Summary: Rapid, large‐scale generation of aDstransposant population was achieved using a regeneration procedure involving tissue culture of seed‐derived calli carryingAcand inactiveDselements. In the F₂progeny from genetic crosses between the sameDsandAcstarter lines, most of the crosses produced an independent germinal transposition frequency of 10–20%. Also, manyDselements underwent immobilization even thoughAcwas expressed. By comparison, in a callus‐derived regenerated population, over 70% of plants carried independentDsinsertions, indicating transposition early in callus formation. In the remaining population, the majority of plants carried onlyAc. Most of the newDsinsertions were stably transmitted to a subsequent generation. An exceptionally high proportion of independent transposants in the regenerated population means that selection markers for transposedDsand continual monitoring ofAc/Dsactivities may not necessarily be required. By analyzing 1297Ds‐flanking DNA sequences, a genetic map of 1072Dsinsertion sites was developed. The map showed thatDselements were transposed onto all of the rice chromosomes, with preference not only near donor sites (36%) but also on certain physically unlinked arms. Populations from both genetic crossing and tissue culture showed the same distribution patterns ofDsinsertion sites. The information of these mappedDsinsertion sites was deposited in GenBank. Among them, 55% ofDselements were on predicted open‐reading frame (ORF) regions. Thus, we propose an optimal strategy for the rapid generation of a large population ofDstransposants in rice.

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