Effects of growing medium on the interactions between biocontrol agents and tomato root pathogens in a closed hydroponic system

Three commercial biocontrol agents [Trichoderma polysporum plus T harzianum (Binab T), Gliocladium cantenitlatum (Gliomix), and Streptomyces griseoviridis (Mycostop)] were evaluated for their Ability to reduce root diseases caused by Pythium aphanidermatum, Phytophthora cryptogea, or Fusarium oxysporum f. sp. radicis-lycopersici in hydroponically-grown tomatoes. Studies were performed using two types of growing medium, peat or pumice, under controlled conditions in a closed irrigation system. The level of disease control varied depending on the biocontrol agent, growing medium, and pathogen. In pumice, amendment with Binab T, Gliomix, or Mycostop reduced the levels and disease incidence of all three pathogens. However, Mycostop had no significant effect on the level of any of the three pathogens in peat, although Binab T and Gliomix both achieved successful biocontrol. In both growth media, biocontrol of F oxysporum f. sp. radicis-lycopersici was poor compared with that of P aphanidermatum or P cryptogea. Overall, tomato plant growth increased after the introduction of any of the biocontrol agents, in the presence of any of the three pathogens, compared with the untreated controls.