Cross protection against severe isolates of citrus tristeza virus on sweet orange (Citrus sinensis Osbeck cv. pera)

• Grant number: 95/04583-0
• Support Opportunities: Research Projects - Thematic Grants
• Start date: October 01, 1996
• End date: October 31, 2000
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal Investigator: Marcos Antonio Machado
• Grantee: Marcos Antonio Machado
• Host Institution: Instituto Agronômico (IAC). Agência Paulista de Tecnologia dos Agronegócios (APTA). Secretaria de Agricultura e Abastecimento (São Paulo - Estado). Campinas , SP, Brazil
• Associated research grant(s): 98/09778-2 - Characterization of citrus tristeza closterovirus isolates by rflp of the coat protein gene., AR.BR; 98/09777-6 - Molecular characterization of three brazilian isolates of citrus tristeza virus., AR.BR; 98/09779-9 - Production of budwood free of Xylella fastidiosa in screenhouse in São Paulo, Brazil, AR.BR; 97/05732-5 - Richardt Frank Lee | University of Florida - Estados Unidos, AV.EXT

Abstract

Cross protection against severe isolates of citrus tristeza virus on sweet orange (Citrus sinensis L. Osb. cv. pera). The citrus tristeza virus (CTV) and its vector, the brown citrus aphid (Toxopetera citricida), are endemic in Brazil, and both play an important role in the low productive of the citrus orchards. The Brazilian citrus industry lives very well together with many weak or mild strains of CTV, as a result of cross protection program using protective strains in tolerant varieties of sweet oranges and rootstocks. However, such approach has not reduced the spreading of very severe strains, like the complex CTV of Capão Bonito (CB), that affect the more used rootstock in brazil, the rangpur lime (Citrus limonia). Although cross protection in the brazilian citrus industry could be considered a very successful approach in controlling severe strains of CTV, its biological and molecular bases are unknown. Protective strains of CTV have been mainly used in varieties of sweet oranges with low tolerance to the virus, allowing their use as commercial varieties, like the sweet orange pera IAC, with more than 50 millions plants in the state of São Paulo. Aiming to obtain new protective isolates of CTV for using in sweet orange pera this project supported by fapesp has the following goals: study of virus genome of protective isolates by analysis of dsRNA (double strand RNA), RFLP (restriction fragment length polymorphism), SSCP (single strand conformation polymorphism), and sequencing of several orfs (P18, P25, P27). Studies of expression, competition and challenge between strains are been carried out using sweet orange pera as a model. (AU)