Molecular and Field Analysis of Somaclonal Variation in Transgenic Plants

Abstract

Transgenic plants are expected to integrate a foreign gene in an otherwise unmodified genome. Indeed, the foreign gene is stably integrated in the genome of selected plants and is transmitted through the sexual progeny (Bellini et al, 1992). On the other hand, there is no reason to exclude that genomic changes may have occurred in transgenic plants and that these determine visible or cryptic phenotypic and metabolic changes. In fact, all transformation protocols foresee cell culture in the dedifferentiated state before plant differentiation and this has been demonstrated to be a powerful mutagenic treatment (Walbot, Cullis, 1983 and 1985). Changes in phenotypic traits, accompanied by decrease in agronomic potential have already been verified in transgenic rice (Shun et al., 1993) and potato plants (Dale, McPartland, 1992). In general, it is normal practice to disregard transgenic plants with undesirable agronomic traits and to select those that show the highest expression of the transgene and are apparently normal for other traits.