Current Geographic Distribution and Host Range of Waitea Circinata Var. Circinata.

Brown ring patch, caused by Waitea circinata var. circinata (Wcc), is an emerging Rhizoctonia disease of cool season turf in the U.S. Symptoms are manifest as yellow to brown rings and semi-circles, and damage is most severe on golf course putting greens. The geographic distribution of the pathogen on different host species was examined. Isolates were obtained by culturing of symptomatic tissues onto media and selection of Rhizoctonia like fungi. Isolate identity was confirmed using PCR-amplification and sequencing of internal transcribed spacer regions 1 and 2 and the 5.8S rRNA subunit using universal fungal primers ITS1F and ITS4. Pathogenicity was confirmed by inoculating isolates back onto the hosts of origin in greenhouse studies, fulfilling Koch's Postulates for the isolates. Amplified sequences amongst isolates were 99 to 100% similar, and Koch's postulates were fulfilled for all isolates. The fungus has so far been confirmed as a pathogen on annual bluegrass (Poa annua) in California, Connecticut, Idaho, Illinois, Massachusetts, Nevada, New York, Ohio, Oregon, Pennsylvania, Rhode Island, Virginia and Washington; as a pathogen of roughstalk bluegrass (P. trivialis) in California and Florida, as a pathogen of ryegrass (Lolium perenne) in California and as a pathogen of creeping bentgrass (Agrostis stolonifera) in Idaho. Variation in isolate virulence on different hosts has not been fully examined, but isolates obtained from annual bluegrass can infect and cause disease on roughstalk bluegrass and creeping bentgrass. Additional genetic markers and methods are currently being used to examine the diversity and population structure of this pathogen. Our results confirm that the pathogen is widespread in the U.S. on different cool season turf species.