|NIU, YING - Louisiana State University|
|Meagher, Robert - Rob|
|YANG, FEI - Louisiana State University|
|HUANG, FANGNENG - Louisiana State University|
Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2013
Publication Date: 9/1/2013
Citation: Niu, Y., Meagher Jr, R.L., Yang, F., Huang, F. 2013. Susceptibility of field populations of the fall armyworm (Lepidoptera: Noctuidae) from Florida and Puerto Rico to purified Cry1F protein and corn leaf tissue containing single and pyramided Bt genes. Florida Entomologist. 96(3):701-713.
Interpretive Summary: Fall armyworm (Spodoptera frugiperda) is a caterpillar pest that attacks many field and vegetable crops in the United States, Caribbean, Central America, and South America. In Florida and Louisiana it is the most serious insect pest of sweet corn. Several corn seed producing companies have winter nurseries in Puerto Rico. In 2007 fall armyworm was found to be resistant to Bt corn, especially those corns that had the Cry1F Bt protein. That resistance has now been found in some populations in Florida and Louisiana. Scientists from Louisiana State University and from USDA-Agricultural Research Service, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, Determined if these populations are also resistant to corns that have several Bt genes (pyramided) and a new type of corn (Viptera). Feeding studies showed that a susceptible population from Florida could not survive on any of the Bt corns but the resistant population from Puerto Rico survived well on all Bt corns except for the Viptera corn. The susceptible population from Florida was crossed with the resistant population from Puerto Rico and those larvae were able to survive on some of the pyramided Bt corn lines. These results suggest that careful selection of Bt genes is essential in use of gene pyramiding strategy for resistance management of fall armyworm.
Technical Abstract: Larval survival of Cry1F-susceptible (FL), -resistant (PR and Cry1F-RR), and -heterozygous (FL x PR and Cry1F-RS) populations of the fall armyworm, Spodoptera frugiperda (J.E. Smith) to purified Cry1F protein and corn leaf tissue of seven Bacillus thuringiensis (Bt) corn hybrids and five non-Bt corn hybrids was evaluated in the laboratory. The seven Bt corn hybrids represent five Bt corn traits: Herculex®I, which expresses a single Bt protein (Cry1F), and Genuity®VT Double ProTM, VT Triple ProTM, SmartStaxTM, and Agrisure® VipteraTM 3111, which contain = two pyramided Bt genes. The original FL and PR populations were collected from corn fields in 2011 in Florida and Puerto Rico, respectively. Diet-incorporation bioassays showed that FL was susceptible to Cry1F protein with a LC50 value of 0.13-0.23 µg/g, while PR was highly resistant to Cry1F protein (>137-fold). FL was also susceptible to all seven Bt corn hybrids with a 7-day mortality of >95%, while PR and a backcrossed and reselected population, Cry1F-RR, were highly resistant to Cry1F corn leaf tissue. The resistance was recessive or incompletely recessive. All five populations of S. frugiperda could survive on VipteraTM 3111, suggesting this Bt corn trait can completely overcome the resistance and thus should provide a means of managing Cry1F resistance in S. frugiperda. However, Cry1F-RR exhibited a significant cross-resistance to the leaf tissue of the other three pyramided Bt corn traits. The possible cross-resistance between single-gene and pyramided Bt corn products suggest that careful selection of Bt genes is essential in use of gene pyramiding strategy for resistance management.