Root rot caused by Pythium species is a major problem in hydroponically-grown crops. Symptoms of canopy stunting are noticed in plants colonized by the pathogen and many times they are not diagnosed by the grower. The aim of this work was to evaluate biological control and plant growth promotion by Pseudomonas chlororaphis 63-28 and Bacillus subtilis GB03, known biocontrol agents of plant diseases. Inoculation of plants with P. aphanidermatum decreased lettuce mass by 20%. The introduction of the biocontrol agents to the nutrient solution was beneficial for plant growth increasing the plant mass (6% to 13%), the number of leaves (4% to 7%) and the chlorophyll content (3%) of the lettuce plants. Further studies are needed, however, to improve the effectiveness of disease control and growth promotion by the biological agents in hydroponic lettuce.
Lactuca sativa; hydroponic; biocontrol
