Seed physiology, production and technology: Fusarium graminearum infection during wheat seed development and its effect on seed quality

Fusarium head blight (FHB) caused by Fusarium graminearum Schwabe causes losses in wheat (Triticum aestivum L.) seed quality and yield. Field studies were conducted in 2000 and 2001 to investigate F. graminearum seed infection (SI) and its relationship to seed germination and vigor and the production of the mycotoxin deoxynivalenol (DON). Seeds from four soft red winter wheat cultivars having different levels of Type II resistance to F. graminearum were harvested at frequent intervals during development and maturity. Low levels of SI occurred late in seed development in 2000, which resulted in high seed quality. In 2001, under heavy disease pressure, F. graminearum increased from <20% at 10 d after anthesis (DAA) to >98% at maturity in both resistant and susceptible cultivars, resulting in unacceptable standard germination (SG) (<80%) and seed vigor [<70% accelerated aging (AA) germination] early in seed development. Although fungicide seed treatment improved the SG of all cultivars, it still remained below acceptable commercial seed quality (80%). Deoxynivalenol was present at significant levels (5 to 25 mg kg^-1) throughout seed development and maturation in all cultivars in 2001. Although the resistant cultivar P25R18 had reduced levels of DON and lower seed damage compared with susceptible P2552, resistance had no effect on SI and seed quality. Therefore, under severe disease pressure, Type II resistance offers little advantage to seed producers in reducing SI and improving seed quality during severe FHB epidemics.