Compost Extracts and the Biological Control of Foliar Plant Disease

Compost Extracts and the Biological Control of Foliar Plant Disease

Summary

Water extracts of slurries of spent mushroom substrate compost inhibit the apple scab pathogen Venturia inaequalis in the laboratory and reduce severity of scab disease in the field.

This project was an attempt to isolate the compound(s) responsible based on the polarity, charge and size of the bioactive molecule(s). The methods used included extraction (partitioning) into nonpolar solvents at acidic, neutral or basic pH; cation exchange column chromatography; paper electrophoresis; and ultrafiltration through membrane filters (microconcentrators) of known porosity or Sephadex G-10 and G-25 columns. Almost all of the activity was associated with polar (water-soluble) molecules and at least some of it was less than 3 kilodaltons in molecular weight.

The objective is to continue determination of the pathogen- and disease-inhibitory principle(s) in the spent mushroom subtrate (SMS) extracts.

We attempted to separate the compound(s) of interest from the crude spent mushroom substrate (compost) extract by using standard organic chemistry methods detailed elsewhere (Cooper 1977; Cronin et al. 1996; Sunshine, 1969). In overview, such methods essentially are based on size (ethanol precipitation, column chromatography, ultrafiltration), polarity (differential solubility in polar/nonpolar solvents), or charge (electrophoresis, cation exchange chromatography). We also developed bioassay methods and a standardized quantification scheme for assessing efficacy of the chemical fraction of interest. North Central Region SARE 1997 Annual Report.