In mutation breeding of chrysanthemum the regeneration in vitro of adventitious shoots from ligulate florets can lead to the separation of chimera components and, as a result, to producing a new original cultivar. The success of that method considerably depends on the result being the number of the shoots formed. The more is produced, the greater the chances for an effective separation of chimera components and creating a new stable cultivar. The present research defines the effect of such factors as the inflorescence development stage, the type of the explant as well as the position of its inoculation on the increase in the efficiency of adventitious shoots regeneration. The ligulate florets of Chrysanthemum × grandiflorum (Ramat.) Kitam. ‘Cool Time’ were inoculated on the Murashige and Skoog [1962] medium supplemented with 2 mg∙dm^-3 BAP and 0.5 mg∙dm^-3 NAA. There was shown no significant effect of the inflorescence development stage (incompletely open with a partially visible disk or with the entire visible disk in which tubular florets do not produce pollen or completely open in which two or half of the whorls of tubular florets produce pollen) on the shoot regeneration efficiency. Most shoots regenerate on transversely- or lengthwise-cut into half or on the entire pierced ligulate florets – horizontally inoculated, with the abaxial side on the medium.

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