Gametoclonal Variation - There is considerable evidence that haploid plants regenerated from callus cultures show genetic variation that is gametoclonal variation. For example, gametoclonal variation for heading date, plant height, etc. has been reported in rice.

Such a variation may be subjected to selection at the haploid level, and the chromosome number of the selected plants may be doubled to obtain homozygous plants. Gametoclonal variation appears to be more desirable than somaclonal variation because