Bt and non-Bt maize growth and development as affected by temperature and drought stress

Seed companies have commercialized new transgenic maize (Zea mays L.) hybri ds that are resistant to European corn borer [Ostrinia nubilalis (Hubner)]. Drought stress may affect the expression of Bt proteins in maize tissues, and its resistance to European corn borer (ECB). This study was conducted a t the Iowa State University Hinds Irrigation Farm, Ames, IA, to characteriz e the effect of drought stress on Bt maize. Growth and development measurem ents 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 plant s grown in buried, 1 m deep, 123-L containers filled with Nicollet loam soi l (fine-loamy, mixed, superactive, mesic Aquic Hapludolls). Water deficit d elayed 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 characteris tics, there was no significant difference between Bt and non-Bt maize plant s. There were significant differences among Bt and non-Bt plants for second generation corn borer damage with Bt plants affected the least. This resul ted 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 dep ended on variety and seemed related to 100-seed weights.