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Establishment of Waterhemp Tissue Culture Lines for Herbicide Resistance Research II

Michael J. Christoffers
Department of Plant Sciences, North Dakota State University

Executive Summary

Research Conducted
Cell suspension cultures, which are living cells suspended in a liquid nutrient solution, are often used in laboratory research. We developed methods to produce and analyze cell suspension cultures of waterhemp, an important and often herbicide-resistant weed commonly found in soybean fields. One of these waterhemp cell suspension cultures was treated with ALS (acetolactate synthase)-inhibiting herbicides (Group 2 herbicides), to see if growth could be reduced in a manner similar to whole plants. Two ALS-inhibiting herbicides were tested: 1) imazethapyr, the active ingredient in Pursuit herbicide, and 2) thifensulfuron-methyl, the active ingredient in Harmony herbicide. Both herbicides were found to inhibit growth of the waterhemp cell suspension culture.

Why the research is important to ND soybean growers
Herbicide-resistant waterhemp represents an important problem in North Dakota soybean production, and new tools are needed to study emerging methods for controlling this weed. When growing herbicide-resistant weeds for research, it is important to minimize the risk of seeds escaping and spreading into fields. This is especially important when researching new genetic methods of weed control, where weed genes may be altered. The cells that make up cell suspension cultures need to be maintained in a laboratory and cannot grow or produce new plants in the field. This makes waterhemp suspension cultures very valuable herbicide resistance research tools.

Final findings of the research
We found that the ability of waterhemp cells to grow in a suspension culture was dependent on the make-up of the nutrient solution. One suitable nutrient solution was identified and used to produce a healthy and actively growing waterhemp cell suspension culture. The growth of this culture was found to be inhibited by ALS-inhibiting herbicides, confirming that waterhemp cell suspension cultures may be a viable option for safely performing laboratory-based experiments investigating herbicide resistance.

Benefits/Recommendations to North Dakota soybean farmers and industry
Waterhemp plant material in the form of a cell suspension culture is now available for further studies investigating herbicide resistance. Conditions for producing additional waterhemp cell suspension cultures have also been identified. These cultures will allow researchers to study herbicide-resistant waterhemp and new genetic control methods without risk of weed escape into North Dakota fields.