Field Resistance of Digitaria sanguinalis (L.) Scop. to Haloxyfop-P-methyl in China’s Cotton Fields

Abstract

Large crabgrass, Digitaria sanguinalis (L.) Scop., is a devastating weed species in the cotton (Gossypium spp.) fields in China. It has developed resistance to haloxyfop-P-methyl, an aryloxyphenoxypropionate herbicide known for its ability to inhibit lipid synthesis and induce oxidative stress in weeds, due to years of continuous and intensive use. Here, we present the results from a nation-wide, long-term resistance monitoring effort. To understand the scale and level of haloxyfop-P-methyl resistance, a total of 65 D. sanguinalis populations from eight cotton production provinces, including Hunan, Jiangxi, Xinjiang, Henan, Hubei, Hebei, Shanxi, and Anhui, were collected from 2014–2017. Based on results from dose response to haloxyfop-P-methyl, we observed a gradient of sensitivity to haloxyfop-P-methyl among 65 field populations, ranging from sensitive (8), to low-level resistance (40; 2 ≤ RI ≤ 10) to moderate-level resistance (17; 10 < RI < 20). Although no high-level resistance (RI > 20) was found among the 65 populations, populations from Hunan and Hebei exhibited a rapid spread of field-evolved resistance. After challenged with haloxyfop-P-methyl (48.600 g a.i./ha at the 4–5-leaf stage), resistant and susceptible D. sanguinalis responded differently in the activity of an array of resistance-related enzymes, including acetyl-CoA carboxylase (ACCase), glutathione S-transferase (GSTs), nicotinamide-adenine dinucleotide phosphate (NADPH) and carboxylesterase (CarE), suggesting the potential involvement of NADPH, CarE and GSTs in D. sanguinalis to haloxyfop-P-methyl resistance.

Cloning and functional characterization of a tau class glutathione transferase associated with haloxyfop‐P‐methyl resistance in Digitaria sanguinalis

“…GST activity in DsGSTU1 ‐overexpressing rice seedlings was 1.18‐fold the control before haloxyfop‐ P ‐methyl treatment, and 1.40‐, 1.07‐ and 1.15‐fold the control at 36, 72 and 120 h after herbicide treatment, respectively. There was consistently higher GST activity in HR D. sanguinalis plants compared to HS plants 19 . These combined results indicate that DsGSTU1 could contribute to resistance of D. sanguinalis to haloxyfop‐ P ‐methyl.…”

“…Our previous work showed that the intrinsic activity of GSTs in HR D. sanguinalis was higher relative to HS plants both with and without haloxyfop‐ P ‐methyl treatment 19 . In this study, to further understand the role of DsGSTU1 in herbicide resistance, a GST activity assay was performed using rice seedlings overexpressing the DsGSTU1 gene.…”

“…Previous research also has demonstrated that GST conjugation confers herbicide resistance in weeds, including atrazine resistance in Palmer amaranth ( Amaranthus palmeri ), 21 glyphosate resistance in goosegrass ( Eleusine indica ) 22 and mesosulfuron‐methyl resistance in Beckmannia syzigachne 23 . Our previous work suggested that GST activity is higher in herbicide‐resistant D. sanguinalis than in sensitive plants, suggesting that enhanced GST activity might be associated with haloxyfop‐ P ‐methyl resistance in D. sanguinalis 19 . However, the molecular basis of GST‐mediated herbicide resistance remains less known 24 …”

“…P450s can facilitate the oxidation or hydroxylation of herbicide molecules, and GSTs can allow herbicide metabolism through conjugation with the tripeptide glutathione (γ‐glutamylcysteinylglycine, GSH) 18 . During haloxyfop‐ P ‐methyl metabolism, haloxyfop esters are first hydrolyzed to haloxyfop acid, 19 followed by phases II, III and IV of herbicide detoxification. In weed species a major evolved resistance mechanism is increased P450 and GST capacity to metabolize herbicides.…”

“…Based on our previous work, D. sanguinalis in China's cotton fields has evolved GST‐mediated resistance to haloxyfop‐ P ‐methyl 19 . According to RNA‐seq analysis (Supporting Information, Table S1), DsGSTU1 , a candidate GST, showed significantly higher expression in haloxyfop‐ P ‐methyl‐resistant (HR) D. sanguinalis in comparison to haloxyfop‐ P ‐methyl‐sensitive (HS) plants.…”