Species Identification of Novel Ectotrophic Root-Infecting Fungi Associated with Decline of Ultradwarf Bermudagrass.

Ultradwarf bermudagrass (Cynodon dactylon x C. transvaalensis) cultivars, in the Deep South region of the United States, often exhibit symptoms of decline during late summer and early fall months.  Root systems appear diminutive in size, brittle, and discolored and are frequently colonized with dark, runner hyphae that are characteristic of ectotrophic root-infecting (ERI) fungi.  Currently, spring dead spot (Ophiosphaerella spp.) and bermudagrass decline (Gaeumannomyces graminis var. graminis) are the only recognized diseases of ultradwarf bermudagrasses caused by ERI fungi. Observations from this study led to the theory that additional ERI fungi have a role in the decline of ultradwarf bermudagrass roots.  Due to laborious and inconclusive identification efforts associated with traditional diagnostic techniques, molecular-based strategies were employed to test the hypothesis.  A multilocus sequence analysis was performed on the concatenated six-gene dataset of the representative Mississippi State University (MSU)-ERI isolates and related taxa.  Phylograms were erected using combined consensuses from maximum likelihood and Bayesian inference analyses.  The 26 MSU-ERI isolates included in the analyses were identified as G. graminis var. graminis (n=3), G. paulograminis sp. nov. (n=7), Magnaporthiopsis incrustans (n=3), M. hawaiiensis sp. nov. (n=1), M. cynodontis sp. nov. (n=4), M. taurocanis sp. nov. (n=5), Candidacolonium cynodontis gen. nov. sp. nov. (n=2), and Pseudophialophora cynodontis sp. nov. (n=1).