Abstract
The chromosome numbers of the natural seedlings of Camellia×vernalis, cv. ‘Gaisen’ (tetraploid, n=15) and cv. ‘Bokyo’ (pentaploid) were determined and the origin of red pigmentation in C. sasanqua is discussed. The seedlings of C.×vernalis cv. ‘Gaisen’ were triploid, tetraploid and pentaploid. When C. sasanqua was abundant around the parent tree, pentaploid seedlings were more numerous than triploid ones. The pentaploid seedlings were considered to be backcrosses with C. sasanqua (hexaploid), and the triploid to he backcrosses with C. japonica (diploid). The chromosome numbers of the seedlings of C.×vernalis cv. ‘Bokyo’, a pentaploid, ranged from 2n=79 to 86, suggesting that only backcrosses to C. sasanqua are occurring. If C.×vernalis hybrids typically only backcross with the C. sasanqua parent, and some fertility is maintained in the interspecific backcrosses with C. sasanqua, then this backcrossing system becomes a mechanism for the flow of C. japonica genes into the species C. sasanqua. Thus, the red flowers of C. sasanqua are thought to have originated from repetitive backcrossing (introgression) with C.×vernalis.
