Production of Embryogenic Callus and Plant Regeneration from Elite Guizhou Waxy Maize Inbred Lines

Immature embryos from three elite Guizhou waxy maize inbred lines (W21019, B7, and QCL5036) were evaluated for their ability of forming callus and regeneration into plants. Immature embryos harvested at different physiological stages were used as explants to initiate callus on N6 basal medium with 0-3.5 mg L-1 of 2,4-dichlorophenoxy acetic acid (2,4-D). The concentration of 2,4-D, physiological age of immature embryos and genotype had a significant effect (P<0.05) on the percentage of embryogenic callus formed. The optimum 2,4-D concentration for the initiation of embryogenic callus was varied among the waxy maize genotypes from 2.0 mg L-1 (B7 and QCL5036) to 3.0 mg L-1 (W21019). The shoots were generated from embryogenic callus which were transferred into the regeneration medium supplemented with 0-2.5 mg L-1 of 6-benzylaminopurine (6-BA). 6-BA in the medium significantly promoted the regeneration of embryogenic callus. Embryogenic size was also an important factor that affected regeneration capacity. 0.6-0.7 cm was proved to be the best size for regeneration from embryogenic callus and the mean number of shoots per primary callus in all genotypes achieved the highest number. The ability of the plant regeneration was also affected by genotype. W21019 had the highest number of shoots formed per primary embryogenic callus. With the optimum condition, the highest mean number of shoots per primary callus was up to 12.13, 5.73, and 3.33 in line W21019, B7, and QCL5036, respectively. The successful regeneration of the two inbred lines provides a basis for development of genetic transformation to improve priority traits such as enhanced insects and drought tolerance.