Visual selection and mannose selection in chrysanthemum safe transgenic engineering

The use of antibiotic resistance genes has played an important role in Chrysanthemum breeding, however, large-scale production raises the question of the safety of transgenic plants.
It is therefore of utmost importance to find a way to replace the use of antibiotic-dependent selection.
The production of transgenic plants involves the use of a selectable gene to favour the regeneration of transformed shoots.
Safe transgenic techniques have been widely used in chrysanthemum breeding.
In this study, we tried two safe-transgenic techniques in transgenic chrysanthemum engineering.

Rosea 1 and Delila genes from Antirrhinum majus regulate the anthocyanin biosynthesis.
Both genes include root specific promoter, and they were introduced into chrysanthemum to determine whether it could be used as a visual selection marker for Chrysanthemum transformation.
After transformation, red colored stems were scored and examined for the presence of the Rosea 1 gene by PCR analysis.
Another one is a mannose selection system which utilizes the pmi gene encoding for phosphomannose-isomerase, an enzyme that converts mannose-6-phosphate to fructose-6-phosphate.
Moreover, only transformed cells are capable of utilizing mannose as carbon source. Agrobacterium-mediated transformation of wounded leaf disk was carried out followed by a selection at a level of 1% mannose and 2% sucrose.
Molecular and genetic analysis showed that the pmi gene had been transmitted into the chrysanthemum.

Safe transgenic breeding techniques have fewer risks for the environment.
Antibiotic marker-free transgenic techniques will increase the range of the application of transgenic plants.