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United States Department of Agriculture

Agricultural Research Service

Research Project: Improving Fruit Quality, Disease Resistance, and Tolerance to Abiotic Stress in Grape

Location: Grape Genetics Research

Title: Sub-lethal glyphosate exposure increases outcrossing potential in Brassica spp. by altering flowering phenology and causing transient male-sterility

Authors
item Londo, Jason
item Mckinney, John -
item Schwartz, Matthew -
item Bollman, Mike -
item Sagers, Cynthia -
item Watrud, Lidia -

Submitted to: Biomed Central (BMC) Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 17, 2014
Publication Date: March 21, 2014
Citation: Londo, J.P., Mckinney, J., Schwartz, M., Bollman, M., Sagers, C., Watrud, L. 2014. Sub-lethal glyphosate exposure increases outcrossing potential in Brassica spp. by altering flowering phenology and causing transient male-sterility. Biomed Central (BMC) Plant Biology. doi:10.1186/1471-2229-14-70.

Interpretive Summary: Herbicide resistance in weedy plant populations can develop through different mechanisms such as gene flow of herbicide resistance transgenes from crop species into compatible weedy species or by natural evolution of herbicide resistance or tolerance following selection pressure. When crop fields are sprayed with herbicides (e.g. Roundup, glyphosate), sub-lethal levels of herbicide can drift into nearby weedy plant populations. In previous work we showed that when weeds that are not herbicide resistant are exposed to sub-lethal levels of glyphosate, the pattern and rate of gene movement between plants can be affected. In this case, the rate at which genes moved from the crop, Canola, to sexually compatible weeds, Brassica spp., was increased when sub-lethal herbicide exposure occurs. This study aimed to examine the effects of both glyphosate, and a second common herbicide, glufosinate, on weedy plant species. Using contained greenhouses, we simulated exposure to different levels of herbicide and measured traits such as seed set, plant size, and flower morphology. Our results indicate that exposure to a sub-lethal dose of glyphosate in Brassica spp. has the potential for altering flowering and gene flow processes. Flowering of all sensitive species was significantly delayed. Reproductive function, specifically male fertility, was suppressed as well. The implications of these results include the potential for increased glyphosate resistance evolution and spread in weedy communities exposed to low-dose glyphosate.

Technical Abstract: Herbicide resistance in weedy plant populations can develop through different mechanisms such as gene flow of herbicide resistance transgenes from crop species into compatible weedy species or by natural evolution of herbicide resistance or tolerance following selection pressure. Results from our previous studies suggest that sub-lethal levels of the herbicide glyphosate can alter the pattern of gene flow between glyphosate resistant Canola, Brassica napus, and glyphosate sensitive genotypes of B. napus and B. rapa. The objectives of this study were to examine the phenological and developmental changes that occur in Brassica crop and weed species following sub-lethal doses of the herbicides glyphosate and glufosinate. We examined several vegetative and reproductive traits of potted plants under greenhouse conditions, treated with sub-lethal herbicide sprays. Our results indicate that exposure to a sub-lethal dose of glyphosate in Brassica spp. has the potential for altering flowering and gene flow processes. Flowering of all sensitive species was significantly delayed. Reproductive function, specifically male fertility, was suppressed as well. The implications of these results include the potential for increased glyphosate resistance evolution and spread in weedy communities exposed to low-dose glyphosate.

Last Modified: 10/24/2014
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