The downy mildew, caused by Plasmopora viticola, is one of the most important grapevine (Vitis vinifera) diseases in Southern Brazil, causing defoliation and economic losses. The evaluation of disease severity is an important decision for adoption of strategies and tactics
Resumo -O objetivo deste trabalho foi avaliar a resistência à ferrugem causada pelo fungo Phakopsora euvitis, em genótipos de videira, e a efi ciência da infecção de acordo com a idade das folhas e concentração de inóculo. A avaliação foi feita em 15 genótipos, com base nos seguintes componentes de resistência: número de pústulas (urédios) por cm 2 ; tamanho das pústulas; número de esporos produzidos por pústula; e período latente. Os componentes de resistência, com exceção do período latente, apresentaram grande variação quantitativa. A análise multivariada desses componentes diferenciou cinco grupos de genótipos. Os genótipos mais resistentes foram as cultivares porta-enxertos IAC313, IAC572 e IAC766, em que a efi ciência da infecção foi baixa, com pústulas menores e menor produção de urediniósporos, além de reação de hipersensibilidade no tecido em torno das pústulas. O grau de infecção aumenta com o aumento na concentração do inóculo. A ferrugem coloniza, indiscriminadamente, folhas jovens e folhas maduras de videira.Termos para indexação: Phakopsora euvitis, Vitis, análise multivariada, reação de hipersensibilidade, resistência genética. Genetic resistance of grape genotypes to rustAbstract -The objective of this work was to evaluate the genetic resistance of grape genotypes to rust, caused by the fungus Phakopsora euvitis, and the infection effi ciency in relation to leaf age and inoculum concentration. The evaluation was carried out on 15 genotypes, based on the following resistance components: number of pustules (uredia) per cm 2 , size of pustules; number of urediniospores produced per pustules; and latent period. The resistance components, except for the latent period, presented considerable quantitative variation. The multivariate analysis of resistance components discriminated fi ve groups of genotypes. The more resistant genotypes were the rootstocks cultivars IAC313, IAC572, and IAC766, in which the infection effi ciency was low, with small pustule sizes, and less urediniospores production, besides hypersensivity response on tissue surrounding the pustules. The infection increases with increasing of inoculum concentration. The rust colonizes young and mature grape leaves.
Myracrodruon urundeuva, a native species from the Brazilian Caatinga, is widely distributed across its endemic region, where it also plays an essential socioeconomic role. The objective of this study was to evaluate the influence of environmental stress on the germination of M. urundeuva seeds harvested in different years (2010 to 2013). Seeds were germinated at constant temperatures between 10 to 40 °C, osmotic potentials from 0 to -0.8 MPa (in polyethylene glycol 6000 solutions), and from 0 to -0.5 MPa (in NaCl solutions). The experiment was conducted according to a completely randomized design, with three replicates of 50 seeds, in a factorial scheme (harvest year x stress intensity) for each environmental stress. Germination data were then analysed using thermal, hydro and halo time models, and future germination responses projected according to climate change scenarios. The germination thermal thresholds ranged from 7.4 to 53.3 oC. The germination base osmotic threshold (using polyethylene glycol) was -0.6 MPa and the base osmotic threshold in NaCl was -0.43MPa. Seeds from different harvest years showed distinct tolerance to environmental stresses. The thermal, hydro and halo-time models were efficient to describe the germinative response of seeds, and the climate models allowed to identify the germination responses of M. urundeuva in future climate. According to the models for future climate (RCP 8.5), the reduction of rainfall by 2100 will directly affect seed germination and seedling recruitment of M. urundeuva.
-The objective of this work was to evaluate the potential impact of climate change on the occurrence of grapevine downy mildew in Brazil. Seedlings containing four to six leaves were sprayed with a sporangia suspension containing 10 5 sporangia per milliliter. After spraying, the seedlings were subjected to temperatures of 26, 28, 29.1, 30.4, and 31.8°C for 24 hours. The percentage of diseased leaf area and the latent period were evaluated. Maps of the geographic and temporal distribution of the disease were made considering the monthly average of the mean air temperature and leaf wetness duration for the reference climate or climate normal ) and the future climates (2011-2040, 2041-2070, and 2071-2100), considering the A2 and B1 gas emission scenarios, designed by the Intergovernamental Panel on Climate Change (IPCC). Favorability ranges were set and used in logic functions of the geografical information system (GIS) to generate monthly maps for grapevine downy mildew. Rising temperatures interfered with the grapevine downy mildew infections, reduced the disease severity, and increased the latent period. Future climate scenarios indicate a reduction of favorability of downy mildew in Brazil, with variability in the different grape producing regions.
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