Citation: Eisa, E.A.; Tilly-Mándy, A.; Honfi,P.; Shala, A.Y.; Gururani, M.A. Chrysanthemum: A Comprehensive Review on Recent Developments on In Vitro Regeneration. Biology 2022, 11, 1774. https://doi.org/10.3390/ biology11121774 Received: 15 October 2022 Accepted: 30 November 2022 Published: 6 December 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). biology Review Chrysanthemum: A Comprehensive Review on Recent Developments on In Vitro Regeneration Eman Abdelhakim Eisa 1,2, *, Andrea Tilly-Mándy 1 ,Péter Honfi 1 , Awad Yousef Shala 3 and Mayank Anand Gururani 4, * 1 Department of Floriculture and Dendrology, Hungarian University of Agriculture and Life Science (MATE), 1118 Budapest, Hungary 2 Botanical Gardens Research Department, Horticulture Research Institute, Agricultural Research Center (ARC), Giza 12619, Egypt 3 Medicinal and Aromatic Plants Research Department, Horticulture Research Institute, Agricultural Research Center (ARC), Giza 12619, Egypt 4 Biology Department, College of Science, United Arab Emirates University, Al Ain P.O. Box 15551, United Arab Emirates * Correspondence: abdelhakim.eman1@gmail.com (E.A.E.); gururani@uaeu.ac.ae (M.A.G.) Simple Summary: Chrysanthemums are the second most important floricultural (cut-flower) crop after roses. A very well-studied topic, in vitro propagation of Chrysanthemums is making signifi- cant strides every year. An overview of in vitro propagation of Chrysanthemum in the wider plant science literature is presented in this review. The review presents a comprehensive understanding of the recently described methods of sterilization, plant growth regulators, hormonal combinations, acclimation efficiency, and light conditions for the rapid and cost-effective in vitro regeneration of Chrysanthemum in the last decade. Abstract: Chrysanthemum is a flowering plant grown worldwide and is one of the most popular ornamental plants. Chrysanthemums are usually cultivated using root suckers and shoot cuttings. This conventional technique is relatively slow. In addition, as cuttings are gained regularly from mother plants, there is a chance of viral infection and degeneration, which raises the production cost. The hurdles mentioned above have been managed by applying in vitro propagation techniques, which can enhance reproduction rates through in vitro culture and use very small explants, which are impossible with the conventional approach. Usually, it is difficult to get true-to-type plants as the parents with good quality, but clonal propagation of a designated elite species makes it possible. Hence, this review highlights recent studies of the in vitro propagation of Chrysanthemum included; the appropriate explant sources, medium compositions, alternative disinfection of culture media, plant growth regulators (PGRs), different mutagenesis applications, acclimatization efficiency, and alternative light sources to overcome the shortcomings of conventional propagation techniques. Keywords: Chrysanthemum; in vitro propagation; true-to-type plants; explant sources; medium compositions; alternative disinfections; mutagenesis; acclimatization; alternative light sources 1. Introduction The floriculture industry is considered one of the most important and rapidly growing commercial trades in the agriculture industry. Many cut flowers and potted plants are being sold worldwide, for instance (Alstroemeria, Anthurium, carnation, Chrysanthemum, Gerbera, Gladiolus, Lilium, Lisianthus, and roses) on a daily basis [1]. The world’s top countries with value-wise production and export of cut plants are the Netherlands, the United States, Japan, Italy, Germany, and Canada. Germany, the United States, France, and the United Kingdom are the leading consumer countries [2]. Biology 2022, 11, 1774. https://doi.org/10.3390/biology11121774 https://www.mdpi.com/journal/biology