Induction and selection of low-temperature-tolerant mutants of Chrysanthemum morifolium Ramat

In the winter of 1984/1985, 23 clones of presumed low-temperature-tolerant mutants (i.e. early flowering at low temperature) of the chrysanthemum cultivar Parliament were grown in the greenhouse for selection on early flowering at 12 deg. C day/night. The plants originated from adventitious plantlets produced by X-irradiated explants. Twenty-one plants were selected previously on a one-plant basis, 15 in a 'Selectron' and 6 in the greenhouse. Two plants (M8204-7 and M8204-8) were selected earlier on a clonal basis. The present results show that these two mutants indeed flowered significantly earlier compared with the control plants. From the 21 plants previously selected, only M8305-6 and M8305-8 were control plants. From the 21 plants previously selected, only M8305-6 and M8305-8 were selected as low-temperature-tolerant mutants. These two belonged to the group of six plants selected in the greenhouse; none of the plants selected under Selectron conditions flowered earlier in the analysis. This indicates that a second selection is necessary to prove the true character of the mutants. In a second experiment, plantlets were regenerated from X-irradiated cell suspensions of the same cultivar and grown under the same winter conditions as mentioned above for selection for low-temperature tolerance. Out of 525 regenerated plantlets, 25 flowered distinctly earlier. Most of them (60%) appeared to be relatively long, as measured after a period of 42 short days. (author)