The nuclear gene Le, the original stem length gene studied by Gregor Mendel, encodes 3B-hydroxylase, a key enzyme in the gibberellic acid biosynthetic pathway. Nucleotide sequences of this single copy nuclear gene were used for phylogenetic analyses of representatives of genera traditionally included in the Trifolieae and Vicieae, with representatives of tribes Cicereae and Galegeae used as outgroups. This gene consists of two exons of approximately 1.1 Kb with a large intron of about 544 bp. Exon sequences are sufficiently conserved to be useful for analyses of genera within these two tribes. Intron sequences are useful only for analyses within genera. Consistent with our earlier results from analyses of matKsequences for these taxa, Medicago, as defined by floral characters associated with an explosive pollination syndrome, forms a well-supported monophyletic group distinct from that formed by Melilotuswhich is nested within Trigonella. Trifoliumis basal to the remainder of Trifolieae (excepting Parochetus).  Within Vicieae Viciais basal to Pisumand Lathyrus. Phylogenetic analyses of these sequence data provide a framework to consider hypotheses about the evolution of trifoliate leaves and floral and fruit characteristics in these clades.

Key words: 3Beta-hydroxylase, Fabaceae, phylogeny, stem length gene Le, Trifolieae, Vicieae