Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2014
Publication Date: 4/1/2014
Citation: Dogramaci, M., Anderson, J.V., Chao, W.S., Foley, M.E. 2014. Foliar application of glyphosate affects molecular mechanisms in underground adventitious buds of leafy spurge (Euphorbia esula) and alters their vegetative growth patterns. Weed Science. 62(2):217-229.
Interpretive Summary: Leafy spurge is an invasive perennial weed infesting rangelands and non-cultivated areas in the Great Plains of the US and Canada. Long term control of leafy spurge requires continual herbicide applications because the plant reproduces vegetatively from abundant underground buds. We are investigating the effects of sublethal glyphosate rates on vegetative growth from underground buds of leafy spurge. After foliar glyphosate application and removal of these aerial tissues, new shoots derived from underground buds were significantly different compare to un-treated plants. New shoots from glyphosate-treated plants had a stunted and bushy growth pattern. Further, molecular studies revealed that interaction among plant growth regulators such as auxin, ethylene, and gibberellins impact these vegetative growth patterns from underground buds of leafy spurge in response to glyphosate.
Technical Abstract: Long term control of leafy spurge with glyphosate requires multiple applications because the plant reproduces vegetatively from abundant underground adventitious buds (UABs). Determining the molecular mechanisms involved in controlling vegetative reproduction in leafy spurge following foliar glyphosate treatment could identify limiting factors or new targets for manipulation of plant growth and development in invasive perennial species. Thus, we treated leafy spurge plants with 0 or 2.24 kg ai ha-1 glyphosate to determine its impact on selected molecular processes in UABs derived from intact plants and plants decapitated at the soil surface 7 d after glyphosate treatment. New shoot growth from UABs of foliar glyphosate-treated plants was significantly reduced compared to controls after growth-inducing decapitation, and had a stunted and/or bushy phenotype. Quantification of a selected set of transcripts involved in hormone biosynthesis and signaling pathways indicated that glyphosate had the most significant impact on abundance of ENT-COPALYL DIPHOSPHATE SYNTHETASE 1, which is involved in a committed step for gibberellin biosynthesis, and auxin transporters including PINs, PIN-LIKES and ABC TRANSPORTERS. Foliar glyphosate treatment also reduced the abundance of transcripts involved in cell cycle processes, which would be consistent with altered growth patterns observed in this study. Overall, these results suggest that interplay among phytohormones such as auxin, ethylene, and gibberellins impact vegetative growth patterns from UABs of leafy spurge in response to foliar glyphosate treatment.