To broaden the spectrum of herbicides useful in potato production, the bxn gene for bromoxynil resistance, which encodes a nitrilase specific for bromoxynil, was introduced into ‘Lemhi Russet’ potato by Agrobacterium tumefaciens-mediated transformation. In GR50 studies, transformed potato clones were at least 70-fold more resistant to bromoxynil than the untransformed control. Resistance was due to rapid metabolism of bromoxynil to 3,5-dibromo-4-hydroxybenzoic acid, followed by conjugation to polar compounds. In yield trials, the best performing transgenic clones had total tuber yields equal to the untreated, untransformed control, but U.S. No. 1 tuber yields were 15 to 30% lower than the untreated, untransformed control. Tubers from three out of four transgenic clones had specific gravities, percent solids, and fry color similar to or better than the untreated, untransformed control. The data suggest that lower U.S. No. 1 yields in the transgenic clones were due to somaclonal variation and that expression of the bxn transgene had no consistent, detrimental effect on internal tuber quality.
