ABSTRACT
ABSTRACT: Prohexadione-calcium (ProCa) is a gibberellin biosynthesis inhibitor and the objective of this study was to evaluate the effect of ProCa on the downy mildew (DM) and Botrytis bunch rot (BBR) epidemiology, and the yield and technological and phenolic parameters of grape Merlot cultivar. Experiments were carried out in a commercial vineyard in São Joaquim Municipality/SC, Southern Brazil, during the 2017-2018 and 2018-2019 growing seasons. ProCa was applied at four doses and three phenological stages: A) 0 g ha−1 (control); B) 1000 g ha−1 (inflorescence fully developed); C) 500 + 500 g ha−1 (inflorescence fully developeted and full flowering); D) 500 + 500 + 500 g ha−1 (inflorescence fully developed, full flowering, and berries pea-sized). DM and BBR incidence and severity were quantified weekly from the first symptom appearance until harvest, and their epidemiology was compared according to: a) the beginning of symptom appearance; b) the time to reach the maximum disease incidence and severity; c) the maximum value of disease incidence and severity; d) the area under the disease progress curve. In general, there were significant differences in the ProCa doses for all epidemiologic parameters of DM and BBR compared with the control plot; however, there was no significant difference among the ProCa doses. The principal epidemiological variables that differentiated the effect of ProCa on the DM and BBR control were the Smax and AUSDPC. Some yield and technological and phenolic parameters were negatively affected by different doses of ProCa, but it was still a good option for DM and BBR control in highland region of southern Brazil during the 2017-2018 and 2018-2019 growing seasons.
RESUMO: A prohexadiona-cálcio (ProCa) é um inibidor da biossíntese de giberelina e o objetivo desse estudo foi avaliar o efeito do ProCa na epidemiologia do míldio da videira (MV) e da podridão de Botrytis (PB) e no desempenho vitícola da cultivar de videira Merlot. Experimentos foram realizados em um vinhedo comercial no município de São Joaquim/SC, Sul do Brasil, durante as safras 2017-2018 e 2018-2019. A ProCa foi aplicada em quatro doses e três estágios fenológicos: A) 0 g ha-1 (controle); B) 1000 g ha-1 (inflorescência totalmente desenvolvida); C) 500 + 500 g ha-1 (inflorescência totalmente desenvolvida e floração completa); D) 500 + 500 + 500 g ha-1 (inflorescência totalmente desenvolvida, floração completa e baga tipo ervilha). A incidência e severidade de MV e PB foram quantificadas semanalmente a partir do aparecimento dos primeiros sintomas até a colheita e a epidemiologia das doenças foram comparadas de acordo com: a) o início do aparecimento dos sintomas; b) tempo para atingir a máxima incidência e severidade da doença; c) valor máximo da incidência e severidade da doença; d) área abaixo da curva de progresso da doença. Em geral, houve diferenças significativas na dose de ProCa para todos os parâmetros epidemiológicos de MV e PB em comparação com o controle; no entanto, não houve diferença significativa entre as doses de ProCa. As principais variáveis epidemiológicas que diferenciaram o efeito da ProCa no controle do MV e PB foram o Smax e o AUSDPC. Algumas variáveis vitícolas da cultivar Merlot foram afetados negativamente por diferentes doses de ProCa, mas ainda foi uma boa opção o uso da ProCa para o controle do MV e PB em região de altitude do sul do Brasil durante as safras 2017-2018 e 2018-2019.
ABSTRACT
Abstract Rain-shelter cultivation has been proven an important cultivation method for grape-plantings in continental monsoon climate zones, of which white plastic films are the most common shelter material. However, while this method and material reduces the occurrence of the disease, it can also decrease the grape berry quality. Five colours (including red, yellow, blue, purple, and white) of plastic films were covered above Cabernet Sauvignon (Vitis vinifera L.) grapevine rows before veraison. Rain-shelter cultivation reduced air temperature, wind speed, and total solar radiation and enhanced relative humidity in the fruit sphere of grapevines. For each particular colour plastic film, the irradiance of its corresponding spectrum band in the canopy of vines was higher than with other colour plastic films. Meanwhile, the blue plastic film treatment significantly promoted the accumulation of total phenolics, anthocyanins, flavonoids, tannins, and phenolic acids more than the other colours of plastic films. Blue plastic films are more beneficial for berry quality promotion of wine grapes, especially Cabernet Sauvignon, under rain-shelter cultivation in continental monsoon climate zones.