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Cry1Ac production is costly for native plants attacked by non‐Cry1Ac‐targeted herbivores in the field

McGale, Erica, Diezel, Celia, Schuman, Meredith C., Baldwin, Ian T.
Thenew phytologist 2018 v.219 no.2 pp. 714-727
Bacillus thuringiensis, Nicotiana attenuata, bacterial proteins, biomass, crystal proteins, flowers, genetic engineering, habitats, herbivores, indigenous species, insecticidal proteins, nontarget organisms, pesticide application, terrestrial ecosystems, transgenic plants, wild plants
Plants are the primary producers in most terrestrial ecosystems and have complex defense systems to protect their produce. Defense‐deficient, high‐yielding agricultural monocultures attract abundant nonhuman consumers, but are alternatively defended through pesticide application and genetic engineering to produce insecticidal proteins such as Cry1Ac (Bacillus thuringiensis). These approaches alter the balance between yield protection and maximization but have been poorly contextualized to known yield–defense trade‐offs in wild plants. The native plant Nicotiana attenuata was used to compare yield benefits of plants transformed to be defenseless to those with a full suite of naturally evolved defenses, or additionally transformed to ectopically produce Cry1Ac. An insecticide treatment allowed us to examine yield under different herbivore loads in N. attenuata's native habitat. Cry1Ac, herbivore damage, and growth parameters were monitored throughout the season. Biomass and reproductive correlates were measured at season end. Non‐Cry1Ac‐targeted herbivores dominated on noninsecticide‐treated plants, and increased the yield drag of Cry1Ac‐producing plants in comparison with endogenously defended or undefended plants. Insecticide‐sprayed Cry1Ac‐producing plants lagged less in stalk height, shoot biomass, and flower production. In direct comparison with the endogenous defenses of a native plant, Cry1Ac production did not provide yield benefits for plants under observed herbivore loads in a field study.