Characterizing The Ectotrophic Root-Infecting Fungal Populations Responsible For Declining Ultradwarf Bermudagrass Putting Greens.

A decline is often observed on ultradwarf bermudagrass (Cynodon dactylon × C. transvaalensis) putting greens throughout the late summer and early fall months in the southeastern United States.  Root systems appear blackened, rotted, and diminutive in size and are frequently colonized with dark, runner hyphae that are indicative of ectotrophic root-infecting (ERI) fungi.  The objective of this study was to isolate and characterize ERI fungi from colonized ultradwarf roots.  The internal transcribed spacer (ITS) regions of rDNA were amplified by PCR using ITS1 and ITS4 primers and compared to known ITS sequences retrieved from the GenBank via BLAST.  Evolutionary analyses of rDNA-ITS regions suggest that MSU isolates belong to six distinct, well-supported clades.  Representative isolates for each of the clades were chosen and used in temperature controlled growth studies and pathogenicity evaluations.  Isolates were subjected to temperatures ranging from 18-38°C and optimal growth occurred between 27-29°C.  Pathogenicity studies, conducted on Champion and Miniverde bermudagrasses, demonstrated colonization and degradation of ultradwarf roots by MSU isolates.