BROMOXYNIL RESISTANCE IN TRANSGENIC POTATO CLONES EXPRESSING THE BXN GENE

To broaden the spectrum of herbicides useful in potato production, the bxn gene for bromoxynil resistance, which encodes a nitrilase specifi c for bromoxynil, was introduced into 'Lemhi Russet' potato by Agrobac terium tumefaciens-mediated transformation. In GR(50) studies, transfo rmed potato clones mere 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 conju gation to polar compounds. In yield trials, the best performing transg enic clones had total tuber yields equal to the untreated, untransform ed control, but U.S. No. 1 tuber yields were 15 to 30% lower than the untreated, untransformed control. Tubers from three out of four transg enic clones had specific gravities, percent solids, and fry color simi lar to or better than the untreated, untransformed control. The data s uggest that lower U.S. No. 1 yields in the transgenic clones were due to somaclonal variation and that expression of the bxn transgene had n o consistent, detrimental effect on internal tuber quality.