Resistance of Inzen™ grain sorghum to multiple PRE- and POST-applied acetolactate synthase–inhibiting herbicides

Abstract

A non-GMO trait called Inzen™ was recently commercialized in grain sorghum to combat weedy grasses, allowing the use of nicosulfuron POST in the crop. Inzen™ grain sorghum carries a double mutation in the acetolactate synthase (ALS) gene Val560Ile and Trp574Leu, which potentially results in cross-resistance to a wide assortment of ALS-inhibiting herbicides. To evaluate the scope of cross-resistance to Weed Science Society of America Group 2 herbicides in addition to nicosulfuron, tests were conducted in 2016 and 2017 at the Lon Mann Cotton Research Station near Marianna, AR, the Arkansas Agricultural Research and Extension Center in Fayetteville, AR, and in 2016 at the Pine Tree Research Station near Colt, AR. The tests included ALS-inhibiting herbicides from all five families: sulfonylureas, imidazolinones, pyrimidinylthiobenzoics, triazolinones, and triazolopyrimidines. Treatments were made PRE or POST to grain sorghum at a 1X rate for crops in which each herbicide is labeled. Grain sorghum planted in the PRE trial included Inzen™ and a conventional cultivar. Visible estimates of injury and sorghum heights were recorded at 2 and 4 weeks after herbicide application and yield data were collected at crop maturity. In the PRE trial, there was no visible injury, sorghum height reduction, or yield loss in plots containing the Inzen™ cultivar. Applications made POST to the Inzen™ grain sorghum caused visible injury, sorghum height reduction, and yield loss of 20%, 13%, and 35%, respectively, only in plots where bispyribac-Na was applied. There was no impact on the crop from other POST-applied ALS-inhibiting herbicides. These results demonstrate that the Inzen™ trait confers cross-resistance to most ALS-inhibiting herbicides and could offer promising new alternatives for weed control and protection from carryover of residual ALS-inhbiting herbicides in grain sorghum.

Modeling the evolution of herbicide resistance in weed species with a complex life cycle

“…2017a, Bowman et al. 2021). Hence, it is possible that Johnsongrass growing in sorghum fields will be regularly exposed to large amounts of sorghum pollen carrying the ALS‐resistance trait.…”

“…Nicosulfuron is one group of herbicides that is used to control Johnsongrass and other weedy sorghum species that inhibits the acetolactate synthase (ALS) enzyme. Corteva Agriscience (Wilmington, Delaware, USA) is in the process of commercially deploying sorghum (Inzen sorghum hybrids) that is tolerant to an ALS-inhibiting herbicide using traditional breeding technology (Werle et al 2017a, Bowman et al 2021). Hence, it is possible that Johnsongrass growing in sorghum fields will be regularly exposed to large amounts of sorghum pollen carrying the ALS-resistance trait.…”

Identification and Characterization of Mesotrione-Resistant Grain Sorghum [Sorghum bicolor (L.) Moench]: A Viable Option for Postemergence Grass Weed Control

“…Apart from lack of options for broad-spectrum POST weed control, the evolution of herbicide resistance in weeds warrants the need for investigation of POST herbicide options in sorghum . The development of herbicide-resistant sorghum technology will broaden the POST weed control options. , In addition to control of broad spectrum of weeds, the use of mesotrione as POST herbicide can also help control weeds that are resistant to acetolactate synthase (ALS)- and photosystem (PS)­II-inhibitors and glyphosate. − Though mesotrione is registered for use as a PRE herbicide in sorghum, it can cause severe crop injury when applied as POST. , The availability of mesotrione-resistant grain sorghum will offer more options for weed management which will provide effective weed control during the critical periods of crop growth …”

“…3 The development of herbicide-resistant sorghum technology will broaden the POST weed control options. 11,12 In addition to control of broad spectrum of weeds, the use of mesotrione as POST herbicide can also help control weeds that are resistant to acetolactate synthase (ALS)-and photosystem (PS)II-inhibitors and glyphosate. 13−15 Though mesotrione is registered for use as a PRE herbicide in sorghum, it can cause severe crop injury when applied as POST.…”

Critical period of grass weed control in ALS-tolerant grain sorghum (Sorghum bicolor) is affected by planting date and environment

“…The aforementioned confer tolerance to the sulfonylurea and imidazolinone families (Werle et al, 2016). Bowman et al (2021) evaluated Inzen sorghum for cross resistance to multiple ALS-inhibitor herbicides and found it to survive herbicides from five chemical families: sulfonylureas, imidazolinones, pyrimidinylthiobenzoics, triazolinones, and triazolopyrimidines. The ALS-inhibiting herbicide active ingredients in this case were nicosulfuron and rimsulfuron.…”