Citation: Koufan, M.; Belkoura, I.; Mazri, M.A. In Vitro Propagation of Caper (Capparis spinosa L.): A Review. Horticulturae 2022, 8, 737. https:// doi.org/10.3390/horticulturae8080737 Academic Editors: Barbara Ruffoni, Alicja Tymoszuk and Dariusz Kulus Received: 17 May 2022 Accepted: 27 June 2022 Published: 17 August 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/). horticulturae Review In Vitro Propagation of Caper (Capparis spinosa L.): A Review Meriyem Koufan 1, *, Ilham Belkoura 2 and Mouaad Amine Mazri 3, * 1 Natural Resources and Local Products Research Unit, Regional Center of Agricultural Research of Agadir, National Institute of Agricultural Research, Avenue Ennasr, BP 415 Rabat Principale, Rabat 10090, Morocco 2 In Vitro Culture Laboratory, Department of Basic Sciences, National School of Agriculture, BP S/40, Meknes 50001, Morocco 3 Agro-Biotechnology Research Unit, Regional Center of Agricultural Research of Marrakech, National Institute of Agricultural Research, Avenue Ennasr, BP 415 Rabat Principale, Rabat 10090, Morocco * Correspondence: meriyem.koufan@inra.ma (M.K.); mouaadamine.mazri@inra.ma (M.A.M.) Abstract: Caper (Capparis spinosa L.) is a shrubby plant species recalcitrant to vegetative propagation and generally difficult to propagate by seeds. This is due to the difficulties associated with seed germination, root induction from stem cuttings, and plant hardening. Propagation by tissue culture would be a good alternative and promising approach to overcome the limitations of conventional propagation. Tissue culture methods can be used for the clonal propagation of caper plants. Indeed, in many plant species, micropropagation has played a decisive role in the rapid and large-scale production of uniform and genetically stable plants. Tissue culture methods can also be used in genetic improvement and conservation programs. In this review, we first provided an overview on caper and its conventional means of propagation, then we described the different methods of caper micropropagation, i.e., in vitro seed germination and seedling development, propagation by nodal segmentation of elongated shoots (i.e., microcuttings), and adventitious organogenesis. These micropropagation methods can make it possible to overcome all the obstacles preventing large-scale propagation and genetic improvement of caper. Thus, the most updated information on the progress made in the field of caper micropropagation is reported and future perspectives are outlined. Keywords: caper; in vitro germination; microcuttings; micropropagation; organogenesis 1. Introduction Caper (Capparis spinosa L.) is a shrubby plant native to the Mediterranean region. It be- longs to the family Capparidaceae and genus Capparis, which includes more than 250 species generally used for ornamental, culinary, cosmetic, pharmaceutical, and medicinal purposes [1]. Capparis spinosa is characterized by high morphological and ecological diversity, which led some authors to differentiate several intraspecific variants and taxa [2–5]. It plays important socio-economic roles in the arid regions of many countries, and is well adapted to high temperatures, intense sunlight, and fluctuating climates [6–8]. Caper is cultivated for both unopened flowers and young fruits that are used in many traditional dishes [9]. The fruits of caper are harvested from both wild and cultivated plants. The main producers are Morocco, Spain, and Turkey [10,11]. Caper is a shrub with high medicinal values. This species is rich in bioactive com- pounds such as flavonoids, glucosinolates, phenolic acids, and alkaloids that can be used for medicinal, culinary, and ornamental purposes. Along this line, many health-promoting properties of caper extracts were scientifically demonstrated, in particular anti-cancer and antioxidant activities [12]. Caper is also used for ecological purposes since it helps in preventing soil erosion and preserving biodiversity and soil water [13,14]. Caper is commonly propagated by seeds. This method allows the maintenance of high genetic diversity within its populations. However, propagation by seeds cannot be used for the production of true-to-type plants [12,15]. Due to the high socio-economic Horticulturae 2022, 8, 737. https://doi.org/10.3390/horticulturae8080737 https://www.mdpi.com/journal/horticulturae