Evaluation of Indirect Immunofluorescence and Ice Nucleation Activity as Rapid Tests for Identifying Foliar Diseases of Tomato Transplants Incited by Fluorescent Pseudomonads

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Abstract
Indirect immunofluorescence (IIF) and ice nucleation activity (INA) were evaluated for detection and identification of 2 bacterial foliar pathogens of tomato transplants. When 127 lesions from 11 transplant fields and 2 research plots were triturated in water and tested by IIF with 2 antisera prepared against Pseudomonas syringae pv. tomato (PST), 74% reacted positively with 1 antiserum. Similar results were obtained when the IIF procedure was used on 117 pure cultures isolated from the lessons. Only 24% of the 117 cultures, however, were PST, whereas most of the remainder were P. syringae pv. syringae (PSS). The antisera (one was cross-absorbed with Xanthomonas campestris pv. vesicatoria [XCV]) reacted negatively with pure cultures of 4 strains of XCV and with lesions from artificially inoculated plants. All lesions that yielded PST tested negatively for INA, whereas 76% of those with PSS tested positively. All pure cultures of PST from field plants tested negatively, whereas 95% of PSS cultures were positive. IIF and INA, when used in combination apparently are useful diagnostic tools for distinguishing PSS from PST on tomato transplants and will assist in certification efforts.