Seed treatment with Trichoderma harzianum strain kd formulation reduced aflatoxin contamination in groundnuts

摘要

Pre-harvest infection of groundnuts (Arachis hypogaea) by Aspergillusflavus creates a major food safety problem worldwide. Many strains of Aspergillus flavus and A. parasiticus produce aflatoxins, which are potent carcinogenic substances. A kaolin-based formulation of a biocontrol agent containing conidia of Trichoderma harzianum strain kd isolate was evaluated for its ability to control A. flavus in both in vitro and in vivo experiments. Plants were water stressed three weeks before harvest to condition infection by A. flavus. Aflatoxin content in groundnut seeds determined using a MaxiSignal (R) Aflatoxin B-1 ELISA test kit showed that seeds of plants treated with T. harzianum strain kd and A. flavus developed 56.9% less aflatoxin B-1 than the seeds of the A. flavus inoculated control plants. In vitro bioassay using dual culture technique showed a 73.3% inhibition of mycelial growth of A. flavus by T. harzianum strain kd, with clear evidence of antibiosis. Interaction studies under environmental scanning electron microscope (ESEM) also revealed mycoparasitism by T. harzianum strain kd, associated with mycelial coiling around hyphae of A. flavus. Overall, the results show that the T. harzianum strain kd isolate used in this study has a great potential for use as a biocontrol agent for pre-harvest aflatoxin contamination in groundnuts under drought stress conditions.