Estratégias de manejo de Spodoptera frugiperda e Chrysodeixis includens em soja: resistência de cultivares BT e não BT e indução de resistência com jasmonato de metila e extrato de NIM

Abstract

Soybean, Glycine max (L.) Merrill, is a crop of great economic importance to Brazil, which stands out as one of the main players in the international market. The crop pest species, the

caterpillars Chrysodeixis includens and Spodoptera frugiperda (Lepidoptera: Noctuidae) de- serve to be highlighted. There is very little knowledge about the levels of resistance in Bt and

non-Bt soybean cultivars adapted to regions where this crop is expanding, such as in the state of Minas Gerais, to C. includens and S. frugiperda. Furthermore, there is a need to find other control strategies to include in the integrated management of these pests in soybeans, such as the use of elicitors and biostimulants. The thesis is divided into two parts, the first of which consists of a general introduction and theoretical reference, which comprehensively covers the themes involved in the construction of this work. The second part consists of two articles. The first of these investigated the efficiency of transgenic Bt and non-Bt soybean cultivars against C. includens and S. frugiperda adapted to the Minas Gerais region. The results showed that the age difference and the species of caterpillar influenced the control efficiency of cultivars with Bt protein, as well as antinutritional effects on insects in food conversion. Furthermore, the level of resistance and susceptibility of Bt and non-Bt cultivars highlighted in the work can be recommended for planting as main crops and refuge areas, respectively. These findings are

important for defining regional strategies for integrated management and resistance to C. in- cludens and S. frugiperda in regions where soybean cultivation is expanding in Brazil. The

second article investigated the effects on soybean plant defenses induced by the application of formulations based on neem alone and in combination with methyl jasmonate (MeJA) to S.

frugiperda. This study showed synergism between Neem and MeJA, demonstrating an induc- tion of resistance in soybeans, so that there was an antinutritive effect S. frugiperda was unable

to convert food into weight gain. Herbivory influenced oxidative enzyme concentrations only

in hydrogen peroxide, this did not occur in catalase. Negative effects of the elicitors were ob- served on the reduction of plant growth parameters in shoots and roots. The knowledge gained

about the performance of transgenic soybean cultivars for the Minas Gerais region in control- ling caterpillars and the discovery of the effects and use of biostimulants associated with elici- tors on caterpillars are of paramount importance for integrated pest management and plant re- sistance and the success of soybean crop production.