Composition comprising species from the genus Glomus and Trichoderma harzianum T78 and use thereof as a plant growth promoter. Composition comprising species from the genus Glomus and the Trichoderma harzianum T78 strain, identified by the deposit number CECT 20714. Species of the genus Glomus are Glomus intraradices, Glomus claroideum, Glomus mosseae and Glomus etunicatum. Composition for use thereof as a plant growth promoter or for preventing or treating infections caused by pathogenic microorganisms in a plant.