Non-Target-Site Resistance Mechanisms Endow Multiple Herbicide Resistance to Five Mechanisms of Action in Conyza bonariensis

Abstract

The repeated use of herbicides can lead to the selection of multiple resistance weeds. Some populations of Conyza bonariensis occurring in olive groves from southern Spain have developed resistance to various herbicides. This study determined the resistance levels to 2,4-D, glyphosate, diflufenican, paraquat, and tribenuron-methyl in a putative resistant (R) C. bonariensis population, and the possible non-target-site resistance (NTSR) mechanisms involved were characterized. Resistance factors varied as follows: glyphosate (8.9), 2,4-D (4.8), diflufenican (5.0), tribenuron-methyl (19.6), and paraquat (85.5). Absorption of 14 Cglyphosate was up to 25% higher in the susceptible (S) population compared to the R one, but 14 C-paraquat absorption was similar (up to 70%) in both populations. S plants translocated more than 60% of both 14 C-glyphosate and 14 C-paraquat toward shoots and roots, while R plants translocated less than 10%. The R population was able to metabolize 57% of the 2,4-D into nontoxic metabolites and 68% of the tribenuron-methyl into metsulfuron-methyl (10%), metsulfuron-methyl-hydroxylate (18%), and conjugate-metsulfuron-methyl (40%). Among the NTSR mechanisms investigated, absorption and translocation could be involved in glyphosate resistance, but only translocation for paraquat. Proofs of the presence of enhanced metabolism as a resistance mechanism were found for tribenuron-methyl and 2,4-D, but not for diflufenican. This research informs the first occurrence of multiple resistance to five herbicide classes (acetolactate synthase inhibitors, 5-enolpyruvylshikimate-3-phosphate synthase inhibitors, photosystem I electron diverters, photosystem II inhibitors, and synthetic auxin herbicides) in C. bonariensis.

Antioxidant Enzyme and Cytochrome P450 activities are involved in horseweed (<em>Conyza sumatrensis</em>) Resistance to Glyphosate

“…Adverse environmental effects associated with herbicide applications have emerged in the form of increases in resistant weed populations 56 . Changes in light, temperature and precipitation regimes, for instance, may collaborate to select plant species able to deal with ROS stress through the activation of antioxidant systems.…”

Reduced Glyphosate Movement and Mutation of the EPSPS Gene (Pro106Ser) Endow Resistance in Conyza canadensis Harvested in Mexico

“…The radioactivity of each sample was measured for 10 min by LSS. The uptake and translocation values of radioactive 14 C were expressed as a percentage of the total 14 C-glyphosate applied and recovered, respectively . On the other hand, 14 C-glyphosate translocation was visualized in the remaining whole plants ( n = 3) that were fixed on filter paper and dried at room temperature for 5 days.…”

“…The uptake and translocation values of radioactive 14 C were expressed as a percentage of the total 14 C-glyphosate applied and recovered, respectively. 18 On the other hand, 14 C-glyphosate translocation was visualized in the remaining whole plants (n = 3) that were fixed on filter paper and dried at room temperature for 5 days. The dried plants were placed on a phosphor storage film (Storage Phosphor System, Perkin-Elmer Packard BioScience BV) for 4 h and then visualized using a phosphor imaging kit (Cyclone Plus, Perkin Elmer, Packard Bioscience BV).…”

Herbicide Resistance Is Increasing in Spain: Concomitant Management and Prevention

“…Therefore, one of the expected outcomes of this improper management is the evolution of multiple herbicide-resistant weeds in different European perennial crops. In fact, multiple herbicide-resistant populations have already been confirmed in perennial crops from Spain for Lolium and Conyza species [ 9 , 10 ], which will be treated in depth here ( Table 1 ).…”

“…In the worst cases, farmers switch from one SoA to another to manage resistant populations. A C. bonariensis -resistant biotype to at least five SoAs is already present in Spanish olive fields [ 10 ].…”