Field performance of derived generations of transgenic tobacco

Two inbred cultivars of Nicotiana tabacum (tobacco), 'Samsun' and 'Xanthi', were transformed with the plasmid pBI 121 using Bin 19 in Agrobacterium tumefaciens. The plasmid carries the nptII gene conferring kanamycin resistance and the uidA gene encoding β-glucuronidase (GUS). Progeny carrying the genes in the homozygous condition were identified and selfed over several generations. One line homozygous for the introduced genes and one untransformed control from each cultivar were then selected and crossed reciprocally to give four families per cultivar. Seeds from each family were grown in a replicated field trial and all plants scored for a range of morphological and agronomic characters. In addition, leaf samples were taken and GUS activity measured. In the 'Samsun' material, which contained one copy of the introduced gene at a single locus and showed high levels of GUS expression, the transformed homozygote showed twice the level of GUS activity as the hemizygotes, wheareas in the 'Xanthi' line, which had a lower level of GUS, the hemizygotes showed the same level of GUS activity as the transformed homozygote. The agronomic data showed differences between the families, but the source of such differences could not be ascribed unambiguously. The results are discussed in the light of related information on gene expression and field performance from other transgenic material.