Field Survey and Resistance Occurrence to ALS-Inhibiting Herbicides in Glebionis coronaria L. in Tunisian Wheat Crops

Abstract

Glebionis coronaria (L.) Cass. ex Spach is a troublesome weed in cereal cropping systems in northern Tunisia. Recently, failures in controlling this weed have been reported by farmers. Field surveys and farmers interviews were conducted to highlight the potential causes of G. coronaria occurrence and the associated yield losses in wheat. Survey results revealed a significant correlation between farmers’ awareness of resistance occurrence and cultural practices, mainly sowing date and tillage, while G. coronaria abundance was related to the lack of herbicide rotation and the frequency of ALS-inhibiting herbicide use. High G. coronaria infestations (more than 20 plants/m2) caused a significant decrease in wheat grain yield, reaching almost 75% at a density of 100 plants/m2. Field and pot experiments showed low efficacies of ALS-inhibiting herbicides to control G. coronaria populations. The application of field rates of tribenuron-methyl and mesosulfuron + iodosulfuron failed to control the tested populations, and generally, G. coronaria dry weight increased compared to nontreated ones (potential hormetic effect). These findings were further investigated in two selected resistant populations through tribenuron dose–response experiments, plants from both populations exhibited high resistance factors (greater than 300), surviving up to 16-fold the recommended field dose. This is the first report for G. coronaria resistance occurrence to ALS-inhibiting herbicides in Tunisia and the second case worldwide.

Point Mutations as Main Resistance Mechanism Together With P450-Based Metabolism Confer Broad Resistance to Different ALS-Inhibiting Herbicides in Glebionis coronaria From Tunisia

“…The main reason was their broad-spectrum weed control at low rates. A previous survey, conducted in the same region, showed that florasulam was frequently used in a mixture with SAH to control G. coronaria in cereal crops ( Hada et al, 2020 ) while imazamox has never been applied on the weed to our knowledge.…”

“…Recent studies characterized P450-based metabolic cross-resistant individuals in L. rigidum and hypothesized that the genetic control was probably of polygenic and quantitative nature at the population level ( Yu and Powles, 2014b ; Han et al, 2021 ). Considering the complexity of metabolic herbicide resistance and the diversity and number of P450s in plants, we hypothesize that the differences observed in metabolism speed and metabolite amounts between the R1 and the R2 populations could be explained by herbicide and environmental selection pressures, particularly the history of herbicide applications in the fields where R populations were collected ( Yu and Powles, 2014b ; Hada et al, 2020 ). Owing to the genetic diversity of the weedy species, differences in the P450 activity and presence of other genes may be involved in the resistance of G. coronaria to imazamox, which can be observed even in different individuals of a single population as reported by Yu and Powles (2014b) .…”

“…For all experiments, three populations of G. coronaria were used. Resistant (R) populations (R1 and R2) were selected from a previous screening of 10 putative R populations collected across the Bizerte region in northern Tunisia, with both populations showing highly resistance levels to SU herbicides ( Hada et al, 2020 ). The susceptible (S) reference population, collected from the roadsides of the National Institute of Agronomy of Tunisia, had never previously received any herbicide treatments.…”

“…For years, Tunisian farmers faced challenges managing this weed in wheat fields. It has been estimated that wheat yield losses associated with high densities of G. coronaria is up to 75% ( Hada et al, 2020 ). Typically, G. coronaria control is still heavily dependent on chemical treatments, mainly acetolactate synthase (ALS)-inhibiting herbicides and synthetic auxin herbicides (SAH).…”

“…Typically, G. coronaria control is still heavily dependent on chemical treatments, mainly acetolactate synthase (ALS)-inhibiting herbicides and synthetic auxin herbicides (SAH). Recently, it has been proven that G. coronaria evolved resistance to sulfonylureas (SU), herbicides with potential cross-resistance to triazolopyrimidines – Type 1 (TP) family ( Hada et al, 2020 ). Both herbicide families target the ALS enzyme, which catalyzes the first common step in the biosynthesis of leucine, isoleucine, and valine in plants ( Duggleby et al, 2008 ; Liu et al, 2015 ).…”