Shoot production from onion callus tissue cultures

Shoots have been produced on callus derived from onion set and from seedling radicle tissue. Whilst callus of set origin responded optimally to medium containing the cytokinin 6-(3-methyl-2-buten-1-ylamino)-purine (2iP) at 2.00 mg l^?1 and naphthaleneacetic acid (NAA) at 0.06 mg l^?1, seedling radicle callus showed a range of response. The medium used for callus initiation, the age of callus, and the provision of a dark period following inoculation on to the organogenesis medium have been shown to be critical for shoot formation. A limited number of embryoids have been produced from cultures; their occurrence was usually associated with an increase in shoot numbers for the generative callus tissue. Meristemoid areas have been observed in light micrographs of callus cultured upon organogenesis media.