Research on pathogenic characters of different virulence isolates of wheat take-all fungi Isolation and variety identification of Gaeumannomyces graminis causing Wheat take-all in Henan Province Pathogenicity of Four Varieties of Gaeumannomyces graminis to Gramineal Grasses Genetic diversity of Gaeumannomyces graminis var.tritici populations in Huang-Huai Winter Wheat Production Region of China Cloning and expression analysis of Stpk-V homologous genes under infection by Gaeumannomyces graminis var. tritici in wheat