Transpiration Responses of Herbicide-Resistant and -Susceptible Palmer Amaranth ( Amaranthus palmeri (S.) Wats.) to Progressively Drying Soil

Koffi Badou-Jeremie Kouame, Mary C. Savin, Gulab Rangani, Thomas R. Butts, Matthew B. Bertucci and Nilda Roma-Burgos
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Koffi Badou-Jeremie Kouame: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR 72704, USA
Mary C. Savin: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR 72704, USA
Gulab Rangani: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR 72704, USA
Thomas R. Butts: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR 72704, USA
Matthew B. Bertucci: Department of Horticulture, University of Arkansas, Fayetteville, AR 72701, USA
Nilda Roma-Burgos: Department of Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, AR 72704, USA

Agriculture, 2022, vol. 12, issue 3, 1-11

Abstract: Drought events are predicted to increase in the future. Evaluating the response of herbicide-resistant and -susceptible weed ecotypes to progressive drought can provide insights into whether resistance traits affect the fitness of resistant weed populations. Two experiments were conducted in the greenhouse between January and May 2021 to evaluate drought tolerance differences between Palmer amaranth accessions resistant to S -metolachlor or glyphosate and their susceptible counterparts. The accessions used were S -metolachlor-resistant (17TUN-A), a susceptible standard (09CRW-A), and glyphosate-resistant (22–165 EPSPS copies) and glyphosate-susceptible (3–10 EPSPS copies) plants from accession 16CRW-D. Daily transpiration of each plant was measured. The daily transpiration rate was converted to normalized transpiration ratio (NTR) using a double-normalization procedure. The daily soil water content was expressed as a fraction of transpirable soil water (FTSW). The threshold FTSW (FTSWcr), after which NTR decreases linearly, was estimated using a two-segment linear regression analysis. The data showed differences between S -metolachlor-resistant and -susceptible accessions ( p ≤ 0.05). The FTSW remaining in the soil at the breakpoint for the S -metolachlor-susceptible accession (09CRW-A) was 0.17 ± 0.007. The FTSW remaining in the soil at the breakpoint for the S -metolachlor-resistant accession (17TUN-A) was 0.23 ± 0.004. The FTSW remaining in the soil at the breakpoint for the glyphosate-resistant and glyphosate-susceptible plants (16CRW-D) was 0.25 ± 0.007 and 0.25 ± 0.008, respectively. Although the mechanism endowing resistance to S -metolachlor might have contributed to increased drought tolerance, follow-up experiments are needed in order to verify this finding. Increased EPSPS copy numbers did not improve the drought tolerance of Palmer amaranth. As droughts are predicted to increase in frequency and severity, these results suggest that S -metolachlor-resistant and glyphosate-resistant Palmer amaranth populations will not be at a competitive disadvantage compared to susceptible genotypes. Alternative and diverse management strategies will be required for effective Palmer amaranth control, regardless of herbicide resistance status.

Keywords: drought tolerance; threshold FTSW; EPSPS gene amplification; S -metolachlor resistance; glyphosate resistance (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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