<p style="text-align: justify;">The imidazolinone-tolerance trait in X81359 was discovered in a wild (weedy) population of sunflower (<i>Helianthus annus</i>). The natural mutation conferring the imidazolinone tolerance was detected in a field where soybeans has been cultivated and treated with imazethapyr for several seasons. The mutant sunflower population expressed a mutation in AHAS gene, conferring tolerance to applications of imazethapyr. Conventional plant breeding techniques were used to introduce the herbicide-tolerance trait into sunflower germplasm, including extensive backcrossing into NuSun sunflower varieties.</p>
