GENETIC EVIDENCE FOR TRACE PATERNAL TRANSMISSION OF PLASTIDS IN LIRIODENDRON AND MAGNOLIA (MAGNOLIACEAE)

Transmission of plastids in Liriodendron and Magnolia was studied by examining inheritance of plastid DNA markers in interspecific crosses. In congeneric hybrids of Liriodendron and Magnolia, 2.9% and 11.1% of progeny, respectively, exhibited uniparental paternal transmission of plastids. This departure from strict uniparental maternal transmission of plastids indicates that mechanisms for the elimination of paternal plastids are not 100% efficient and that any proposed model for plastid transmission must account for a continuum of variation. Our results, and other results reviewed here, show a discrepancy with data obtained by cytological observations and point to the need of confirming the mode of plastid inheritance by genetic analysis. In addition, if paternal plastids are occasionally inherited, intensive sampling of plastid DNA in a putative hybrid population could identify both parents of hybrids and thereby aid in the phylogenetic reconstruction of hybrid zones.