Publisher Summary This chapter explains the use of the bar gene as a selectable marker in plant transformation, as a screenable marker in tissue culture and plant breeding, and as a reporter gene in plant molecular biology. The bar gene has served as a useful assayable marker gene in plant molecular biology. To guarantee correct translation initiation in plants, an ATG initiation codon was introduced instead of the GTG codon used in the streptomyces strain and the second codon was changed to introduce an NcoI site at the 5’ end of the coding region. Chimeric gene constructs, containing the bar coding region under control of different promoters, have been transferred to several crops. The bar gene has also been successfully used as a selectable marker in some plant species, using PPT or bialaphos as a selective agent. Transgenic plants were resistant to herbicide applications in the greenhouse and in field conditions.