Ornamental chrysanthemum (Dendranthema × grandiflorum Ramat.) belongs to genus Chrysanthemum in the Asteraceae (Compositae) family and is a top leading ornamental plant worldwide. During the last two decades, advances in biotechnology (genetic engineering) and nucleotide sequencing techniques have enabled a deep understanding of biological processes of many ornamental plants at a molecular level. The blue-colored chrysanthemum has been generated and commercialized, and various DNA markers were developed using advanced techniques. Ornamental chrysanthemums are hexaploidy (2n = 2x = 54) and self-incompatible, making it challenging to generate a pure line as breeding resources and a model platform for chrysanthemum research. However, recently, self-compatible pure lines of chrysanthemum (C. seticuspe) were developed, and whole-genome sequencing datasets have been open to the public. Other datasets of whole-genome sequences and transcriptome have been elucidated from wild chrysanthemums, C. nankingense and C. morifolium. In this review, recent progress in the study of ornamental chrysanthemums and the potentiality and importance of wild chrysanthemums as bioresources for ornamental chrysanthemum studies and breeding resources is discussed briefly. Many important resources for studying chrysanthemums are now available and easily accessible. Comprehensive studies with important resources will shed light on chrysanthemum research and breeding of ornamental chrysanthemums at a molecular level. Additionally, this review provides comprehensive information and should pave the way for successful research on ornamental chrysanthemums.

Abstract
Introduction
The Progress in Genetic Engineering ofChrysanthemums
Wild Chrysanthemums: Important Bioresourcesfor Chrysanthemum Studies
Genomic Database of Wild Chrysanthemums
Conclusion
References

• Seung Won Kang(Faculty of Life and Environmental Sciences, University of Tsukuba) Corresponding author