Soybean (Glycine max) cultivar differences in response to sulfentrazone

Greenhouse-grown soybean cultivars varied in their tolerance to preemergence application of sulfentrazone. The cultivars Ransom, Hutcheson, Kato, Gasoy 17, and Cobb exhibited relatively low tolerance to 0.5 kg ai ha−1 sulfentrazone with 38, 41, 46, 50, and 58% height reduction compared to respective controls. The growth of tolerant cultivars Centennial, Edison, and Hartz 5164 was not affected by this treatment. However, the growth of all cultivars was reduced at the excessive rate of 2.0 kg ha−1 preemergence application of sulfentrazone. No differences in root uptake or translocation of [14C] sulfentrazone were observed between the relatively tolerant and less tolerant cultivars tested. Centennial and Hutcheson cultivars rapidly metabolized sulfentrazone via oxidative degradation of the 3-methyl group on the triazolinone ring of the herbicide. Only 4.7 and 4.9% of the active ingredient remained in the foliage of Hutcheson and Centennial 24 h after treatment, respectively. While there were no differences in Protox inhibition or Proto IX accumulation between the two cultivars, Hutcheson was more sensitive than Centennial to peroxidative stresses induced by either Proto IX accumulation or rose bengal. Therefore, tolerance to sulfentrazone is due to rapid metabolism of the herbicide; however, the intraspecific difference in response to sulfentrazone appears to be due to intrinsic differential tolerance to the herbicide-induced peroxidative stress.