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Poster Presentations


Poster Presentations


The effect of Roundup® (glyphosate) on the Asian soybean rust pathogen (Phakopsora pachyrhizi) in the field and in vitro

Presenter: Wayne M. Jurick, II(1)

Other authors and affiliations: Natalia Nequi(1), Charles R. Semer, IV(1), Tristan Mueller(2), Carrie L. Harmon(1), James J. Marois(2), David L. Wright(2), Amanda Gevens(1), Philip F. Harmon(1). (1)University of Florida, Plant Pathology, Gainesville, FL 32611, U.S.A.; (2)University of Florida - NFREC, Plant Pathology, Quincy, FL 32351, U.S.A.

Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, is an economically important disease that impacts soybean yield, seed size, and quality. Research efforts have focused on identifying effective chemical controls due to the lack of durable genetic resistance in soybean against ASR. Previous investigations using Roundup®, a broad-spectrum herbicide containing the active ingredient glyphosate, have shown that on Roundup®-tolerant crops it decreases both wheat rust in the field and ASR on soybeans in the greenhouse. In this study, we investigated the effects of Roundup WEATHERMAX® on ASR severity and yield on Roundup Ready® soybeans in the field in Florida. Data from trials conducted in Citra and Quincy, FL, in 2006, indicated that Roundup WEATHERMAX® reduced ASR severity and increased yield (bu/acre) when compared with untreated controls. In Quincy and Citra in 2007, we did not see the same effects as in the previous year’s study, which may be due to differences in disease pressure and/or environmental conditions. The effects of chlorothalonil, azoxystrobin, tebuconazole, and glyphosate (ECHO 720®, Headline®, Folicur®, Roundup WEATHERMAX®, and Roundup technical-grade) on P. pachyrhizi urediniospore germination were examined in vitro using pesticide-amended water agar plates. All fungicides (except Folicur®) and glyphosate (WEATHERMAX® and technical grade) inhibited urediniospore germination in a dose-dependent manner. Effective concentrations to inhibit 50% of urediniospore germination (EC50) were calculated. These results indicate that Roundup® has an effect on ASR spore germination in vitro. However, more research is required to understand the effect of Roundup® on ASR in the field.

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