Resistance to imazamox in Clearfield soft wheat (Triticum aestivum L.)

•The benefits and capabilities of Clearfield wheat in Europe are shown by first time.•This is the first time the different cultivars of Clearfield wheat are compared.•Corroborate that the involved resistant mechanisms in each cultivar are different.

Imidazolinone (IMI)-resistant crops exhibit relative tolerance to herbicides that inhibit the enzyme acetolactate synthase (ALS). The principal objective of this work was to evaluate the different resistance levels to imazamox between five Clearfield wheat cultivars. The IMI-resistant wheat cultivars (Bicentenario, Dollinco, Impulso, Invento, and Ikaro), widely planted in large areas in Latin America, were compared to a sensitive cultivar (Pandora) using several in vivo and in vitro experiments. The imazamox dose, expressed as g ai ha−1 that reduced the wheat fresh biomass by 50% (ED50), ranged from 151.0 (Ikaro) to 1.6 (Pandora). The herbicide concentrations (μM) that inhibited the ALS activity by 50% (I50) were in agreement with the ED50 values, suggesting that imazamox resistance could be due to a mutation in the ALS enzyme. The order of Clearfield wheat cultivars by the level of resistance to imazamox was: Ikaro > Impulso > Invento > Bicentenario = Dollinco >>> Pandora.The finding that IMI-resistant wheat cultivars regained their photosynthetic activity with time and the fact that Ikaro plants showed an increased level of resistance over time suggest that other resistance mechanisms might be involved in the differential tolerance to imazamox in these wheat cultivars.

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