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Fate of Dwarf Bunt Fungus Teliospores During Milling of Wheat into Flour

¹USDA-ARS, Grain Marketing and Production Research Center, Grain Marketing Research Laboratory, Manhattan, KS 66502. ²Corresponding author. E-mail: don@usgmrl.ksu.edu ³Department of Grain Science and Industry, Kansas State University, Manhattan, KS 66506. ⁴USDA-ARS, North Carolina State University, Raleigh, NC 27695. ⁵USDA-ARS, Foreign Disease-Weed Science Research, Fort Detrick, Frederick, MD 21702.

Wheat contaminated with teliospores of Tilletia controversa Kühn (TCK) was mixed with uncontaminated wheat and processed through the Kansas State University pilot mill. Two 50-bu lots of the contaminated mixture were cleaned, tempered, and milled. Approximately 500 samples of wheat, cleanings, and mill fractions were collected and examined for the presence of intact and broken TCK teliospores. Whole wheat samples (50 g) were washed, sieved through a 60-μm nylon sieve, and pelleted by centrifugation. Contents of the pellet were examined microscopically for the presence of TCK spores. The procedure was modified as needed to accommodate cleanings and mill fractions. Levels of spore contamination in whole wheat samples decreased at each step during the handling process, and large numbers of spores were found in materials that were sieved or aspirated from the grain. Very few spores were found in bran, germ, and shorts; none were detected in red dog or straight-grade flour. The results showed that a high percentage of spores can be removed from wheat by mechanical cleaning but that it is not feasible to remove all of them.