Plant regeneration from mature embryo-derived callus of Australian rice (Oryza sativa L.) varieties

In vitro plant regeneration from callus induced from embryos of mature seeds of 4 Australian varieties of rice was studied. Observations of callus induction on MS and N6 media indicated that MS medium supplemented with 0.5-2 mg/L of 2,4-D is suitable for callus formation from the varieties tested. Comparison of shoot initiation on medium containing BAP, BAP + NAA, and TDZ + NAA indicated that these varieties prefer BAP + NAA or TDZ + NAA in the shoot initiation medium. Partial desiccation, resulting in up to 20% loss of fresh weight of callus, significantly increased the regeneration frequency of the 4 rice varieties tested. The varieties showed varied response to number of shoots produced per callus. Regenerated shoots were rooted on plant growth regulator free medium. The plants regenerated were phenotypically normal and fertile. Our study showed that callus derived from mature embryos of these rice varieties are amenable to multiple shoot formation, and could be used for genetic transformation studies.