FIELD PERFORMANCE OF DERIVED GENERATIONS OF TRANSGENIC TOBACCO

Two inbred cultivars of Nicotiana tabacum (tobacco), 'Samsun' and 'Xan thi', were transformed with the plasmid pBI 121 using Bin 19 in Agroba cterium tumefaciens. The plasmid carries the nptII gene conferring kan amycin resistance and the uidA gene encoding beta-glucuronidase (GUS). Progeny carrying the genes in the homozygous condition were identifie d and selfed over several generations. One line homozygous for the int roduced genes and one untransformed control from each cultivar were th en selected and crossed reciprocally to give four families per cultiva r. Seeds from each family were grown in a replicated field trial and a ll plants scored for a range of morphological and agronomic characters . In addition, leaf samples were taken and GUS activity measured. In t he 'Samsun' material, which contained one copy of the introduced gene at a single locus and showed high levels of GUS expression, the transf ormed homozygote showed twice the level of GUS activity as the hemizyg otes, wheareas in the 'Xanthi' line, which had a lower level of GUS, t he hemizygotes showed the same level of GUS activity as the transforme d homozygote. The agronomic data showed differences between the famili es, but the source of such differences could not be ascribed unambiguo usly. The results are discussed in the light of related information on gene expression and field performance from other transgenic material.