Impacts of powdery mildew on wheat grain sugar metabolism and starch accumulation in developing grains.

Powdery mildew ( Blumeria graminis f. sp. tritici, Bgt) is a destructive disease responsible for yield reductions in wheat. In this study, we quantify the impacts on grain starch accumulation and yield of different wheat cultivars in response to powdery mildew under field conditions. A coupled spectrophotometer assay, enthrone colorimetric method, 2-DE and MS/MS were used to analyse starch, total soluble sugars (TSS) and metabolic proteins, respectively. Results indicated that AM concentration increased significantly while AP and total starch concentrations decreased with the increase of powdery mildew severity. Powdery mildew suppressed the transformation of sugar to starch in wheat grains at the early infection stage, and there was insufficient substrate for starch synthesis in susceptible cultivars at the later infection stage. A proteomic analysis of metabolic protein showed that plastid α-1,4-glucan phosphorylase, sucrose synthase, β-amylase and glyceraldehyde-3-phosphate dehydrogenase related to starch synthesis were all down regulated and hence starch production was accordingly suppressed. Powdery mildew stress appeared to influence expression of starch synthesis-related enzymes, repressed transformation of sugar to starch, and then inhibited starch (especially AP) synthesis, leading to yield losses. [ABSTRACT FROM AUTHOR]