Characterization of the Novel Tomato Mutant HRT, Resistant to Acetolactate Synthase–Inhibiting Herbicides

The tomato mutant line HRT was obtained by ethyl methanesulfonate seed mutagenesis of the commercial tomato line M82. Greenhouse studies were conducted to determine whole-plant response to the imidazolinone herbicides imazamox, imazapic, and imazapyr; pyrithiobac-sodium (a herbicide from the pyrimidinylthiobenzoic acid group); and propoxycarbazone sodium (sulfonylaminocarbonyltriazolinone group). The mutant was highly resistant to imazamox, imazapic, and imazapyr, but did not differ from M82 in its response to the sulfonylurea herbicides Envoke (trifloxysulfuron), Monitor (sulfosulfuron), and Glean (chlorsulfuron). Equip (foramsulfuron), a sulfonylurea herbicide, was toxic to M82 but less so to HRT plants. Under field conditions, HRT showed high resistance to imazapic and imazapyr. The herbicides at a rate of 144 g ai ha −1 did not cause any reduction in HRT plant vigor, development, or yield. Results of greenhouse and field experiments demonstrated high Egyptian broomrape–control efficacy with the imidazolinone herbicides imazapic and imazapyr. Two imazapic applications of 9.6 or 14.4 g ai ha −1 and three applications of 4.8 g ai ha −1 in pot experiments completely prevented appearance of broomrape shoots aboveground. Three and four applications of the same herbicides in the field at a rate of 12 or 24 g ai ha −1 completely prevented shoot appearance without any yield losses. Single imazapic application as high as 144 g ai ha −1 did not damage the plants or reduce HRT yield.