In vitro formation of nodular calli in soybean (Glycine max L.) induced by cocultivated Pseudomonas maltophilia

Soybean calli with nodular characteristics (nodular calli) and high regeneration potential were found to be induced by cocultivated with strains of bacteria Pseudomonas maltophilia in vitro. Upon subculture of the nodular calli, somatic embryos were regenerated. Unfortunately no complete plants have been obtained from the cultures so far because the somatic embryos were malformed to various degrees. Histological analysis revealed that the nodules were well organized. Young nodules possessed mostly small cells with densely stained nuclei, which are considered to have high potential to yield somatic embryos under improved culture conditions. Besides the cocultivated bacteria, the age and physiological state of the calli and ingredients of culture mediurn were also important factors affecting nodular callus formation. The findings on this experiment suggest that the cocultivtion system may be developed to solve the serious problems in regenerating plants from callus culture of soybean.