Pathogenicity of a Novel Biotype of Limonomyces roseipellis in Tall Fescue.

Abstract

An unusual and undescribed foliar blight of tall fescue was observed in a home lawn and in turf grass research plots near Griffin, GA in May and June, 2000 and 2001. Isolation from lesions yielded mycelium of a basidiomycete with hyphal characteristics (binucleate cells, absence of clamp connections) associated with Laetisaria and Limonomyces spp. Isolates from blighted tall fescue and an isolate of Limonomyces roseipellis formed a clade distinct from isolates of Laetisaria fuciformis based on ribosomal DNA sequences. These data, in conjunction with cultural morphology, indicate that the basidiomycete from tall fescue represents a biotype of Limonomyces roseipellis that lacks clamp connections. In a controlled environment, isolates of the biotype induced foliar blight in the fescue cvs. Kentucky 31 and Rebel III. Histological observations revealed that the fungus colonized leaf surfaces as branched hyphae and aggregated hyphal strands. Penetration occurred via stomatal pores on the abaxial leaf surface. Colonization of leaf tissues was inter- and intracellular, with no evidence of papilla formation in response to invading hyphae. The name "cream leaf blight" is proposed for this new disease of tall fescue.