Geostatistical Analysis of Dollar Spot Epidemics Occurring on a Mixed Sward of Creeping Bentgrass and Annual Bluegrass

Horvath, Brandon J.; Kravchenko, Alexandra; Robertson, G. Philip; Vargas, J. M.

doi:10.2135/cropsci2006.09.0565

Cited by 15 publications

(9 citation statements)

References 40 publications

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“…Heavy reliance on synthetic fungicides has led to the development of fungicide resistant fungal populations (4), imposes a significant financial burden on the turfgrass manager (5), and increases the risk of human and on March 29, 2021 by guest http://aem.asm.org/ Downloaded from environmental contamination resulting from repeated chemical exposures (6). The development of dollar spot symptoms in uniformly managed turfgrass with nearly identical environmental conditions is often highly variable, even at a scale of several meters (7). It is unclear why dollar spot develops in such a variable manner, but plausible explanations include a link to hyperlocal variations in microbial antagonists or local variations in soil physical, chemical, or biological properties.…”

Section: Introductionmentioning

confidence: 99%

Hyperlocal Variation in Soil Iron and the Rhizosphere Bacterial Community Determines Dollar Spot Development in Amenity Turfgrass

Chou

Shrestha

Rioux

et al. 2021

Appl Environ Microbiol

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Dollar spot, caused by the fungal pathogen Clarireedia spp., is an economically important foliar disease of amenity turfgrass in temperate climates worldwide. This disease often occurs in a highly variable manner, even on a local scale with relatively uniform environmental conditions. The objective of this study was to investigate mechanisms behind this local variation, focusing on contributions of the soil and rhizosphere microbiome. Turfgrass, rhizosphere, and bulk soil samples were collected from within a 256 m2 area of healthy turfgrass, transported to a controlled environment chamber, and inoculated with C. jacksonii. Bacterial communities were profiled by targeting the 16S rRNA gene, and 16 different soil chemical properties were assessed. Despite their initial uniform appearance, the samples differentiated into highly susceptible and moderately susceptible groups following inoculation in the controlled environment chamber. The highly susceptible samples harbored a unique rhizosphere microbiome with suggestively lower relative abundance of putative antibiotic-producing bacterial taxa and higher predicted abundance of genes associated with xenobiotic biodegradation pathways. In addition, stepwise regression revealed that bulk soil iron content was the only significant soil characteristic that positively regressed with decreased dollar spot susceptibility during the peak disease development stage. These findings suggest that localized variation in soil iron induces the plant to select for a particular rhizosphere microbiome that alters the disease outcome. More broadly, further research in this area may indicate how plot-scale variability in soil properties can drive variable plant disease development through alterations in the rhizosphere microbiome. IMPORTANCE Dollar spot is the most economically important disease of amenity turfgrass, and more fungicides are applied targeting dollar spot than any other turfgrass disease. Dollar spot symptoms are small (3-5 cm), circular patches that develop in a highly variable manner within plot-scale even under seemingly uniform conditions. The mechanism behind this variable development is unknown. This study observed that differences in dollar spot development over a 256 m2 area were associated with differences in bulk soil iron concentration and correlated with a particular rhizosphere microbiome. These findings provide interesting avenues for future research to further characterize the mechanisms behind the highly variable development of dollar spot, which may inform innovative control strategies. Additionally, these results suggest that small changes in soil properties can alter plant activity and hence the plant-associated microbial community, which has important implications for a broad array of important agricultural and horticultural plant pathosystems.

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Section: Introductionmentioning

confidence: 99%

Hyperlocal Variation in Soil Iron and the Rhizosphere Bacterial Community Determines Dollar Spot Development in Amenity Turfgrass

Chou

Shrestha

Rioux

et al. 2021

Appl Environ Microbiol

View full text Add to dashboard Cite

show abstract

“…Heavy reliance on synthetic fungicides has led to the development of fungicide resistant fungal populations (4), imposes a significant financial burden on the turfgrass manager (5), and increases the risk of human and environmental contamination resulting from repeated chemical exposures (6). The development of dollar spot symptoms is often highly variable within several meters distance, even in uniformly managed turfgrass with nearly identical environmental conditions (7). While it is not known why dollar spot symptoms develop in such a variable manner, one plausible explanation is a link to hyperlocal variations in microbial antagonists or variations in soil physical, chemical, or biological properties.…”

