Recombination between chloroplast DNAs does not occur in sexual crosses of Oenothera

Crosses of Oenothera result in the transmission of chloroplasts from both parents to their offspring. In spite of this biparental inheritance, no wild-type recombinants were recovered from crosses between different chloroplast mutants. Since more than 7500 progeny were examined, the results indicate that recombination between the chloroplast DNAs of higher plants must be a very rare event.