Abstract
This investigation aimed to evaluate the effect of some biocontrol agents against the powdery mildew of Thompson seedless grapevines. The study was carried out during the two successive seasons (2016 and 2017) at a private organic vineyard orchard located at El Beheira Governorate, Egypt. Uncinula necator (syn. Erysiphe necator) is a fungus that causes powdery mildew of grapevine. It causes severe loss in yield quantity and quality. Application of different biocontrol agents, e.g., Trichoderma harzianum, T. hamatum, T. viride, and their combinations, as well as the Blight stop (Trichoderma spp.), a commercial biocide and micronic sulfur, was an attempt to control the disease. The mixture of the three Trichoderma spp. showed the highest efficacy (80.16 and 89.95%) of controlling the disease incidence and severity in the two seasons 2016 and 2017, respectively, followed by the treatment of Blight stop + micronic sulfur (77.12 and 84.02%), while micronic sulfur showed the lowest effect (57.02 and 41.32%). At all treatments, the yield was increased and the chemical characteristics, e.g., “total sugars, total soluble solids (TSS), total anthocyanin (% in mg/100 g F.W.), and total phenols (mg/g betties as gallic acid equivalent)” of berries were improved. On the contrary, the percentage of total acidity was decreased at all treatments than in the control.
Highlights
Grapevine (Vitis vinifera L.) is one of the most important commercial fruits grown in Egypt
Preparations of the biocontrol agents Trichoderma harzianum, T. hamatum, and T. viride were prepared as follows: each of the antagonistic fungi was grown for 10 days at 25 ± 2 °C on a liquid Gliotoxin fermentation (GF) medium under complete darkness conditions (Ahmed 2013)
The results may be explained according to the dual effect of the bioagents, which produce growth regulators in addition to the chemical effect of antioxidants, which plays a clear role in improving plant physiology, metabolism (Sawant and Sawant (2010) and induce systemic resistance (ISR) (Compant and Mathieu 2016)
Summary
Grapevine (Vitis vinifera L.) is one of the most important commercial fruits grown in Egypt. It is considered one of the most widely cultivated crops in temperate, sub-tropical, and tropical regions of the world. Grapevine cultivation offers a great economic potential due to its higher yield and monetary returns owing to the export (Vinothini et al 2014). Grapevine is subjected to the infection with powdery mildew, caused by Uncinula necator (Schwein.) Burrill. Renamed Erysiphe necator Schwein and placed into the section Uncinula of the genus (Braun and Takamatsu 2000). Powdery mildew is a worldwide economically important fungal disease in the grapevine farms and the most enduring and widespread problem (Gadoury et al 2012)
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