Section: Introductionmentioning

confidence: 99%

Hyperlocal Variation in Soil Iron and Rhizosphere Microbiome Determines Disease Development in Amenity Turfgrass

Chou

Shrestha

Rioux

et al. 2020

Preprint

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Dollar spot, caused by the fungal pathogen Clarireedia spp., is an economically important disease of amenity turfgrass in temperate climates worldwide. This disease often occurs in a highly variable manner, even on a local scale with relatively uniform environmental conditions. The objective of this study was to investigate mechanisms behind this local variation, focusing on contributions of the soil and rhizosphere microbiome. Turfgrass, rhizosphere, and bulk soil samples were taken from within a 256 m2 area of healthy turfgrass, transported to a controlled environment chamber, and inoculated with C. jacksonii. Bacterial communities were profiled targeting the 16s rRNA gene, and 16 different soil chemical properties were assessed. Despite their initial uniform appearance, the samples differentiated into highly susceptible and moderately susceptible groups following inoculation in the controlled environment chamber. The highly susceptible samples harbored a unique rhizosphere microbiome with lower relative abundance of antibiotic-producing bacterial taxa and higher predicted abundance of genes associated with xenobiotic biodegradation pathways. In addition, stepwise regression revealed that bulk soil iron content was the only significant soil characteristic that positively regressed with decreased dollar spot susceptibility during the peak disease development stage. These findings suggest that localized variation in soil iron induces the plant to select for a particular rhizosphere microbiome that alters the disease outcome. More broadly, further research in this area may indicate how plot-scale variability in soil properties can drive variable plant disease development through alterations in the rhizosphere microbiome.

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“…Geostatistical analysis of dollar spot epidemics demonstrated limited spread of this pathogen within a season, indicating that equipment does not contribute to spread of inoculum. Consequently, the authors concluded that epidemics initiated from individual clusters of infection centers [13] .…”

Section: Introductionmentioning

confidence: 99%

Sclerotinia homoeocarpa Overwinters in Turfgrass and Is Present in Commercial Seed

et al. 2014

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Dollar spot is the most economically important disease of amenity turfgrasses in the United States, yet little is known about the source of primary inoculum for this disease. With the exception of a few isolates from the United Kingdom, Sclerotinia homoeocarpa, the causal agent of dollar spot, does not produce spores. Consequently, it was assumed that overwintering of this organism in soil, thatch, and plant debris provides primary inoculum for dollar spot epidemics. Overwintering of S. homoeocarpa in roots and shoots of symptomatic and asymptomatic creeping bentgrass turfgrass was quantified over the course of a three-year field experiment. Roots did not consistently harbor S. homoeocarpa, whereas S. homoeocarpa was isolated from 30% of symptomatic shoots and 10% of asymptomatic shoots in the spring of two out of three years. The presence of stroma-like pathogen material on leaf blades was associated with an increase in S. homoeocarpa isolation and colony diameter at 48 hpi. Commercial seed has also been hypothesized to be a potential source of initial inoculum for S. homoeocarpa. Two or more commercial seed lots of six creeping bentgrass cultivars were tested for contamination with S. homoeocarpa using culture-based and molecular detection methods. A viable, pathogenic isolate of S. homoeocarpa was isolated from one commercial seed lot and contamination of this lot was confirmed with nested PCR using S. homoeocarpa specific primers. A sensitive nested PCR assay detected S. homoeocarpa contamination in eight of twelve (75%) commercial seed lots. Seed source, but not cultivar or resistance to dollar spot, influenced contamination by S. homoeocarpa. Overall, this research suggests that seeds are a potential source of initial inoculum for dollar spot epidemics and presents the need for further research in this area.

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Geostatistical Analysis of Dollar Spot Epidemics Occurring on a Mixed Sward of Creeping Bentgrass and Annual Bluegrass

Cited by 15 publications

References 40 publications

Hyperlocal Variation in Soil Iron and the Rhizosphere Bacterial Community Determines Dollar Spot Development in Amenity Turfgrass

Hyperlocal Variation in Soil Iron and the Rhizosphere Bacterial Community Determines Dollar Spot Development in Amenity Turfgrass

Hyperlocal Variation in Soil Iron and Rhizosphere Microbiome Determines Disease Development in Amenity Turfgrass

Sclerotinia homoeocarpa Overwinters in Turfgrass and Is Present in Commercial Seed

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