Angiosperm Flora of India

Molecular Analysis of Hexazinone-Resistant Shepherd's-Purse ( Capsella bursa-pastoris ) Reveals a Novel psbA Mutation

Publication Type:Journal Article
Year of Publication:2009
Authors:Perez-Jones, A, Intanon, S, Mallory-Smith, C
Journal:Weed Science
Date Published:2009
ISBN Number:00431745
Keywords:Capsella, Capsella bursa-pastoris

A population of shepherd's-purse suspected to be resistant to the triazinone herbicide hexazinone, a photosystem II (PS II) inhibitor, was collected from an alfalfa field in 2007 in Oregon. A whole-plant, dose—response assay confirmed that the putative-resistant population was highly resistant to hexazinone. The resistant population was 22-fold more resistant to hexazinone than the susceptible population. However, the hexazinone-resistant population was susceptible to other PS IIinhibiting herbicides, including atrazine, diuron, and terbacil. DNA sequence analysis of the chloroplast psbA gene encoding the Dl protein of PS II, the target site of PS II inhibitors, identified a point mutation from Phe to Ile at position 255 in the hexazinone-resistant population. Single-and double-point mutations at position 255, which is located in the Q B binding niche of the D1 protein, were previously reported in Chlamydomonos reinhardtii, Synechococcus species, and Synechocystis species after site-directed mutagenesis and were associated with decreased binding of PS II inhibitors. To our knowledge, this is the first report of a mutation of the psbA gene at Phe₂₅₅ in a field-selected, herbicide-resistant plant.

Short Title:Weed Science
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