Using Insect Resistant Crops Pyramided with Native and Exotic Transgenes to Manage Invasive and Indigenous Pests

Summary

Using crops such as corn, soybean, and cotton that are pyramided with multiple insect-resistant genes has proven to be an effective and profitable tool for managing new invasive pests such as the kudzu bug and indigenous pests.

Situation

Pest problems in corn, cotton, and soybean are worse in Georgia and the Southeast than anywhere else in the USA. New invasive insects such as the kudzu bug and soybean aphid along with indigenous pests find the climate in Georgia ideal. Development of high yielding insect-resistant crops would be highly profitable for farmers by reducing costs of insecticides and other pest control practices. Insecticidal transgenic cotton, corn, and soybean all express toxins derived from the bacterium Bacillus thuringiensis (Bt). In corn and cotton, multiple Bt transgenes are pyramided in plant cells to express different protein (Cry) toxins as a means to increase crop resistance. Pyramiding Bt transgenes is also considered to be a method to prevent insect populations from developing resistance to individual Cry proteins. The first insect resistant pyramided soybean was developed at the University of Georgia and these traits have been introgressed into a high yielding cultivar (Benning). These lines combine Bt and native resistance genes and differ from pyramided cotton and corn, which combine two Bt transgenes. Field tests were conducted in Georgia with the pyramided cotton, corn, and soybean to determine the practical potential for resisting major pest infestations in natural environments and whether they may be used with other nonchemical control tactics for integrated pest management programs.

Response

A new invasive pest, the kudzu bug, invaded Georgia soybeans in 2010 and research was conducted to determine if varieties resistant to indigenouse pests controlled this insect. Cooperative research with a UGA crop breeder and seed industry scientists was conducted with pyramided cotton, corn, and soybean. In soybean at UGA, marker assisted selection technology was used to identify five quantitative trait loci (QTL) for resistance to insects. These native resistance traits were incorporated individually and collectively in near-isogenic breeding lines with Benning (and elite variety) background. Also, backcrossing with a Bt soybean line resulted in generation of near-isogenic breeding lines with Bt, and Bt with one or more native resistant genes. We further characterized insect responses to the resistant QTLs using laboratory and greenhouse testing on whole plants. Field tests, regulated by APHIS (Animal and Plant Health Inspection Service), verified that certain pyramided lines had sustained resistance to the soybean looper, corn earworm, and lesser cornstalk borer. Controlled tests with several major pests were conducted in the greenhouse and lab with pyramided cotton and corn. Field tests with transgenic cotton and corn were conducted in three locations across Georgia using a variety of cultural practices to evaluate sustainability of resistant crops in different environments.

Impact

Using resistant crops to manage invasive pests, such as the kudzu bug on soybean, as well as to control indigenous pests is a profitable and sustainable method of crop production. Pyramiding cotton, corn and soybean with insecticidal transgenes (Bt) with native resistant genes not only provides excellent control of key pests, but also could be a critical component (as a type of refugia) for preventing pests from developing resistance to Bt transgenes. All three crops provide as good or better control as insecticides of major pests in most cropping environments used by farmers in Georgia.

State Issue

Agricultural Profitability and Sustainability

Details

• Year: 2010
• Geographic Scope: International
• County: Clarke
• Program Areas:
  • Agriculture & Natural Resources