Genetic basis and origin of resistance to acetolactate synthase inhibitors in Amaranthus palmeri from Spain and Italy.

BACKGROUND: Amaranthus palmeri is an aggressive annual weed native to the United States, which has become invasive in some European countries. Populations resistant to acetolactate synthase (ALS) inhibitors have been recorded in Spain and Italy, but the evolutionary origin of the resistance traits remains unknown. Bioassays were conducted to identify cross-resistance to ALS inhibitors and a haplotype-based genetic approach was used to elucidate the origin and distribution of resistance in both countries. RESULTS: Amaranthus palmeri populations were resistant to thifensulfuron-methyl and imazamox, and the 574-Leu mutant ALS allele was found to be the main cause of resistance among them. In two Spanish populations, 376-Glu and 197-Thr mutant ALS alleles were also found. The haplotype analyses revealed the presence of two and four distinct 574-Leu mutant haplotypes in the Italian and Spanish populations, respectively. None was common to both countries, but some mutant haplotypes were shared between geographically close populations or between populations more than 100 km apart. Wide genetic diversity was found in two very close Spanish populations. CONCLUSION: ALS-resistant A. palmeri populations were introduced to Italy and Spain from outside Europe. Populations from both countries have different evolutionary histories and originate from independent introduction events. ALS resistance then spread over short and long distances by seed dispersal. The higher number and genetic diversity among mutant haplotypes from the Spanish populations indicated recurrent invasions. The implementation of control tactics to limit seed dispersal and the establishment of A. palmeri is recommended in both countries. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Evaluation of the Anti-transpirant Activity of ABA Receptor Agonists in Monocot and Eudicot Plants.

ABA receptor agonists capable of improving plant performance under drought conditions have been described during the last years. However, monocot and eudicot plant species respond differently to various agonists. Here, we provide a detailed methodology to evaluate the anti-transpirant activity of ABA receptor agonists in both monocot and eudicot plant species using infrared imaging and image data analysis. Plant growth conditions, chemical application, and infrared image analysis are explained in detail to evaluate the anti-transpirant activity of ABA receptor agonists in the eudicot model Arabidopsis thaliana and in the C4-monocot model Setaria viridis.