Master of Science (MS)
The fall armyworm, Spodoptera frugiperda (J.E. Smith), is a target pest of Bacillus thuringiensis (Bt) corn in North and South America. In this study, multiple tests were conducted in the laboratory and greenhouse to 1) determine the susceptibility of two field populations of S. frugiperda collected from Florida (FL) and Puerto Rico (PR) to purified Cry1F protein and Bt corn leaf tissue and 2) evaluate larval survival of and plant injury by Cry1F-susceptible, -resistant, and –heterozygous genotypes of S. frugiperda on whole plants of transgenic corn containing single and pyramided Bt genes. Corn hybrids evaluated in this study included five non-Bt corn hybrids, two single-gene Bt corn products, Herculex®I (Cry1F corn) and YieldGard® (Cry1Ab corn), and four pyramided Bt corn traits: Genuity®VT Double ProTM, VT Triple ProTM, SmartStaxTM, and Agrisure® VipteraTM 3111. Diet-incorporated 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 (>137-fold). Leaf tissue bioassays also exhibited that FL was susceptible to all Bt corn hybrids, while PR was highly resistant to Cry1F corn leaf tissue. Both FL and PR could not survive on leaf tissue of VipteraTM 3111. However, PR exhibited a significant cross-resistance to the leaf tissue of the other three pyramided Bt corn traits. In greenhouse whole plant tests, larvae of the three insect genotypes on non-Bt corn hybrids survived well and caused serious plant damage. Cry1Ab corn was ineffective against all three insect genotypes. On Cry1F corn plants, resistant larvae survived on 72.9% plants after 12-15 d and caused significant leaf injury. In contrast, no live larvae and little or no leaf injury were observed on the Cry1F corn plants that were infested with susceptible or heterozygous genotypes, or on the pyramided Bt plants infested with the three insect genotypes. The results demonstrated that the Puerto Rico population of S. frugiperda was highly resistant to both purified Cry1F protein and Cry1F corn plants and the resistance was recessive. Corn hybrids containing any one of the four pyramided Bt traits are effective for managing the Cry1F resistance in S. frugiperda.
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Niu, Ying, "Resistance of fall armyworm, Spodoptera frugiperda (J.E. Smith) to Bacillus thuringiensis" (2014). LSU Master's Theses. 244.