ABSTRACT
Plants derived from undifferentiated callus cultures as well as their progenies display many visually apparent variants. Propagation by meristem culture has been successful in regenerating numerous genetically uniform plants. However, once cells enter an undifferentiated state in the formation of calli, mutations frequently arise. Perhaps of greater importance is the myriad of quantitative traits that vary extensively in same genetic materials. Somaclonal variation occurs at both the phenotypic as well as genotypic level reflected by techniques of morphogenic, cytogenetic, restriction fragment length polymorphism, randomly amplified polymorphic DNA, and isozyme analysis. Aside from detecting aneuploidy and polyploidy in culture, cytology has identified many forms of chromosomal abnormalities in both cell cultures and regenerant plants. Genetic variation in somaclones can also be measured by using restriction fragment length polymorphisms. An understanding of the epigenetic nature of many of the alterations now appears to be fundamental to controlling somaclonal variation. These changes can be important at the genic as well as genome levels.
