Identification and Characterization of Bacteria Associated with Creeping Bentgrass Putting Greens.

While the majority of turfgrass diseases are caused by fungi, the role of bacteria as turfgrass pathogens remains poorly understood.  In recent years, bacterial pathogens have been implicated in the decline of creeping bentgrass (CBG; Agrostis stolonifera L.) putting green turf; however, little research has been done to characterize the associated bacteria.  In 2011, 134 bacteria were isolated from CBG greens in the southeastern and mid-atlantic U.S. exhibiting symptoms of etiolation, chlorosis, or general decline.  Sequences of the 16S and ITS rDNA regions were obtained for each isolate to assist in preliminary identification to species.  Sixteen genera including several species of Pseudomonas, Pantoea, Microbacterium, and Acidovorax were identified.  To test the pathogenicity of each species, 4-wk-old ‘G2’ CBG seedlings were cut, submerged in a 10⁹ colony forming units (CFU) ml^-1 suspensions of bacteria representing the most frequently isolated species for 5 min, and replanted in 3.8 cm diameter conetainers containing calcined clay.  Inoculated plants were maintained in a greenhouse at 30 C/19 C day/night and misted for 5 minutes every 6 hours to maintain leaf wetness and high soil moisture.  A. avenae and P. ananatis reduced visual turf quality compared to the untreated check within 10 days post inoculation.  Inoculated plants first showed dieback from the leaf tip, with continued overall decline.  ‘A1’ CBG plants were inoculated in the field with 10⁸ CFU ml^-1 suspensions of A. avenae, Xanthomonas translucens, or P. ananatis using an atomizer sprayer.  A. avenae resulted in significantly more etiolation compared to X. translucens, P. ananatis, and non-inoculated plants.  However, dieback or decline was not observed and plants eventually recovered.  To our knowledge, this is the first confirmation of etiolation being stimulated by A. avenae in CBG.  Additional research is needed to determine the pathogenicity of X. translucens and P. ananatis on CBG turf.