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United States Department of Agriculture

Agricultural Research Service

Title: Rust Resistance in Glyphosate Tolerant Wheat Conditioned by Application of Glyphosate Herbicide

Authors
item Anderson, J - UNIVERSITY OF MINNESOTA
item Kolmer, James

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 13, 2005
Publication Date: November 1, 2005
Citation: Anderson, J.A., Kolmer, J.A. 2005. Rust control in glyphosate tolerant wheat following application of the herbicide glyphosate. Plant Disease. 89:1136-1142.

Interpretive Summary: Leaf rust is a disease of wheat caused by the fungus Puccinia triticina. Wheat cultivars grown throughout the U.S. are attacked every year by this fungus. Wheat that is tolerant to the common herbicide Roundup (active ingredient glyphosate) has been developed by the Monsanto Company using biotechnology. Wheat plants that are tolerant to glyphosate application also have very good resistance to leaf rust when the glyphosate is sprayed on the plants for a period of up to three weeks prior to exposure to leaf rust infections. The resistance to leaf rust is due to the application of glyphosate, and not due to other compounds present in Roundup. Given these results and evidence from the literature that glyphosate can have adverse effects on other pathogens, including other rust fungi, additional investigation of the fungicidal properties of glyphosate are warranted, with particular attention to the timing of glyphosate application relative to fungal infection. The effects of glyphosate on the soybean rust fungus, Phakopsora pachyrhizi, an emerging pathogen in North America, merit immediate investigation. Although Monsanto has deferred commercial development of Roundup wheat, application of glyphosate to other crops for which Roundup Ready cultivars are available may reduce losses due to fungal diseases in these crops.

Technical Abstract: In greenhouse and field trials, application of labeled rates of the herbicide glyphosate to transgenically modified glyphosate tolerant wheat reduced the amount of infection caused by Puccinia triticina, the causal agent of wheat leaf rust. Wheat genotypes with tolerance to glyphosate had extremely low infection types to leaf rust when treated with a glyphosate solution prior to inoculation with leaf rust. A surfactant solution and a non-glyphosate herbicide had no effect on leaf rust development on the glyphosate tolerant wheat. Glyphosate had a systemic effect in reducing leaf rust development. The resistance effect of glyphosate decreased with reduced application rates and longer periods of time between glyphosate application and leaf rust infections. The field and greenhouse tests indicated that resistance to leaf rust in wheat conditioned by glyphosate is transitory and is effective for at least 21, but not more than 35 days after application. Application of glyphosate also reduced infection types on wheat caused by the stem rust fungus, P. graminis f. sp. tritici. Given these results and evidence from the literature that glyphosate can have adverse effects on other pathogens, including other rust fungi, additional investigation of the fungicidal properties of glyphosate are warranted, with particular attention to the timing of glyphosate application relative to fungal infection. The effects of glyphosate on the soybean rust fungus, Phakopsora pachyrhizi, an emerging pathogen in North America, merit immediate investigation.

Last Modified: 7/22/2014
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