Complementary DNAs to turnip mosaic potyvirus (a radish isolate) genomic RNA were synthesized using oligo (dT) as primer and cloned into the vector lambda -ZAP II. After hybridization with a single-stranded cDNA probe and sequencing of the inserted DNA, positive clones with poly-A tails were obtained. One clone containing a 1429 bp insert was sequenced. The coat protein was identified based on the MW of the TuMV coat protein and the consensus sequences of the polyprotein processing sites of potyviruses. The 5' end of the coat protein gene was modified by PCR to introduce an initiation codon, ATG, and 2 restriction enzyme sites. The gene was then manipulated into a binary vector pBIN437 which was derived from pBI121 and the plant expression vector could be used to transform Brassica napus.