Callus initiation and somatic embryogenesis in root cultures of the maize inbred line 21A-6

Callus production from root explants of the maize (Zea mays L.) inbred line 21A-6 was optimal on a Murashige and Skoog medium to which 2% sucrose and 1.0mgl−1 2,4-dichlorophenoxyacetic acid (2,4-D) had been added. Embryogenic and non-embryogenic callus as well as somatic embryos were produced, and an organogenic type of root meristem formation was observed. The cultures became more embryogenic with time on the initiation medium, and a concurrent change in the callus morphology was noted. Stele explants which included the endodermis and pericycle produced no callus. Cortical explants, however, produced callus which appeared to arise from parenchyma cells or from the four layers of epidermal and subepidermal tissue present. Although various stages of embryogenesis were observed in these cultures, plant regeneration was not achieved