Helicoverpa zea caterpillar growth on tomato plants exposed to ozone and mechanical wounding

Rising levels of environmental pollutants (e.g., ozone) compounded with damage from biotic stresses (e.g., insect pests) have large impacts on plant health and ecology. Plants respond to these stresses in different, but very specific ways. Insect herbivory induce specific plant defenses that are anti-nutritive to the insects. However, plants responding to ozone turn on other defense pathways. Due to the interconnection between these plant defense pathways, environmental stress can also affect how plants respond to other pressures. We examined the effects of ozone and mechanical wounding individually and combined, on tomato plants, and how these plant defense responses affect Helicoverpa zea (Boddie) caterpillar growth. The gene expression profile of several plant defense genes was determined with quantitative real-time polymerase chain reaction (qPCR) and enzyme assays. We determined that ozone attenuated the plant defense response to physical wounding. Caterpillar growth rates were different based on a diet of leaflets from the various treatments. This response is due to the induction of plant defenses by ozone and wounding that can be detrimental to the insect. The information obtained in this project is important in elucidating how plants respond to increasing ozone levels and damage as well as how this affects the insects that feed on them.