Smilansky, Z., Department of Ornamental Plants, The Volcani Centre, ARA, Beit Dagan, Israel
Umiel, N., Department of Ornamental Plants, The Volcani Centre, ARA, Beit Dagan, Israel
Zieslin, N., The Department of Ornamental Horticulture, The Hebrew University of Jerusalem, Rehovot, 76100, Israel

Stem cuttings of roses cv. Mercedes were exposed to various doses of gamma rays or ethyl methanesulphonate (EMS). More mutants were obtained from irradiation than by chemical mutagenic treatment. Individual budding on a rootstock was found to be a more rapid method of isolation of mutations than the usual applied 'cutting-back' method. Stem tissue was more sensitive to irradiation than bud-tissue. Most mutations obtained were due to changes in the content and relative ratio of cyanin and pelargonin pigments. This resulted in a range of petal color changes, from light orange cream through pink, salmon, orange, red to dark red. The appearance of mutations such as changes in flower size, shape, number of petals, thorniness, etc. was less frequent. © 1986.