Meaning of Somaclonal Variation
It has been recognised that all plants regenerating from the tissue culture are not exactly the replicas of a parental form. Phenotypic variation is frequently observed amongst regenerated plants. Phenotypic changes are associated with genetic changes of an organism. The frequently genetic changes could result from mutations, epigenetic changes or combination of both mechanisms. Since genetic mutations are irreversible and likely to persist in the progeny of regenerated plants whereas epigenetic changes are not transmitted by sexual reproduction. It has been found that cells or tissues in cultures undergo frequent genetic changes resulting in new phenotypes on organogenesis or embryogenesis. Plant cell and tissue culture provides increased genetic variability. Variants selected in tissue cultures have been referred to as “calliclones” or “Protoclones”.
According to Larkin and Scowcroft (1981), “Somaclonal variation is the genetic variability which is regenerated during tissue culture” or plant variants derived from any form of cell or tissue cultures.
Evans et.al.prefer the term “Gametoclonal variation” for variant clones specifically raised from gametic or Gametophytic cells.