An integrated in planta infection and in vitro selection strategy for Agrobacterium-mediated transformation of Tagetes erecta

Marigold (Tagetes erecta) is an important ornamental plant valued for its diverse flower colors and morphological variation. Enhancing the genetic variability of this species can be achieved through biotechnological approaches, particularly genetic transformation mediated by Agrobacterium tumefaciens. This study aimed to evaluate an integrated transformation strategy that combines in planta infection with in vitro selection and regeneration in T. erecta. Gene transfer was initiated through in planta infection, followed by hygromycin-based selection and shoot regeneration under in vitro conditions. This approach resulted in a transformation efficiency of 20.93% and a regeneration efficiency of 2.32%, calculated based on the number of hygromycin-resistant explants and regenerated shoots relative to the total number of treated seeds. PCR-based molecular analysis detected the presence of the target gene fragment in putative transformants, suggesting that gene transfer events may have occurred during the transformation process. However, PCR detection alone cannot confirm stable genomic integration or inheritance of the introduced gene. Despite the relatively low regeneration efficiency, the integration of in planta transformation with in vitro selection demonstrates potential as a preliminary strategy for further optimization of transformation protocols in T. erecta, and may support the development of more practical transformation approaches in ornamental plant breeding.