Genomic platforms applied to citrus breeding

Abstract

The citrus industry is one of the leading activities of the agribusiness in Brazil, with the states of Sao Paulo, Sergipe and Bahia as the main citrus producers. Brazil is by far the main producer and exporter of frozen concentrated (FCOJ) and not from concentrated (NFC) orange juice in the world. The low Brazilian yield (approximately 2 boxes 40.8 kg/tree/year) is highly associated to the incidence of pests and diseases (resulting in a substantial influence over the production costs), the production in non-irrigated areas, and the narrow genetic basis that has been used. It is estimated that more than 60 % of the costs for citrus production in Brazil are associated with control of pests and diseases. Diseases like citrus variegated chlorosis, leprosis, black and brown spot, sudden death, citrus canker, gummosis, tristeza and, recently, huanglongbing (HLB, former greening). Indeed, in recent years, the citrus industry has witnessed substantial structural changes in its structures due to diseases like HLB. Most of the models for the management of the disease vectors, including chemical control, have failed due to their high economic and environmental costs, which enhance even more the importance of studies on genetic breeding as a powerful and durable strategy to control diseases. The Centro de Citricultura Sylvio Moreira (CCSM) – IAC and Embrapa have been investigating citrus breeding for a long time as well as producing and evaluating new genetic materials by using biotechnological tools to accelerate genetic gains. As the leading member of the Millennium Institute of CNPq /MCT (2002-2005), CCSM constructed an extensive database on expressed citrus genome (CitEST), which comprises tools for studying genetic breeding and comparative and functional genomics of citrus and some of its pathogens. Besides producing the largest collection of genomic data worldwide, the project enlarged profoundly the number of new citrus hybrids under field evaluation, molecular markers for genetic mapping and discovery of new genes discovery with potential association to disease resistance. This proposal reflects the continuation of the program “Millennium Institute”, not only bringing together the main groups that investigate citrus in Brazil, but also focusing on subjects related to genetic breeding and functional genomics of the citrus group, looking forward on the integration of three platforms: Platform of Genomic Information, which focuses on studies regarding comparative and functional genomics to enlarge the basis of information, including the complete genome associated with the International Consortium on Citrus Genome and the database on expressed citrus genome, studies on gene expression (microarrays) of citrus and some of its pathogens, support to bioinformatics and genetic transformation to produce modified plants based on data from the citrus genome. Platform for Genomic Application, which the focus is the plant-pathogen interaction in limiting pathosystems faced by the citrus industry and the plant-environment interaction (water stress). Such studies will allow enlarging the knowledge useful in other activities of the Program. Platform of Apllied Genetics, which represents the advanced interface of breeding from which previously generated data (markers, maps, genes, promoters), as well as genetic material (hybrids of controlled crosses and events of transformation already available) will be validated under field conditions, to permit a reliable approach to the strategy of marker-assisted breeding. From this platform, new materials will be released for the Brazilian citrus industry. The multi-disciplinar and multi-institutional network of the Program includes, besides the CCSM as the coordinator member, Embrapa Mandioca e Fruticultura and its network for citrus breeding, Embrapa Recursos Genéticos e Biotecnologia, Escola Superior de Agricultura Luiz de Queiróz (ESALQ/USP) and Centro de Energia Nuclear na Agricultura (Cena), Universidade Estadual de Campinas (Unicamp), Instituto Biológico, Universidade Federal de Campina Grande, Universidade Estadual do Sudoeste da Bahia (Vitória da Conquista), Universidade de Mogi das Cruzes (UMC), and University of Florida. (AU)