The gibberellic 20-oxidases are important enzymes that catalyze some of the later steps in the gibberellic acid biosynthetic pathway. The GA 20-oxidases are encoded by three nuclear of a gene family that encodes other enzymes active in the gibberellic acid biosynthetic pathway, such as 3b-hydroxyase encoded by Mendelís stem length gene Le. The GA 20-oxidases are members of the 2-oxoglutarate dependent dioxygenase group of enzymes. The genes encoding the three GA 20-oxidases have diverged sufficiently so as to make it possible to design ortholog specific primers for each paralog using published sequence data from Pisum, Phaseolus, and Glycine. We are using these sequence data to test or provide additional support for selected phylogenetic relationships among genera in subfamily Papilionoideae that have been hypothesized on the basis of morphological data and/or phylogenetic analyses of the family based on chloroplast gene sequences. Two examples are as follows. Phylogenetic analyses of matK data indicate that Trifolium is basal to a clade composed of genera in the Vicieae, Vicia, Lens, Pisum, and Lathyrus rather than being in a clade with other genera in the Trifolieae, the tribe in which Trifolium is placed. The relationship suggested by matK data is supported by phylogenetic analyses of genes encoding GA 20-oxidases. Within the Millettieae/Phaseoleae clade analyses of matK data indicate that Dalbergiella is sister to a clade consisting of core Millettieae, Phaseoleae and related genera, but this relationship is weakly supported; however analyses of genes encoding GA 20-oxidases provide strong support for this relationship. Genes encoding GA 20-oxidases provide phylogenetically informative characters that support a number of hypothesized relationships within subfamily Papilionoideae.

Key words: Fabaceae, nuclear-encoded genes, phylogenetic analyses