principales formas de defensa directa de las plantas contra los insectos. En el presente estudio, cultivares de soya en estadio V3, susceptibles y resistentes a insectos herbívoros fueron utilizadas para investigar las alteraciones en la actividad de LOX y la concentración de PIs, en respuesta al ataque de orugas en cuarto y quinto instar de Anticarsia gemmatalis (Lepidóptera: Noctuidae) por 24 y 48 horas. La actividad de LOX (0,00 a 0,007 nm s-1/mg) y la concentración de inhibidores de proteasa (60 a 125 mg de inhibidor de tripsina/ mg de proteína y 90 a 120 mg de inhibidor de tripsina/mg de proteína después de 24 y 48 horas del ataque respectivamente) aumenta en respuesta a los daños ocasionados por A. gemmatalis. La actividad proteolítica disminuyó aproximadamente en 50% en los cultivares con diferentes grados de resistencia. El aumento del perfil enzimático del intestino medio de A. gemmatalis puede estar relacionado al aumento de las enzimas trípticas para compensar la inhibición de proteasas por sustancias entomotóxicas de los cultivares de soya.

As espécies do gênero Eucalyptus são as mais utilizadas no setor florestal graças, principalmente, ao seu rápido crescimento e à sua boa adaptação às diferentes condições de solo e de clima, no Brasil. Entretanto, alguns insetos podem-se tornar pragas dessa espécie florestal, como é o caso de Compsosoma perpulchrum (Coleoptera: Cerambycidae), que apresenta registro roletando árvores de E. grandis no Paraná. Este trabalho teve como objetivo caracterizar o dano de C. perpulchrum em plantio comercial de eucalipto, no município de Paula Cândido-MG. Em março de 2008, foi vistoriado o plantio, cujas árvores e galhos roletados foram mensurados. As árvores danificadas eram de E. urophylla e a maioria dos roletamentos ocorreram no terço mediano. O comprimento e o diâmetro dos galhos roletados foram de 0,94±0,04m e de 0,90±0,06cm, respectivamente. O comprimento da faixa de roletamento foi 3,63±0,18cm. C. perpulchrum roleta a parte média das árvores de E. urophylla, causando perda da sua dominância apical. Este é o primeiro relato da ocorrência desse serrador, danificando plantio comercial de E. urophylla no Estado de Minas Gerais.

The species of genus Eucalyptus are the most used in the forestry sector, mostly because of its fast growth and adaptation to the different conditions of soil and climate in Brazil. However, a few insects, such as Compsosoma perpulchrum (Vigors, 1825) (Coleoptera: Cerambycidae) can become pests of girdled E. grandis Hill ex. Maiden in the State of Paraná. The objective of this work was to report the occurrence of C. perpulchrum in an eucalypt stand in the municipality of Paula Cândido, Minas Gerais State, Brazil. Girdled trees and branches were inspected and measured in March, 2008. The damaged trees were E. urophylla S. T. Blake and most of the girdle occurred in the middle third of the tree height. The length of the girdle range was 3.63±0.18 cm. The length and diameter of the girded branches were 0.94±0.04 m and 0.90±0.06 cm, respectively. This is the first report of the insect damage to this eucalypt species in the State of Minas Gerais.