Reaction of citrus plants to the bacteria Xylella fastidiosa related to different methods of inoculation

Author(s)

Ariane Busch Salibe

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2001-04-05
• Advisor: Francisco de Assis Alves Mourao Filho

Abstract

Citrus variegated chlorosis is a bacterial disease presently affecting the citrus industry in Brazil, markedly decreasing the productivity of the orchards. In this research work, two different experiments were conducted with objective of enlarging the knowledge about the disease, determining the range of hosts of the pathogen Xylella fastidiosa in the sub-family Aurantioideae and finding the best method of the bacteria in the citrus plants. The experiments were conducted in the laboratories and facilities of the Department of Plant Production of the ESALQ/University of São Paulo, in Piracicaba, SP and evaluated with the use of molecular and serological tests accomplished in the Laboratory of Biotechnology of the Citrus Research Center/IAC, Cordeirópolis, SP. In the first experiment, test plant of 31 varieties and species representatives of the sub-family Aurantioideae were produced, budded on 'Rangpur' lime. They were inoculated by two methods, lateral approach grafting and introduction of bacterial suspension into the main stem of the nursery plants. The results of the PCR molecular test indicated that all varieties of sweet orange tested as well as 'São Paulo' sour orange and the 'Etrog' citron were hosts of the pathogen. The highest concentration of the bacteria was determined by ELISA test to occur in the test plants of 'Hamlin' orange. In the second experiment, the efficiency of four methods of inoculation of the bacteria X. fastidiosa were evaluated: A. approach grafting of infected seedlings, B. petiole budding, C. grafting of young branches and D. inoculation of bacterial suspension with needle. Tests plants were those of 'Pera' sweet orange selections Pirangi, IAC 2000 and Ipiguá and 'Cravo' mandarin. Monthly evaluations with PCR test carried on during a period of eight months revealed a marked difference between the methods of inoculation, according with the decreasing order of efficiency B, A, C and D. (AU)