Sorghum [Sorghum bicolor (L.) Moench] is an important crop for human consumption, feed, fiber and recently biomass production. Understanding the genetic mechanisms controlling plant architecture traits will be beneficial for developing superior plant ideotypes for both grain and bioenergy production. The Sorghum Association Panel (SAP) with a remarkable diversity (>300 lines) is an excellent natural resource to dissect the genetic basis of plant architecture. We have utilized a genome-wide association study (GWAS) to investigate the genetic mechanisms underlying natural phenotypic variation in plant height, flowering time, panicle exsertion, panicle length, stem circumference, seed number, internode number, tiller number, leaf angle. The genotypic data used in this study included both publicly available GBS data and gene-specific markers developed by Sequenome for the gibberellin (GA) biosynthesis and signaling pathways. A total of 101 SNP representative regions were associated with at least one of the nine plant architecture traits investigated and two of them corresponded to GA candidate genes affecting plant height and seed number, respectively. The candidate gene SbKS3, associated with variation in seed number per panicle had two alternative haplotypes that corresponded to high and low seed number lines. The second project confirmed the effect of SbKS3 on seed number and, preliminary evidence suggests that this effect is generated by a modification in panicle branch length.