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Genetic structure of Guignardia citricarpa in different period of time and metagenomics approach in environments with different levels of control of citrus black spot

Abstract

Citriculture is one of the most important sections of Brazilian agribusiness, especially in the state of Sao Paulo, the major Brazilian citrus producer. Citrus are affected by severe plant health problems, particularly the Citrus Black Spot (CBS), whose causal agent, the fungus Guignardia citricarpa, is an A1 quarantine pathogen for relevant importers of in natura fruits, including the European Union. All commercial varieties of citrus are susceptible to CBS and the control is dependent on sequential application of fungicides. These chemicals are applied several times a year and, among the currently available systemic fungicides, only the strobilurin group may be used due to recent commercial barriers. Such fact undermines the longevity of this chemical group and can therefore influence changes in the genetic structure of G. citricarpa populations allowing the emergence of tolerant genotypes. Thus, it is essential to monitor this species behavior over time. Also, the culture management, including the use of fungicides, can affect both pathogens and the complex microbial community that is in association with plants and is a fundamental part to the equilibrium of these biological systems. Thus, this work aims to compare G. citricarpa populations obtained in 2005 and in 2012, from one of the largest citrus producers of Sao Paulo State. For that, sequence analyses of ITS, TEF-1, GPDH regions, fAFLP molecular markers and sensibility analysis to fungicides will be performed. This way, we intend to assess possible genetic changes in the sampled individuals. Furthermore, a metagenomic approach will be applied to evaluate the microbial community living in citrus leaves under different levels of control of CBS under the same environmental conditions. This study will result in new information on possible harmful impacts of chemicals on the microorganisms that host citrus, as well as provide relevant data to the conduction of future studies in this important crop. (AU)