Field performance of imazamox-resistant spring wheat

Abstract

. 2004. Field performance of imazamox-resistant spring wheat. Can. J. Plant Sci. 84: 1205-1211. The imidazolinone herbicides possess high biological potency at low application rates, and are an attractive alternative for weed control in spring wheat (Triticum aestivum L.). Four mutation-derived spring wheat lines resistant to the imidazolinone class of herbicides were evaluated in field trials to investigate the levels of resistance to imazamox. Imazamox was applied post-emergence at 0 g (hand-weeded control; HWC) 20 g, 40 g, 80 g and 160 g active ingredient (a.i.) ha -1 . A standard herbicide treatment (SHT; clodinafoppropargyl, bromoxynil and MCPA ester) representing a common herbicide application to spring wheat in western Canada was also included. The cultivar CDC Teal was included as a susceptible control. At 160 g ha -1 , imazamox reduced yield in lines with a single resistance gene (TealIMI 10A, TealIMI 11A, and BW755) by up to 43% and delayed maturity up to 13 d. TealIMI 15A, the only line evaluated with two resistance genes, was the most resistant of all lines, with no significant increases in days to spike emergence (DSE), days to physiological maturity (DPM), and no reduction in yield at the highest rate of imazamox. The susceptible control was killed within 2 wk of imazamox application, regardless of application rate. These results indicate that two resistance genes are preferable for ensuring satisfactory levels of resistance to the formulation of imazamox used in these studies.

Recovery of Imidazolinone‐Resistant Hard Red Wheat Lines Following Imazamox Application

“…It is diffi cult to predict if stunting 21 DAT observed in the greenhouse also would reduce biomass and grain yield under fi eld conditions. In contrast to previous reports (Hanson et al, 2006;Pozniak et al, 2004aPozniak et al, , 2004b, we did not observe marked diff erences between winter and spring growth habit or between B-and D-genome resistance although the two-gene wheat was injured less than either single-gene resistant spring wheat. The lack of diff erence between winter and spring lines in these experiments may have been due to relatively poor growth of untreated spring wheat plants caused by warmer conditions compared to previous biomass experiments In contrast to the whole plant data, the ALS enzyme activity was strongly infl uenced by genome location, number of genes, and growth habit.…”

“…Although a temporary reduction in ALS activity usually does not result in reduced productivity of imidazolinone‐resistant‐winter wheat, injury from imazamox occasionally does occur. Imazamox injury on imidazolinone‐resistant wheat generally consists of minor chlorosis, dark green color of developed leaves, and delayed or stunted growth (Pozniak et al, 2004b). Imidazolinone‐resistant‐spring wheat cultivars appear to be slightly more susceptible to injury compared to winter wheat and do not have adequate tolerance to U.S. labeled rates of imazamox (Pozniak et al, 2004b; Tan et al, 2005; Hanson et al, 2006).…”

“…Imazamox injury on imidazolinone‐resistant wheat generally consists of minor chlorosis, dark green color of developed leaves, and delayed or stunted growth (Pozniak et al, 2004b). Imidazolinone‐resistant‐spring wheat cultivars appear to be slightly more susceptible to injury compared to winter wheat and do not have adequate tolerance to U.S. labeled rates of imazamox (Pozniak et al, 2004b; Tan et al, 2005; Hanson et al, 2006). Wheat injury can be influenced by high imazamox rates, surfactants, application timing, and environmental conditions (Frihauf et al, 2005; Geier et al, 2004; Stougaard et al, 2004; Hanson et al, 2005b).…”

Pleiotropic effects of herbicide-resistance genes on crop yield: a review

“…In the first group, there are those that fall under the registered trade mark Clearfield®: Ser‐653‐Asn in maize, rice, oilseed rape and wheat; Ala‐205‐Val in sunflower; and Trp‐574‐Leu in maize and oilseed rape that also confers resistance to sulfonylureas . A Canadian study did not reveal any effect of Ser‐653‐Asn on yield of spring wheat and a greenhouse study also found no effect on seed production in Arabidopsis . There was no difference in seed production between resistant sunflower and similar susceptible varieties, or among their progeny in crosses and their hybrids with Helianthus petiolaris in the USA and Brazil; there were some differences in leaf size and reduced competition in mixed stands.…”

Response of Selected Hard Red Wheat Lines to Imazamox as Affected by Number and Location of Resistance Genes, Parental Background, and Growth Habit

“…While IR-winter wheat generally has adequate safety to labeled rates of imazamox [(RS)-2-(4-isopropyl-4methyl-5-oxo-2-imidazolin-2-yl)-5-methoxymethylnicotinic acid], crop injury occasionally occurs (Geier et al, 2004). IR-spring wheat appears to be more sensitive to imazamox than winter wheat and single-gene resistant cultivars do not have adequate tolerance to U.S. labeled rates of the herbicide (Pozniak et al, 2004b, Tan et al, 2005. Wheat injury consists of minor chlorosis, dark green color of developed leaves, or stunting and yield loss can occur (Pozniak et al, 2004b).…”