The potential of Trichoderma asperellum organic extract and its emulsion to inhibit cocoa ( Theobroma cacao L.) black pod disease and induce biochemical defenses against Phytophthora megakarya

Abstract

This work aimed to evaluate the potential of Trichoderma asperellum organic extract and its emulsion to control cocoa black pod disease caused by Phytophthora megakarya. Organic extract was obtained after fermentation of T. asperellum and its emulsion prepared by emulsification. The in vitro antimicrobial assays of organic extract and its emulsion were evaluated and the in situ tests were carried out on detached cocoa pods. T. asperellum inhibited the mycelia growth of P. megakarya at the rates of 52% and 100%, respectively, on dual culture and the cellophane plate. This antagonist produced lytic enzymes such as cellulase, amylase, lipase and protease. The organic extract contained alkaloid, flavonoid and phenol compounds. The emulsion obtained was stable. At 100 μg · ml -1, the extract and its formulation completely inhibited the mycelial growth of P. megakarya. Similarly, when infected detached cocoa pods were sprayed with extract or emulsion, there was a significant reduction of necrosis both for healing and prevention with the latter being the most efficient. For the preventive tests, the total inhibition was recorded at 3000 μg · ml -1 and 1000 μg · ml -1, respectively, with crude organic extract and its emulsion· For curative tests, total inhibition was obtained at 4000 μg · ml -1 and 3000 μg · ml -1, respectively, for preventive and curative tests. There was a significant and positive correlation between the content of biochemical markers and the reduction of necrosis on cocoa pods after treatment with the extract or its formulation. T. asperellum organic extract emulsion could be used as an alternative in the bio- protection of cocoa black pods disease.