In vitro somatic embryogenesis from thin cell layers (TCLs) explants of shallot (Allium cepa L.)

Regeneration through somatic embryogenesis needs to be developed to facilitate genetic improvement, micropropagation, and the seed production system for shallot. The thin cell layers (TCLs) have been used as explants for more efficient micropropagation and induction of somatic embryogenesis. The objective of this study was to establish a simple protocol for the somatic embryogenesis of shallot. Embryonic callus culture was induced from the transverse section or TCL of shallot basal bulb scales cv. Bima-Brebes and Rubaru-Sumenep in BDS medium supplemented with 2,4-D alone or combined with NAA and BAP. The higher percentage of explants forming embryogenic callus occurred when the medium was supplemented with 2,4-D 1.0 mg L−1 alone or combined with NAA 1.0 – 2.0 mg L−1. For the proliferation, medium supplemented with 2,4-D 1.0 mg L−1 was sufficient to maintain the embryogenic callus growth. The embryogenic callus was friable, yellowish, and granular or nodular. A high frequency of somatic embryos developed and matured when culture on a hormone-free medium with high sucrose (45 g L−1) and Gelrite (4 g L−1) concentration. There is no difference in response capacity for regeneration of somatic embryo between cultivars Bima-Brebes and Rubaru-Sumenep. This protocol is simple in inducing somatic embryogenesis to mature somatic embryos.