The fate and impact of chemical and biological control measures on the microbial ecology of the turfgrass ecosystem

• Main Author: Sigler, William Von
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2000
• Subjects: Microbiology; Soil sciences
• ISBN: 0493290095; 9780493290096

Frequent fungicide and biological control organism applications are common to high-value sites such as golf courses, vegetable crops, and athletic fields for the suppression of plant pathogens. However, little research has examined the effect of such treatments on the indigenous ecology of these ecosystems or the environmental parameters influencing pathogen control by fluorescent pseudomonads. This study was initiated to determine the fate and impact of both chemical (chlorothalonil) and biological control (Pseudomonas aureofaciens) measures on the microbial ecology of the turfgrass ecosystem and to assess environmental constraints surrounding the lack P. aureofaciens biocontrol efficacy. Denaturing gradient gel electrophoresis of PCR-amplified 16S rDNA indicated that applications of chlorothalonil and P. aureofaciens modified the soil and leaf bacterial communities, respectively. However, P. aureofaciens applications did not result in detectable impacts on the thatch or soil communities. PCR amplification and DNA hybridization with a Pseudomonas-specific primer and probe combination revealed that P. aureofaciens was capable of overwintering in turfgrass soil following a season of repeated applications. An assay of the indigenous soil bacteria population suggested that no indigenous fluorescent pseudomonads were capable of the cell density-driven production of the pathogen-suppressing antibiotic phenazine-1-carboxylic acid (PCA). This implies that the native soil environment lacks a key component required for the pathogen suppressing activity of applied P. aureofaciens. We conclude that although the turfgrass bacterial community structure is altered following applications of chlorothalonil and P. aureofaciens, the impact to bacterial diversity is minimal. Additionally, the lack of PCA production by indigenous fluorescent pseudomonads suggests that the soils studied exhibited a low cell density of PCA-producing bacteria, which may have been a factor in the limited phenazine-based control of turfgrass pathogens.