Result of a decrease in initial annealing temperature of the touch-down PCR on the amplification of UGT genes with different couples of primers. Location of amplicons of the expected size is indicated by an asterisk. The same couples of primers were tested with two cDNA libraries made out wheat seedlings treated (+) or not (-) with cloquintocet-mexyl and phenobarbital for inducing herbicide metabolism. Some couples of primers such as PUGTb/PUGTer did not provide any amplified fragment, even at low annealing temperatures. Some (e.g. PUGTe/PUGTer) were effective using stringent annealing temperature.