Determination of Navelina ISA 315 orange tree tolerance to citrus variegated chlorosis

Abstract

The citrus fruits are the most produced in the World. Brazil are among the three largest world producers with EUA and China, which has about 46% of world production. The Citrus variegated chlorosis (CVC) caused by bacterium Xylella fastidiosa is currently a disease of major importance in Brazilian citriculture. It was found in 1987 in São Paulo state and later in Minas Gerais and Paraná, actually it reaches the most states producers. Because to be a bacterium that colonizes the xylem of plant, it causes obstruction of the waterflow and nutrients to root for the crown of plants, resulting in smaller fruits that mature early and can get the loss of 75% of their weight. The control methods used nowadays involve high cost of execution and may be inefficient depending on the age of the plant. The use of resistant or tolerant varieties is one of the major alternative for management of the disease. In preliminary studies the sweet orange tree (Citrus Sinensis Osbeck) cultivar Navelina ISA 315, it was originated in Italy in 1976 being derived from a clone recovered in vitro by ovuln culture not developed. It was introduced in Brazil and established in the field in 2000 to start of studies related to CVC resistance, it was verified the presence of cachexia-xiloporose at biological indexing, infection that can be attributed to sampling of the bubbles variety in experiment of dwarfed by viroids inoculation proceeding in Italy at the introduction time. There is the necessity of harder studies on pathogen-host interaction, for can be used commercially or in plant improvement programs. The objective of the actual study is to evaluate and quantify the resistance or tolerance levels of the CVC Navelina ISA 315, through the observation of the bacterium presence and typical symptoms of CVC, quantifying them if they occur. Also Navelina ISA 315 plants with and without the viroid of cachexia-xiloporose will be challenged to X. fastidiosa to check a possible relationship between the presence of the viroid and the tolerance of the CVC bacterium. (AU)