A facile method for screening for phosphinothricin (PPT)-resistant transgenic wheats

A bioassay was developed for identifying transgenic wheat plants based on De Block et al.'s [8] ammonium-multiwell assay which allows qualitative and quantitative evaluation of the expression of the enzyme phosphinothricin acetyl transferase (PAT). Important parameters in the assay are the use of young leaf tissues, short incubation period (6 h) and a high light intensity during incubation (250 μmol s−1m−2). The assay is quick and results are obtained within a day. Ammonium measurements based on a colourimetric (modified Berthelot) reaction are conducted using sodium salicylate to avoid the use of phenol. Results of the assay show high correlation with Basta leaf painting tests and polymerase chain reaction (PCR) results. Thus, the assay may be used as a facile screen for bar-expressing transgenic cereals.