The Development of the Highly Regenerable Seed Line Jemalong 2HA for Transformation of Medicago truncatula — Implications for Regenerability via Somatic Embryogenesis

Abstract

Summary Medicago truncatula is an annual legume that can be regenerated from tissue explants via somatic embryogenesis at low frequency using the cultivar Jemalong. Regenerated plants from Jemalong show very large increases in somatic embryogenesis. This large increase in somatic embryogenesis is inherited with progeny segregating into classes we categorised as high, moderate and low regenerators. The low regenerators have a similar frequency of somatic embryogenesis to Jemalong. Continued selection from the high regenerators allowed the development of the highly regenerable seed line Jemalong 2HA in which the progeny are all high regenerators. Jemalong 2HA is isogenic with Jemalong except for the enhanced somatic embryogenesis in Jemalong 2HA. A cycle of tissue culture resulting in an increase in somatic embryogenesis, may be a tool that can increase somatic embryogenesis in some recalcitrant species. Jemalong 2HA can be described as a super-embryogenic mutant and is valuable not only for its ease of transformation but also can provide insights into the nature of totipotency.