Brazil is the largest sweet orange producer in the world, and citriculture is an important economic activity in the country. Citriculture is threatened by Asian citrus canker (ACC), a disease caused by the Gram-negative bacteria Xanthomonas citri subsp. citri (X. citri), and responsible for great losses to citrus production. According to the new ACC control legislation, the state of São Paulo is an area of risk mitigation system (SMR); control is done by planting cultivars less susceptible to ACC, installing windbreaks in orchards with the aim to avoid the spread of the bacteria by the combined action of wind and rain, and the use of regular sprays of copper. Copper is bio cumulative, toxic and the pressure imposed by its continuous application may drive the selection of resistant strains and favor a gradual increase in the frequency of such strains within the bacterial population. Here, we intend to investigate if there are phenotypic differences amongst newly isolated strains of X. citri collected in areas of São Paulo state showing different levels of ACC incidence. These isolates will be tested for their susceptibility to copper, and in case of resistance, we plan to search for genetic markers normally associated to this phenotype. For those isolates possibly identified as tolerant to Cu, we shall conduct tests to define the altered activity of efflux pumps, which seems to be correlated with such phenotype. Finally, isolates will be assessed for their ability to form a biofilm, and motility, two characteristics long accepted as necessary for the early stages of plant infection. In our analyses, we hope to be able to identify differences in virulence markers and correlate them with the isolation area of the strains under study.
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