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United States Department of Agriculture

Agricultural Research Service

Research Project: ECOLOGY, MANAGEMENT AND ENVIRONMENTAL IMPACT OF WEEDY AND INVASIVE PLANT SPECIES IN A CHANGING CLIMATE

Location: Global Change and Photosynthesis Research Unit

Title: Do common waterhemp (Amaranthus rudis) seedling emergence patterns meet criteria for herbicide resistance simulation modeling?

Authors
item Schutte, Brian -
item Davis, Adam

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 6, 2013
Publication Date: April 1, 2014
Citation: Schutte, B.R., Davis, A.S. 2014. Do common waterhemp (Amaranthus rudis) seedling emergence patterns meet criteria for herbicide resistance simulation modeling? Weed Technology. 28:408-417.

Interpretive Summary: Computer simulation models have become an important tool for identifying effective approaches for delaying and coping with herbicide resistance in agricultural weeds. Many such models treat individual plants within a population as coming from the same seed source, an assumption that could lead to faulty predictions if differences in vital rates among different seed sources were large. We conducted a field study to address this assumption for common waterhemp (Amaranthus tuberculatus), a weed species that has rapidly developed resistance to multiple herbicide modes of action, and is becoming a threat to corn and soybean production in the upper midwest. In 2008 and 2010, seedling emergence patterns in in undisturbed soil were determined for replicated samples of maternal families (progeny from one individual) separately harvested during the previous year from four plants within four agricultural fields (16 maternal families yr-1) at a university research farm near Urbana, IL. When we combined data across years, we found that seed sample within maternal family explained 48% of total variation in germination rate. Differences within, rather than among, maternal families also accounted for large fractions (60 to 99%) of total variation in cumulative percentage emergence at specific points during periods conducive to emergence. Within years, seed samples characterized by delayed or accelerated emergence patterns did not originate from specific maternal plants. These results indicate that common waterhemp seed populations are without maternal effects that limit emergence to narrow intervals within the overall emergence period. The results of this study support the use of contemporary modeling approaches for simulation of herbicide resistance evolution in common waterhemp.

Technical Abstract: A study was conducted to quantify the magnitude of, and sources of variation in, common waterhemp temporal patterns of emergence over 1 yr. In 2008 and 2010, emergence patterns in the absence of soil disturbance were determined for replicated samples of maternal families (progeny from one individual) separately harvested during the previous year from four plants within four agricultural fields (16 maternal families yr-1) at a university research farm near Urbana, IL. Combining data across years, variance partitioning indicated that seed sample within maternal family explained 48% of total variation in the percentage of viable seeds that produced seedlings. Differences within, rather than among, maternal families also accounted for large fractions (60 to 99%) of total variation in cumulative percentage emergence at specific points during periods conducive to emergence. Within years, seed samples characterized by delayed or accelerated emergence patterns did not originate from specific maternal plants. These results indicate that common waterhemp seed populations are without maternal effects that limit emergence to narrow intervals within the overall emergence period. The results of this study support the use of contemporary modeling approaches for simulation of herbicide resistance evolution in common waterhemp. Such models assume cohorts distinguished by time of emergence contain offspring from all individuals occurring within the maternal population.

Last Modified: 9/22/2014
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