Induction with <sup>60</sup>Co gamma rays of modification variability and mutation of China aster (Callistephus chinensis Nees

Abstract

The effect of radiation on variability was investigated in plants of five varieties of China aster, grown from seeds pretreated with various doses of gamma rays (generation M<sub>1</sub>) and in the progeny of these plants (generation M<sub>2</sub>). Both in generation M<sub>1</sub> and in M<sub>2</sub> the frequency of occurrence of radiation induced changes varied. In the M<sub>1</sub> generation, beside teratological changes found most frequently in early periods, the observed variability concerned mostly leaves, their colour and size and the form of the lingual flowers. Plants with a different colour of flowers or a different habit were only sporadic. The changes induced by radiation were more frequently observed in the M<sub>2 </sub>generation than in the M<sub>1</sub> They involved the following characters: height and habit of plants, colour of shoots, leaves and flowers, the forms of lingual marginal flowers, the time of flowering and the perfume. Most frequently changes were observed in several characters. When the shoots and leaves colour showed changes of anthocyanin type, the colour of the flowers was usually also modified. Most changed plants were noted after a dose of 9 kR in the M<sub>1</sub> generation, and after 6-9 kR in the M<sub>2</sub> generation. These doses were described in generation M<sub>1</sub> at the stage of flowering in most of the tested varieties as LD<sub>50</sub>.