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.