Polyploid Induction and Identification of Tagetes erecta

INTRODUCTION: Tagetes erecta is divided into ornamental and pigment types, among which the pigment type has petals rich in lutein, widely used in food additives, health supplements, and meat coloring. The demand is steadily increasing year by year, and supply is insufficient. It is urgent to accelerate the high-yield breeding of marigold. RATIONALE: We treated diploid marigold seeds with colchicine solutions at concentrations of 1.5, 2.0, and 2.5 g∙L–1, screened for plant lines exhibiting hypocotyls thickened, leaves widened, and stems thickened. We identified and selected homozygous tetraploids using a flow cytometer and finally measured the flower diameter and petal size of the polyploids. RESULTS: In this study, seeds of diploid marigold Jinxiu No.1 were treated with colchicine. After seed germination, the hypocotyl thickened. During the vegetative growth period, the variation types were rich and diverse. Through measurement with a vernier caliper combined with paraffin section analysis, it was found that the The M7 polyploid exhibited leaves with increased width and thickness. Simultaneously, owing to the expansion of stem cells, the stem became thicker. Flow cytometry confirmed that the M7 line was a pure tetraploid, characterized by significantly enlarged ligulate petals. When observed under scanning electron microscopy, the cells were clearly enlarged, which ultimately led to an increase in flower diameter and fresh weight per head. Through high-performance liquid chromatography detection, it was found that the lutein content in marigold was significantly increased, with the highest concentration found in the darker petals. CONCLUSION: This study successfully obtained the homozygous tetraploid marigold, characterized by large fresh flower weight and high lutein content, thereby laying a solid foundation for its further promotion and application.