Risk assessment of sugarcane borer resistance to transgenic maize expressing Bacillus thuringiensis proteins

Document Type

Article

Publication Date

12-1-2011

Abstract

Sugarcane borer, Diatraea saccharalis, is a major maize stalk-boring pest in many areas of the mid-south region of the United States. In Louisiana, transgenic maize expressing Bacillus thuringiensis (Bt) Cry1Ab protein was first commercially planted in 1999 and now is the primary tool for managing stalk boring pests. Resistance development in target pest populations is an important issue in the sustainable use of Bt crops. Since 2004, a coordinated research program has been established to assess the risk of D. saccharalis resistance to Bt maize. This paper summarizes the major accomplishments and presents up-to-date results of this research program. Field surveys showed that a complex of D. saccharalis; southwestern corn borer, Diatraea grandiosella; and European corn borer, Ostrinia nubilalis could occur in Louisiana maize fields. D. saccharalis is the dominant species across the state, accounting for 88% of the total maize borers sampled during 2004-2009. Both D. saccharalis and D. grandiosella were able to overwinter in the major maize growing areas of the state. During 2004-2009, a total of 2,061 feral individuals of D. saccharalis were collected from four geographical locations in Louisiana and examined for Cry1Ab resistance alleles using F1/F2 screening methods. Cry1Ab resistance allele frequency was low (0.0011) for the populations collected during 2004-2008, but increased in 2009 (0.0136). A highly Bt resistant strain (Cry1Ab-RR) of D. saccharalis was isolated from a field population by using the F2 screen. The Cry1Ab-RR strain was able to survive and complete larval development on commercial Cry1Ab maize plants. Relative to a susceptible strain of D. saccharalis, the resistant strain showed an approximately 100-fold resistance to Cry1Ab and also exhibited a significant resistance to Cry1Aa and Cry1Ac. Larvae of the resistant heterozygotes demonstrated relatively high survivorship rates on Cry1Ab maize hybrids which were commonly planted in Louisiana, suggesting most Cry1Ab maize hybrids planted in the state did not express a "high dose" against D. saccharalis. Cry1Ab resistance in D. saccharalis was likely controlled by one (or a few linked) autosomal gene. However, effective dominance level of resistance varied depending on bioassay methods and maize hybrids, ranging from incompletely recessive to incompletely dominant. In addition, the Cry1Ab resistance in D. saccharalis was not associated with any fitness costs and the resistance was stable after 24 generations without selection. The results of the 6-year study suggest that there appears to be a high risk for development of Cry1Ab resistance in D. saccharalis if Cry1Ab maize continues to be widely used in the U.S. mid-south region. © 2011 by Nova Science Publishers, Inc. All rights reserved.

Publication Source (Journal or Book title)

Genetically Engineered Crops: Biotechnology, Biosafety and Benefits

First Page

89

Last Page

104

This document is currently not available here.

Share

COinS