Master of Science (MS)
The sugarcane borer, Diatraea saccharalis (F.), is a major target of Bacillus thuringiensis (Bt) corn in the U.S. mid southern region. Corn expressing pyramided Bt proteins has recently become commercially available in the U.S. The objectives of this study were 1) to determine survival and plant injury of Cry1Ab-susceptible (Cry1Ab-SS), -resistant (Cry1Ab-RR), and –heterozygous (Cry1Ab-RS) genotypes of D. saccharalis on Bt corn containing single and pyramided Bt genes and 2) to assess larval movement of D. saccharalis in different planting patterns of non-Bt and Bt corn. One laboratory leaf tissue bioassay and two independent greenhouse trials were conducted to evaluate larval survival and plant injury on five corn hybrids. On intact plants of non-Bt corn, 43-62% larvae survived after 21 days. Larval survivorship on Cry1Ab corn was 4.7- 5.6% for Cry1Ab-SS, 29.4-32.5 % for Cry1Ab-RS, and 36.6- 45.6% for Cry1Ab-RR. In contrast, the 21-day survivorship on the two pyramided Bt corn hybrids was <5% for the three insect genotypes. Results of the leaf tissue bioassays were consistent with the greenhouse tests. Larval movement of D. saccharalis was evaluated in four planting patterns of non-Bt and Bt plants containing Genuity® SmartStaxTM traits. The four planting patterns were: 1) pure stand of Bt corn, 2) a non-Bt corn plant surrounded by 26 Bt corn plants, 3) pure stand of non-Bt corn, and 4) a Bt corn plant surrounded by 26 non-Bt corn plants. Studies were conducted in three conditions: 1) greenhouse; 2) open field with artificial infestations of 50 eggs on the center plants; and 3) open field study with artificial infestations of 10 neonates on every plant. Larvae of D. saccharalis showed the ability to move from infested plants to at least four plants away and from the infested rows to adjacent rows. The results showed that the pyramided Bt corn can overcome the Cry1Ab resistance and thus should offer a means for Cry1Ab resistance management in D. saccharalis. Together with previous data, the results indicate that the seed mixture strategy might be able to provide a similar refuge population of D. saccharalis as the structured refuge planting.
Document Availability at the Time of Submission
Release the entire work immediately for access worldwide.
Wangila, David Sindani, "Evaluation of Bacillus thuringiensis corn containing pyramided traits for management of sugarcane borer, Diatraea saccharalis (F.)" (2012). LSU Master's Theses. 1578.