The study on the relationship between leaf colors and ptDNA inheritance in intersectional cross of Rhododendron kiusianum × R. japonicum f. flavum, resulting in an unexpected triploid progeny

The relationship between leaf color and plastid/nuclear genome construction of 45 seedlings from two crosses of R. kiusianum (2n=2x=26) × R. japonicum f. flavum (2n=2x=26) was examined to resolve the frequent appearances of albino progenies among crosses involving Rhododendron species. Leaf color of seedlings segregated into green, pale green, and albino at a ratio, ca. 1: 2: 7. An unexpected triploid green plant with 2x and 1x nuclear genome from R. kiusianum and R. japonicum f. flavum, respectively, was detected among the hybrids through isozyme analysis and chromosome observation. PCR - RFLP analysis of matK region revealed that plastid DNA (ptDNA) of all albino hybrids was inherited from R. kiusianum, whereas that of six of seven green hybrids inherited it from R. japonicum f. flavum. The triploid green progeny had ptDNA of R. kiusianum.