Avaliação do efeito do estrato, fração proteica e lectina da casca de Genipa americana L. sobre a broca dos frutos das anonáceas Cerconota anonella (Lepidoptera: Depressaridae)

Abstract

The fruit borer, Cerconota anonella (Sepp., 1830), is a species belonging to the order Lepidoptera: Depressaridae, that is considered a pest of Annonaceae, which includes, for example, the species Annona squamosa (pine cone) and Annona muricata (soursop). The significant damage caused to the fruits is evidenced by the rotting of the pulp caused by opportunistic microorganisms, such as fungi, which enter through the holes produced by the caterpillars feeding, which reduces their commercial value. In order to control this pest, green fruits are bagged using perforated bags or conventional chemical insecticides are used. However, these methods are labor intensive and have high toxicity to the environment and non-target organisms, respectively. In this sense, the search for natural products free of toxicity and effective in the control of this and other insect pests is stimulated. The jenipapeiro (Genipa americana L.) belongs to the Rubiaceae family and has already recognized its insecticidal potential. Among the plant compounds that can act against insects are lectins - proteins or glycoproteins – which can bind to carbohydrates in a specific and reversible way and have many possible targets. Additionaly, insecticidal activity of lectins have been extensively investigated since the bodies of insects have a variety of glycan structures. In this perspective, the present study aimed to evaluate the effect of ingestion of the extract, lectin fraction and purified lectin from the bark of G. americana on C. anonella. For this purpose, the crude extract was prepared in Tris-HCl 50 mM, pH 8.0 from the bark, from which the protein fraction was obtained through saline fractionation with ammonium sulfate. Then, the lectin was isolated by gel filtration chromatography. These samples (extract, protein fraction and lectin) were inserted into the artificial diet and the insects were observed for survival and body mass for 7 days. After the end of the bioassays, the deterrent effect and the effects on the nutritional parameters of the insects were analyzed. It was observed that the extract of G. americana did not have a deterrent effect for the caterpillars, but it caused changes in the conversion of food ingested into biomass, with weight reduction being observed in all repetitions. Regarding adult insects, it was found that G. americana caused mortality of up to 80% in 3 days. The protein fraction and lectin caused food deterrence and all samples significantly interfered with nutritional parameters and biochemical profile. Based on the results obtained, this work presents the potential of G. americana on the development of caterpillars and adults of C. anonella, which can be used in association with other strategies in integrated pest management.