Response of Herbicide-Resistant Palmer Amaranth (Amaranthus palmeri) Accessions to Drought Stress

Abstract

Palmer amaranth is a very problematic weed in several crops in the southern USA due to its competitive ability and resistance to herbicides representing different mechanisms of action. Variation in growth and subsequent interference of North Carolina Palmer amaranth accessions has not been examined. A greenhouse experiment determined response of 15 North Carolina Palmer amaranth accessions to drought stress beginning 15 days after seedling emergence (DAE) for a duration of 3, 5, 7, and 9 days. Following exposure to drought, plants were grown under optimal moisture conditions until harvest at 30 DAE. Five accessions each of glyphosate-resistant (GR), acetolactate synthase inhibitor-resistant (ALSR), and acetolactate synthase inhibitor-susceptible and glyphosate-susceptible (ALSS/GS) were compared. Variation in response to drought stress, based on height and dry weight reduction relative to nonstressed controls, was noted among accessions. Stress for 3 or more days affected height and dry weight. Height and dry weight of GR and ALSR accession groups were reduced less by drought than the ALSS/GS accession group. Results suggest a possible relationship between herbicide resistance and ability of Palmer amaranth to withstand drought stress and thus a possible competitive advantage for resistant accessions under limited moisture availability.

Evaluating Effect of Degree of Water Stress on Growth and Fecundity of Palmer amaranth (Amaranthus palmeri) Using Soil Moisture Sensors

“…Amaranthus palmeri maintained at 100% FC achieved a maximum height of 178 cm compared with 124 and 88 cm at 75% and 50% FC, respectively (Table 1; Figure 2B). Similarly, Chandi et al (2013) reported 5% to 15% reduction in the height of 15 A. palmeri biotypes under water stress conditions employed for 3 to 9 d compared with no water stress. Sarangi et al (2015) also reported an A. tuberculatus height of 163 cm at 100% FC compared with 146 and 115 cm at 75% and 50% FC, respectively, in a greenhouse study.…”

“…In addition, a single A. palmeri plant was grown in each pot without any inter- or intraspecific competition; however, plants growing with crops might produce flowers earlier or later in the season depending on the competitive nature of the crops (Bolmgren and Cowan 2008; Franks et al 2007). Additionally, water stress treatments were imposed throughout the growing season in this study, and timing of water stress can also play an important role in determining A. palmeri ’s growth response (Chandi et al 2013). Therefore, A. palmeri grown under field condition will have better chance of survival and higher seed production due to limited periods of water stress compared with continuous water stress conditions in this study.…”

“…With increasing soil water stress, some studies have reported reduced growth and fecundity of different weed species, including A. palmeri (Chauhan 2013; Chauhan and Johnson 2010; Sarangi et al 2015; Webster and Grey 2008). In addition, a few studies have reported the growth response of A. palmeri exposed to different durations of levels of water stress for a few weeks and then irrigated back to saturated conditions (Chandi et al 2013; Paudel et al 2016). However, A. palmeri fecundity and seed germination parameters were not studied.…”

“…Studies evaluating a plant’s response to water stress are often performed under greenhouse or controlled environmental conditions, with the plants growing in pots to maintain them at a certain water stress level for a limited time or throughout the growing period. The most common approach used to maintain desired water stress level in previous studies has been to weigh the pots to determine water loss from the soil and then add the desired amount of water (Chandi et al 2013; Chauhan 2013; Chauhan and Johnson 2010; Earl 2003; Sarangi et al 2015). Because it is not possible to separately determine the weight of the plant growing in the pot when using this method, plant weight is normally included along with the weight of soil and water, resulting in inaccurate information regarding the actual amount of water present in the pot soil.…”

Biology and Management of Glyphosate-Resistant and Glyphosate-Susceptible Palmer Amaranth (Amaranthus palmeri) Phenotypes from a Segregating Population

“…No differences were reported in growth and reproduction between GS and GR Palmer amaranth plants under greenhouse conditions (Giacomini et al 2014; Vila-Aiub et al 2013). Chandi et al (2013a) found disadvantages of glyphosate resistance in terms of interference with corn, cotton, peanut, and snap bean ( Phaseolus vulgaris L.) and response to atrazine and dicamba in a greenhouse study. In that study, 19% fresh biomass reduction of crops was reported in the presence of GR populations compared with 25% in the presence of GS populations.…”