Study of the occurrence of herbicide resistance in weed species and modeling of the dynamic of resistant weed populations in field crops: case studies of Papaver rhoeas and Sinapis arvensis.

The establishment and spread of weeds that are resistant to the main modes of action of herbicides are one of the most serious and fastest growing problems in modern agriculture. In Tunisia, the control of Papaver rhoeas L., Sinapis alba L. and Sinapis arvensis L. in cereal crops with acetolactate synthase (ALS)-inhibiting herbicides and auxins is increasingly decreasing. This study was undertaken to (i) determine the occurrence of resistance to ALS-inhibiting herbicides and auxins in the three weed species, (ii) study the mechanisms of weed resistance and (iii) study the dynamics of resistant weed populations through the development of germination and emergence models of sinapis species. The resistance was confirmed in the three weed species. Levels of resistance were investigated using dose–response experiments, and to study the mechanism(s), ALS gene sequencing, metabolism experiments and ligand docking were conducted. Dose–response experiments revealed the development of cross-resistance in the three weed species to different families of ALS-inhibitors, namely Sulfonylureas and Imidazolinones. Sequence analysis revealed different point mutations, mainly at positions 197, 376, and 574. Docking confirmed the cross-resistance patterns in Sinapis spp. Metabolism was confirmed through the application of cytochrome P450 monooxygenases (Cyt. P450s) inhibitor for ALS-inhibitors in the three species. Resistance to dicamba was found in P. rhoeas and S. alba and enhanced metabolism-involving Cyt. P450s is confirmed too. These two species were characterized multiple or/and cross-resistance to ALS-inhibiting herbicides and auxins. To establish the most effective control measures for weeds, a thorough understanding of weed biology and ecology is essential. In this context, P. rhoeas has been extensively studied. Laboratory germination experiments at various constant temperatures, along with field emergence experiments, were conducted on Sinapis spp to (i) determine the base temperature for germination of both species; (ii) develop a germination model for each species; and (iii) create temperature-based emergence models applicable to two different Mediterranean climates, specifically in Spain and Tunisia. Our results showed that the base temperature of S. arvensis and S. alba were 1.47 °C and 2.85, respectively. Laboratory germination models for Sinapis spp were successfully developed. Emergence models based on hourly thermal time accurately predicted field emergence patterns. S. arvensis was found to be more difficult to manage than S. alba due to staggered emergence. These models are crucial for the development of decision support systems and integrated weed management programs. Key words: ALS-inhibiting herbicides, TSR, enhanced metabolism, cross-resistance, Synthetic auxin herbicides, emergence model, germination