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Biological control of Agrobacterium rhizogenes in hydroponic tomato using Pseudomonas strains

Cecilia Chagas de Freitas: The Ohio State University

<div><em>Agrobacterium rhizogenes</em> is the causative agent of Hairy Root Disease (HRD) on many dicotyledonous plants. This disease is characterized by the over-production and proliferation of transgenic adventitious roots. These roots alter the plant’s source-sink relationship to favor root growth over fruit or shoot production. Moreover, under hydroponic conditions, the over-proliferation of roots can block the flow of water in the hydroponic troughs, impairing downstream water and nutrient absorption. HRD has emerged as a problem in hydroponic cultivation throughout Europe and Canada and is now an emerging disease in the greenhouse vegetable production in the United States. Since chemical control of bacterial plant diseases via antibiotics has limited effectiveness and is highly regulated we seek alternative ways to control the disease. We are studying whether members of the <em>Pseudomonas</em> genus (widely known for their ability to inhibit plant-pathogens) can inhibit HRD. We tested the activity of over 50 different <em>Pseudomonas</em> strains and identified three different strains (1B1, 48G9 and 93G8) that were able to reduce bacterial growth <em>in vitro</em> and <em>in planta</em>. Currently these strains are being tested on hydroponic cultivated tomato to determine if HRD can be inhibited. These results suggest that certain <em>Pseudomonas</em> strains have the ability to inhibit <em>A. rhizogenes</em> growth and disease development and can be a potential biocontrol agent for hydroponic growers in the future.</div>