No, it is not Fukushima. Yes, it is a mutation. This is a curious case of fasciation.
It is rare, but not unusual for Marguerite daisies.

According to Wikipedia:

Fasciation, is a relatively rare condition of abnormal growth in vascular plants in which the apical meristem (growing tip), which normally is concentrated around a single point and produces approximately cylindrical tissue, instead becomes elongated perpendicularly to the direction of growth, thus producing flattened, ribbon-like, crested (or “cristate”), or elaborately contorted, tissue.

Fasciation can be caused:

• by hormonal imbalances in the meristematic cells of plants
• by random genetic mutation
• by bacterial and viral infections
• by environmental factors: fungi, mite or insect attack, exposure to chemicals and exposure to cold and frost.

This mutant Marguerite daisy was found on the edge of a cereal crop in Córdoba, where you can see that there are no other plants like poppies or daisies. This is due to the pressure of herbicides that have been selected to prevent the growth of these species.
I am inclined to think that the use of these products may be behind this fasciation.

To prevent this damage in the genetic material, it is recommended to protect plants from sources that cause fasciation.