Anna Sherwood

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UC Davis Department of Plant Sciences
Plant Biology Program
University of California
Davis, California 95616

Phone: (530) 752-8284

Email: amsherwood [at]


Graduate Student


1998-2002: B.S. Botany, Washington State University

Research Interest:

The potential for sympatric population subdivision when a varying selective pressure is applied to a pan-mictic population

Research Summary:

Glyphosate (the active ingredient in Roundup) is a commonly used broad spectrum herbicide. It is also a potent selection agent, since 1996 seven different weed species have evolved resistance to glyphosate. One of the species, Lolium rigidum (ryegrass), is a common agricultural and wildland weed in California. Populations of Lolium with glyphosate resistance were first identified within California in 1998. Resistance has since spread throughout the Sacramento Valley. Surprisingly, given the strong selection pressure of glyphosate, many susceptible populations remain. This suggests that herbicide resistance carries a cost, and within non treated habitats susceptible plants are more fit. Using SSR (simple sequence repeats) markers I am testing if the Central Valley population of Lolium is divided into discrete subpopulations. Given the location of population subdivision, I will then test if the subpopulation boundaries are correlated with the presence of glyphosate and/or R or S phenotype.