Constitutive resistance in bean genotypes to Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae)

Control of the soybean looper Chrysodeixis includens (Walker) in bean cultivation has been achieved mainly through the application of chemical insecticides. However, this pest is acquiring resistance to common agents, and its habit of sheltering under leaves in the middle or lower thirds makes contact with control products difficult. The use of resistant plant genotypes is promising, as plants have complex defense mechanisms against herbivorous insects. The objective of this work was to evaluate the expression of potential sources of constitutive resistance to C. includens, by twelve commercial common bean genotypes. Attractiveness and non-preference for feeding were evaluated by free-choice and no-choice tests, using leaf discs to determine the percentage of caterpillars present on leaf discs, as well as the leaf area consumed. Biological development was assessed by growth parameters such as weight, developmental period and survival. On analyzing the data, BRS MG Madreperola (antixenosis and antibiosis), BRS Sublime (antixenosis) and IAC 1850 (antibiosis) were found to be resistant to the pest. In contrast, IAC Sintonia (Antiga selecao), IAC Sintonia (Nova selecao) and IAC Imperador, showed susceptibility. The results of this work are important for the selection of new sources of common bean resistance to C. includens, since thus far there are few published studies of this phenomenon. Additional investigations should be carried out to identify the mechanisms responsible for resistance to C. includens, with a view to increasing their expression or to incorporating them into common bean breeding programs.