Coronatine production in vitro and in vivo and its relation to symptom development in bacterial blight of soybean

Abstract
Coronatine was detected in culture filtrates of 12 out of 19 pathogenic strains of Pseudomonas glycinea examined, but not in culture filtrates of strains of P. phaseolicola, P. syringae, or P. tabaci. A reversed-phase high-performance liquid chromatographic procedure was developed for coronatine quantitation. Generally, coronatine production by strains in culture correlated with their ability to induce systemic symptoms (chlorosis and stunting) in inoculated soybean plants. Application of purified preparations of coronatine to unifoliate leaves of soybean plants resulted in localized chlorosis, development of chlorosis in subsequently developing trifoliate leaves, and stunting of plant growth, similar to symptoms induced by infection. Coronatine was demonstrated in soybean leaves infected with P. glycinea but was not detected in healthy leaves. The results indicate that coronatine can play an important role in the development of symptoms of bacterial blight of soybean, but the demonstration that some pathogenic strains do not produce coronatine indicates that it may not be essential for pathogenicity.