| Plants provide all the energy that animals use. Therefore, herbivory is an inevitable selection pressure on every plant species. Producing axillary meristems is one solution to the problem of losing reproductive structures to herbivores. As long as a plant's primary apex is intact, axillary meristems are often in a dormant state, but as soon as the apex is removed or damaged, axillary buds start to grow. This phenomenon is known as apical dominance. This dissertation focuses on the genetic basis of developmental and physiological aspects of this response which we call the Inflorescence Replacement Program (IRP) of Arabidopsis thaliana.;The long-term goal of this project is to characterize the genes responsible for IRP variation in Arabidopsis. The research presented here began by surveying accessions from a collection of geographically diverse Arabidopsis accessions. Five major phenotypic clusters within 85 accessions were identified. High heritability was seen for IRP phenotypes among the 85 genotypes. Principal component analysis (PCA) suggested several distinct IRP strategies within each cluster. Twelve accessions that represented each cluster were chosen and intercrossed in a partial diallel design with the ultimate aim of mapping quantitative trait loci (QTL) in the populations derived from these crosses. Owing to time constraints, a Bay x Sha recombinant inbred (RI) population rather than the diallel progeny was used to map QTL for IRP traits. A total of 11 QTL were detected for IRP traits, and several candidate genes involved in the apical dominance were identified near the QTL. |
