Production of Black Cumin via Somatic Embryogenesis, Chemical Profile of Active Compounds in Callus Cultures and Somatic Embryos at Different Auxin Supplementations

Black cumin or Nigella sativa L. is a medicinal plant of the Ranunculaceae family that has enormous importance. It has traditionally been used to cure a lot of diseases since ancient times. In the current study, the effects of different auxins on callus induction and subsequent somatic embryo formation of N. sativa L. cv. Black Diamond were examined. The best result of callus induction was observed when cotyledon explants were incubated in a Murashige and Skoog (MS) medium supplemented with 1.0 mg L-1 alpha-naphthaleneacetic acid (NAA). The formation of somatic embryos was achieved efficiently from cotyledon-derived calli cultured on a 2 mg L-1 Indole-3-butyric acid (IBA)-containing medium. Furthermore, histological analysis of embryogenic calli was used to detect the presence of different developmental stages of somatic embryos. In contrast to the calli and embryos of N. sativa 'Black Diamond', which initiated in the dark, light was necessary for the complete differentiation of callus and embryo cultures into shoots/developed plants. Hypocotyl-derived calli and embryos were successfully differentiated on IBA at 2.0, 1.0 mg L-1, and NAA at 2.0 mg L-1. To the best of our knowledge, this work can be considered the first report on the differentiation of N. sativa 'Black Diamond' somatic embryos into developed plants. Moreover, the metabolic profiles of secondary products of N. sativa 'Black Diamond' callus and embryo cultures originated from the best auxin treatments identified and were compared with that of intact seeds. Callus cultures of N. sativa 'Black Diamond' contained thymoquinone (TQ) in a significant percentage of the peak area (2.76%). Therefore, callus cultures could be used as a perfect alternative source of TQ for pharmaceutical and therapeutic purposes. In addition, fatty acids and/or their esters were recorded as the major components in callus and embryo cultures. These vital compounds could be isolated and used for numerous industrial applications.