Cytology and digoxin production in hybrids between Digitalis lanata and D. grandiflora

Summary Digitalis lanata is the only commercial source of the cardiac glycoside digoxin. It is an outbreeder and displays considerable variation. An attempt to increase uniformity was made by making D. lanata × D. grandiflora diploid hybrids and from these produce allotetraploid hybrids using colchicine treatment. Such tetraploid plants would be homozygous. Tetraploid hybrids were shown to contain digoxin but at lower levels than in D. lanata. Progeny of selfed tetraploid hybrids were significantly more uniform than D. lanata grown from commercial seed, but were considerably less vigorous.