Bt and Non-Bt Maize Growth and Development as Affected by Temperature and Drought Stress
2000
Traore, Seydou B. | Carlson, Richard E. | Pilcher, Clinton D. | Rice, Marlin E.
Seed companies have commercialized new transgenic maize (Zea mays L.) hybrids that are resistant to European corn borer [Ostrinia nubilalis (Hübner)]. Drought stress may affect the expression of Bt proteins in maize tissues, and its resistance to European corn borer (ECB). This study was conducted at the Iowa State University Hinds Irrigation Farm, Ames, IA, to characterize the effect of drought stress on Bt maize. Growth and development measurements were taken in 1997 and 1998 from Bt and non-Bt maize plants subjected to various soil water deficit treatments during peak ECB egg laying periods (late June, first generation; late July, second generation) on maize plants grown in buried, 1 m deep, 123-L containers filled with Nicollet loam soil (fine-loamy, mixed, superactive, mesic Aquic Hapludolls). Water deficit delayed leaf appearance up to 6 d, depending on leaf number and tasseling up to 3 d. It also reduced leaf area as much as 33% and plant height by 15%, depending on leaf number and timing of water deficit. For these characteristics, there was no significant difference between Bt and non-Bt maize plants. There were significant differences among Bt and non-Bt plants for second generation corn borer damage with Bt plants affected the least. This resulted in significant yield differences between Bt and non-Bt plants. Compared with non-Bt plants, Bt plants exhibited significantly greater total plant weight in 1997 (9.7%) and grain yield in 1998 (9.4%). These differences depended on variety and seemed related to 100-seed weights.
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