Utilization of a banker plant to potentiate Ampelomyces quisqualis’ efficiency as a biocontrol agent of grapevine powdery mildew (Eryshiphe necator) and, Effects of Erysiphe necator in quality and yield of grapes (Vitis vinifera L.) at harvest

• Autor(a) principal: Valério, Fátima Alexandra Palma
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/20.500.12207/4537
• topic: Ampelomyces quisqualis; Banker plant; Crop damage; Erysiphe necator; Organoleptic test; Videira; Doenças das plantas; Oídio

To study the hypothesis of building up a system were Ampelomyces quisqualis could develop in time, on a plot, to parasitize grapevine powdery mildew (Erysiphe necator) when the first contamination occurs, a banker plant was installed in a trial plot. The chosen banker plant was purple clover, and its phenological stages were observed during 2016. When purple clover reached its early flower stage, it was infected with Erysiphe trifolii and, after visual symptoms of the fungus were spotted, an inoculation with Ampelomyces was made. This season, no visual symptoms of powdery mildew were observed on leaves of the grapevine, there was only infection on clusters with a frequency of attack of 10% and a severity of 5%, in average. A series of samples were collected for further investigation with Polymerase Chain Reaction technique. A second trial was conducted to evaluate the impact of powdery mildew disease on quality and yield of clusters and musts, of Chardonnay and Cabernet Franc, at harvest period. It was concluded that, powdery mildew has negative effects on quality and yield of grapes at harvest period, even in lower levels of infection (11%), by decreasing the size and number of berries. An increase in total acidity was spotted in both cultivars. In Cabernet Franc the composition in anthocyanins decreased. Regarding the triangular tests, no statistical differences were found between samples however, the sensory panel noted some of the most aromatic attributes given by the fungal disease, according to literature (viscosity/oil, mould/dust).