Submitted to: Gatersleben Research Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 15, 1996
Publication Date: N/A
Technical Abstract: A major goal in the USDA-ARS maize genetics research program at Raleigh, North Carolina, USA, has been the development and evaluation of more efficient methods for improving quantitative traits, particularly grain yield. Rapid advancements in marker technology in plants have provided the tools for accomplishing this goal. Initial efforts involved the use of isoenzymes, but these have been largely replaced by several DNA-based tech nologies. A major recent study in maize focused on the genetic basis of heterosis in a widely used single-cross hybrid (B73 x Mo17). Using isozymes and DNA-based markers, QTLs affecting grain yield (and several other quant- itative traits) were found on most of the 10 maize chromosomes. Although there was some evidence for overdominant gene action, much of the heterotic response affecting grain yield could be attributed to dominance. In a companion study, QTLs were identified in two other elite maize inbred lines, Tx303 and Oh43, that were expected to enhance the heterotic respons found in the B73 x Mo17 hybrid. Marker-facilitated backcrossing was used to transfer one to four targeted QTLs from Tx303 into B73 and from Oh43 into Mo17. The resulting "Enhanced" B73 lines were crossed with the "Enhanced" Mo17 lines and these "Enhanced" hybrids were evaluated in field tests with the original hybrid and a commercial hybrid as checks. A large proportion of the "Enhanced" hybrids yielded as much or more grain than the check hybrids and the highest yielding "Enhanced" hybrids exceeded the checks by 10 to 12% (1.0 to 1.25 t/ha). These results have been corroborated in field tests over three years (including tests in Iowa and Indiana) and have demonstrated that marker-facilitated technology can be successfully employed to manipulate complexly inherited traits, such as grain yield.