Early Stages of Somatic Embryo Differentiation from Callus Cells of Bean (Phaseolus vulgaris L.) Grown in Liquid Medium.

Shoot apices of bean cultivars (Phaseolus vulgaris) were cultivated in vitro. Callus induced by MS medium in the presence of KIN (10 μM), 2,4-D (5 μM), and IAA (10 μM) displayed optimum proliferation for 14 cultivars, intermediate growth for 8 cultivars, and poor growth for the remaining 14 cultivars. Callus derived from shoot apices of these 36 bean cultivars were transferred into liquid media. Inorganic PC-L2 salts with 2,4-D (10 μM) and casein hydrolysate (2 g · 1-1) was sufficient to sustain growth of cells in liquid medium. These liquid cultures had different growth characteristics dependent upon genotype, amount of initial inoculum, and culture media. Cultivars Moruna, Pirata-1, and Linea-29 were able to produce globular embryo structures during liquid culture. Callus cells of «carioca» when transferred to a new liquid medium containing KIN (0.5 mg · l(-1)), 2,4-D (0.2 mg · l(-1)) and casein hydrolysate (50 mg · l(-1)) produced embryogenic cells and somatic embryos at an early state of development. The globular structures, embryogenic cells, and somatic embryos did not develop further following transfer to solid media.