An in vitro evaluation of a Pseudomonas Syringae pv. Tagetis strain as a potential biocontrol agent

Date

1997-12

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Publisher

Texas Tech University

Abstract

The potential of SL Pseudomonas syringae pv. tageris Tox strain to provide control of the Tox* strain was tested using competition as a basis for comparison. Initially, growth curves of individual strains in both complex and defined media were developed In the complex medium 523, the Tox strain did exhibit greater growth than the other two strains tested and was significantly greater at two points during the assay. In all othCT media tested, the growth of the three strains was almost identical. Ratios of the Tox to Tox*/Rif strains -1:1 and 3:1, WCTC then tested in minimal salts (defined) and 523 (complex) media. In the defined medium, the ratio began and ended at the same point, either 1:1 or 3:1. In the complex medium, only the 1:1 ratio was tested and this ended in a 4:1 ratio in favor of the Tox strain. The 3:1 ratio as well as individual strains were then tested using sunflowCT leaf disks. The Tox and Tox*/Rif strains alone grew much faster than the Tox' strain in the ratio, while the Tox^/Rif strain grew almost as well as it did inoculated as a single strain. The ratio behaved in contradiction of the behavior obsoved in culture. The Tox strain seemed to be inhibited in the ratio and the data taken at 48 hours was 1:5 in fiavor of the Tox*/Rif strain. While still contradicting the results obtained in culture media, the whde plant assay did not follow the same pattern as that seen in the leaf disk assay. At 24 hours, the ratio between the Tox and Tox^/Rif strains which began at 3:1, had shnmk to a little more than 1:1. Data taken at 48 hours showed that the Tox^/Rif strain's population had outgrown that of the Tox' strain reversing the ratio to 1:1.4. From the data presented, it can not be concluded that the Tox strain is capable of providing any measure of biological control of the Tox*/Rif strain.

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