Research PaperMicrowave treatment can induce chrysanthemum phenotypic and genetic changes

- Microwaves at higher doses affect the regeneration potential of explants.
- Irradiation of callus is more efficient in comparison to treatment of leaves.
- Microwaves stimulate the development of longer stems and bigger inflorescences.
- In vitro irradiation of explants can lead to the production of new plant phenotypes.
- Microwaves can be a useful and easy-to-access tool in mutation breeding.

The impact of microwaves on the DNA of plant cells is still ambiguous, but the usage of this electromagnetic radiation as a source of variation in mutation breeding could be very advantageous. The aim of the study was to examine the influence of microwave radiation on the in vitro regeneration and acclimatization efficiencies, as well as on the genetic and phenotypical variation of chrysanthemum 'Alchimist'. Leaf explants with or without callus were subjected to microwave treatment for various periods and in different milieus. Microwaves were generated by a domestic magnetron at 2.45 GHz, 800 W·cm−2. Irradiation negatively affected shoot formation if applied for longer periods. On the other hand, it did not affect the rooting and acclimatization steps which were fully successful. Chrysanthemums produced from MW-treated explants had longer shoots with inflorescences of greater diameter and altered phenotypes. It was also noticed, that MW-treatment affected the generative phase by prolonging the bud colouration period. The evaluation of genetic variation was performed with the RAPD technique by using 10 primers for all regenerated shoot; a total of 116 genotypes were analysed. Approximately 22% of plants regenerated from MW-treated explants showed band profiles different from the reference control. Most plants (86%) with altered band profiles originated from irradiated callus. These plants also showed higher mean genetic distance coefficient. In conclusion, microwaves can be considered as an efficient and easy-to-access tool in mutation breeding of chrysanthemum 'Alchimist'.