Effects of wheat bug (Eurygaster maura) protease on glutenin proteins

Proteolytic degradation of 50% I-propanol insoluble (50PI) glutenin of six common wheat cultivars by wheat bug (Eurygaster maura) protease was investi gated using reversed-phase HPLC. Wheat at the milk-ripe stage was manually infested with adult bugs. After harvest, bug-damaged kernels were blended ( 2:1, kernel basis) with undamaged grain of the same cultivar. Samples of gr ound wheat were incubated in distilled water for different times (0, 30, 60 , and 120 min). The incubated whole meal samples were subsequently freeze-d ried and stored until analysis. The degree of proteolytic degradation of 50 PI glutenin was determined based on the quantity of total glutenin subunits (GS), high molecular weight GS (HMW-GS), and low molecular weight GS (LMW- GS). For ground wheat samples incubated for greater than or equal to 30 min , 50PI glutenin was substantially degraded as evidenced by a >80% decrease on average in total GS, HMW-GS, and LMW-GS. Some cultivars showed different patterns of glutenin proteolysis as revealed by differences in the ratios of HMW-GS to LMW-GS between sound and bug-damaged samples; a significant de crease in this ratio was found for four cultivars. This evidence, combined with other observations, indicated that there were intercultivar difference s in polymeric glutenin resistance to the protease of the wheat bug Eurygas ter maura. While the nature of this resistance is unknown, it should be pos sible to select and develop wheat cultivars with improved tolerance far whe at bug damage. Propanol insoluble glutenin, which corresponds to relatively large glutenin polymers, appears to be an excellent quantitative marker fo r this purpose.