Effects of infestation by Rhyzopertha dominica in different development stages on wheat storage protein structure

Abstract: As a kind of the stored grain insect pests bored inside grains, the damages caused by Rhyzopertha dominica are very serious in the process of wheat storage, and it has severe impacts to wheat quality in many aspects, such as starch, lipid, protein, and so on. In order to explore the effects of infestation by Rhyzopertha dominica in different growth and development stages on wheat storage protein structure, and provide some references for the detection of wheat quality and the growth and development of stored grain insect pests in the process of wheat storage,the wheat infected by Rhyzopertha dominica was taken as the research material. The glutenin macropolymer content, Zeleny sedimentation value, gluten moisture capacity and protein secondary structure were inspected and analyzed, as well as the content of thiol (-SH) and disulfide bond (-S-S-)and gluten microstructures of wheat infected by Rhyzopertha dominica in different growth and development stages i.e. egg stage, larval stage, pupa stage and adult stage. The results showed that in the 4 growth and development stages of lesser grain borer, the Zeleny sedimentation value, glutenin macropolymer conten and β-turn had an increasing trend in general, while the content of -SH and β-pleated sheet showed a completely opposite change trend. The gluten water absorption capacity, and the content of -S-S- and α-helix showed a downward trend first and then an upward trend, and the change of random curl content showed an opposite trend. The lesser grain borer in the egg stage did less harm to wheat storage protein structure, and just the gluten water absorption capacity and β-turn content had a great change (P<0.05), while the lesser grain borer in larval stage and pupa stage had a serious damage to wheat storage protein structure. Compared to the control samples of the insect-free wheat with the relevant infection stages under the same experimental conditions, the Zeleny sedimentation value, content of glutenin macropolymer, β-turn and random curl of wheat infected by lesser grain borer in the larval and pupa stages increased significantly (P<0.05), but the gluten water absorption capacity, content of -SH and -S-S-, α-helix and β-pleated sheet decreased (P<0.05). In addition, the microstructure analysis results showed that the micro fiber filament increased and the surface of gluten got rough, the structure got loose and scattered, and the structure fracture became more and more severe with the growth and development of lesser grain borer. Until the stage of adult, some microstructure of gluten could not even be identified. All the experiment results show that the damages on wheat protein structure are severe with the growth and development of lesser grain borer inside wheat granules. Accordingly, timely control on lesser grain borer is necessary and it will reduce the damage to wheat storage protein structure before infestation by Rhizopertha dominica in the larval and pupa stages. The research results provide the reference for the control of the lesser grain borer for the wheat during the storage.