Growth stimulation and fruit yield improvement of greenhouse tomato plants by inoculation with Pseudomonas putida or Trichoderma atroviride: Possible role of indole acetic acid (IAA)

• Published in: Soil biology & biochemistry Vol. 39; no. 8; pp. 1968 - 1977
• Main Authors: Gravel, Valérie, Antoun, Hani, Tweddell, Russell J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.08.2007; New York, NY Elsevier Science
• Subjects: Agronomy. Soil science and plant productions; Biochemistry and biology; biodegradation; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; crop yield; Fruit yields; Fundamental and applied biological sciences. Psychology; greenhouse production; Greenhouse tomato; growth promotion; Hydroponic; hydroponics; Indole acetic acid; Physics, chemistry, biochemistry and biology of agricultural and forest soils; plant growth; Plant growth-promoting microorganisms; Plant growth-promotion; seed inoculation; soil bacteria; soil fungi; Soil science; Solanum lycopersicum var. lycopersicum; tomatoes; Indole acetic acid; Fruit yields; Hydroponic; Plant growth-promoting microorganisms; Plant growth-promotion; Greenhouse tomato; Pseudomonadales; Trichoderma; Auxin; Growth; Stimulation; Protected cultivation; Fungi; Inoculation; Dicotyledones; Hydroponic cultivation; Indoleacetic acid; Angiospermae; Lycopersicon esculentum; Bacteria; Pseudomonadaceae; Plant growth substance; Soil science; Fungi Imperfecti; Solanaceae; Pseudomonas putida; Thallophyta; Microorganism growth; Fruit; Vegetable crop; Spermatophyta; Yield; Greenhouse
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2007.02.015

Five bacteria ( Pseudomonas fluorescens, P. fluorescens subgroup G strain 2, P. marginalis, P. putida subgroup B strain 1 and P. syringae strain 1) and three fungi ( Penicillium brevicompactum, P. solitum strain 1 and Trichoderma atroviride) were evaluated to determine their promoting effect on the growth of mature healthy tomato plants grown under hydroponic conditions. P. putida and T. atroviride were shown to improve fruit yields in rockwool and in organic medium. The production or degradation of indole acetic acid (IAA) by the two microorganisms was investigated as possible mechanisms for plant growth stimulation. Both P. putida and T. atroviride were shown to produce IAA. The production of IAA by the two microorganisms was stimulated in vitro by the addition of l-tryptophan, tryptamine and tryptophol (200 μg ml −1) in the culture medium. P. putida and T. atroviride also increased the fresh weight of both the shoot and the roots of tomato seedlings grown in the presence of increasing concentrations of l-tryptophan (up to 0.75 mM). Both microorganisms showed partial degradation of IAA in vitro when grown in a minimal medium with or without sucrose. In addition, the capacity of these microorganisms to reduce the deleterious effect of exogenous IAA was investigated using tomato seedlings. The results showed that the roots of tomato seedlings grown in the presence of increasing concentrations of IAA (0–10 μg ml −1) were significantly longer when seeds were previously treated with P. putida or T. atroviride. The reduction in the detrimental effect of IAA on root elongation could be associated with a reduced ethylene production resulting from a decrease of its precursor 1-aminocyclopropane-1-carboxylic acid (ACC) by microbial degradation of IAA in the rhizosphere and/or by ACC deaminase activity present in both microorganisms.