Inheritance and expression of transgenes in white clover

Abstract

White clover plants from a range of cultivars can now be routinely transformed with cloned foreign genes. However, before transgenic white clover cultivars can be developed, these inserted genes must be stably inherited and expressed at appropriate levels in progeny. Primary transgenic white clover plants containing a uidA (GUS) reporter transgene were outcrossed and the inheritance and expression of the uidA gene was examined over two generations, in several different cultivar backgrounds. Both Mendelian inheritance and consistent expression in different genetic backgrounds were obtained from strongly expressing primary transgenic plants. However, primary transgenic plants with weak or variable expression gave non-Mendelian inheritance and inconsistent expression of the transgene in progeny plants. Transgenic BC1 plants were also intercrossed to produce a segregating F2 population containing individuals heterozygous or homozygous for the transgene. In these populations heterozygous and homozygous plants had similar levels of uidA gene expression. These results indicate that F2 plants, homozygous for a transgene, might be used to develop a transgenic cultivar. However, both selection of a primary transgenic plant with stable, high level expression of the introduced gene and progeny testing, to determine the influence of genetic background, are prerequisites to such a development. Keywords: gene expression, inheritance, transgene, uidA reporter, white clover