Instability of the gene nptII expression in transgenic tobacco (Nicotiana tabacum L.) plants during inbreeding

The expression persistence and inheritance of the marker gene nptII were in vestigated in inbred transgenic tobacco (Nicotiana tabacum) plants. The inh eritance of nptII in most examined plants corresponded to mono- and dihybri d segregation. Two successive self-pollinations of the plant T-0-5 resulted in the silencing of the marker gene with a frequency of 33.3%. The silenci ng persisted in the subsequent self-pollinating generations. Reversions of the nptII gene expression were found in crosses between Km-sensitive transg enic tobacco plants (2 x 10(-4)) and in plants regenerated from explants of Km-sensitive genotypes (about 50%).