Variability analysis of gene cytB on the genomic region associated with resistance to QoI fungicides on pathogens of Niagara grapes (Vitis labrusca)

• Grant number: 14/19711-7
• Support type: Scholarships in Brazil - Master
• Effective date (Start): June 01, 2015
• Effective date (End): February 29, 2016
• Field of knowledge: Biological Sciences - Genetics - Molecular Genetics and Genetics of Microorganisms
• Cooperation agreement: Coordination of Improvement of Higher Education Personnel (CAPES)
• Principal researcher: Claudia Barros Monteiro Vitorello
• Grantee: Nathália de Moraes
• Home Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Associated research grant: 13/24003-9 - Grape diseases: epidemiology, damage assessment and control, AP.TEM

Abstract

Grape is one of the oldest plants cultivated by mankind, and its production in Brazil is in third place when counted the profits from its sale, only behind banana and orange. Although it production allows small rural properties to survive due to its planting, grape is susceptible to several diseases that affect up to 30% of the farmers' budget with products used for the control of diseases. In São Paulo among the diseases three, caused by four distinct organisms, are important: anthracnose (caused by Colletotrichum sp and Sphaceloma ampelinum), the downy mildew (caused by Plasmopara viticola) and rust (caused by Phakopsora euvitis). The producers use chemical control intensively and preventively, reaching 100 fungicide applications per cycle. The main fungicides used are the quinone inhibitors (QoI) that act by preventing the transport of electrons from cytochrome b to cytochrome c1, in the respiratory chain. However, there are reports in other countries, such as France, of cases of individuals with resistance even after application of the fungicide in the field. The mutation in the gene which leads to the substitution of an amino acid in the cytochrome b protein prevents the fungicide to bind to its target site. The sequence of the gene encoding cytochrome b (cytB) has regions (named hotspots) that are known to harbor mutations related to possible resistance of some individuals. Besides the identification of these mutations it was found that the presence of an intron in the gene sequence may influence the establishment and the localization of these mutations. The phenomenon of resistance of these pathogens to fungicides used on grape has never been reported in Brazil, although the lack of studies does not imply that this problem does not really occur. Thus, the aim of this work is to isolate, sequence and characterize the gene cytB and the hotspot region in several strains of the aforementioned organisms obtained from different locations of the state of São Paulo. Results from sensitivity to QoI fungicides' tests will be compared to that obtained by sequencing the hotspot region. The variability of this region among the different isolates will also be studied. Thus, it will be possible to characterize the structure of cytB and also find mutations related to resistance present on isolates from Brazilian state of São Paulo, enabling later that other researches try to establish suitable management plans supported with the results obtained here. (AU)