A protocol for synthetic seed production in Rosmarinus officinalis

The synthetic seeds strategy is an effective method for conservation, germplasm exchange, and distribution of Rosmarinus officinalis. R. officinalis is one of the plants of the Lamiaceae family that originates from the Mediterranean region. According to our knowledge, there is no report on the production of synthetic seeds from somatic embryos obtained from shoots of R. officinalis. In this study, a method for synthetic seed production and regeneration was investigated from shoot explants of R. officinalis. Shoots of R. officinalis were cultured on the MS medium containing various concentrations of NAA and 2,4-D. The best callus induction (41.66%) was obtained on the MS medium fortified with 1 mg/L 2,4-D. The friable embryogenic calli were transferred to a half-strength MS medium with various concentrations of BAP and 2,4-D. Somatic embryos were obtained after 45 days. The highest somatic embryogenesis was obtained on the MS medium containing 1 mg/L 2,4-D and 0.5 mg/L BAP. Somatic embryos at the torpedo stage were encapsulated in sodium alginate and synthetic seeds were obtained. The highest growth ability of synthetic seeds (80.55%) was obtained in the MS medium supplemented with 1.5 mg/L kinetin and 0.5 mg/L BAP. Moreover, the germination percentage of synthetic seeds decreased with increasing storage period and temperature. However, a higher reduction in the synthetic seed germination was recorded at 20±2 °C. The highest germination percentage of the synthetic seeds (85%) was obtained 30 days after storage at 4±1 °C.