CHEMICAL INVESTIGATIONS OF WHEAT: I. THE EFFECT OF LOCATION AND CULTIVAR ON SCAB INFECTION IN WHEAT FROM KANSAS IN 1982 AND 1983. II. ALKYLRESORCINOLS IN WHEAT (DEOXYNIVALENOL, ALKYLPHENOL, ERGOSTEROL, MILL FRACTIONS, FUSARIUM GRAMINEARUM)

Samples of wheat from test plots across Kansas in 1982 and 1983 were studied to determine effects of cultivar, location, weather, and other factors on degree of scab infection in the grain. Scab is a disease caused primarily by the fungus F. graminearum which may invade developing wheat kernels during relatively extended periods of wet weather. Results from assays for deoxynivalenol (DON, a metabolite of F. graminearum), ergosterol (an index of total fungal invasion), and viable F. graminearum showed that scab infection was most severe in northeastern Kansas where rainfall, high relative humidity, and cloud cover was frequent during a 25 day critical period when the plants are considered most susceptible to infection. In 1982 differences among some locations were better explained by humidity data than by rainfall or temperature data. In 1983 weather was generally not favorable for scab infection, but a low-degree of infection was found in susceptible cultivars grown in northeast Kansas. Cultivars showed significant and consistent differences in susceptibility to scab infection which could not generally be explained by anthesis dates or other maturity factors. Positive correlations (r (GREATERTHEQ) 0.97) were observed for ergosterol vs. DON, ergosterol vs. F. graminearum, and DON vs. F. graminearum. For samples containing greater than 5 ppm DON, the ergosterol/DON ratio averaged 2.4.;A spectrophotometric determination of alkylresorcinol was developed. Tetrazobenzidine formed a purple precipitate with alkylresorcinols which was extracted into toluene, and absorbance at 465 nm was measured. This method and HPLC determination of individual homologs were used to analyze wheat milling fractions.;Another homologous group of alkylphenols was found in acetone extracts of wheat. These appeared to be structurally related to the 5-n-alkylresorcinols. (Abstract shortened with permission of author.).;An extraction and clean-up procedure was developed for the determination of 5-n-alkylresorcinols in cereal grains. The clean-up was selective for low polarity alkylresorcinols having alkyl chain lengths from 17 through 25 carbons. The alkylresorcinol homologs were separated by reversed-phase high performance liquid chromatography (HPLC) using a C(,18) column and methanol-water mobile phase. Each homolog was individually quantified. Identification of these compounds as 5-n-alkylresorcinols was confirmed by spectroscopic methods including ultraviolet, mass, and nuclear magnetic resonance.