Effect of Aphid Feeding on the Glutenin, Gliadin and Total Protein Contents of Wheat Flour

Plant sucking aphids cause both quantitative and qualitative yield losses in cereals; moreover aphid-transmitted viruses are responsible for other quantitative and qualitative damages, thus direct or indirect effects of aphid infection are in focus of interest. Bread-making quality of wheat flour is determined primarily by the protein content and composition, the gluten proteins (glutenins, gliadins) being the prime factors. Allelic composition of the gliadin- and glutenin loci as well as the absolute amount and/or the relative ratio of gliadins to glutenins are very important in dough making and in determining baking quality. Wheat plants were caged at the beginning of stem elongation. Cages were treated with 0.1% methyl parathion. One week later, the caged plants were artificially infected with 5 alata individuals of Metopolophium dirhodum, Diuraphis noxia, Sitobion avenae and Rhopalosiphum padi. Flour from grains originating from plants infected artificially with cereal aphids were analyzed for glutenin and gliadin and total protein content, using Size Exclusion HPLC. It was found that aphid infection had significant effect on the glutenin and gliadin content, the total protein content and the gliadin/glutenin ratio. Both the glutenin and gliadin content was significantly higher in the seeds harvested from aphid infected plants. However, the gliadin/glutenin ratio was significantly lower in wheat flour prepared from aphid infected plants than in those from uninfected control. The most significant decrease in gliadin/glutenin ratio was caused by M. dirhodum, D. noxia, S. avenae infection followed by R. padi at high-abundance and low-abundance, respectively. As the gliadin/glutenin ratio was significantly lower in flours made from aphid infected wheat seeds, it may be suggested that aphid feeding results in decreased bread making quality of wheat flour.