Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/22/2007
Publication Date: 9/1/2007
Citation: Hanson, B.D., Fandrich, L., Shaner, D.L., Westra, P., Nissen, S.J. 2007. Recovery Of Imidazolinone-Resistant Hard Red Wheat Lines Following Imazamox Application. Crop Science. Vol.(47):2058-2066 Interpretive Summary: Imidazolinone resistance is incomplete in currently available wheat cultivars and injury occasionally occurs following treatment with imazamox. Biomass production and enzyme activity of several hard red wheat lines were measured following imazamox treatment in greenhouse experiments. The wheat lines included spring and winter growth habits and cultivars carrying the resistance trait on either the B, D or both B and D genomes. There were large differences in enzyme activity among the various wheat cultivars but reductions in biomass accumulation were not consistently observed. Genotype does affect recovery of imidazolinone-resistant wheat but injury in the field is likely also influenced by other factors.
Technical Abstract: Imidazolinone-resistant hard red wheat cultivars are occasionally injured by imazamox applications because a portion of the acetolactate synthase remains susceptible to the herbicide. The growth and enzyme activity of two groups of hard red wheat near-isolines with spring or winter growth habit were examined following imazamox application. Each group of near-isolines contained a susceptible cultivar and cultivars with the IR trait on either the B or D genome. The spring wheat group also contained a line carrying both the B and D genome copies of the resistance gene. In whole plant experiments, growth of all single gene resistant lines was delayed by both 35 and 105 g/ha imazamox while the two gene line was delayed at only the highest rate. There was a herbicide rate effect on biomass accumulation but no differences among genome locations in the single gene resistant lines or among spring vs winter growth habit. On an enzyme basis, however, there were differences among B vs D genome resistance and between winter and spring growth habit. Spring wheat cultivars with the B genome resistance had greater reductions in ALS activity compared to the D genome cultivars, while in winter wheat, B and D genome lines responded similarly. Foliar imazamox treatment reduced the extractable ALS activity more than predicted by in vitro imazamox treatment and this reduction was constant throughout the experiment. Differences among genotypes existed in the recovery of ALS activity in imidazolinone wheat but other factors also likely influence the injury occasionally observed in the field.