| All plants pass through several different phases during development. The timing and duration of the transition between these phases is important both for plant fitness as well as agronomically. In maize, those phases are the juvenile vegetative, adult vegetative and reproductive. Juvenile and adult tissues differ dramatically in their anatomical and biochemical composition, which affects both potential for animal feed and biofuel feedstock as well as disease and insect resistance. While the timing of the vegetative to reproductive transition is well characterized and studied, the molecular network controlling juvenile to adult vegetative phase change in maize is poorly understood. The objective of my thesis was to characterize the genetic structure of this developmental transition as well as assess it's agronomic potential for use in the lignocellulosic ethanol industry.;The Nested Association Mapping Population (NAM) as well as two novel mapping populations, without the use of B73 as a parent, were used to characterize the genetic structure and identify QTL controlling the timing of vegetative phase change. Using high-resolution genomic maps, novel QTL and candidate genes were identified. Stover of extreme genotypes for early and late timing of vegetative phase change were identified from the NAM population and evaluated as inbreds per se as and in a hybrid context. Although phenotypic diversity for the timing of vegetative phase change existed, none of the composition or digestibility traits were significantly different between early and late transitioning lines. Our results show that stover composition will not change with extended juvenility. |
