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1 September 2004 Ecological fitness of acetolactate synthase inhibitor–resistant and –susceptible downy brome (Bromus tectorum) biotypes
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Abstract

Studies were conducted to determine the relative fitness and competitive ability of an acetolactate synthase (ALS) inhibitor–resistant (R) downy brome biotype compared with a susceptible (S) biotype. In previous research, the mechanism of resistance was determined to be an altered ALS enzyme. Seed germination of the R biotype was compared with that of the S biotype at 5, 15, and 25 C. There were no different germination characteristics between R and S biotypes at 15 and 25 C. However, the R biotype germinated 27 h earlier than the S biotype and had reached over 60% germination when the S biotype initially germinated at 5 C. Under noncompetitive greenhouse conditions, growth of the R biotype was similar to that of the S biotype on the basis of shoot dry weight, leaf area, and plant height. Seed production of the R biotype was 83%, when compared with the S biotype, but seeds of the R biotype were larger than those of the S biotype. Replacement series experiments were conducted in the greenhouse to determine the relative competitive ability of R and S biotypes. No difference in competitive ability was observed between R and S biotypes on the basis of shoot dry weight, leaf area, or plant height. Thus, it appears that ALS-resistance trait is not associated with growth penalty in either noncompetitive or competitive conditions. In the absence of ALS inhibitors, these results suggest that the R biotype would remain at a similar frequency in a population of R and S biotypes.

Nomenclature: Downy brome, Bromus tectorum L. BROTE.

Kee Woong Park, Carol A. Mallory-Smith, Daniel A. Ball, and George W. Mueller-Warrant "Ecological fitness of acetolactate synthase inhibitor–resistant and –susceptible downy brome (Bromus tectorum) biotypes," Weed Science 52(5), 768-773, (1 September 2004). https://doi.org/10.1614/WS-04-081R
Received: 8 April 2004; Accepted: 1 April 2004; Published: 1 September 2004
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