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Southern Division - Pathogenicity evaluations of novel ectotrophic root-infecting fungi on ultradwarf bermudagrass
P. L. VINES (1), M. Tomaso-Peterson (2), T. Allen (2). (1) Mississippi State Univ, Mississippi State, MS, U.S.A.; (2) Mississippi State University, Mississippi State, MS, U.S.A.

Ultradwarf bermudagrass root systems affected by summer decline are typically diminutive in size, brown to black in color, and are frequently colonized with dark runner hyphae, growth cessation structures, and simple and lobed hyphopodia, which are characteristic signs of ectotrophic root-infecting (ERI) fungi.  Research at Mississippi State University led to the identification of six novel fungal species and two previously recognized species from colonized roots.  The objective of this study was to screen ERI fungal species for pathogenicity on ‘Champion’ and ‘MiniVerde’ ultradwarf bermudagrasses.  Representative isolates from each of the eight fungal species were selected and grown on potato dextrose agar (PDA) under 24 hour fluorescent light for 14 days.  The experiment was conducted in a randomized complete block split-plot design with three replications.  Ultradwarf bermudagrass cultivars (n=2) were whole plots and fungal isolates (n=10) were split-plots.  <i>In vivo</i> inoculations were performed in 7.6 cm diameter pots and placed in light- and temperature-controlled growth chambers for eight weeks.  Pathogenicity of root systems was assessed via pixel color analyses in WinRhizo and Koch’s postulates were confirmed by reisolation of the fungus from roots within each pot.  All ERI fungi were pathogenic to both ultradwarf bermudagrass cultivars; however, severity levels varied among species.  The greatest root disease severity was incited by two novel species.  

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