Bioecology of Xanthomonas axonopodis pv. Citri, causal agent of "Citrus Canker" in São Paulo State

Abstract

Research groups in the State of São Paulo will carry out studies on the development of molecular diversity of bacterial strains of Xanthomonas axonopodis pv. citri (Xac) associated with citrus bactéria) canker. The integration of a pathogen's epidemiology and population genetics will provide better knowledge of disease complex and guindance on strategies for disease control and/or management. Beside this feature other techniques will be developed for bactéria detection and diagnostic, as well as the survival of the pathogen in diferent substrates or plants. With media and long term objectives in cooperation with different research groups on a thematic network, this project consists of five subprojects were will be search. the genetic diversity, detection techniques for diagnostic and the ecology of Xanthomonas axonopodis pv. citri. The objective of the first subproject is the stablishment of a world wide Culture Collection of Xanthomonas axonopodis pv. citri strains, and mainly strains isolated in the state of São Paulo, preserving the strains by means of lyophilization and deep-freezing and acting as a depository of pure culture of strains that will be available in the subsequent projects. The purpose of the second subproject is the development of molecular tools usable in the state of São Paulo for molecular typing of Xanthomonas axonopodis pv. citri strains associated with citrus canker epidemics. Methods based on cloning and determination of the nucleotide sequence of highly repeated elements, evaluation of the amount of polymorphism using cloned repetetive elements and avr genes, stability of IS elements and development of RFLP and LMPCR, and plasmidial analysis from Xanthomonas axonopodis pv. citri strains will be evaluated for discrimination and reproducibility, as well as the spacer regions of 16S-23S and gene groEL. The aim of the third project is the development of several techniques for detection and diagnostic of Xanthomonas axonopodis pv. citri including the formulation of semi- selective media, and the use of DNA probes as a tool for detection in comparison with ELISA tests. The objective of the fourth subproject is to study the ecology of Xanthomonas axonopodis pv. citri, in the aspect of their survival as epiphitic or resident in plant material and in the surface of soils. Informations provided by this subproject will be very usefull to the definition of strategics for erradication or management purposes. The fifth subproject will study the bacteriocin production by strains of Xac and the possibilities of the usage of the producer genes in plants througth biothecnology. (AU)