The flower is one of the important ornamental organs of garden plants. The phenomenon of phyllody will lead to the partial or total transformation of flower organs into leaf-like structures, thus having high ornamental and research value. In order to explore the main causes and regulatory mechanisms of phyllody formation, this paper comprehensively analyzes the research progress at home and abroad and finds that the phenomenon of phyllody is mainly influenced by factors such as gene regulation, plant pathogens and external environment. The flower development process is closely related to the five types of genes （A, B, C, D and E） in the floral organ development model. This article focuses on reviewing the intrinsic molecular mechanism of the formation of phyllody. It is speculated that pathogens may induce organ alienation by inducing protein changes in plants. Environmental factors such as temperature and hormones may affect gene expression patterns through epigenetic modification, and form organs with leaf-like structures through multi-gene synergistic regulation. The study on the causes of phyllody is helpful to further analyze the process of flower development, so as to provide theoretical basis for the directional regulation of plant flower development and its molecular breeding.

Marigold (Tagetes erecta L., African marigold) is a widely grown ornamental plant and a main source of the carotenoid lutein for the industrial production of pharmaceuticals, food coloring, and feed additives. To gain a deeper understanding of the genetic mechanism of lutein in marigold, a chromosome-scale assembly of the marigold (T. erecta V-01) genome was completed based on Illumina, PacBio, and Hi-C reads. The 707.21-Mb assembled genome consisted of 35 834 annotated protein-coding genes, with 97.7% genomic integrity. We anchored 87.8% of the contigs (covering 621.20 Mb) to 12 pseudochromosomes, bringing the scaffold N50 length to 54.15 Mb. Phylogenetic analysis showed that marigold was closely related to the Asteraceae species bitter vine (Mikania micrantha) and sunflower (Helianthus annuus), all three of which originated in the Americas. Marigold diverged from the sunflower clade 23.57 million years ago (MYA) and from M. micrantha 19.59 MYA. Marigold has undergone three whole-genome duplication events, as well as a recent whole-genome duplication event (WGD-2) common to H. annuus and M. micrantha. Marigold gene families were significantly less expanded than those of M. micrantha or H. annuus, and the marigold genome contained significantly fewer interspersed repeats, which might account for its smaller genome. In addition, a range of candidate genes involved in the lutein biosynthetic pathway were identified. The high-quality reference genome obtained in this study provided a valuable genomic resource for studying the evolution of the Asteraceae family and for improving marigold breeding strategies.