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| Author(s): |
Meyriele Pires de Camargo
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2017-10-11 |
| Examining board members: |
Lilian Amorim;
Maria Cândida de Godoy Gasparoto;
Maísa Ciampi Guillardi;
Geraldo José da Silva Junior;
Marcel Bellato Sposito
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| Advisor: | Lilian Amorim |
| Abstract | |
Downy mildew (Plasmopara viticola) and rust (Phakopsora euvitis) are important diseases on vineyards located in São Paulo State. The aims of this study were: i. characterize the population genetic structure and identify cryptic species of P. viticola; ii. evaluate the temporal progress of grapevine downy mildew, the disease effect on yield, and verify the contribution of sexual and asexual reproduction of P. viticola on disease epidemic and; iii. evaluate the temporal progress of grapevine rust. A total of 516 isolates of P. viticola were collected from 11 locations of São Paulo State. The isolates were genotyped with 7 microsatellite markers. To identify cryptic species of P. viticola, a subsample of 130 isolates were analized by Cleaved Amplified Polymorphic Sequence (CAPS), and 94 isolates were sequenced for ITS1 region. Temporal progress of downy mildew and rust were evaluated in 3 growing seasons (2014/15, 2015/16 and 2015/16) on vertical trellis (VT), Y-trellis without plastic cover (YWP), and Y-trellis with plastic cover (YPC). The experimental area, located in Piracicaba-SP, was composed by plants of the variety Niagara Rosada. The variables analyzed were phenology, number of leaves per shoot, disease incidence and disease severity. To verify the effect of downy mildew on yield were evaluated bunch weight, yield per plant, total soluble solids content (TSS) and titratable acidity (TA) of the fruits. Area under the curve (AUC) was calculated for number of leaves per shoot, downy mildew and rust incidence and downy mildew and rust severity. The values of bunch weight, yield per plant, TSS and TA, and AUC results for the analyzed variables, were submitted to variance analysis and the mean values were compared by Tukey test (P<0.05). In the growing season of 2015/16, 166 isolates of P. viticola were collected at three different moments of downy mildew epidemic. The isolates were genotyped with the 7 microsatellites previously mentioned. P. viticola clado aestivalis was the only cryptic species identified in São Paulo State. Among the 516 isolates analyzed, 55 multilocus genotypes (MLG) were identified. Four dominant MLGs represented 65.7% of the observed genotypes. For downy mildew, 2 of the 3 growing seasons evaluated were observed early defoliation of the diseased plants. The maximum average values of disease severity observed were 14.3% in ESP and 30.9% in YD. For these disease severity values, the disease reduced yield per plant (0.7 to 0.9 kg per plant) and bunch weight (67 to 78 g). No effect of downy mildew was verified on TSS and TA in none of the growing seasons. Higher AUC values for downy mildew severity were observed in YWP compared to the VT, suggesting that YWP favors the disease progress. On the YPC, incidence of downy mildew was reduced by up to 93.7% compared to the uncovered systems, indicating that Y-trellis associated with plastic cover was an efficient tool to control the disease. The monitoring of genotypes of P. viticola in the 2015/16 growing season revealed that disease epidemic was drived predominantly by multiple clonal infections caused by a single genotype. Early defoliation due to grape rust epidemic was observed on YWP and YPC with disease severity lower than 5.6%. Due to defoliation caused by rust modification on plant phenology were verified in the final stages of plant development. The progress of rust incidence was faster in YWP and YPC than in VT. Unlikely grape downy mildew epidemics, the use of plastic cover was not sufficient to effectivly control grape rust. (AU) | |
| FAPESP's process: | 14/05522-8 - Spatio-temporal progress of grapevine rust and downy mildew in plants with different architectures |
| Grantee: | Meyriele Pires de Camargo |
| Support Opportunities: | Scholarships in Brazil - Doctorate |