Submitted to: Natural Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/1999
Publication Date: N/A
Interpretive Summary: Insects cause hundreds of millions of dollars of direct crop losses each year and also contribute to the near billion dollar problem of fungal toxins in corn and other crops. Plants are thought to have natural defenses against insects, but understanding what they are and how they work is necessary if they are to be transferred to plants lacking adequate insect defenses. Transgenic tomato plants that produce high levels of a tobacco plant enzyme were found to have resistance to some insects when the insects were small, but not when the insects were larger. The results were very similar to those for transgenic tobacco that produce high levels of the enzyme. These results, of interest to plant biotechnologists, suggest enzyme-based insect resistance mechanisms can still be effective when derived from one plant and then transferred to another, closely related plant.
Technical Abstract: Different parts of genetically transformed tomato, Lycopersicon esculentum L., plants that express the tobacco anionic peroxidase were compared for insect resistance with corresponding wild-type plants. Leaves of transgenic plants were as susceptible to feeding damage by third instar Helicoverpa zea (Boddie) as wild-type plants. Leaf feeding by first instar H. zea was significantly reduced on intact transgenic plants compared to wild-type plants. Green fruit was equally susceptible to third instar larvae of H. zea in both type plants, but fruit of transgenic plants were more resistant to first instar larvae as indicated by significantly greater mortality. Basal stem sections were more resistant to neonate larvae of H. zea and adults of Carpophilus lugubris Murray compared to wild-type plants as indicated by significantly greater mortality and/or reduced feeding damage. Field tests suggested reduced numbers of aphids on transgenic vs. wild-type plants as reflected by populations of aphids and predatory lady beetles (Coleoptera: Coccinelidae). Thus, tobacco anionic peroxidase activity can increase plant resistance to insects in tomato, a plant species closely related to the original source plant species, when expressed at sufficiently high levels. However, the degree of resistance is dependent on the size of insect and plant tissue involved.