Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Genetics, Development and Cell Biology

First Advisor

Erik Vollbrecht


Branching architecture of the flower-bearing structures in grasses, known as inflorescences, is a morphological trait that is subject to natural and artificial selection since it affects both reproduction and grain yield. Genes underlying this trait are sought to explain the molecular basis underlying the phenotypic diversity of these structures. The ramosa1 (ra1) gene encodes a transcription factor that controls branching architecture in maize inflorescences (tassel and ear). Reduced ra1 activity in maize produces ears with crooked rows of kernels due to the generation of extra spikelets, a phenotype that may have been selected on during the derivation of modern maize. Patterns of nucleotide diversity coupled with statistical tests and phylogenetics suggest a regulatory element at the ra1 locus was a target of artificial selection during maize's domestication from its wild progenitor teosinte. We also narrowed the timeframe for the probable origin of ra1 during the evolution of grasses and found sequence variations in some species correlate with their respective inflorescence architectures. These results suggest this gene was important in the evolution of inflorescence architecture in other grasses, most notably in sorghum where statistical tests show ra1 may have been a target of artificial selection during its evolution, most likely to increase grain yield. Since this gene may have been important during the domestication and cultivation of two crops, maize and sorghum, this research may lead to future breeding projects to increase grain yield in these and other cereal grasses.


Copyright Owner

Brandi Adell Sigmon



Date Available


File Format


File Size

161 pages