Fusarium infected grain removal efficacy in cleaning wheat grain prior to milling

Abstract

Four wheat cultivars with different levels of tolerance to Fusarium head blight (FHB) were grown in small plots and were inoculated with spores of Fusarium fungi during the anthesis. The harvested grain was cleaned by a special cleaner which separated it in 4 size fractions: F1->2.4 mm, F2-2.0-2.4 mm, F3-1.8-2.0 mm, F4-<1.8 mm. These were further divided manually in four sub-fractions according to the rate of FHB symptom expression, i.e. grain without any visible symptoms, grain with changes in colour without changes in shape, grain with changes in colour and moderate changes in shape or size, and heavily infected malformed grain. Deoxynivalenol (DON) content in grain of different fractions was determined by high-performance liquid chromatography with UV detection (HPLC-UV) analysis. Comparisons between initial DON content before cleaning and DON content in individual fractions after cleaning were made. The cleaning efficacy (rate of DON content reduction) due to the cleaning and separating of grain in size fractions was higher in semi-tolerant and susceptible cultivars than in FHB tolerant cultivar. Due to the low cleaning efficiency, cleaned grain of tolerant cultivar (without any symptom of FHB), contained twice more DON (870-1350 μg kg-1) than cleaned and apparently healthy grain of semi-tolerant cultivar (160-570 μg kg-1); its DON content was comparable to that of the susceptible cultivar (905-1140 μg kg-1). Our results indicate that FHB tolerant cultivars may contain a high proportion of grain which is apparently healthy, but contains excessive DON levels. Such tolerant cultivars can contribute a lot to minimisation of yield loss caused by FHB, yet they may present a potential health hazard of organic whole-grain flour produced in non-industrial grain processing systems.