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Effects of Pythium arrhenomanes Infection and Root-Tip Amputation on Wheat Seedling Development. L. L. Singleton, Assistant professor, Department of Plant Pathology, Oklahoma State University, Stillwater 74078; Oded Ziv, research associate, Department of Plant Pathology, Oklahoma State University, Stillwater 74078. Phytopathology 71:316-319. Accepted for publication 23 July 1980. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1981. DOI: 10.1094/Phyto-71-316.

An in vitro system was developed for studying the effects of Pythium infection on wheat seedlings. Root length, leaf length, dry kernel weight, dry plant weight, and percent water content of the plant were used to quantify the effect of Pythium arrhenomanes infection on wheat seedling development at 2-day intervals beginning at the fifth day and continuing up to the 13th day after emergence. P. arrhenomanes infection treatments were compared to root-tip amputation, no treatment, and Ridomil seed treatment with and without P. arrhenomanes. Ridomil was completely ineffective for controlling P. arrhenomanes in these tests. Infection with P. arrhenomanes significantly reduced root and leaf length and dry plant weight accumulation during the observation period. Uninoculated root-tip amputation treatments temporarily reduced root and leaf elongation, and dry plant weight accumulation 57 days after emergence. However, with the initiation of lateral root development nearly normal growth was resumed. With P. arrhenomanes infection, dry kernel weights remained relatively constant throughout the experimental period in contrast to a rapid decline in treatments without P. arrhenomanes. Percent water contents were significantly lower in plants infected with Pythium than in uninfected plants.