Abstract: The pigment background of the chrysanthemum cultivar 'Wandai Fengguang' is suitable for the cultivation of blue flowers by using molecular breeding techniques to regulate the concentration of iron ions in petals. While it can bloom in both summer and autumn, it is also an important material for studying the molecular regulation mechanism of chrysanthemum flowering period. However, it lacks an efficient regeneration and genetic transformation system. In this study, this variety was used as the experimental material to study the effects of different explant types and different combinations of plant growth regulators on its regeneration, and to investigate the effects of relevant factors on the efficiency of genetic transformation in the agrobacterium-mediated genetic transformation method. It was experimentally determined that the most suitable explant for the regeneration of 'Wandai Fengguang' was the transverse thin cell layers, and the optimal culture medium was MS+1.5 mg·L-1 6-BA+0.6 mg·L-1 NAA, with a differentiation rate of 70.06% and an adventitious shoot coefficient of 3.37. The kanamycin selection pressures for the differentiation of the transverse thin cell layers and the adventitious bud rooting were 7.5 mg·L-1 and 5.0 mg·L-1, respectively. After experimentation, the optimal system for genetic transformation treatment was determined to be pre-culture for 1 day, OD600=0.8, treatment for 5 minutes, and co-culture in the dark for 3 days. Fifteen resistant plantlets were screened on kanamycin medium, and two positive plantlets were revealed by PCR identification, with a transformation efficiency of 13.33%. This study laid the foundation for the gene function analysis and targeted improvement molecular breeding of chrysanthemum by using this kind of unique variety resource, and provided reference for the establishment of regeneration and transformation system for other chrysanthemum varieties.

Key words: chrysanthemum, explant, transverse thin cell layers, regeneration system, genetic transformation system