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Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/13/1996 Publication Date: N/A Citation: N/A Interpretive Summary: Vegetables, especially tomatoes and peppers are propagated from seed in planting mixes in flats in greenhouses prior to transplanting in the field. During this phase of propagation, planting mixes can be amended with biological control agents to protect roots against plant pathogenic agents. In this study, commercial and experimental isolates of five bacteria and fungi, known to have biological control properties were tested for their longevity and compatibility with Glomus intraradices, a mycorrhizal fungus in a planting mix seeded with tomato. Bacillus subtilis, a bacterium, and Trichoderma harzianum, a fungus, did not change much from original levels during the 6 to 7 week long test. Serratia plymuthica, Streptomyces griseovirdis, a Pseudomonas fluorenscens parent and its lacZY mutant declined about 1 log10 unit during the tests. All biological control agents were compatible with Glomus. Bacillus and Trichoderma retained the best survival potential. Technical Abstract: Commercial sources of the biological control agents Bacillus subtilis, Trichoderma harzianum, Streptomyces griseovirdis, and experimental single isolates of Serratia plymuthica and a Pseudomonas fluorescens parent and its lacZY mutant were evaluated for their survival and compatibility with the mycorrhizal fungus, Glomus intraradices in a commercial planting mix. Control treatments were the unamended mix and mix amended with G. intraradices alone, and all were applied to 128 cell Speedling styrofoam flats and planted with the Sunny tomato cultivar. At 4 to 5 intervals during the growing period (6.5 to 8 wks.) each organism was quantified by dilution plating and G. intraradices infection (%) was determined at the end of each test. Trichoderma isolates increased slightly within two weeks after application and then stabilized through the end of the test. Serratia and Streptomyces isolates declined throughout the test from about 7.75 log10 cfu/g to numbers at the end (6.2 log10 cfu/g) similar to the controls. Bacillus isolates declined about 1 log10 cfu/g the first week, but then stabilized. Glomus intraradices had no influence on numbers of these four genera nor those of their controls. The Pseudomonas parent and its lacZY mutant declined about 1 log10 cfu/g unit during the test with the mutant yielding higher cfu each sampling period. |
