Confirmation of Sphaerobolus stellatus as a Causal Organism of Thatch Collapse of Turfgrasses

Open Access
Author:
Baetsen, Amy Marie
Graduate Program:
Agronomy
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 25, 2013
Committee Members:
  • John Edward Kaminski Iii, Thesis Advisor
Keywords:
  • Sphaerobolus stellatus
  • thatch collapse
  • organic matter
  • degradation
  • turfgrasses
  • lignin degrading enzymes
Abstract:
In 2011, previously unreported disease symptoms were observed on golf course putting greens in the United States and New Zealand. Symptoms of this disease, referred to as thatch collapse, include dark green depressed patches approximately 8 to 46 cm in diameter. The patches of degraded organic matter result in a disruption of playability of golf course tees, fairways and greens. A single fungal species was commonly isolated from turfgrass grown in California, Michigan, Montana, South Dakota, and New Zealand. Sequences of the internal transcribed spacer region (ITS) revealed 695 to 724-bp sequences that were a 98% to 99% match to Sphaerobolus stellatus in the NCBI database. S. stellatus is a basidiomycete commonly found within wood mulch. Little is known about S. stellatus within turfgrass systems. When mature turf was inoculated with S. stellatus and incubated for 6 weeks, thatch layer depth and total organic matter was reduced 28% and 21%, respectively. Studies were conducted to assess the morphology, growth rates and gleba production of S. stellatus isolated from turf. The general morphology of gleba were closer to S. iowensis, but basidiospores were similar to S. stellatus. Optimal temperatures for growth of S. stellatus ranged from 21 to 30°C. Higher quantities of gleba were produce at 10, 15 and 20°C than at 25°C with the highest quantities occurring within 11 weeks of incubation at 10°C. To understand the mechanism by which organic matter was degraded by S. stellatus, the structure of lignin and lignin modifying enzymes were assessed. Utilizing tetramethylammonium hydroxide thermochemolysis, a significant depolymerization of lignin was found when S. stellatus colonized organic matter for 6 weeks. The presence of laccase in an isolate of S. stellatus from turf, manganese independent peroxidase in S. stellatus isolates and xylanse in all fungal extracts illustrates the mechanism of organic matter reduction in turf. Overall, S. stellatus isolated from turf effectively degrades lignin within organic matter through laccase and peroxidase production, and therefore is confirmed to serve a causal agent of thatch collapse.