A derived Polymorphic Amplified Cleaved Sequence assay for detecting the Δ210 PPX2L codon deletion conferring target-site resistance to protoporphyrinogen oxidase-inhibiting herbicides

Background: Resistance to protoporphyrinogen oxidase (PPO)-inhibiting herbicides in Amaranthus rudis from corn/soybean production systems in the USA appears to be mainly due to a codon deletion at position 210 of the target PPX2L gene. In this study, we have developed a simple and cost-effective derived Polymorphic Amplified Cleaved Sequenced (dPACS) marker for detecting this resistance-causing deletion in A. rudis and other relevant weed species.

Results: Ninety-six plants from 16 diverse fomesafen-sensitive and resistant A. rudis populations from Illinois and Iowa were used to establish the dPACS procedure. The assay requires forced mismatches in both the forward and reverse PCR primers and uses the restriction enzyme XcmI for the positive identification of wild type glycine residue at PPX2L codon position 210. The data from the dPACS method, using either leaf tissues or seeds as starting material, were completely correlated with direct Sanger sequencing results for samples that gave readable nucleotide peaks around codon 210 of PPX2L. Furthermore, the assay was directly transferable to all four other Amaranthus species tested, and to Ambrosia artemisiifolia using species-specific primers.

Conclusion: The proposed assay will allow the rapid detection of the Δ210 codon deletion in the PPX2L gene and the timely development of management strategies for tackling growing resistance to PPO-inhibiting herbicides in A. rudis and other broadleaf weed species. © 2019 Society of Chemical Industry.