CHLOROPLAST DNA VARIATION IN POPULUS .3. NOVEL CHLOROPLAST DNA VARIANTS IN NATURAL POPULUS X CANADENSIS HYBRIDS

A rare phenomenon of the occurrence of novel non-parental chloroplast DNA (cpDNA) variants in natural sexual interspecific hybrids between P opulus deltoides var deltoides and P. nigra, P. x canadensis is descri bed. Restriction fragment variation of cpDNA in 17 P. x canadensis cul tivars was examined and compared with that of representative samples o f P. deltoides and P. nigra using 83 combinations of 16 restriction en zymes and six Petunia hybrida cpDNA probes. Twelve cultivars had one t o five novel non-parental cpDNA fragments in the chloroplast genome re gion homologous to the 9.0-kb PstI cpDNA fragment of Petunia from the large single-copy region.