Preliminary studies on recombination in two groups of rice were carried out by measuring the D-loop forming activity of cellular extracts from shoots and calli. In the shoots, japonica group showed higher recombinatory activities than indica group. In calli, both groups had nearly equal activities. The recombination activity was measured by using plasmid DNAs. In calli and enriched flowers, japonica showed higher frequencies of intermolecular recombination between homologous DNAs than indica. The higher frequencies in the enriched flower fraction, at a certain developmental stage of spike, suggested a contribution from meiotic cells which had been shown to a have high recombinatory activity in earlier studies.
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