Abstract
Compost can suppress soilborne plant pathogens that cause significant damage on globally important food crops. However, reports of plant pathogen suppression are inconsistent likely because there are no established standards for feedstock material, application rate, and maturity age upon application. Excellent results can be achieved in greenhouse trials, but field applications are much less reliable. Disease suppression occurs through the activity of biocontrol organisms (direct antagonism), and general microbial competition. Biocontrol species are hypothesized to colonize the pile during the curing phase, but single species may not be as important as microbial consortia. Substrate composition during maturation may give rise to a suppressive microbial community. More research is needed to understand the relationships between feedstock, maturity, and production process on compost microbial ecology. The thesis had two main objectives: 1) identify biological indicators in compost that could (a) characterize maturity, process, and feedstock, and (b) predict disease suppression against R. solani, and 2) identify bacterial and fungal community composition and/or structure that is associated with suppression of soilborne disease. Rhizoctonia solani is a facultative saprophytic fungus and soilborne plant pathogen that attacks many globally important food crops and turfgrass. Prior research suggests that managing carbon quality and compost maturity will alter relative competition between biological control microbes and the R. solani pathogen. The pathogen is responsible for economic losses to organic vegetable production in Vermont and there are no available methods to manage the disease that meet organic certification. R. solani on radish was chosen as a model system given its global importance, competitiveness affected by carbon quality, and lack of disease management options for organic production. Compost samples were most abundant in the bacterial phyla Proteobacteria and Bacteroidetes, and known biocontrol species were not detected in abundance. Compost samples did not differ significantly in fungal community composition, suggesting a dominance effect from the native soil fungal community. Overall, anaerobic digestate and vermicompost were most suppressive against R. solani. Thermophilic composts were not very suppressive overall, though a specially made hardwood bark compost was comparable to the suppressiveness of vermicompost application. Ecoenzyme analysis was able to integrate information on environmental substrate composition, microbial nutrient acquisition, and microbial community metabolism, offering the best view of current ecological conditions in compost. Ecoenzyme analysis showed that the most suppressive composts, anaerobic digestate and vermicompost, were most nutrient limited. All compost samples were severely nitrogen (N) limited, and anaerobic digestate and vermicompost were severely limited in both N and phosphorus (P). The additional P limitation may support non-pathogenic species to outcompete R. solani. The key to disease suppression may lie in matching up the ecology of the plant pathogen with the ecology of biocontrol, which may be engineered in compost.
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Claims 11
Claim · model-written summary
Proteobacteria and Bacteroidetes were the most abundant bacterial phyla in compost samples.
- Taxon
- radish
Raphanus sativust0 - Outcome
- bacterial phyla Proteobacteria and Bacteroidetese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compost samples were most abundant in the bacterial phyla Proteobacteria and Bacteroidetes”
t0“R. solani on radish was chosen as a model system”
Claim · model-written summary
Known biocontrol species were not abundant in compost samples.
- Taxon
- radishRaphanus sativust0
- Outcome
- known biocontrol species were not detected in abundancee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“known biocontrol species were not detected in abundance”
t0“R. solani on radish was chosen as a model system”
Claim · model-written summary
Compost samples did not differ significantly in fungal community composition.
- Taxon
- radishRaphanus sativust0
- Outcome
- fungal community compositione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Compost samples did not differ significantly in fungal community composition”
t0“R. solani on radish was chosen as a model system”
Claim · model-written summary
Anaerobic digestate was among the most suppressive composts against R. solani.
- Taxon
- radishRaphanus sativust0
- Treatment
- anaerobic digestatee0
- Interactor
- R. solani
Rhizoctonia solanie0pathogen - Outcome
- suppressive against R. solanie0
- Direction
- most suppressivee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Overall, anaerobic digestate and vermicompost were most suppressive against R. solani”
t0“R. solani on radish was chosen as a model system”
Claim · model-written summary
Vermicompost was among the most suppressive composts against R. solani.
- Taxon
- radishRaphanus sativust0
- Treatment
- vermicomposte0
- Interactor
- R. solaniRhizoctonia solanie0pathogen
- Outcome
- suppressive against R. solanie0
- Direction
- most suppressivee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Overall, anaerobic digestate and vermicompost were most suppressive against R. solani”
t0“R. solani on radish was chosen as a model system”
Claim · model-written summary
Thermophilic composts were generally not very suppressive.
- Taxon
- radishRaphanus sativust0
- Treatment
- Thermophilic compostse0
- Outcome
- suppressivee0
- Direction
- not very suppressivee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Thermophilic composts were not very suppressive overall”
t0“R. solani on radish was chosen as a model system”
Claim · model-written summary
A hardwood bark compost had suppression comparable to vermicompost.
- Taxon
- radishRaphanus sativust0
- Treatment
- hardwood bark composte0
- Outcome
- suppressivenesse0
- Direction
- comparablee0
- Comparator
- vermicompost applicatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a specially made hardwood bark compost was comparable to the suppressiveness of vermicompost application”
t0“R. solani on radish was chosen as a model system”
Claim · model-written summary
Ecoenzyme analysis integrated substrate, nutrient acquisition and microbial metabolism information.
- Taxon
- radishRaphanus sativust0
- Outcome
- integrate information on environmental substrate composition, microbial nutrient acquisition, and microbial community metabolisme0
Not reportedValue
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ecoenzyme analysis was able to integrate information on environmental substrate composition, microbial nutrient acquisition, and microbial community metabolism”
t0“R. solani on radish was chosen as a model system”
Claim · model-written summary
Anaerobic digestate and vermicompost were the most nutrient limited composts.
- Taxon
- radishRaphanus sativust0
- Treatment
- anaerobic digestate and vermicomposte0
- Outcome
- nutrient limitede0
- Direction
- moste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ecoenzyme analysis showed that the most suppressive composts, anaerobic digestate and vermicompost, were most nutrient limited”
t0“R. solani on radish was chosen as a model system”
Claim · model-written summary
All compost samples were severely nitrogen limited.
- Taxon
- radishRaphanus sativust0
- Outcome
- nitrogen (N) limitede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“All compost samples were severely nitrogen (N) limited”
t0“R. solani on radish was chosen as a model system”
Claim · model-written summary
Anaerobic digestate and vermicompost were severely limited in nitrogen and phosphorus.
- Taxon
- radishRaphanus sativust0
- Outcome
- limited in both N and phosphorus (P)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“anaerobic digestate and vermicompost were severely limited in both N and phosphorus (P)”
t0“R. solani on radish was chosen as a model system”
The same questions in other papers
fertilization · Rhizoctonia solani · Raphanus sativus (radish)Results agree
2 papers in the same direction as this paper
- positive
- positive
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.