Enhanced vigor of dry somatic embryos of Medicago sativa L. with increased sucrose

Abstract

The vigor of seedlings from dry somatic embryos of Medicago sativa, line RL-34, is considerably less than the vigor of those from true seeds. Sucrose, maltose and ammonium levels in the development and maturation media were manipulated in an attempt to enhance this seedling vigor. Increasing the sucrose concentration in both media from 3 to 6% almost doubled vigor without substantially reducing the quantity of embryos formed or their synchrony. Maltose was superior to sucrose when included in the development medium only at low concentrations, whereas the inclusion of maltose in the maturation medium reduced survival of desiccation, plant conversion and vigor. At high sugar concentrations, the inclusion of increased ammonium was ineffective and at low sugar concentrations was determental to desiccation tolerance, conversion and vigor. Improvements in the quality of dry somatic embryos can be accomplished by increasing the sucrose concentration of the standard development and maturation media to 5–6%, but the inclusion of maltose or ammonium is either ineffective or detrimental to the survival of desiccation and therefore not warranted.