An Optimized Protocol for In Vitro Indirect Shoot Organogenesis of Impala Bronzovaya and Zanzibar Green Ricinus communis L. Varieties

Abstract

The castor bean is an important industrial and ornamental crop. In the industry, it is used as a source of castor oil. Moreover, it has a large potential as a feed crop, because the seeds contain a high amount of protein. A main problem with castor bean use is the presence of toxins in the plants. Today, detoxification is carried out using various approaches, including biotechnological methods such as CRISPR/Cas9 technology. A successful application of these methods requires the availability of an efficient in vitro protocol for callus induction and shoot organogenesis. We present the results of in vitro condition optimization for two castor bean varieties (Impala Bronzovaya and Zanzibar Green). Eight different Murashige–Skoog (MS) culture media characterized by different plant growth regulator (PGR) combinations, as well as explant types (hypocotyls, cotyledonous leaves, and cotyledon petioles), were tested. The highest frequency of shoot organogenesis and average number per explant were observed during the cultivation of cotyledon petioles in both varieties on the Murashige and Skoog culture medium (MS) containing 1 or 2 mg/L of zeatin in combination with 0.1 mg/L of 3-indoleacetic acid (IAA). An optimized protocol for in vitro callus induction and shoot organogenesis may be used for biotechnological applications to obtain toxin-free castor bean, as well as Ricinus communis L. plants, with new ornamental traits and their combinations.