Somatic Embryogenesis and Plant Regeneration from Commercial Soybean Cultivars

The efficient regeneration of plants from commercial genotypes is a pre-requisite for successful genetic transformation, to apply modern crop improvement techniques such as CRISPR-based genome editing. Plant regeneration through the somatic embryogenesis pathway offers an advantage over the organogenesis approach, avoiding the risk of developing chimeras. Plant genotype, explant type, and media compositions play an essential role in the in-vitro regeneration of plants. This study aimed to characterize the commercially grown Australian soybean genotypes for their potential to induce somatic embryos, embryo proliferation, maturation, germination, and plant regeneration. Overall, nine soybean cultivars belonging to different maturity groups were evaluated. Immature cotyledon ranging from 2–4 and 4–6 mm in size were used as explants for somatic embryogenesis induction. Maximum somatic embryo induction frequency (86%) was observed from 4–6 mm immature cotyledons of the cv. Jack (MG III), followed by 66%, 26%, 21%, and 6% in cultivars Williams (MG III), Snowy (MG III), MoonB1 (MG V), and PNR791 (MG V), respectively. On the other hand, cv. Snowy showed maximum somatic-embryo-inducing potential (67%) in 2–4 mm immature cotyledons followed by Williams, Jack, MoonB1, and PNR791. Somatic embryos from Jack, Williams, and Snowy cultivars were further tested for embryo proliferation, maturation, and germination. Maximum proliferation and maturation were observed in cv. Jack, followed by Snowy and Williams. However, cv. Snowy showed a significantly higher conversion of cotyledonary stage embryos to plantlets (85%), than both Jack and Williams cultivars (53% each). In conclusion, this study outlined a protocol for somatic embryogenesis and plant regeneration from three soybean cultivars. Our findings suggest commercial cv. Snowy could be a good candidate for developing transgenic plants through somatic embryogenesis.

Two ways of plant regeneration from immature cotyledons of pea

Two different systems of plant regeneration via organogenesis and embryogenesis from immature cotyledons of pea (<i>Pisum sativum</i> L.) were developed. The first system was direct multiple shoot regeneration from the proximal to the embryo axis, injured part of cotyledon. The ability of six Polish cultivars to shoot formation was very high. The percent of regenerating cotyledons was from 73 to 86 and mean number of shoots from 3.5 to 9.9 after seven weeks of culture. This multiplification could be prolonged for next several months. The second system was somatic embryogenesis, initiating from the same part of cotyledon simultaneously with slowly proliferating callus. Only three out of six cultivars formed embryoids. The differences of ability to embryo formation ranged between 43% of responding explants for Heiga cultivar to only 6% for Cud Ameryki. The mean number of embryoids was from 4.2 to 2.3.

In vitro Induction and Proliferation of Callus from Immature Cotyledons and Embryos of Juglans regia cv. 'Xiangling'

Callus holds great potential for biotechnology applications in plants. In this study, several experiments were performed to establish a protocol for in vitro induction of good quality callus by using immature cotyledons and embryos of Juglans regia cv. ‘Xiangling’ as the explants. DKW basal media supplemented with different concentrations of plant growth regulators were applied to determine the induction rate, texture and color of the recovered callus. Results showed that the optimum culture medium for the callus induction from these explants was a DKW basal medium consisting of 1 mg/L BA, 2 mg/L KT 250 mg/L glutamine, 500 mg/L casein hydrolysate, 200 mg/L Vc, 50 g/L sucrose and 2.8 g/L Gelrite (i.e., the T8 medium). The average rate of callus induction on the medium reached 80.7% for the immature cotyledons and 66.7% for the immature embryos, and all the callus was characterized by a friable, creamy or yellow appearance. In vitro proliferation of callus was not very successful as a result of the fact that the friable callus with creamy or yellow color grew very slowly, whereas the fast-growing callus was easy to turn brown and died eventually. Even though further investigation will be required to overcome the problem of browning and assess the regeneration ability of the callus, this approach for the production of friable callus may have valuable applications for walnut and other woody trees.