ACC is caused by the bacterium Xanthomonas. citri subsp. citri (X. citri), which causes premature fruit drop, stem dieback and defoliation of infected plants. We currently know little about the diversity of strains of bacteria causing ACC in São Paulo as there have been few published studies and most of these have used poorly discriminatory methodologies that are unsuitable for robust epidemiological or evolutionary analyses. Genomic DNA sequencing is the gold-standard method for examining bacterial populations that cause disease and tracing the spread and the evolution of antimicrobial resistance and virulence but this has only been applied in a small number of published studies of X. citri that include just one isolate from São Paulo.In this project we will examine the genetic diversity and epidemiology of X. citri from infected plants in Sao Paulo using genome sequencing. We will sample plants from 48 sites throughout the state in the summer of 2018/19 when disease incidence is highest and compare these to historical isolates and to those from other countries. This study of X. citri sampled from regions with high, medium and low levels of ACC will yield important information on how ACC has spread, whether hyper-virulent strains are present, frequency of DNA exchange with strains of the same and other species, and the scale of the problem of copper resistance.
News published in Agência FAPESP Newsletter about the scholarship: