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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: Pollen biology and dispersal dynamics in waterhemp (Amaranthus tuberculatus)

Authors
item Liu, J -
item Davis, Adam
item Tranel, P -

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 13, 2012
Publication Date: August 6, 2012
Citation: Liu, J., Davis, A.S., Tranel, P.J. 2012. Pollen biology and dispersal dynamics in waterhemp (Amaranthus tuberculatus). Weed Science. 60:416-422.

Interpretive Summary: As herbicide resistance traits have become more common in weeds of U.S. field crops, it has become increasingly important to understand how these traits spread among weed populations, so that appropriate management protocols may be developed to slow down or prevent the invasion of resistant genotypes into newe areas. Waterhemp is a major weed of field crops in the midwestern U.S. Its prevalence is at least partly due to its rapid evolution of resistance to many groups of herbicides over the last two decades. Movement of pollen by wind in waterhemp is considered to be an important factor in the spread of herbicide resistance genes. Thus, the biology and dispersal profile of waterhemp pollen are critical determinants for understanding and predicting the spatial population dynamics of herbicide resistance in this species. In this study, pollen longevity was investigated with greenhouse experiments, and pollen dispersal and the effect of pollen competition were investigated in field plots.Waterhemp pollen remained viable up to 120 hr, suggesting a low limitation of pollen dispersal by its longevity. Most pollen fertilized female waterhemp plants within 50 m of the pollen source, however long distance pollen dispersal (800 m) was also observed. These results will aid future efforts at developing landscape and regional models of the spread of herbicide resistance traits in waterhemp.

Technical Abstract: Waterhemp is a major weed of field crops in the midwestern U.S. Its prevalence is at least partly due to its rapid evolution of resistance to many groups of herbicides over the last two decades. In light of its dioecy and anemophily, pollen movement in waterhemp is considered to be an important factor in the spread of herbicide resistance genes. Thus, the biology and dispersal profile of waterhemp pollen are critical determinants for understanding and predicting the spatial population dynamics of herbicide resistance in this species. In this study, pollen longevity was investigated with greenhouse experiments, and pollen dispersal and the effect of pollen competition were investigated in field plots. Pollen dispersal was determined by measuring the frequency of seeds produced on receptor plants positioned at various distances from a pollen source, which flowered in synchrony with the receptor plants. Results indicated that waterhemp pollen can remain viable up to 120 hr, implying a low limitation of pollen dispersal by its longevity. Effective pollen dispersal declined exponentially with distance, with most pollen fertilizing recipient plants within 50 m of the pollen source. However, long distance pollen dispersal (800 m) was also observed. We also saw evidence for pollen swamping in this species. Under conditions of pollen competition among distinct genotypes, pollination success was inversely related to distance between pollen donors and receptors. However, relative pollen density may also play an important role in determining the rate of long distance gene flow. This study confirmed the potential of waterhemp pollen to effect long distance gene flow, and provides supporting data for quantitative spatial modeling of waterhemp resistance dynamics.

Last Modified: 8/30/2014
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