Abstract
Abstract A transgenic Pioneer Brand corn, ‘3 IB 13’, expressing an insecticidal protein CrylA(b) (produced by the cryLA(b) gene from Bacillus thuringiensis ssp. kurstaki, i.e., YieldGard®, Monsanto Company), and the nontransgenic near-isoline, Pioneer Brand 3223 (Pioneer Hi-Bred International, Inc.), were planted 26 Mar at Texas A&M University Research and Extension Center, Corpus Christi, TX. Field plots were 4 row (38 inch centers) X 30 ft. The four treatments were the two corn hybrids, with and without an artificial infestation of CEW on ears at silking. The treatments were arranged in a RCB design and each plot was replicated 4 times. All plots also had natural infestations of CEW and FAW. The entire test was treated at planting with a band (6 inch) application of Counter 15G (1.04 lb (AI)/acre) over the seed drill for control of corn rootworms. Rainfall was 5.63 inches during the crop season. Supplemental drip irrigation was provided in Jun, 1.9 inches, and in Jul, 1.4 inches. Artificial infestations of silk with CEW eggs were made at the green silk stage on 5 Jun. Eggs were suspended in a 0.2% agar solution and applied with an Eppendorf® Repeater Pipette (Brinkmann Instruments, Westbury, NY) at the rate of 30^10 eggs/ear. The treatments were evaluated for whorl injury on 27 May by sampling 20 plant whorls/plot for CEW and FAW leaf feeding using the 0-9 rating scale method (least feeding to most feeding, respectively) developed by F. Davis (1992). CEW and FAW larvae were collected from the 2 outside rows in each plot to determine the proportion of CEW and FAW feeding in whorls (collected 30 May) and ears (collected 19 Jun). On 28 Jul 10 plants/plot were sampled from the center 2 rows to determine stalk tunneling, measured as inches per plant and ear shank tunneling, measured as 0 = absent or 1 = present. Ear kernel injury was determined at harvest, 25 Jul, by sampling 20 ears from the middle two rows. Kernel injury was rated with the Neil Widstrom (1967) method. Corn was hand harvested from the middle two rows on 25 Jul, thrashed, weighed, and adjusted to 15.5% moisture.
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