Cross-resistance to short residual sulfonylurea herbicides in transgenic tobacco plants.

Transgenic Nicotiana tabacum plants, produced by Agrobacterium tumefaciens-mediated transformation with a mutant gene (csr1-1) coding for acetohydroxyacid synthase (AHAS) from a chlorsulfuron resistant Arabidopsis thaliana line GH50 (GW Haughn et al. [1988] Mol Gen Genet 211: 266-271; GW Haughn, C Somerville [1986] Mol Gen Genet 204: 430-434), were selected directly on 80 micrograms per liter (225 nanomolar) chlorsulfuron. The expression of csr-1 in two separate transgenic lines CHL-1 and CHL-2 was confirmed by biochemical and genetic analyses. The AHAS activity of GH50 and the equivalent component of AHAS activity in CHL-2 was resistant to three short residual sulfonylurea herbicides, DPX-M6316, DPX-A7881, and DPX-L5300, in addition to chlorsulfuron but not to the sulfonylurea CGA 131'036. Cross-resistance to the imidazolinones AC 263, 499, AC 252, 214, and AC 243,997 was not observed. Parallel observations were made on the inhibition of seedling growth in soil or on culture medium. The relevance of these findings for the application of transgenic plants in agriculture is discussed.