Pathogenicity Evaluations of Newly Identified Ectotrophic Root-Infecting Fungi on Ultradwarf Bermudagrass.

Dark runner hyphae, growth cessation structures, and simple hyphopodia, characteristic signs of ectotrophic root-infecting (ERI) fungi, were observed on roots of ultradwarf bermudagrasses (Cynodon dactylon x C. transvaalensis) expressing symptoms of summer decline. Two recognized species (Gaeumannomyces graminis var. graminis and Magnaporthiopsis incrustans) and six novel species (G. paulograminis, M. hawaiiensis, M. cynodontis, M. taurocanis, Candidacolonium cynodontis, and Pseudophialophora cynodontis) were identified from colonized roots. The objective of this study was to evaluate the pathogenicity of the eight ERI fungi on ultradwarf bermudagrass. Two cultivars, ‘Champion’ and ‘Miniverde’, were used. Aerial stolons were placed in contact with fungal inoculum in 3 inch diameter pots. The study was conducted in light and temperature controlled growth chambers and terminated after ample time was provided for root development. Pathogenicity was assessed through a series of evaluation parameters and Koch’s postulates were confirmed by reisolation of the fungus from roots within each pot. Preliminary trials demonstrated colonization and degradation of ultradwarf bermudagrass roots by these fungi. Results of pathogenicity from this study will be discussed in detail.