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

Abstract

Mesotrione is effective in controlling a wide spectrum of weeds in corn but not registered for postemergence use in sorghum because of crop injury. We screened a sorghum germplasm collection and identified two mesotrione-resistant sorghum genotypes (G-1 and G-10) and one susceptible genotype (S-1) in an in vitro plate assay. A mesotrione dose−response assay under greenhouse and field conditions confirmed that G-1 and G-10 are highly resistant compared to S-1. We found enhanced metabolism of mesotrione in G-1 and G-10 using HPLC assay, and a significant reduction in biomass accumulation was found in G-1 and G-10 plants pretreated with cytochrome P450 (CYP)-inhibitors malathion or piperonyl butoxide, indicating the involvement of CYPs in the metabolism of mesotrione. Genetic analyses using F 1 and F 2 progenies generated by crossing G-1 and G-10 separately with S-1 revealed that mesotrione resistance in sorghum is controlled by a single dominant gene along with several genes with minor effects.

Metabolism of Tembotrione, a Triketone Herbicide, confers Differential Sensitivity in Winter Wheat (Triticum aestivum)

“…31 There was no difference in tembotrione absorption and translocation among all of the genotypes tested (Figure 3A,B), and hence, this mechanism cannot be attributed to the differential sensitivity of wheat to tembotrione. Similarly, no difference in absorption and translocation of another triketone herbicide, mesotrione was found between the susceptible and resistant crop and weed species such as sorghum 32 or Palmer amaranth 29,33 The HPPD inhibitors, including triketones, are known to be metabolized in tolerant crops, such as corn, via Phase I biochemical reactions mediated by P450 enzyme activity. For example, topramezone (pyrazolone family of HPPD inhibitor) is detoxified by P450 enzymes via N-demethylation.…”

“…The plants treated with malathion followed by tembotrione application died at 3 WAT (Figures and ). Similarly, HPPD-resistant crop and weed species also showed sensitivity to triketones, upon treatment with malathion followed by mesotrione or tembotrione. ,,, Several P450 genes have been characterized and shown to confer metabolic resistance to herbicides in crops and weed species, including potential overexpression of the CYP81E gene likely to confer metabolic resistance to tembotrione in Palmer amaranth. ,, …”

Characterization of Wheat (Triticum aestivum) Response to Mesotrione, a Triketone Herbicide

“…Mesotrione and tembotrione are commonly used in corn for post and pre-emergence options . In sorghum ( Sorghum bicolor L. Moench), mesotrione is registered only as preemergence but not as a postemergence option . HPPD-inhibitors can be used in transgenic soyabean ( Glycine max (L.) Merr.…”

“…These transgenic soybeans showed low sensitivity to mesotrione compared to wild-type plants. , Although rice ( Oryza sativa L.) is naturally tolerant to HPPD-inhibitor, pyrazolate, a rice gene HIS1 conferring resistance to several triketone herbicides such as benzobicyclon, sulcotrione, tefuryltrione, mesotrione, and tembotrione has been identified . Recently, we found rapid metabolism of mesotrione, likely mediated by P450 activity in two sorghum genotypes . Similarly, an evolved resistance to mesotrione via the metabolism of herbicide likely mediated by P450 enzyme activity was also documented in weed species such as Palmer amaranth ( Amaranthus palmeri S. Watson ), waterhemp ( Amaranthus tuberculatus (Moq.)…”

“…The visible injury symptoms, in response to the mesotrione application, were recorded using an injury rating scale of 0 to 100 (0 = no injury, 100% = plant mortality) at 2 weeks after treatment (WAT). The experiments were conducted similar to the study on mesotrione response in sorghum …”