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Background <p>Glyphosate [N-(phosphonomethyl) Glycine], commonly known as Roundup, is one of the most widely used herbicides for controlling crop weeds. However, its extensive use has led to the rapid evolution of glyphosate-resistant (GR) weed populations, often <i>via</i> amplification of the target gene <i>EPSPS</i> (<i>5-enolpyruvylshikimate-3-phosphate synthase</i>), sometimes accompanied by chromosomal abnormalities.</p> Objective <p>This study investigates the occurrence and characteristics of aneusomaty in GR <i>Amaranthus palmeri</i> and its interspecific hybrids with <i>A. tuberculatus</i>.</p> Methods <p>Fluorescence in situ hybridization (FISH) was used to cytologically characterize glyphosate resistance and aneusomaty in <i>A. palmeri</i>.</p> Results <p>Aneusomaty was observed in GR <i>A. palmeri</i> and its hybrids with <i>A. tuberculatus</i>. Root tips from a single GR <i>A. palmeri</i> plant exhibited two distinct chromosome numbers: 2n = 34 and 2n = 68. Similarly, F1 hybrid root tips [<i>A. tuberculatus</i> (2n = 32) x <i>A. palmeri</i> (2n = 34)] displayed 2n = 33 and 2n = 66. The pseudo F<sub>2</sub> plants, apomictically derived from F<sub>1</sub> hybrids, consistently showed 2n = 50 chromosomes. FISH targeting 5&#xa0;S rDNA loci, was used to distinguish the genomes of <i>A. palmeri</i> and <i>A. tuberculatus</i> in the F<sub>1</sub> and pseudo F<sub>2</sub> plants. The pseudo F<sub>2</sub> plants (2n = 50) contained the diploid chromosome set of <i>A. palmeri</i> (2n = 34) and the haploid chromosome set of <i>A. tuberculatus</i> (<i>n</i> = 16). Notably, these sporadic chromosome duplications occurred only in glyphosate-resistant (GR) plants and were absent in glyphosate-sensitive (GS) plants.</p> Conclusion <p>Our results suggest that aneusomaty-related increases in chromosome numbers during the sporophytic phase may facilitate <i>EPSPS</i> gene duplication, offering a previously unrecognized mechanism contributing to glyphosate resistance in <i>A. palmeri</i>.</p>

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Aneusomaty in glyphosate-resistant Amaranthus palmeri and its hybrid with Amaranthus tuberculatus

  • 期刊论文

  • 发表日期：

    2025年7月24日

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  • Yoonha Ju,
  • Rajendran Sathishraj,
  • Bikram S. Gill,
  • Dal-Hoe Koo

摘要

Background

Glyphosate [N-(phosphonomethyl) Glycine], commonly known as Roundup, is one of the most widely used herbicides for controlling crop weeds. However, its extensive use has led to the rapid evolution of glyphosate-resistant (GR) weed populations, often via amplification of the target gene EPSPS (5-enolpyruvylshikimate-3-phosphate synthase), sometimes accompanied by chromosomal abnormalities.

Objective

This study investigates the occurrence and characteristics of aneusomaty in GR Amaranthus palmeri and its interspecific hybrids with A. tuberculatus.

Methods

Fluorescence in situ hybridization (FISH) was used to cytologically characterize glyphosate resistance and aneusomaty in A. palmeri.

Results

Aneusomaty was observed in GR A. palmeri and its hybrids with A. tuberculatus. Root tips from a single GR A. palmeri plant exhibited two distinct chromosome numbers: 2n = 34 and 2n = 68. Similarly, F1 hybrid root tips [A. tuberculatus (2n = 32) x A. palmeri (2n = 34)] displayed 2n = 33 and 2n = 66. The pseudo F2 plants, apomictically derived from F1 hybrids, consistently showed 2n = 50 chromosomes. FISH targeting 5 S rDNA loci, was used to distinguish the genomes of A. palmeri and A. tuberculatus in the F1 and pseudo F2 plants. The pseudo F2 plants (2n = 50) contained the diploid chromosome set of A. palmeri (2n = 34) and the haploid chromosome set of A. tuberculatus (n = 16). Notably, these sporadic chromosome duplications occurred only in glyphosate-resistant (GR) plants and were absent in glyphosate-sensitive (GS) plants.

Conclusion

Our results suggest that aneusomaty-related increases in chromosome numbers during the sporophytic phase may facilitate EPSPS gene duplication, offering a previously unrecognized mechanism contributing to glyphosate resistance in A. palmeri.