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

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.     

Identification of Wheat Lines Possessing the 1AL.1RS or 1BL.1RS Wheat-Rye Translocation by Near-Infrared Reflectance Spectroscopy

Wheat-rye chromosomal translocations, particularly those involving the short arm of rye chromosome 1R, have been used during the past 25 years to instill resistance to plant pathogens and insects and improve the hardiness, adaptation, and yield of wheat. Unfortunately, the presence of the 1AL.1RS or 1BL.1RS rye translocations in wheat has been shown to impart inferior dough handling and baking characteristics. Although numerous analytical techniques (e.g., HPLC, monoclonal antibody tests, high-performance capillary electrophoresis) have been developed for detecting these translocations, the complexity of the analytical procedures restricts their use to research and analytical laboratories. The purpose of this study was to examine the potential of diffuse reflectance near-infrared spectroscopy, a well-accepted technique in the grain industry, for detecting 1RS-containing genotypes. This research used three independent groups of wheat samples, ranging in genetic diversity from sister lines derived from 1RS breeding populations to commercial cultivars. Based on the diffuse reflectance spectra (1,100–2,500 nm) of flour, partial least squares (PLS) models, through cross-validation, exhibited misclassification rates as low as 0%, particularly for commercial cultivars. Misclassification rates for corresponding, but separate, test sets were as low as 1%. When the same modeling procedure was applied to samples of more closely related genetic backgrounds, cross-validation misclassification rates rose to 15–20%. Most problematic were samples that were heterogeneous for 1RS such as the cultivar Rawhide. Incorporating heterogeneous samples into a calibration equation improved the classification accuracy of these samples but diminished the prediction accuracy of nonheterogeneous samples.     

Relationships Between Small-Scale Wheat Quality Assays and Commercial Test Bakes

Typical commercial bakeries in the United States are highly mechanized, mass-production facilities. U.S. hard wheat breeding programs use small-scale physical dough testing and pup loaf bake procedures to identify and select improved quality genotypes. The accuracy of such approaches in the prediction of commercial-scale quality performance is poorly understood. Samples from six hard red winter wheat cultivars grown in 11 locations over three harvest years were used to correlate grain hardness, small-scale test bakes, mixograph variables, and various measures of flour protein composition with quality assessments from commercial test laboratories. Samples were milled on both pilot- and small-scale mills. Protein content and 100-g pup loaf volume were more often significantly correlated with commercial test bake variables than all other small-scale variables. Stepwise multiple regression models explained, on average, ≈40% of the variation in commercial test bake procedures. Mixograph properties, pup loaf volumes and absorption, and flour protein content were the most frequent variables identified in model development. Pup loaf bake results on pilot- and small-scale milled flours were highly correlated. Differences in milling technology do not appear to be a significant source of error in relating small-scale test bakes to commercial quality.