Damping off is the most common disease caused by edaphic fungi in Spanish crops, among which Rhizoctonia solani AG-4 stands out. In the present work, two possible methods of control were evaluated, incorporation of different doses of organic matter (OM; obtained from strawberry crops) and Pseudomonas fluorescens as a plant growth promoting rhizobacteria (PGPR). The highest inhibition (43% less) against the pathogen was found in the assays that used 20 g of biofumigant/kg soil. Inoculation of the P. fluorescens strain (PGPR) did not protect against the pathogen. In addition, the microbial evolution during incubation with OM was studied. For this purpose, the bacterial and fungal catabolic profiles were determined (using Biolog Eco and FF plates, respectively) as well as bacterial counts of total aerobes, Pseudomonas sp. and aminocyclopropane-1-carboxylate (ACC)-degrading populations, during OM incorporation. This agro-technique produced changes in microbial catabolic community profiles, increasing bacterial metabolic activity and minimizing metabolic diversity of micro-organisms under control with and without pathogen. As for microbial counts, aerobic and ACC-degrading populations decreased while Pseudomonas sp. population increased with OM treatments.
The OM amendment applied to control the damping off caused by R. solani is viable; it is more environmentally friendly and has a lower economic cost than chemical controls and, therefore, it could serve as a component in integrated-management programmes.