Amaranthus palmeri a New Invasive Weed in Spain with Herbicide Resistant Biotypes

Abstract

<jats:p>Amaranthus palmeri is the most prominent invasive weed in agricultural land from North America, partly due to its propensity to evolve resistance to multiple herbicide sites of action. In the last two decades, reports of this species have increased throughout the American continent and occasionally in other continents. In 2007, A. palmeri populations were found in three localities in northeastern Spain, and they are still present today. To determine whether these three populations resulted from a common or independent introduction events—and when and from where they could have occurred—research was carried out aiming to characterize the resistance profile and mechanisms to 5-enolpyruvylshikimate-3-phosphate synthase-and acetolactate synthase (ALS)-inhibiting herbicides and to analyze the relationship between these three populations using inter simple sequence repeat DNA fingerprinting. Dose–response trials confirmed that the three populations were susceptible to glyphosate but resistant to nicosulfuron-methyl. Resistance to ALS inhibitors was due to several amino acid substitutions in positions Pro197, Trp574 and Ser653. Moreover, the substitutions Ser653Ile and Pro197Thr are described for the first time in this species. At field-labeled rates, all populations were fully controlled with alternative herbicides with other sites of action. Amaranthus palmeri individuals were clustered in three groups based on unweighted pair group method with arithmetic mean analysis, which corresponded to the three sampled populations, with a 67% of genetic relationship among them. Considering this high genetic variability and the different positions and amino acid substations found between populations, it was hypothesized that different colonization events occurred from the American continent probably prior to the introduction of glyphosate resistant crops. Prevention from new introductions is warranted because new herbicide resistance traits could arrive, complicating the management of this invasive weed species, while managing or eradicating the already established populations.</jats:p>

Recent Discovery of Amaranthus palmeri S. Watson in Italy: Characterization of ALS-Resistant Populations and Sensitivity to Alternative Herbicides

“…The presence of the same resistance-endowing mutation in most resistant individuals of the three populations clearly indicates that field-applied ALS inhibitors exerted a strong selective pressure. ALS-resistant populations of A. palmeri have also been described in Spain [12]. In that case, the populations were found along roadsides and field borders, while no persistent field infestations were reported.…”

“…Three populations of A. palmeri were confirmed to be cross-resistant to thifensulfuronmethyl and imazamox. The negligible effect of these herbicides on plant biomass and the presence of the Trp574Leu substitution at ALS, known to confer broad spectrum resistance to ALS inhibitors in various weed species [12], proved that the main resistance mechanism is target-site related. Some plants had no mutations at position 574: the presence of other mutations or other resistance mechanisms cannot be excluded.…”

“…However, worldwide, A. palmeri has evolved resistance to eight sites of action (SoA) [7] and a population from Kansas has evolved multiple resistance to up to six SoA [8]. All records of herbicide resistant A. palmeri were found in the United States until 2008, when it was first reported in Israel [9], then in Brazil [10], Argentina [11] and, more recently, in Spain, where the introduction of already resistant biotypes was suspected [12]. The most common mechanism endowing ALS inhibitors resistance in A. palmeri is target-site mediated and involves several point mutations at the ALS gene [13], but a few cases of non-target-site mechanism have recently been reported [8,14].…”

A review of the biology, distribution patterns and management of the invasive species Amaranthus palmeri S. Watson (Palmer amaranth): Current and future management challenges

“…Amaranthus palmeri S. Watson (Palmer amaranth) is an erect, broadleaf, herbaceous plant that has currently emerged as an invasive and economically destructive weed within several countries across Africa, Asia, Europe, North America and South America (Duzy et al, 2016; Kanatas et al, 2021; Milani et al, 2021; Norsworthy et al, 2008; Torra et al, 2020; Ward et al, 2013). Belonging to the family Amaranthaceae, A. palmeri is a major weed of concern that aggressively competes against and significantly reduces the yield of several crops including Arachis hypogaea L. (peanut), Glycine max L. (soybean), Gossypium hirsutum L. (cotton), Ipomoea batatas L. (sweet potato), Sorghum bicolor L. (grain sorghum) and Zea mays L. (maize), together with orchards including Carya illinoinensis Wangenh.…”

“…These weedy characteristics have resulted in A. palmeri dominating agroecosystems within several countries, where it now causes severe environmental and economic damage (Bensch et al, 2003; Briscoe Runquist et al, 2019; Kanatas et al, 2021; Küpper et al, 2017; Mennan et al, 2021; Milani et al, 2021; Sukhorukov et al, 2021). Exacerbating this global problem is the identification of herbicide resistance in several A. palmeri populations in Argentina, Brazil, Israel, Mexico, Spain, Turkey and the United States of America, involving several herbicide mechanisms of action, with examples including acetolactate synthase (ALS) inhibiting herbicides (cloransulam‐ethyl, cloransulam‐methyl, imazethapyr, foramsulfuron, iodosulfuron‐methyl‐Na, metsulfuron‐methyl, nicosulfuron, rimsulfuron, trifloxysulfuron‐Na), synthetic auxins (2,4‐D, dicamba), 5‐enolpyruvylshikimate‐3‐phosphate synthase (EPSPS) inhibitor (glyphosate), 4‐hydroxyphenylpyruvate dioxygenase inhibitors (HPPD) (mesotrione), photosystem II (PSII) inhibitors (atrazine), protoporphyrinogen oxidase (PPO) inhibitors (acifluorfen), tubulin inhibitors (dinitroaniline, trifluralin) and long chain fatty acid inhibitors (LCFA) (metolachlor) (Berger et al, 2016; Culpepper et al, 2006; Heap, 2021; Küpper et al, 2017, 2018; Mennan et al, 2021; Norsworthy et al, 2008; Torra et al, 2020; Wise et al, 2009).…”