Maternal nuclear genome controls paternal ptdna inheritance in progeny from interspecific crosses of rhododendron spp.

The genetic factor controlling the mode of plastid DNA (ptDNA) inheritance in Rhododendron was investigated using polymerase chain reaction-single-stranded conformation polymorphism (PCR-SSCP) analysis at the trnL– trnF intergeneric region. In the cross of R kaempferi var. macrogemma × R. simsii, a low frequency of paternal ptDNA inheritance was observed in the progeny. In the cross of R transiens × R. simsii, a high frequency of paternal ptDNA was observed in the progeny. When the F₁ plants from R kaempferi var. macrogemma × R transiens were used as seed parents and were crossed with R simsii, the pattern of ptDNA inheritance was segregated into 2 types among cross combinations at a ratio of 1:1, namely, low (2.0-11.1%) and high (32.6-66.6%) frequencies of paternal ptDNA inheritance, although the F₁ plants had identical ptDNA from R kaempferi var. macrogemma. From these results, we conclude that the mode of ptDNA inheritance is controlled by at least one major gene in the maternal nucleus.