Unusual inheritance of the mitochondrial genome organization in the progeny of reciprocal crosses between alloplasmic hexaploid wheat regenerants

The transmission of a structurally-hypervariable fraction of the mitochondrial genome has been studied in 42 F₁ progenies obtained from reciprocal crosses between self-pollinated alloplasmic wheat plants regenerated after long-term somatic embryogenesis. This fraction of the genome is maternally and stoichiometrically inherited. In contrast, some additional restriction fragments specific to regenerated plants display a more complex mode of sexual transmission: one of the additional fragments was stoichiometrically and systematically inherited whereas two others were detected only in certain F₁ hybrids. Assuming that the detection, by Southern analysis, of such a fragment in regenerated plants is due to the amplification of a pre-existing substoichiometric molecule generated by the activation of a rare recombination event, our results suggest that the probability of detecting a novel fragment in the F₁ hybrids could be determined by the length of the repeated sequence at which recombination occurs.