First Report of Gaeumannomyces graminicola Causing Bermudagrass Decline of Ultradwarf Bermudagrass Putting Greens in North Carolina

Abstract

HomePlant DiseaseVol. 104, No. 5First Report of Gaeumannomyces graminicola Causing Bermudagrass Decline of Ultradwarf Bermudagrass Putting Greens in North Carolina PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Gaeumannomyces graminicola Causing Bermudagrass Decline of Ultradwarf Bermudagrass Putting Greens in North CarolinaCameron M. Stephens and James P. KernsCameron M. Stephens†Corresponding author: C. M. Stephens; E-mail Address: cmsteph2@ncsu.eduhttp://orcid.org/0000-0002-4708-9669Varsity Research Building, Raleigh, NC 27695Search for more papers by this author and James P. KernsVarsity Research Building, Raleigh, NC 27695Search for more papers by this authorAffiliationsAuthors and Affiliations Cameron M. Stephens † James P. Kerns Varsity Research Building, Raleigh, NC 27695 Published Online:23 Feb 2020https://doi.org/10.1094/PDIS-10-19-2147-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Bermudagrass decline is a detrimental disease of ultradwarf hybrid bermudagrass maintained at <5 mm for golf course putting greens. Stand symptoms include off-color to white, irregular patches, chlorosis of older leaf tissue, basal necrosis at plant crowns, and a decrease in stand density. Gaeumannomyces graminis is reported to be the causal agent of this disease (Elliott 1991); however, multiple closely related fungi within the Magnaporthaceae have recently been associated with take-all root rot and bermudagrass decline (Vines et al. 2015). When bermudagrass decline stand symptoms are present, darkly pigmented ectotrophic runner hyphae and lobed hyphopodia are ubiquitous on necrotic roots, the stoloniferous matrix, and the plant crown under severe disease pressure. Symptomatic turf samples from a golf course in Greensboro, NC, were collected using a golf course cup cutter (10.8-cm diameter) in October 2018. Pure cultures of Gaeumannomyces sp. were obtained through isolation from symptomatic root and stolon tissue. Symptomatic roots and stolons were surface disinfested for 1 min in 0.5% sodium hypochlorite solution, rinsed in three consecutive sterile water baths for 30 s, and air dried on sterile filter paper. Once dry, surface-disinfested samples were set on antibiotic-amended water agar containing 0.5 g/liter of streptomycin sulfate and penicillin-G potassium for 5 to 8 days and then subcultured onto potato dextrose agar. Gaeumannomyces sp. was successfully isolated from 80% of the symptomatic tissue evaluated following the aforementioned protocol. Colony morphology was consistent with Gaeumannomyces graminicola M. Hern.-Restr. & Crous sp. nov. (Hernández-Restrepo et al. 2016; Lin et al. 2019). The internal transcribed spacer (ITS) region was sequenced because this marker has the ability to distinguish between the majority of the species within the Gaeumannomyces genus (Hernández-Restrepo et al. 2016). The ITS region of Gaeumannomyces sp. isolates 31282-1A to 1D (accession nos. MN559724, MN559725, MN559726, and MN559727) had 506/507, 503/504, 495/495, and 502/504 similar nucleotides (99.6 to 100% homology) when compared with a known G. graminicola isolate, CPC 26025 (accession no. KX306495), originally isolated from Stenotaphrum secundatum (Walt.) Kuntze (Hernández-Restrepo et al. 2016). Koch’s postulates were performed on healthy ‘Champion’ ultradwarf hybrid bermudagrass plugs (4.4-cm diameter) that were processed by removing the root system and washing the remaining below-ground material with water. G. graminicola was grown on sterile oats for 3 weeks at 25 ± 2°C, and infested oats (n = 10) were placed in the center of 10-cm pots filled with 250 cm3 of sterile sand. A processed bermudagrass plug free of ectotrophic root-infecting fungi was placed directly on the inoculum and lightly top dressed (∼20 cm3 of sterile sand). Experimental units were maintained in the greenhouse at 28 ± 2°C and watered once daily. Basal necrosis, a decrease in plant density and turfgrass quality, and lobed hyphopodia (16.5 to 24 × 15.5 to 23.5 μm) were observed 4 weeks after inoculation. Symptoms were not present on noninoculated and noninfested oat inoculated control plants. G. graminicola was reisolated from symptomatic root and stolon material of inoculated plants and confirmed with ITS sequencing. To our knowledge, this is the first report of G. graminicola causing bermudagrass decline of ultradwarf hybrid bermudagrass in North Carolina, which may influence management of this important disease.The author(s) declare no conflict of interest.