Response of Weedy Rice (Oryza spp.) Germplasm from Arkansas to Glyphosate, Glufosinate, and Flumioxazin

Abstract

Abstract Weedy rice (Oryza spp.) is one of themost competitive weeds in rice (Oryza sativa L.) production. Rapid growth, high tillering, enhanced ability to uptake fertilizers, asynchronous maturation, seed shattering, and high seedbank longevity make Oryza spp. more competitive than cultivated rice and highly persistent. Oryza spp. may be a source of useful traits for crop improvement such as herbicide tolerance. Greenhouse studies were conducted to evaluate the response of 54 Oryza spp. accessions collected between 2008 and 2009 from Arkansas to glyphosate, glufosinate, and flumioxazin applied at field rates. Rice cultivars ‘CL163’ and ‘REX’ were included for comparison. Accessions B20, B2, and S11 and B49, B51, and S59 showed reduced sensitivity to glyphosate and flumioxazin, respectively. These accessions had less than 40% injury 5 wk after treatment (WAT). Rice cultivars (CL163 and REX) were sensitive to both glyphosate and flumioxazin, with more than 95%plant mortality at 5WAT.On average, blackhull accessions weremore tolerant to glyphosate and flumioxazin than strawhull accessions. Dose–response analysis of B20, B2, and S11 confirmed 3- to 8-fold higher tolerance of these accessions to glyphosate. All Oryza spp. and cultivated rice were not affected by glufosinate applied at 874 g ai ha-1 (1X) and were controlled 100% by 1,311 g ai ha-1 (1.5X). Oryza spp. lines with reduced sensitivity to glyphosate and flumioxazin will be studied further for use in rice crop improvement.