The response of ACCase-resistant Phalaris paradoxa populations involves two different target site mutations

Authors

  • O HOCHBERG,

    1. RH Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agricultural, Food and Environmental Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel
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  • M SIBONY,

    1. RH Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agricultural, Food and Environmental Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel
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  • B RUBIN

    1. RH Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agricultural, Food and Environmental Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel
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Prof. Baruch Rubin, J & R Liss Professor of Agronomy & Weed Science, RH Smith Institute of Plant Sciences & Genetics in Agriculture, Faculty of Agricultural, Food and Environmental Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel. Tel: (+972) 8 948 9248; Fax: (+972) 8 936 2083; E-mail: rubin@agri.huji.ac.il

Summary

Phalaris paradoxa (awned canary-grass) is an aggressive annual winter weed in wheat and other arable crops that is controlled mainly by ACCase-inhibiting herbicides: cyclohexanediones (DIMs), aryloxyphenoxypropionates (FOPs) and phenylpyrazolines (DENs, e.g. pinoxaden). The selection pressure imposed on the weed populations by repeated use of these herbicides has resulted in the evolution of increased numbers of ACCase-resistant populations of P. paradoxa in Israel and other countries. Two populations, Revadim (RV) and Mishmar Ha’emek (MH) that were exposed to differing weed and crop management tactics were investigated. Both populations were highly resistant to all FOPs, pinoxaden and cycloxydim, but responded differently to some DIMs. RV plants exhibited much higher resistance to tralkoxydim than MH plants, while showing similar low levels of resistance to tepraloxydim and clethodim. Both populations were equally susceptible to graminicides with other modes of action. The mutations responsible for the observed resistance were identified using PCR-RFLP and by sequencing the carboxyl transferase domain of the chloroplastic ACCase gene. RV plants possess a substitution of Asp2078 to Gly, whereas in MH population a mixture of Ile2041 to Asn or Asp2078 to Gly was found. Our study demonstrates that lack of herbicide and crop rotation may result in the evolution of diverse target site mutations and differential response of the whole plant to ACCase inhibitors.

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