Influence of water stress and common bean genotypes on biological aspects of Chrysodeixis includens and Trichogramma pretiosum

Abstract

Water scarcity is expected to intensify, posing major challenges for crop production. Insect pests such as Chrysodeixis includens further reduce yields, especially in large monocultures. Water stress and plant resistance operate as bottom-up forces affecting herbivores and their natural enemies, whereas parasitoids impose top-down control. This study evaluated the effects of two common bean genotypes (a landrace variety and a commercial cultivar) on the growth and survival of C. includens under well-watered and water-stressed conditions. We also assessed whether the performance of the egg parasitoid Trichogramma pretiosum was influenced when developing in eggs from moths previously reared on the different genotypes and water regimes. Levels of hydrogen peroxide, malondialdehyde, and antioxidant enzymes were quantified. Water stress did not affect any biological parameter of the pest, although preliminary assays indicated reduced larval weight. The Manteigado genotype lowered larval survival by 27% and showed greater tolerance to C. includens defoliation compared with BRS Esplendor; however, neither genotype exhibited tolerance to water stress. None of the biological parameters of T. pretiosum were affected by bean genotype or water availability. Potential defense mechanisms were detected in Manteigado plants, including a 13–21% increase in superoxide dismutase activity, which detoxifies superoxide radicals, and a 21% reduction in total protein content, which may limit herbivore development. Manteigado therefore displays promising resistance traits for managing C. includens and may serve as a donor in breeding programs. Moreover, both genotypes appear compatible with T. pretiosum use even under water deficit, supporting sustainable pest management in bean crops.