Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

A. Susana Goggi


Pollen movement and the resulting flow of genes between plant populations have been an integral part of corn evolution. However, the adventitious presence of bioengineered genes in conventional varieties due to gene flow is a serious concern when producing grain for specialty markets, organic products, crops with valued added traits, and seed. An additional concern is the release of corn bioengineered to produce pharmaceutical and industrial compounds. The objectives of this study were to detect the presence of transgenes in corn DNA from pollen and to compare the gene flow and outcross in a seed and grain fields using a combination of three markers genes, seed color, Bt, and RR. Chapter 1 contains a pollen DNA extraction protocol for corn and a comparison of the efficiency of 11 primer pairs at detecting the Bt transgene; Chapter 2 presents the study of outcross in large-scale corn fields with different pollen density, grain and seed fields; and Chapter 3 presents the resulting outcross in large-scale corn fields with similar pollen density, grain fields, across environments. The proposed pollen DNA extraction method was very effective in extracting DNA from pollen samples and the primer pair 35S168F/35S317R was the most efficient in identifying the CaMV35S promoter sequence in transgenic varieties. There were significant differences of outcross at different distances and directions from the pollen source associated with wind speed and direction. The differences in outcross distribution between grain and seed fields in 2003 were statistically significant, but inconclusive in grain fields in 2003 and 2004. Our results showed that segregation of transgenic and nontransgenic corn can not be achieved within the 250 m distance because the outcross level seldom reached zero percent.



Digital Repository @ Iowa State University,

Copyright Owner

Higinio Lopez-Sanchez



Proquest ID


File Format


File Size

111 pages