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Population structure and sensitivity of Plasmopara viticola and Phakopsora euvitis to fungicides in Brazil

Grant number: 17/21412-6
Support type:Scholarships in Brazil - Post-Doctorate
Effective date (Start): January 01, 2018
Status:Discontinued
Field of knowledge:Agronomical Sciences - Agronomy
Principal Investigator:Lilian Amorim
Grantee:Ricardo Feliciano dos Santos
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
Associated scholarship(s):18/25596-7 - Molecular characterization of Plasmopara viticola and Phakopsora meliosmae-myrianthae with different levels of sensitivity to QoI and DMI fungicides in Brazil, BE.EP.PD

Abstract

Grapevine is an important crop in Brazil. The area of vineyards is 75,906 ha and grape production reached 1.47 million tons in 2017. The production of grapes is concentrated in Rio Grande do Sul, São Paulo and Pernambuco States, where 83% of the vineyards and 87% of the production are concentrated (IBGE, 2017). Several factors can affect grapevines potential yield and grapevines longevity, including diseases. Downy mildew (Plasmopara viticola) and rust (Phakopsora euvitis) are the most important grapevine diseases in Brazilian vineyards due to both quantitative and qualitative losses they cause. In a survey carried out in Jales region-SP, it was observed that the number of fungicide applications has been excessive with 103 and 59 fungicide spraying each season in vineyards of European (Vitis vinifera) and American grapes (Vitis labrusca), respectively (Costa et al., 2012). The excessive frequency of applications performed at fixed intervals leads to an increase of the production costs and of the risks of selection of resistant pathogenic isolates, jeopardizing the efficiency of chemical control. High risks of fungicide resistance occur for pathogens with short latent periods, high sporulation rates and high dissemination efficiency, characteristics presented by both P. viticola and P. euvitis. Risks of fungicide resistance are also high in site-specific fungicides, as demethylation inhibitors (DMI) and quinone outside inhibitors (QoI), widely used in Brazilian viticulture. However, there is limited information about the sensitivity of P. viticola and P. euvitis to fungicides in the country. The monitoring of the sensitivity of P. viticola and P. euvitis isolates to fungicides registered for the crop is essential to define the fungicides groups that should be used in the management of the diseases. Studies using microsatellite markers show that isolates continuously exposed to fungicides presented several mutations in the genome that do not were observed in isolates without contact with the fungicide. The increase of the mutagenesis may confer greater plasticity to the pathogen population, and it is possible that some isolates may adapt to new environmental stresses such as resistance to new chemical classes of fungicides. Therefore, the main objective of this project is to characterize the sensitivity of P.viticola to QoI, relating the different levels of sensitivity with the population genetic structure of the pathogen, and assess the sensitivity of P. euvitis to QoI and DMI in Brazil. (AU)