| Common bean (Phaseolus vulgaris L.), an important legume in the human diet, is recalcitrant to in vitro culture, so the establishment of alternative propagation protocols, including somatic embryogenesis and organogenesis, has been a challenge. In the present work, we evaluated conditions to induce somatic embryogenesis and organogenesis from explants of seedlings of two F3 interspecific bean hybrid lines. In order to induce embryogenic callus, different types of explants were cultured under concentrations of 0, 0.01, 0.05 and 0.1 mg/L of 2,4-D in presence of 1mg/L of BA or at 29°C. Hypocotyls were the type of explant showing the highest production of nodular calli, and 0.1 mg/L of 2,4-D was the most favorable concentration. Treatments to induce maturation of nodular callus included air-drying, transfer from solid to liquid medium, culture with AgNO3 and combinations of these factors. Air-drying and transfer liquid medium (with or without AgNO3) enabled the development of heart-shaped or elongated embryo-like structures within calli. Organogenesis was also induced in buds from epicotyls, which were subsequently transferred to two treatments to proliferate: 0.5mg/L of BA and 2.25mg/L of BA with 1.7mg/L of AgNO 3. The combination of 2.25mg/L of BA with 1.7mg/L of AgNO3, and 1.5 mg/L GA3, was used for the induction of bud elongation. Proliferation of buds was achieved with 2.25mg/L of BA and 1.7mg/L of AgNO 3. Combinations of BA, AgNO3, GA3 and ANA were tested to shoot rooting, but were ineffective. To study the structure of calli by scanning electron microscopy, chemical fixation and cryofixation were carried out. Cryofixation treatments included rapid freezing, slow freezing and slow cooling. Although none of the treatments effectively preserved the calli, some observations and inferences could be made about the structural organization of calli. |
