- Additional Plants: mulch
- Pest Management: biological control
Phytophthora root rot (PRR), caused by P. cinnamomi and other soilborne Phytophthora species, impairs production in a wide variety of food and ornamental crops worldwide. In some cropping systems, organic mulches have proven to be a valuable tool in suppressing this disease. Suppression has been linked to biological activity within the mulch, and is correlated with total and cellulase enzyme activity. The production of cellulases by mulch microflora has been suggested as a primary mechanism of PRR suppression, but it has not been shown that the levels of cellulase produced in mulch are sufficient to inhibit Phytophthora growth or infectivity. The goal of this research is to elucidate the role of cellulases in PRR suppression within mulching systems, with the aim of improving current mulch applications to provide greater disease control. In vitro assays will allow us to identify concentrations of cellulase with activity similar to levels observed in mulches from ongoing field trials, and to determine the effects of those levels on Phytophthora growth and infection. Bench and container studies will be used to ascertain the effects of cellulases on the density of viable Phytophthora propagules in soil and mulch and on PRR development in Fraser fir seedlings, and to examine the potential use of several known cellulase-producing fungi as biocontrol agents in mulching systems. Results are expected to identify threshold levels of cellulase activity which should facilitate disease suppression, and may provide an organic, sustainable means of improving mulches for use in biological and cultural disease control efforts.
Project objectives from proposal:
The objectives of this research are to: (1) Establish levels of cellulase enzyme products (Units/ml) in vitro which yield enzyme activities (µmol Glucose Equivalents/g·h) similar to those achieved in organic field mulches, and determine the impact of cellulase levels on P. cinnamomi (2) Ascertain the effects of exogenously applied cellulases on density of viable Phytophthora propagules in soil and mulch and on subsequent PRR development in Fraser fir seedlings; (3) Track the duration of cellulase activity associated with exogenous cellulase applications; and (4) Determine the effects of several known cellulytic fungi, added to mulch as potential biocontrol agents, on both cellulase activity and disease progress.