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ORIGINAL RESEARCH article

Front. Plant Sci.
Sec. Plant Pathogen Interactions
Volume 15 - 2024 | doi: 10.3389/fpls.2024.1420009

First case of evolved herbicide resistance in the holoparasite sunflower broomrape, Orobanche cumana Wallr

Provisionally accepted
Shiv S. Kaundun Shiv S. Kaundun 1*Alberto Martín-Sanz Alberto Martín-Sanz 2Maribel Rodriguez Maribel Rodriguez 2Tiberius Serbanoiu Tiberius Serbanoiu 3Jose R. Moreno Jose R. Moreno 1Eddie Mcindoe Eddie Mcindoe 1Gael Le Goupil Gael Le Goupil 4
  • 1 Syngenta Jealott’s Hill International Research Centre, Bracknell, United Kingdom
  • 2 Independent researcher, Carmona-Lora de Rio, Sevilla, Spain
  • 3 Syngenta, Agro, Bucharest, 73-81 Bucaresti-Ploiesti road, Romania
  • 4 Syngenta, Crop Protection AG, Basel, Switzerland

The final, formatted version of the article will be published soon.

    The development and commercialisation of sunflower varieties tolerant to acetolactate synthase (ALS)-inhibiting herbicides some 20 years ago provided farmers with an alternative method for the cost-effective control of Orobanche cumana. In 2020, however, two independent sunflower broomrape populations from Drama (GR-DRA) and Orestiada (GR-ORE), Greece, were reported to be heavily infested with O. cumana after application of the ALS-inhibiting herbicide imazamox. Here we have investigated the race of GR-DRA and GR-ORE and determined the basis of resistance to imazamox in the two Greek O. cumana samples.Using a set of five diagnostic sunflower varieties characterised by different resistant genes with respect to O. cumana infestation, we have clearly established that the GR-ORE and GR-DRA populations belong to the invasive broomrape races G and G+, respectively. Live underground tubercles and emerged shoots were identified at the recommended field rate of imazamox for GR-DRA and GR-ORE but not for two other standard sensitive populations in a whole plant dose response test using two different herbicide-tolerant sunflower hybrids as hosts.Sequencing of the ALS gene identified an alanine 205 to aspartate mutation in all GR-ORE samples. Most GR-DRA tubercles were characterised by a second serine 653 to asparagine ALS mutation whilst a few GR-DRA individuals contained the A205D mutation. Mutations at ALS codons 205 and 653 are known to impact on the binding and efficacy of imazamox and other imidazolinone herbicides. The knowledge generated here will be important for tracking and managing broomrape resistance to ALS-inhibiting herbicides in sunflower growing regions.

    Keywords: sunflower broomrape, Orobanche cumana, Virulence, Imazamox, Herbicide Resistance

    Received: 19 Apr 2024; Accepted: 21 May 2024.

    Copyright: © 2024 Kaundun, Martín-Sanz, Rodriguez, Serbanoiu, Moreno, Mcindoe and Le Goupil. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Shiv S. Kaundun, Syngenta Jealott’s Hill International Research Centre, Bracknell, CB21 5XE, United Kingdom

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