Phialomyces macrosporus decreases anthracnose severity on coffee seedlings by competition for nutrients and induced resistance

Abstract

Colletotrichum gloeosporioides is a phytopathogenic fungus that gradually weakens both coffee seedlings and adult plants and reduce the quality of the berries. There are no commercial products in the market to control this disease, and therefore, the prospection of different biocontrol agents is a viable option. Phialomyces macrosporus was selected among 10 saprophytic fungi for its higher activity against C. gloeosporioides on coffee seedlings. Foliar application of P. macrosporus to coffee seedlings seven days before the inoculation of C. gloeosporioides reduced disease severity by 32 to 41%. Phialomyces macrosporus grew on the surface of coffee leaves and increased the permeability of the cuticle followed by increased activities of guaiacol peroxidase (POX), catalase (CAT) and phenylalanine ammonia-lyase (PAL) and the buildup in total phenol content and lignin deposition, consistent with the induced resistance phenomenon. No evidence of mycoparasitism either in vivo or in vitro was observed. However, this fungus reduced the sporulation of the pathogen both in culture medium and on necrotic leaf lesions by competition for nutrients, which was confirmed by in vitro experiments on the utilization of different sources of carbon and nitrogen. This antagonistic saprophyte was able to promote plant growth and colonize roots and stems endophytically. The results of this study indicate that the saprophytic fungus P. macrosporus acts by a combination of induced resistance and competition for nutrients in the reduction of anthracnose severity on coffee seedlings.