A recombinant vector which can transform potato plants so as to confer upon the potato plant immunity against potato virus Y necrosis line is disclosed. The recombinant vector according to the present invention comprises a promoter which functions in a potato plant cell; an operably linked leader sequence of RNA4 of cucumber mosaic virus, which is located downstream of the promoter; and an operably linked sequence which encodes a coat protein of potato virus Y necrosis line, which is located downstream of said leader sequence; and the recombinant vector is capable of transforming potato plants.