Exploring the antimicrobial properties of seaweeds against Plasmopara viticola (Berk. and M.A. Curtis) Berl. and De Toni and Uncinula necator (Schwein) Burrill causing downy mildew and powdery mildew of grapes

Abstract

Plasmopara viticola and Uncinula necator are the causative agent for the downy mildew and powdery mildew, which becomes a major problem in grapes. The use of natural products like seaweed provide a rich source of structurally diverse and biologically active secondary metabolite and is the ultimate way of combating this diseases. In this context, six different seaweeds such as Chnoospora implexa, Dictyota dichotoma, Gracilaria corticata, Hynea panosa, Enteromorpha intestinalis and Caulerpa racemosa used to control the downy mildew and powdery mildew of grapes. Evaluation of marine products used against both the pathogens were carried out under field trial. The disease incidence was observed on fruits, leaves and inflorescens. But the disease incidence was reduced in fruits @ 10% on 70 and 80 days will be 51.13 and 81.27% for downy mildew. For powdery mildew, 63.76 and 78.18% on 70 and 80 days interval. For both the mildews, the growth and yield attributes @10% on 50 days interval is 69.93%. The Phytotoxicity level were analysed for both mildews. There were no symptoms exhibited on the plants but when the Bordeaux mixture applied it ranges from 1 to 10% damage. The antifungal compounds were identified through gas chromatography mass spectroscopy. The results revealed that 19n compounds were present in Liagora ceranoides. Among those compounds, d-Mannitol, 1–decylsulfonyl shows the highest peak to reduce the mildew diseases. The present study was undertaken to evaluate whether various seaweed (brown seaweed, red seaweed and green seaweed) extracts along with commonly available fungicides are against powdery mildew and downy mildew of grapes.