Our studies in the grass family Poaceae have concentrated on understanding diversity in inflorescence morphology. We have focused on the analysis of inflorescence evolution in the panicoid ‘bristle grass’ clade (including Setaria, Pennisetum and Cenchrus), as an example of the way in which molecular phylogenetic hypotheses can be combined with developmental and genetic data to understand morphological evolution. Analysis of developmental morphology with phylogenies derived from molecular data sets has enabled us to identify a small number of parameters that can control morphological diversification. These include numbers of orders of branching, numbers of primordia produced on each branch, and timing and amount of branch axis elongation. Changes in these characters occur numerous times throughout the phylogeny, suggesting that only minor changes in a few genes are required to change inflorescence morphologies. We are testing this hypothesis by a quantitative trait loci (QTL) analysis of a Setaria italica by S. viridis cross. Preliminary results indicate that numbers of primary branches and length of the inflorescence are controlled by only a few genes, as predicted.

Key words: developmental morphology, inflorescence evolution, phylogeny, Poaceae, quantitative trait loci (QTL) analysis, Setaria