Plant & Soil Sciences

“Genomic and molecular studies to investigate glyphosate resistance in Giant Ragweed (Ambrosia trifida)”

Burkhard Schulz
University of Maryland

Giant ragweed is a very competitive annual weed in corn and soybean cropping systems. The introduction of glyphosate resistant crops (“Roundup®-ready”) in 1996 provided an effective tool to manage giant ragweed. Weed management with glyphosate led to recurring use of glyphosate over long periods of time, which resulted in high selection pressure for glyphosate resistance in weeds.

Glyphosate-resistant giant ragweed (GRGR) has been reported throughout the USA. The goal of our research program is to determine genes responsible for glyphosate resistance in GRGR. We found that glyphosate resistance in giant ragweed is associated with reduced herbicide translocation, combined with induced rapid necrosis of exposed leaf tissue within 12 hours of treatment. These plants do not die from a glyphosate treatment but resume normal growth from axillary meristems and reproduce.

The progression of symptoms resembles a typical hypersensitive response (HR) similar to that observed after pathogen attack. Hallmarks of HR reactions in plants such as rapid ROS production and reduction of photosynthetic activity accompany resistance. To study the transcriptome of giant ragweed under glyphosate conditions, total RNA from both biotypes was analyzed after glyphosate treatment in a time-course from 0 to 6 hours. Sequence data analysis showed differential gene expression in resistant and sensitive plants upon glyphosate treatment. GO term analysis revealed that a great number of differentially expressed genes are involved in pathogen and stress responses. To our surprise we found that even in untreated plants differential expression of pathogenesis-related gene sets can be found. This indicates that the HR system is involved in cellular reactions of GRGR plants upon glyphosate treatments.

Dr. Schulz received a diploma in Biology and a PhD in Molecular Biology from the Free University Berlin in Germany. After a postdoc stay at the University of Arizona, working on T-DNA insertion mutagenesis in Arabidopsis he was employed as group leader at the Max-Planck-Institute for Plant Breeding Research, University of Cologne and Tuebingen in Germany. As a faculty member at Purdue University he developed a program on maize plant architecture and herbicide resistance in weeds.

The main plant species he works with are maize, Arabidopsis thaliana, barley, giant ragweed, and sorghum. A major focus of his work in maize is on brassinosteroid biology in maize and its contribution to sex determination in plants.

University of Delaware
132 Townsend Hall
531 South College Avenue
Newark, DE 19716

Hosting Organization:
Mark Van Gessel
Plant & Soil Sciences
University of Delaware

September 11, 2015

12:20 - 1:15 pm