ABSTRACT.


ADRIANA PINTO DE TORRES1
 

For several years, the Instituto de Investigaciones Agropecuarias has been interested in the study of some of the bacterial diseases which affect the bean crop in Chile.
During the past summer, bacterial coloriies were isolated from fifteen beanvarieties seeded in the central zone -and from several others grown in Valdivia, in the southern part of the country. The colonies were of a creamy yellow color and showed similar characteristics when cultured on different media in the laboratory; this permitted their identification as a single bacteriurn of the genus Xanthomonas.
Tests of the pathogenicity of the isolated bacterium were made in the greenhouses of the Experiment Station "La Platina". Plants of different varieties were inoculated, leaving corresponding check plants. All of theinoculated plants developed symptoms similar to those seen in the field, while thecheck plants remained healthy. The most characteristic symptoms observed were green spots between the veins and angular spots on the edges of the leaves, which later tendedto become distorted and in sorne cases withered and died. Longitudinal reddish streaks appeared on the stems and the plants were easily broken. The first symptoms on the pods were green, water-soaked spots, which laterexuded a yellow bacterial secretion. This symptomatology is similar to that presented by "common bacterial blight of beans" caused by Xanthomonas phaseoli in other countries.
At the same time, serological tests of. the bacterium were made in the Agricultural Experiment Station, Rinconada de Maipú, of the University of Chile. When subjected ta serum of Pseudomonas phaseolicola (Burkholder) Dowson and Pseudomonas syrillgae Van Hall, the reaction was negative. However, when subjected to serum of Xanthomonas phaseoli .(E. F. Smith) Dowson, the reaction was positive, permitting the identification of both strains.
Given these results, it can be said w

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1 Ingeniero Agrónomo Proyecto Fitopatología. Instituto de Investigaciones Agropecuarias. Profesor Cátedra de Patología Frutal. Facultad de Agronomía. Universidad de Chile