Somatic Embryogenesis

Abstract

Somatic embryogenesis (SE) has a great potential in the near future for mass multiplication and genetic improvement of several leguminous species. In the recent past, a significant progress has been made in the development of regeneration systems for various legumes, and many legumes are now amenable to regeneration via somatic embryogenesis. The purpose of this review is to focus on recent advances in the initiation and development of somatic embryos in various leguminous plants. Much emphasis has been given to identify the successful protocols for the establishment of an efficient somatic embryogenic system in legume species. It reveals that, in legumes, somatic embryogenesis can easily be achieved when young plant tissues are used as initial explants. 2,4-dichlorophenoxy-acetic acid (2,4-D) is widely used auxin for somatic embryogenesis in most of the leguminous species. Recently thidiazuron (TDZ) has been shown to induce high frequency direct somatic embryogenesis. Plant regeneration from somatic embryogenic tissue involves several steps. Firstly, the embryogenic tissue is developed from initial explant tissues, secondly, embryogenic tissue is allowed to proliferate into mature somatic embryos and thirdly somatic embryos germinate into plantlets. Although plants have been regenerated via somatic embryos from various legumes in the last two decades, low-frequency embryo induction, poor percentage of germination and conversion of somatic embryos into plants and somaclonal variations are the major obstacles limiting the exploitation of somatic embryogenic technology for biotechnological applications in legume improvement. The sequential and interactive action of many genes is clearly involved in the establishment of somatic embryos and plant regeneration. The precise role of these genes remains to be determined in most cases. Similarly, little is known of how regulatory genes function to specify major events. Many genes, e.g. calnexin-like homologues (early) and SNQ2-like genes (late), have been identified which express during somatic embryogenesis. In order to overcome these limitations, a systematic study of these patterns could help to identify various conditions such as the effect of carbohydrates, plant growth regulators, amino acids, media composition, explant age, biochemical markers and regulation of gene expression for fundamental understanding of somatic embryogenesis and the development of regeneration system for most legumes. It is our hope that as the technology develops further, it may become possible to produce large numbers of somatic embryos in bioreactors for use as artificial seeds to propagate elite or hybrid and genetically modified legume genotypes in the future.KeywordsSomatic EmbryoSomatic EmbryogenesisZygotic EmbryoSomaclonal VariationLegume SpeciesThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.