Abnormalities in Chrysanthemum Regenerated from Long Term Cultures

Plants regenerated from leafy callus of Chrysanthemum morifolium Ramat. maintained for 9 years (LC plants) were compared to those regenerated from leafy callus maintained for 1 month (SC plants) in order to assess the effects of long-term culture. LC plants differed morphologically from those derived from the 1-month culture. Aberrant forms, proliferation of apical buds, variable leaf shapes and stunted growth were observed in 15 per cent of the LC plants. The remaining 85 per cent were characterized by excessive growth of lateral shoots. Flowers were smaller and irregularly formed in most LC plants. Although the growth rates of plants in both LC and SC groups were similar, flowering was delayed considerably in the LC plants. Application of GA3 or IAA had no effect in restoring normal form. Genetic instability, chimeral rearrangement and residual hormone effects are offered as possible explanations for the abnormalities observed.