A study on evening-primrose (Oenothera biennis L.) callus regeneration and somatic embryogenesis

Evening primrose (Oenothera biennis L.) is a wild flower with high and valuable oil content. High seed shattering, indeterminate inflorescence and heterogeneous germination limit the commercial cultivation of this plant. Besides agronomical research, breeding programs can also remedy the above mentioned problems. Since traditional breeding methods take a long time, using techniques such as tissue culture and somatic embryogenesis accelerate the breeding process. In the present study, callus formation was accomplished in MS (Murashik and Skoog) medium, but no embryogenesis was observed in the presence or absence of plant hormones like 2,4-D (2,4-dichlorophenoxy) acetic acid. In contrast, B5 (Gamborg) medium containing 2,4-D induced embryogenesis. Different parts of plants exhibited good callus production potency and the hypocotyl was found as the best plant explants. In B5 medium, various concentrations of 2,4-D (0,2.26 mM, 4.52 mM, and 9.04 mM) were applied as a complete randomized design experiment with 4 replications. For embryogenesis, hypocotyls (1cm long) were cultured in B5 liquid medium at the induction phase. After 3 weeks, induced organs were sub-cultured to realization phase and the number of embryos (different stages of embryogenesis) was counted 4 weeks later. The results indicated that variation in hormone concentrations caused significant differences with respect to somatic embryogenesis. Embryo development were not observed in hormone-free media. The highest numbers of globular, heart, torpedo, cotyledonary, and total embryo was recorded at 9.04 mM of 2, 4-D. Histological studies of embryos after the realization phase revealed large nuclei and abundance of starch grains indicating the presence of embryonic cells in evening primrose hypocotyls.