**1. Introduction**

Saffron (*Crocus sativus*; Iridaceae) is a sterile autotriploid and stemless monocotyledonous geophyte plant [1,2]. Therefore, obtaining daughter corms from mother corms is the only available method of saffron propagation [3]. Within the life cycle of saffron, flowering occurs during autumn (October–November), and the vegetative stage, including the formation of replacement corms at the base of the shoots, occurs throughout winter. At the beginning of the dry season (April–May), the leaves senesce and wither, and the corms go into dormancy. The transition from the vegetative stage to the reproductive stage can occur shortly afterwards in the apex of the buds of underground corms [4]. Saffron is a valuable spice obtained from the stigmas of *C. sativus*, and the value of saffron is enhanced by its potential use in biomedicine [5]. Thus, the demand for saffron is expected to increase in the coming years owing to its nutraceutical and medicinal properties.

In vitro culture technologies could facilitate the sustainable indoor production of saffron through the growth of pathogen-free stock corms. Saffron microcorm production under in vitro conditions is a promising technique with respect to the rate of multiplication and the number of cormlets produced. However, few studies have investigated the production of complete plants with roots and/or corms [6–9]. Saffron flowers grown in vitro could also serve as a source of saffron spice; however, the induced in vitro flowering of saffron plants has not been reported previously.

In in vitro propagation, liquid culture/bioreactor systems enable automation and reduce the costs of plantlet production [10]. Liquid culture systems provide uniform

**Citation:** Dewir, Y.H.; Alsadon, A.; Al-Aizari, A.A.; Al-Mohidib, M. In Vitro Floral Emergence and Improved Formation of Saffron Daughter Corms. *Horticulturae* **2022**, *8*, 973. https://doi.org/10.3390/ horticulturae8100973

Academic Editor: Sergio Ruffo Roberto

Received: 15 September 2022 Accepted: 15 October 2022 Published: 20 October 2022

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**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/).

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culture conditions in which the nutrient medium is renewed without changing the container. Moreover, the container can be cleaned with ease after the culture period. Plant tissues and organs from various plant species exhibit higher levels of growth performance in a liquid medium than in solid or semi-solid media. Liquid culture/bioreactor systems and their characteristic culture conditions have several advantages over solid cultures, including the convenient handling of cultures and enhanced plant growth [11]. Although bioreactor culturing has been used to grow many plant species, to the best of our knowledge, the use of bioreactors to produce saffron microcorms has not been reported previously. The main disadvantages of saffron tissue culture are the low frequency and the small size of cormlets induced from in-vitro-derived shoots [12–14].

The aim of the present study was to compare in vitro flower induction and the formation of daughter corms in gel and liquid cultures. Additionally, different concentrations of glutamine (as a nitrogen source), salicylic acid, and jasmonic acid were tested with the aim of improving the formation of saffron daughter corms. Overall, this study demonstrates that saffron flowering can be induced in vitro. Moreover, compared with solid cultures, liquid cultures/bioreactors improved daughter corm diameter and fresh weight. Thus, the production of saffron under controlled in vitro conditions is a viable option.
