Interspecific Hybridization of Melilotus alba × M. Officinalis Using Embryo Culture 1

OWEETCLOVER breeders have been striving for several O years to develop productive strains which are free from or relatively low in coumarin. Following Smith's (8) successful transfer of genes for low coumarin content from Melilotus dentata to white sweetclover, M. alba, more rapid progress has been made toward this goal. The resulting low coumarin strains are all of the M. alba type, whereas there is considerable evidence that varieties of the yellow-flowered species, M. officinalis, are more drought tolerant and better adapted over much of the Great Plains Region. Selection within strains and varieties of M. officinalis has failed to produce plants which are low enough in coumarin to be of use in a breeding program. Efforts to introduce genes for low coumarin directly from M. dentata have not been successful, since this species and M. officinalis appear to be completely incompatible even though their chromosome numbers are the same. Reciprocal crosses between M. officinalis and M. alba frequently result in a stimulation of ovule development, although viable seed from this cross has never