Abstract
Somaclonal variations in pigmentation occurred repeatedly during the clone propagation of the landrace ‘Okinawa A’ of water yam, Dioscorea alata L. An initial variation appeared when clone propagation of ‘Okinawa A’ started in 2000. Reverting variants, closely resembling the original type appeared several times during the cloning of the initial variants. In 2009, a second variant without pigmentation emerged from the initial one. Every observed trait of the original type and the three types of variants was ordinarily transmitted to later generations during clone propagation by tuber. Genealogical tracing of clone pedigrees and analyses of variance in leaf and stoma traits indicated that these variants might be caused by tissue chimeras resulting from changes in the number or structure of chromosomes. However, the possibility that transposable elements were involved could not be excluded. The recurring somaclonal variations are considered to affect the genetic diversity within the species and to provide useful genetic resources for improvement of water yam.
