New selection marker for plant transformation . A number of systems to insert foreign DNA into a plant genome have been developed so far . However , only a small percentage of transgenic plants are obtained using any of these methods . Stable transgenic plants are selected by co - introduction of a selectable marker gene , which in most cases are genes that confer resistance against antibiotics or herbicides . In this chapter we describe a new method for selection of transgenic plants after transformation . The selection agent used is the nontoxic and common sugar glucose. Wild - type Arabidopsis thaliana plantlets that have been germinated on glucose have small white cotyledons and remain petite because the external sugar switches off the photosynthetic mechanism . The selectable marker gene encodes the essential trehalose-6 - phophate synthase , AtTPS1 , that catalyzes the first reaction of the two - step trehalose synthesis . Upon ectopic expression of AtTPS1 driven by the 35S promoter , transformed Arabidopsis thaliana plants became insensitive to glucose in comparison to wild - type plants . After transformation using AtTPS1 as a selection marker and 6% glucose as selection agent it is possible to single out the green and normal sized transgenic plants amid the nontransformed plantlets .