Dose effect gamma-irradiation in obtaining color mutants of inflorescence of chrysanthemum (Dendranthema grandiflorum).
Mutation induction in ornamental plant breeding is intensively used in several countries including Brazil, resulting in the
release of several new cultivars. Mutation induction can affect the frequency and spectrum of the resulting mutants as well
as the types of chimerism (sectorial or mericlinal or periclinal chimeras). Among these, the dose used in the mutagenic
treatment is of high importance. Therefore, preliminary experiments evaluating sensitivity of the material to be used are
indispensable. The objective of this study was to evaluate the effect of different doses of gamma-rays on mutation
frequency in color of inflorescence and type of chimerism of non-rooted cuttings of chrysanthemum ‘Cherry Dark’. The
doses tested were 0, 10; 12.5; 15; 17.5; 20; 25 and 30 Gy of gamma-rays in seven consecutive experiments. Survival
number, total number of mutants, number of mutants of inflorescence color and type of chimerism were evaluated. Plant
height was evaluated only in the first experiment. Tendency of linear decrease in plant height and quadratic tendency in
survival percentage was observed with increased doses of the mutagen. The GR50 (reduction of 50% in the growth) for
this variety was estimated to be 18.1 Gy. Higher frequencies of mutants, including inflorescence color, were observed in
the doses of 10 and 12.5 Gy, with a tendency of reduction in higher doses. Periclinal mutants were observed in 15 Gy and
upper doses. The observed tendency was of increasing frequency of mutations with increasing dose.