Improvement of the diagnosis of plum yellow based on the detection and quantification of the phytoplasma and its sistemic seasonal distribution in the host tissue

• Grant number: 14/05042-6
• Support Opportunities: Regular Research Grants
• Start date: June 01, 2014
• End date: November 30, 2016
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal Investigator: Ivan Paulo Bedendo
• Grantee: Ivan Paulo Bedendo
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

In Brazil, plum crops have significant economic importance, yielding about US$ 5,200.00/ha and giving opportunity of work for a lot of people. The conditions of market are highly favorable and 65.000 tons are commercialized by year. Besides, the culture may expand since 50% of commercialized plum is imported from other countries. Based in this information, growers have been stimulated by government programs to increase the production. The main producers are the states of São Paulo, Minas Gerais, Paraná, Santa Catarina and Rio Grande do Sul. In countries that produce plants belonging to Prunus genus, phytoplasmas are recognized as causal agents of significant losses. Species of plum cultivated in Brazil were introduced from plant material originated from these countries, leading to the hypothesis this type of pathogen is present also in Brazilian crops. Preliminary studies have pointed the association of phytoplasmas with plum plants cultivated in commercial orchard. Thus, based on this evidence, the present research proposal has the objectives of: demonstrate the presence of phytoplasmas in orchards located in the state of São Paulo; investigate the genetic diversity of these phytoplasmas; understand the model of systemic distribution of pathogen in distinct phonological stages of the plants.For detection and identification of phytoplasmas associated with the disease, symptomatic and asymptomatic plants will be collected in commercial orchards. Total DNA will be extracted and used as template in PCR assays. Products from PCR will be analyzed by RFLP. Genomic fragments of 16S rRNA gene will be cloned, sequenced and analyzed using software programs and phylogeny. For studies about systemic colonization of plant tissues, labeled plants will be monthly sampled, during a period of two years. DNA will be used to determinate the concentration of phytoplasmas present in the tissues, using qPCR. The results will be analyzed to evaluate the season more favorable to concentration of phytoplasmas in the tissues of leaves and roots sampled during the two years.Expected results may contribute for reliable diagnosis; generate methodology for the phytossanitary inspection in order to avoid the introduction of infected material in Brazilian areas; contribute for certification of commercial seedlings produced in nurseries and mother plants; obtain information for development of a good management system of the disease. (AU)