The transgenic  Sunset' papaya lines 55-1 and 63-1 have been developed to resist infection by papaya ringspot virus (PRV). <br> The gene conferring viral resistance was introduced via recombinant DNA (genetic -<br> engineering) techniques rather than conventional breeding techniques.  The<br> recombinant techniques enabled the developer to introduce a viral coat protein gene<br> from a mild strain of PRV into the genome of  Sunset' papaya.   Incorporation of the<br> PRV coat protein gene into papaya to yield the transgenic  Sunset' papaya lines 55-1<br> and 63-1 does not cause plant disease, but rather enables the plants to resist infection by<br> PRV.  The PRV coat protein gene was introduced into the papaya as part of a genetic<br> construct that also included the nptII and uidA (gus) genes which serve as genetic<br> marker genes.