A chimeric gene functional in a plant cell, which chimeric gene comprises: a) at a position 5' to coding region (c), a plant-expressible promoter sequence;
b) at a position 3' to coding region (c), a terminator signal sequence; and
c) a coding region of an aphIV gene, which coding region:

1. encodes a functional hygromycin phosphotransferase enzyme; and
2. is positioned between such plant-expressible promoter sequence (a) and such terminator signal sequence (b) so as to be expressible,
   wherein expression of such coding region in a plant cell confers resistance to hygromycin B on such plant cell and
   wherein such resistance to hygromycin B is capable of providing a basis for selection of such plant cell.

Plasmid pCEL40 shown in Fig. 2 and derivable by ligating the Bgl II digest of plasmid pCEL30, to the about 1.3 kb BamH I-Bgl II fragment of plasmid pOW20, such plasmids pCEL30 and pOW20 being obtainable from NRRL B-15915 and NRRL B-15838, respectively.