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Characterization of Freezing Inhibitors from Winter Wheat Cultivars¹

The activity of freezing kinetics inhibitors was characterized by a visual rating technique for several wheat (Triticum aestivum L.) cultivars. The procedure allowed a single test of a cultivar with a minimum of 13 g of seed, and 10 tests per day with the equipment available. Comparisons between several replications of kinetic inhibitor ratings and cultivar survival of high-intensity freezing showed expected relationships. The activity of kinetic inhibitors from some cultivars was commensurate with survival ability. However, other cultivars exhibited better kinetic inhibitor activity than indicated by their survival rating. The ability to identify cultivars with high activity with no confounding effect by plant weaknesses in other areas that can affect survival, is a distinct advantage of this test. All wheat cultivars tested had lower ratings than "Rosen" rye, the standard for the maximum rating. A large number of cultivars with varied genetic backgrounds are now being screened for unproved kinetic inhibitor activity using this technique.

As an initial inquiry leading to the screening technique, the validity of using seed as the polysaccharide source in the kinetic inhibitor tests was substantiated by hydrolysis and chromatography. Monosaccharide components were similar for polysaccharides extracted from crown tissues, the important area of freezing resistance, and from seed tissue. Purifying the polysaccharide extracts has proved difficult. In the best preparations, no compositional differences were seen between those polysaccharides exhibiting activity as kinetic inhibitors and those showing inactivity.

Key Words: Winterhardiness • Cell wall polysaccharides • Laboratory screening procedures

² Instructor, Department of Crop and Soil Sciences, Michigan State University; Plant Physiologist and Biological Laboratory Technician, ARS, USDA, East Lansing, Michigan; and Professor, Department of Crop and Soil Sciences Michigan State University, East Lansing, Michigan 48823.

Received for publication January 22, 1973.