FIELD EVALUATION OF TRANSGENIC RICE (Oryza sativa L.) PRODUCED BY AGROBACTERIUM AND PARTICLE BOMBARDMENT METHODS

¹ Agronomy Department, Louisiana Agric. Exp. Stn., Louisiana State Univ. Agric. Center, Baton Rouge, LA 70803-2110

² Rice Research Station, Louisiana Agric. Exp. Stn., Louisiana State Univ. Agric. Center, Crowley, LA 70527

Field evaluation of transgenic plants is necessary to determine utility and ultimate success of a particular gene transfer method. We have produced numerous independent transgenic rice lines from six elite U.S. lines including the cultivar Cocodrie by particle bombardment or Agrobacterium-mediated transformation. Using scutellum-derived embryogenic calli as target tissues and bialaphos or hygromycin B as a selection agent, a total of 379 independent transformed calli producing 1,268 transgenic glufosinate-resistant plants were recovered from 5,201 bombarded calli. Co-cultivation of 1,875 scutellum-derived calli with Agrobacterium tumefaciens strain LBA4404 (pTOK233) produced 209 independent transformed calli and 158 hygromycin-resistant, GUS expressing transgenic rice plants. In terms of average callus transformation frequency, Agrobacterium (11.4%, 209/1875) was more efficacious than particle bombardment(7.5%, 389/5201). Under field conditions 67 R2, 150 R3, and 9 R4 bombardment-generated transgenic lines of Cocodrie and LA9502065 showed both desirable agronomic traits and a wide range of phenotypic aberrations. Dwarfism, early- or late-maturity, mosaic pink to dark purple pigmentation in hulls were the predominant aberrations. In comparison, 15 R2 lines derived from Agrobacterium exhibited greater uniformity in terms of six agronomic traits including maturity and fecundity. Morphological variation was only observed in plant height. Southern blot hybridization analysis revealed that approximately 1-8 copies of the hph gene were inserted into the genome of transgenic rice by particle bombardment whereas only 1-2 copies of the hph gene were inserted by Agrobacterium, indicating Agrobacterium is an attractive alternative approach for introduction of useful genes into rice.