Development of Novel DNA-Based Methods for Detection of Bt Resistant Fall Armyworms


During the past 22 years, pest control efficacy and the potential for higher net returns have driven a global increase in the adoption of transgenic crops which produce insecticidal proteins (Cry and Vip toxins) from the bacterium Bacillus thuringiensis (Bt crops). In the US alone, Bt corn and cotton adoption represent >80% of the national acreage devoted to the two commodities, which has unfortunately led to increasing selection pressure for evolution of Bt toxin resistant insect pests.

One such devastating pest is the fall armyworm (Spodoptera frugiperda) which has become a growing threat to the use of transgenic corn technology in the Western Hemisphere and more recently the African continent. The fall armyworm is the insect pest with the highest number of field-evolved practical resistance cases to Bt crops. In fact, fall armyworms displaying resistance to Bt corn have now been documented in Puerto Rico, Florida, North Carolina, Brazil, and Argentina.

Research funded by a grant from the USDA-NIFA Biotechnology Risk Assessment Grant program (BRAG) and published in the journal Scientific Reports in 2017 by a team of investigators led by Professor Juan Luis Jurat-Fuentes, from the Department of Entomology and Plant Pathology (EPP) at the University of Tennessee, identified a particular DNA mutation in a gene designated SfABCC2 which provides fall armyworms with field resistance to Bt corn. This team was also able to further track changes in the mutant gene frequency in fall armyworm populations in Puerto Rico, the first successful case of DNA-based detection of insects exhibiting emerging field-evolved practical resistance to a transgenic Bt crop.

Building on the findings of that study, Professors Jurat-Fuentes and Kurt Lamour (EPP), submitted and were successfully awarded a multi-year research grant from the USDA-NIFA Agriculture and Food Research Initiative program (AFRI) to develop a high throughput DNA-based method that would detect fall armyworms displaying resistance to the Bt toxins produced by transgenic corn.


“Fall armyworm samples collected by our collaborators from Brazil, Colombia and Africa will allow us to determine the frequency of candidate resistance alleles in populations from different continents. This information is critical to current efforts to control the pest here in the US, South America and in Africa, where it is threatening half of the corn harvest,” Juan Luis Jurat-Fuentes said.


The DNA high throughput method they are exploring takes advantage of technology that Dr. Kurt Lamour has developed with his company, Floodlight Genomics, LLC. The expected outcomes of the research are a rapid and sensitive method that will help determine: 1) which gene/s should be screened for resistance alleles, 2) are there resistant insects present in a location? 3) how is insect migration affecting resistance dispersal?

The ongoing research in the laboratories of Professors Jurat-Fuentes and Lamour will lead to a greater understanding of the genetic mechanisms involved and drive the development of rapid, sensitive methods to detect emerging resistance to Bt crops among insect pests.

Reference:

Banerjee, R., J. Hasler, R. Meagher, R. Nagoshi, L. Hietala, F. Huang, K. Narva, and J. L. Jurat-Fuentes (2017) 'Mechanism and DNA-based detection of field-evolved resistance to transgenic Bt corn in fall armyworm (Spodoptera frugiperda)' Sci. Reports 7(1): 10877. https://www.nature.com/articles/s41598-017-09866-y

USDA-NIFA-AFRI: 2017-08481. Receptor-Cry Toxin Interactions and High Throughput DNA-based Tools to Predict Resistance to Bt Crops in Fall Armyworm. https://portal.nifa.usda.gov/web/crisprojectpages/1015328-receptor-cry-toxin-interactions-and-high-throughput-dna-based-tools-to-predict-resistance-to-bt-crops-in-fall-armyworm.html

David White