Somatic Embryogenesis in Spinach-A Review

A spinach-supplemented diet exerts numerous health benefits, but high levels of oxalic acid and nitrate can cause medical problems, so their levels should be reduced, while the levels of vitamins and phytochemicals could be further increased by breeding. Conventional spinach breeding is limited by the very complex sex determination. However, these limitations could be circumvented in synergy with a biotechnological approach. Accordingly, tissue culture techniques allow rapid and efficient clonal propagation of selected valuable genotypes, and somatic embryogenesis has been recognized as a superior process for clonal propagation because somatic embryos resemble zygotic embryos and therefore can spontaneously develop into complete plants. Since spinach has been considered recalcitrant to in vitro regeneration for decades, a deeper insight into the mechanisms underlying somatic embryogenesis is important for a better understanding and further improvement of the efficiency of this process. In this review, a comprehensive overview of the major factors affecting somatic embryogenesis in spinach is presented and discussed, with particular emphasis on the synergistic effects of a-naphthaleneacetic acid, gibberellic acid, light, and the intrinsic predisposition of individual seedlings to somatic embryogenesis, as well as the expression of genes encoding key enzymes involved in the maintenance of gibberellin homeostasis and the levels of endogenous gibberellins.