Métodos de inoculação de Phytophthora citrophthora (RE Sm. & EH Sm.) Leonian em citros

Abstract

Citricultura has achieved prominence in the Brazilian economy. Citrus (Citrus spp.) Are among the most planted, consumed and researched fruit trees in the world. But what has interfered in its production are the diseases that affect the culture and, among the main diseases is Citrus Gum. The objective of this work was to select an efficient method of inoculation for studies of resistance and susceptibility of rootstocks to this disease. In this case present different methods of inoculation of Phytophthora citrophthora were tested on two rootstocks: Sicilian lemon tree (Citrus lemon) known to be susceptible to the pathogen and Poncirus (Poncirus trifoliata 'Kryder') considered more resistant than the previous one. The methods used were: inoculation with drops of the zoosporus suspension in the branches, inoculation by mycelial disk in branches, inoculation by immersion of detached branches in suspension of zoospores for 20, 40 and 60 minutes, inoculation of zoospore suspension in leaves with wound caused by abrasive and without injury on the abaxial and adaxial surfaces, inoculation of mycelium disc on leaves with abrasive injury and without injury on the abaxial and adaxial surfaces. The work was developed in the Laboratory of Phytopathology of Embrapa Mandioca and Fruticultura located in the municipality of Cruz das Almas-BA. The evaluations were done using the Assess program measuring the size of the lesion and later submitted to analysis of variance (ANOVA), in order to verify the existence of significant differences by the F test and Scott-Knott test between inoculations. For methodologies involving leaves the evaluation was done using multivariate factorial analysis. From the results it was possible to choose an efficient method for tests of resistance of citrus materials to Gomose in a short period of time and at low cost. The best results were obtained in inoculations of P. citrophthora by means of disc insertion of culture medium containing the pathogen in detached branches, a method that can be used in inoculations of Citrus plants at different stages of development. By allowing the evaluation of genotypes with highlighted parts of the plants in a short time, the methodology can be an auxiliary tool for genetic breeding programs of Citrus.