MANEJO DA RESISTÊNCIA: NA ERA DAS PLANTAS TRANSGÊNICAS

Abstract

RESISTANCE MANAGEMENT: IN TRAGENIC PLANTS AGE. The evolution of resistance of many target pests to the chemical control agents is a constant concern of farmers and agricultural workers. The development of resistance is usually controlled by a number of procedures applied to the agricultural land to overcome or reduce the resistance of the pests to the control agents utilized. The form of evolution of the insect´s resistance to the control agents is of considerable relevance and involves ecological, genetic and economic aspects. When Bt plants were developed and widely cultivated, research and studies in this field became more and more important and are now essential for the maintenance of productivity of these cultures. The management of the evolution of the resistance of the Bt plants is a question with many polemical aspects, from both practical and theoretical standpoints. The principal strategy applied to “manage” the evolution of the resistance of the Bt plants is known as “high doses - structured refuge”. Also, it is of considerable importance that methods of monitoring the plant populations are implemented to detect the presence, or an increase in the numbers, of resistant insects. In this context the underlying biological principles that are employed to substantiate the management strategy adopted must be clearly understood and the principal uncertainties associated with generalized applications recognized. What would happen if the resistance was determined by recessive genes, or when the crossing of resistant and susceptible individuals does not happen in a random manner? One of the important points in the strategy of resistance management is to monitor the cultivated areas with the objective of detecting the presence of resistant insects. The efficiency of the monitoring methods depends on their capacity to detect the presence of the allele that confers resistance while the frequency is still very low (in general less than 0.001). Among these methods, bio-testing the response dose, diagnosis bio-testing and the characterization of F2 are considered best. A clear understanding of all the aspects involved in managing and monitoring the evolution of the resistance is essential because our evolutionary relation with the insect pests can be compared to an armament race. Also, it becomes possible to understand why resistance management is considered one of the great problems linking ecology, evolution and economy at the present time.

Keywords: Bt-crops; resistance management; high doses; structured refugee; monitoring.