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Agronomic Performance of Sulfonylurea-Resistant Transgenic Flue-Cured Tobacco Grown under Field Conditions

Agriculture Canada, Research Station, P.O. Box 186, Delhi, Ontario, Canada, N4B 2W9
Agriculture Canada, Plant Research Centre, Ottawa, Ontario, Canada, K1A 0C6

^* Corresponding author.

Field testing of transgenic crops is an essential step towards commercialization. This study was conducted to assess the agronomic performance of herbicide-resistant transgenic tobacco (Nicotiana tabacum L.) lines relative to untransformed controls and to evaluate their sensitivity to sulfonylurea herbicides in a field situation. Two transgenic flue-cured tobacco lines harboring the csr1-1 gene for sulfonylurea resistance were evaluated after application of three rates of two sulfonylurea herbicides [chlorsulfuron (2-chloro-N[(4-methoxy-6-methyl-1,3,5 triazin-2-yl) aminocarbonyl]-benzenesulfonamide) and DPXR9674, a 2:1 mixture of thifensulfuron (methyl-3-[[4-methoxy-6-methyll, 3,5-triazin-2-yl aminocarbonyl]aminosulfonyl]-2-thiophenecarboxylate) and tribenuron (methyl-2[[[|4-methoxy-6-methyl-l,3,5-triazin-2-yl]carbonyl]amino]sulfonyl]benzoate)]. We showed that one of the lines was resistant to 10 g a.i. ha^–1 of chlorsulfuron but not to 20 g a.i. ha^–1 and that both lines were susceptible to DPX-R9674. Comparison of transgenics to an untransformed control in the absence of herbicide treatment showed that both transgenics were lower yielding than the controls. This impairment of agronomic performance could be attributed to any of a number of factors. Resistance to chlorsulfuron was adequate, but margins of safety need to be increased before any farm level use of these transgenic lines can be considered. Selection among lines for maximum expression of the transgene and selection or backcrossing to recover the parental phenotype may further improve agronomic performance.

Received for publication April 21, 1992.