The role of some elicitors on the management of Roumy Ahmar grapevines downy mildew disease and it's related to inducing growth and yield characters

Many elicitors (silicon, chitosan, bion or fungicide) were investigated on grapevines grown under natural infestation to evaluate their capacity on inducing defense from downy mildew disease and enhancing growth, yield, berries quality as well as some physiological and anatomical characteristics of Roumy Ahmar grapevines. Foliar application of any elicitors used, in special, silicon was significantly increased yield per vine, cluster weight, 100 berry weight, soluble solids%, total anthocyanin and total phenols while reducing the total acidity% in berries as well as increasing leaf area and potassium percentage in leaves and antioxidant enzyme activities comparing with control. Chitosan application was significantly superior than using other elicitors in increasing shoot length, nitrogen and phosphorous percentage, photosynthetic pigment, ascorbic acid, proline and phenolic compounds in the leaves, and decreased hydrogen peroxide and lipid peroxidation leading to improved membrane permeability. All tested elicitors, in special, Si reduced downy mildew disease severity as compared with untreated control vines. Also, the chloroplast exhibited different degrees of malformation and lysis. The mitochondria were highly vacuolated and the nucleus was misshapen in infested vines. It could be suggested that spraying Roumy Ahmar grapevine with 1000 mg/1 silicon four times controlled downy mildew disease in grapevine as well as improving its growth, yield and quality.