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Growth of Puccinia graminis f. sp. tritici on a Defined Medium. Arnold S. Foudin, Graduate Assistant, Department of Plant Pathology, University of Georgia, Athens 30601; Willard K. Wynn, Associate Professor, Department of Plant Pathology, University of Georgia, Athens 30601. Phytopathology 62:1032-1040. Accepted for publication 29 March 1972. DOI: 10.1094/Phyto-62-1032.

Sustained axenic growth of Puccinia graminis f. sp. tritici, race 126-ANZ-6,7, was obtained on a defined medium consisting of 1% agar, 3% glucose, Czapek’s minerals, Burkholder and Nickell’s trace elements, and a mixture of 16 amino acids in the proportions found in purified casein hydrolysate. Mycelial growth from uredospores, measured at 28 days, on this medium was equal to that on media containing casein hydrolysates and superior to that on Evans’ peptone. We developed the defined medium initially screening 25 commercial peptones and then comparing representative products which did and did not support growth. Only six peptones were effective when incorporated directly into a basal medium; however, six more products supported growth after additional acid hydrolysis. Analyses showed distinct amino acid patterns (high levels of glutamate in nine out of 10 effective hydrolysates and high levels of glycine in noneffective ones) but no unique levels of trace elements. Since purified casein, hydrolyzed 24 hr, supported growth as well as the best commercial products, its amino acid composition was mimicked to prepare the artificial medium. When amino acids were supplied in the proportion found in Bactopeptone or when trace elements were omitted, the defined medium did not support growth.